Sunday, December 30, 2007

Human Auditory System: Mosquito test your hearing

I've blogged before about the Mosquito ringtone - the teenagers' ringtone that adults mostly cannot hear.  Brian Dipert's excellent blog over at EDN (a technical magazine for the electronics industry) calls our attention to an in-depth article from last year in Sound and Vision Magazine on the Mosquito ringtone.  The article includes links to various MP3 recordings. Brian, who still has some high frequency hearing left even though, as I recall, he enjoys attending, as well as recording, live music performances that use sound reinforcement (i.e. loud, loudspeakers), is running a poll to see how many of us can hear the higher frequencies.

I missed the Sound and Vision article when it came out, but read it with interest today.  I do have some nits to pick with it though.  For starters, exposure to loud sounds is understood to be less harmful to young people than to us older folks.  The human ear has some automatic protection built in and although its effectiveness degrades as we age, it does enable younger people to be exposed to louder sounds without permanent damage.  Of course, there are limits to this ability, so this should not be taken by anyone as a license to go and blow their eardrums or cilia out(!).

My second nit is the author (David Ranada) slams higher sample rate audio formats.  His comments are certainly valid from the standpoint of continuous tones, but I believe that there are a good number of audiophiles and audio engineers who would argue that higher sample rates provide better reproduction of transient sounds.  This technical argument is based around the limitations of Fourier Transforms, which, very simply put, try to model all sounds as continuous sine waves.  There are also technical arguments for higher sampling rates based around the design of the anti-alias filters, which are easier and cleaner to implement at the higher rates.  Finally, I've heard that there has been some scientific research related to endorphin release in the brain - simply put, at low sample rates, we don't emotionally respond to digitally sampled music nearly as well as we do at high ones.

Now, I know that the whole topic of sampling rates is almost guaranteed to get most audiophiles riled, so let me close by saying that my opinion is not fixed on this point.  I was merely pointing out the arguments for the other side from a technical point of view. There are, of course, application, environmental, cost, convenience, and other factors that are involved in deciding what audio format to use and I have addressed none of those in this post.  That being said, I'll be happy to discuss them in the comments if anyone would care to.  I also have the best of intentions to write something on the use of high sampling rates in forensic audio and video processing in the near future.

Keith McElveen

P.S. For the record, Brian could hear the highest frequencies on his machine, but I could not, at least on my MacBook's speaker.

Thursday, December 27, 2007

Noise Cancellation: Quieting an aircraft

Aviation Week has a short but fascinating article on the design of passive and active noise cancellation for the King Air airplane.  The design seems very sensible for an aircraft application - use passive cancellation (absorption) for the high frequencies and active cancellation for the low frequencies.  

Aside:  For those unfamiliar with active cancellation, this is the same technology that is used in the Bose line of headphones where an out-of-phase signal is induced under the ear cup that cancels out the sounds that leak in from outside, thereby letting you hear the audio being cabled in from the media player/device (e.g. MP3 player, radio, etc.) even in moderately noisy environments.

The design trade-off is governed by the constraints that active noise cancellation does not work very well at high frequencies but does work well at low frequencies, while passive cancellation at the low frequencies requires massive (i.e. heavy) sound absorbing materials, which would weigh the airplane down.  At high frequencies, the materials can be much lighter. So, as you can see, the design trade-off works out very neatly - active at low frequencies and passive at the high frequencies.

One design detail that stood out to me is that they use 24 microphones to provide feedback to the cancellation algorithm so it can continuously adapt to the changing noise environment in the cabin.  Those 24 microphones are coupled to 12 loudspeakers to produce the anti-phase cancellation signal.  The numbers of microphones and loudspeakers tell me that this is a serious system that is designed to reduce noise through-out the cabin, not just in a limited area.  My hat is off to them as this was a seriously challenging design problem.

Human Auditory System: Apple patent application for hearing protection

The iPodObserver, among others, is reporting on an Apple (US consumer electronics and computer company) patent application on a way to automatically protect a listener's hearing based not only on a maximum level constraint but also adding the total listening time variable.  To put it another way, the longer one listens to elevated sound levels, the quieter they need to be as the time progresses to avoid hearing damage.  I haven't read the patent application yet, so I am uncertain as to exactly what the novel aspect of the invention is, but taken by itself, I see it as a good move an industry leader to make their product safer.

Off Topic: Interesting end of year stories

I'll admit it up front - I load up my browser with lots of tabs during the normal work week with stories that I have the best of intentions to read and report (the best of) and thanks to my surfing over the holidays, I've got way too many to blog in my normal way about. SO, I'll post links below of a bunch of them that are interesting from a forensics point of view or simply just interesting on their own. I hope you enjoy them.

New Scientist Round-up of 2007 Biology and Medicine stories

Acoustic Recognition: Toward teaching a machine to label music

The New Scientist Technology Blog posts about Major Minor, an on-line music labeling game by Dan Ellis and Michael Mandell at Columbia University (USA).  The goal is to build up a database of sounds that have been tagged by users (all humans, presumably) with descriptive words.  The scoring system seems very well thought out to generate appropriate tags, weed out inappropriate ones, and to motivate participation.  

Why does the world need such a database?  Well, just like with humans, in order to teach a machine (e.g. a computer) to recognize some characteristic of a sound, you have to feed it many, many examples of sounds with that characteristic for it to learn from.  In this case, the researchers use the Internet to provide the means to efficiently and effectively get people to the "test site" and their well-constructed, slightly addictive game for the incentive to get the test subjects to willing participate and give up their neural processing time to help out.  Good luck to the team at Columbia U!

Tuesday, December 18, 2007

Military: Long Range Acoustic Device (LRAD)

The Strategy Page has been on a roll lately with interesting audio and video articles. This week they discuss the Long Range Acoustic Device (LRAD), which allows long range broadcast of intelligible speech (up to 300 meters or yards).

The device was originally developed for the US Navy for spoken communications at sea (to warn off vessels approaching without permission), but has also found use as a less-than-lethal weapon in Iraq.  It also is being used for what may be impromptu PSYOPS, referring to the "Voice of God" field applications mentioned in the Strategy Page article.  The device has been around for several years, so news articles on it are easy to find - I think I have blogged on it at least once.  For an overview, you can refer to the Wikipedia entry.  From published information, it appears to be a high-volume loudspeaker array, i.e. a collection of speakers driven in-phase with each other, thereby creating a directional beam pattern.

Monday, December 17, 2007

Computer Audio: Audacity 1.3.4 Released for Windows and Linux

Audacity 1.3.4 has been released for Windows and Linux - sorry, but we'll have to wait for Mac OS-X!  To download, click here (

Wednesday, December 12, 2007

Military: Digital camouflage- now on warplanes

I've posted before about digital camouflage being used on military uniforms.  Now, StrategyPage tells us about how it is being used on warplanes, at least on the tops of the airplanes. On the bottoms, which would be seen by people looking up at the sky, they are still using a sky-colored monochrome.  Interestingly, there are multiple patterns for the top sides to match different terrains, such as arctic and desert.

Sunday, December 09, 2007

Biometrics: Battlefield forensic identification

The Strategy Page has a brief article on how the United States' military has adopted tactics used by law enforcement, such as the collection of fingerprints, photographs, retinal scans, and DNA samples for use in identification by biometrics.  

One thing to notice in the article is the taking of photographs from multiple angles in order obtain more information than is possible from single one.  You can immediately demonstrate to yourself why it is useful to have shots from at least two angles by closing one eye while looking at someone - you immediately lose the depth information provided by your own stereoscopic vision, assuming you are normally-sighted.  This same depth information is useful in calculating biometrics for face recognition.

Friday, December 07, 2007

Human Visual System: Chemical identified that improves visual sensitivity

ScienceDaily reports on research findings by a team of neuroscientists at New York University (USA) that identified the chemical acetylcholine (ACh) and its effect on the human visual system - namely to enhance its ability to detect weak signals.

Speech Recognition: Application to university lectures

Technology Review (an MIT publication) has a comprehensive article on an up-to-date application of speech recognition, including both the recognition engine and the user interface layers - namely, MIT's Lecture Browser website, a search application for video lectures.  The article is very well written and is approachable by anyone with a bit of science background.

Equipment: In defense of audiophiles

Slate Magazine has an article by Fred Kaplin on why high-end audio equipment is indeed worth the money if one is interested in experiencing the nuances of well performed and recorded music. 

N.B. I normally would not link to something that was not G-rated, but in this case there is one occurrence of sexually-oriented language that I found in bad taste.  After some consideration, I decided to post this after all with this warning to those of sensitive natures.

Friday, November 23, 2007

Forensics: Target gets recognition

The WCCO television station profiles the audio/video forensic guys at Target - yes, Target, the department store chain.  They truly are heroes in our profession, and largely unsung ones at that.  Target encourages and supports their in-house forensic unit in assisting law enforcement agencies in solving their audio/video forensic problems and they do it for free.  It is nice to see them getting some well deserved attention.

Human Auditory System: Hearing the Aurora

Damn Interesting has an article about reports of people "hearing" the Aurora Borealis.  Different explanations are presented but the author leans toward something called electrophonic hearing, which is the phenomena where electromagnetic fields stimulate the auditory nerves and thereby create the sensation of sound in human subjects.

Monday, November 12, 2007

Fun: Foreign words and phrases that have no exact English translation

English has absorbed many words and phrases from many different languages over the centuries, but there are some that haven't quite been imported yet.  A new book titled Toujours Tingo has quite a collection of very interesting, and perhaps even occasionally useful, words and phrases that exist in other languages but have no corresponding English equivalent.  The Mirror (UK tabloid) has a review.

I have no idea if the translations of these are accurate or not, but a couple that I particularly found amusing, at least the way they are presented in the book, are:

Vrane Su Mu PoPile Mozak - Croatian: crazy, literally "cows have drunk his brain"
Gadrii Nombor Shulen Jongu - Tibetan: giving an answer that is unrelated to the question, literally "to give a green answer to a blue question"

If you want a copy of the book, the details are Toujours Tingo: More Extraordinary Words to Change the Way We See the World, by Adam Jacot de Boinod, published by Penguin Books.

(Hat tip: GeekPress)

Wednesday, November 07, 2007

Physics: How are sound and light different?

Sound and light are very different, even though they are both waves.  For instance, one can travel in outer space and the other one cannot - at least outside of Hollywood, sound doesn't travel in a vacuum! 

To explain more fully, let's start off with how light and sound are the same.  Both are indeed waves and therefore have amplitudes, frequencies, wavelengths, and speeds.  Wavelength is the distance a wave travels before repeating, or, put another way, it is the distance between two successive troughs or peaks on a periodic (repeating) wave.  Frequency is the number of times a wave repeats in a second and is closely (and inversely) related to wavelength.  The speed of a wave is the frequency times the wavelength.

One way that they differ is in how they propagate. Sound requires a media to travel in because it is basically just a change in pressure.  For example, in air, it is a change in air pressure that carries the sound.  Sound can also be carried by other media, such as water (e.g. sonar).  Light, on the other hand, is an electromagnetic wave, which means that it is a combination of electric and magnetic fields that travel together.  Therefore, it does not need air, water, or any other medium to carry it - in essence, it carries its medium with it.

Another way in which they differ is in their speeds.  Sound travels about a foot (approximately a third of a meter) in a millisecond.  Light, on the other had, travels 186,000 miles (300,000 kilometers) per second.  Talk about the tortoise and the hare!

So, despite many similarities, sound and light differ in ways that are significant and have consequences for many different life forms - but that is a topic for another posting.

Saturday, November 03, 2007

Acoustics: A next generation microphone needs a special test chamber

I certainly hope it is not a sin to be envious of someone else's funded research work, because if it is, I have a penance coming.  The University of Alabama and Tuskegee University got an NSF (National Science Foundation) grant for research into a next generation microphone that will sense more than just changes in sound pressure and they are getting a new anechoic chamber to test it in as a bonus.  ScienceDaily has a write-up that focuses on the chamber, while the Tuscaloosa News has more details on the microphone research.

Thursday, November 01, 2007

Photography: 13 things to teach a child about digital photography

I probably am not the only parent who has, upon purchase of a newer digital camera, turned around and given the older model to the children and said something amounting to "Here,  go take some photos with this and come back when its full."  This, of course, leads to some impromptu lessons in photography for the children who are interested.  So, with that lead in, here is a link to an excellent blog posting that summarizes those lessons for you.

Wednesday, October 31, 2007

Military: Concealment and Deception or a "Magic Trick"?

The British Ministry of Defence is making news with its "invisible tank" demonstration.  Not to trivialize what their engineers have accomplished, but there are obvious parallels between what they've done and magic tricks - controlled conditions, including the viewing angle of the observers, and unseen technology, including cameras and projectors.  

That is exactly what "concealment and deception", as it is called, is all about, isn't it?  Exploit your control of the local environment and the limitations of your "opponent" to deceive them.  In this case, it involved a tank and not David Copperfield and the Statue of Liberty  (YouTube).

Monday, October 29, 2007

Human Auditory System: Blind detectives

The International Herald Tribune (US center-left newspaper published in Europe) has a very interesting article on a group of blind detectives working for the Belgian Federal Police.  This group puts their more sensitive and highly trained hearing to good use by picking up on clues that normally-seeing detectives would often miss, such as accents, background noises, and softer or obscured sounds.  If there hasn't been one already, we should expect an episode of CSI to feature blind detectives just as soon as they can get one shot!

Acoustics: Noise levels at college football game

I have mixed feelings about my alma mater, Clemson University, holding the record for 126 dB (decibels) of sound pressure at a football game, but it does get the nod in this article about noise levels and hearing safety.  Go Tigers (but heaven help our ears)!

Wednesday, October 24, 2007

Human Auditory System: Researchers identify how blind people hear better

If you have ever wondered if there was any truth to the idea that blind people can hear better than sighted people, now you have a scientific answer - apparently it is so.   Alexander Stevens at Oregon Health & Science University has just published the results of an imaging study to identify which areas of the brain are activated when blind (at birth) people hear sounds.  It turns out that part of the area normally used for vision processing is co-opted into performing aural processing. New Scientist has a short write-up and a link to the journal article abstract.

Tuesday, October 23, 2007

Computer: MacBook update

In case you are interested in the experiences of a recent convert to the "Cult of Apple", my impressions of the Apple MacBook are still very positive. At this point, I have had far fewer issues with this laptop than with any previous laptop that was 'designed and built for Windows'.  I phrased it that way because, as you might recall, I am running Mac OS-X and Windows XP Pro on this machine.  I've had no significant problems with either one.

As far as tested software packages, I've extended the list of applications I've installed and tested on the Mac OS to include Matlab (a signal processing software environment useful for filtering and plotting data, including audio and video), Octave (a freeware alternative to Matlab), Remote Desktop (for connecting to a networked Windows desktop in the office), QuickSilver (a desktop search application to beat all desktop search applications), and Gimpshop (a freeware alternative to Adobe Photoshop).  I haven't fully tested all of them, but I can say that they all install and run correctly.  Octave did give a bit of trouble during installation, but once I got it to launch the first time, it seems to be behaving properly now.

Photography: Google Earth

Technology Review (a technical magazine published by MIT) has an excellent article on the technology behind Google Earth - the satellites, the airplanes, the corrections (filtering), elevation mapping, data streaming, et al.

Thursday, October 18, 2007

Photography: Cleaning digital camera sensors

For the amateur and professional photographers out there interested in cleaning their digital camera sensors, I highly recommend checking out episode 90 of the Shutters Inc podcast by Shelton Muller and Bruce Williams (who also does the excellent Sine Language and Building the Pod podcasts).  Mr. Williams reports on his own DIY (Do It Yourself) experience cleaning his camera.  During all this, he mentions a very informative website, which I will give the link to - Cleaning Digital Cameras.  There is some follow up information on cleaning in episode 91 also.

Tuesday, October 16, 2007

Fun: How To video on making your own infrared goggles

Geeks are Sexy Technology News links to a Metacafe video clip on how to make your own low-cost infrared goggles out of a pair of welding safety goggles and some red and blue light filter material.  The basic idea is that the human visual system can see into the near infrared spectrum and by blocking out visible red and blue light, one can see the left-over infrared.  Watch the video to get an idea of the effect.

Forensics: Power Line Signatures and other Audio Forensics in the news

A frequent contributor to this blog (a.a.) found this Wired article about audio forensics that came out of the annual AES  (Audio Engineering Society) convention in New York City (USA) last week.  Aural steganography (hiding data in audio files, such as MP3s), power line signature recognition, and digital editing/tampering all get mentioned.

Aside: a.a. and I have discussed the technique of power line signature recognition on several occasions.  The basic idea of this technique is that the the fundamental frequency of each local power grid varies over time. In other words, if you measured the frequency at your wall outlet, it would not read 50 Hz or 60 Hz, depending on what country you are in, exactly and constantly.  Instead, the frequency would constantly move around a little bit, perhaps as much as a few Hz up and down, all day and night, in a somewhat random fashion.  This power line "hum" leaks out too - into devices that are plugged into the power grid and even out through the air into nearby devices such as handheld audio recorders.  If one can then extract this frequency or its harmonics (i.e. multiples) from a recording and compare this "signature" to a database of the frequency variations of the same power grid, one could theoretically determine what time the recording was made.

Returning to the article, one has to wonder exactly how power line signature recognition could be used to determine the date of a recording made in a cave - do they typically wire up caves to the power grid?  I could believe that a cave would have a portable power generator, but how would the examiner get a record of its frequency variations?  Perhaps I am missing something here or the author misunderstood something from the presentation and/or interview.

Thursday, October 11, 2007

Photography: What can you do with a 1.4 BILLION pixel camera?

Hunt for killer asteroids, that is what!  It is going to be part of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Maui, Hawaii, USA.  By the way, it took sixty digital image sensor chips to construct the imager.  A news article can be found at New Scientist.

Wednesday, October 10, 2007

Forensics: Reversing digital image masking

Interpol has released pictures of a suspected pedophile who had posted incriminating pictures of himself on the Internet.  His face was masked in the images using a standard Photoshop filter but Interpol's forensic unit was able to reverse the effect to restore those portions of the images.  A news report about the case can be found here.  

In filtering terminology, this can be thought of as "image restoration", i.e. the restoration of an image to its condition before the addition of "noise". In this case, the noise was an intentional blurring or smearing of the image pixels by twirling.  It appears that the particular Photoshop filter in question did not alter the pixel values (at least significantly but possibly not at all).  Instead, it simply moved the pixels' locations.  

To reverse the effect required figuring out where the correct pixel locations should be.  In general, this process is known as image deconvolution.   Deconvolution can be done completely blind (where the filtering algorithm is operating "in the dark" and has to estimate the pixel relocation parameters automatically) but works best when there is a priori information (i.e. where helpful information is known "prior" to the filtering).  

Image deconvolution has been used in astronomy for some years now to reverse the effects of smearing by Earth's atmosphere and motion of the telescope optics, which make the images of the deep space and other objects appear less sharp.  In the last eight years or so, deconvolution to deblur images suffering from focus and motion blur has been taken up by the image forensics community, thanks in part to my own efforts (Aside: I hope I don't break my arm off patting myself on the back).

In this case, the Photoshop filter is well known and available, and therefore, once the particular filter was identified, it made it possible to identify how it behaved in order to help in the deconvolution (as a priori information).  Very elegant image forensic work indeed.

Monday, October 08, 2007

Document Forensics: Recovering Archimedes' prayer book

Multi-spectral and x-ray fluorescence imaging were needed to recover the text and diagrams from a long-lost copy of Archimedes' own prayer book.  The book was in very bad condition (written on parchment that had since been re-used to make another book) and it has taken nearly a decade to recover the content. Details can be found in this Science News Online article. Fascinating stuff, not just because of the insights gained into Archimedes, but also from the laborious forensic work required to recover the content.

Sunday, October 07, 2007

Human Auditory System: Protecting your hearing

MacWorld has a comprehensive article on protecting your hearing using different aids - ear plugs, muffs, noise-canceling headphones, etc.

Thursday, October 04, 2007

Noise: Learning problems associated with noise

The issue of noise in everyday life seems to be getting more and more attention from health advocates and researchers.  The latest thing I've come across is this medical news report on schools and noise.  It struck home with me because my wife and I just recently toured an elementary school where the cafeteria was so reverberant that it was uncomfortable and even painful to be anywhere in it.  I didn't have a sound pressure meter with me, but it was easily in the 90+ dB SPL-A range.  My ears are not as young as they used to be, as they say, so I could not tolerate it for long.  I think that we will be hearing more and more about this type of thing (pun intended) and, as far as I am concerned, that is a good thing.

(Source: Medical News Today)

Wednesday, September 26, 2007

Admin: MacBook replaces lemon Windows notebook

I won't bore everyone with details about the last rites on my old notebook, but suffice it to say that the manufacturer agreed to fully refund the purchase price of the notebook and I am back to blogging again.

What may not be so boring is that I replaced that Windows notebook with a MacBook.  The MacBook has a dual core Intel processor and is running both Apple's OS-X and Microsoft's Windows XP Pro.  The Windows operating system is running in virtualization mode using a program called Parallels (note: I had to purchase a copy of Windows and Parallels separately, but they were fairly inexpensive).

As far as audio and video processing goes, I have been able to load and run Acoustica, Audacity, Audition, Clarifying Technologies, and Signalscape on the MacBook and all have worked in real-time for the types of files I tested with.  Due to work commitments, I have not been able to take enough time to "make friends" with the native Mac sound and video applications, but hope to do that slowly over the next few months. I'll report back my on observations.  If anyone has a preference as to a specific application for audio or video forensics they would like me to give priority to, just let me know in the comments or off-line.

In the meantime, Brian Dipert (Senior Technical Editor over at EDN) has also been transitioning over to a MacBook and has blogged about his experiences in several posts, this one being the latest as of this writing.

Image Recognition: License plate scanners

The technology manufacturing cycle is at work with license plate (tag) scanners - decreasing prices lead to more sales and deployments, which lead to further cost decreases and so on.  We've all seen it with personal computers, cell/mobile phones, DVD players, flat screen displays, and a multitude of other devices.  Now this market force is at work with license plate scanners , which are now being deployed on police cars.  The scanners are automating what was before a completely manual process - namely running stolen tag numbers and such - and doing it much faster.

Tuesday, September 25, 2007

Human Auditory System: Mobile/Cell Phones Can Harm Hearing

I have not tracked down the conference paper on this yet, but the results do go hand in hand wiht what I have noticed with my own hearing - talking on a cell/mobile phone for over an hour a day can harm your hearing.  The research was conducted by Dr. Naresh Panda (an ear, nose, and throat specialist in India).

Some time ago, I began noticing the feeling of my ear warming up - as was described in the article - and I associated it with a decrease in my sensitivity of hearing.  At first, I just made a point of switching the phone to the other ear every few minutes.  Over time, I switched to speaker phone mode when possible and ear buds when not.  That is how I still behave today. Of course, I try to be overly protective of my hearing anyway - for example, when using ear plugs on airplanes and when operating lawn mowers and blowers.  Better safe than sorry, as the saying goes....and in this study, it seems that I may have erred on the correct side.

Sunday, September 16, 2007

Human Auditory System: Ability to listen to two things at once is inherited

Researchers at the National Institute on Deafness and Other Communication Disorders (NIDCD) have found evidence that the ability to listen to listen to and comprehend two things at once was mostly an inherited skill.  

On a personal level, I have known for a long time that my wife can do this while I can not, and assumed that there might be a gender-based component to the cause.  Hmm... Might be time for a re-think of that hypothesis.

Aero-Acoustics: Making airplanes quieter

Here is an article in the Deccan Herald on redesigning aircraft engines, engine placement, and landing approach procedures to reduce noise levels on the ground by up to 25 dB (a very significant decrease if achieved).  The article is very readable.  Enjoy!

Monday, August 20, 2007

Acoustics: Ultrasonic stethoscope

The US Army Aeromedical Research Laboratory (USAARL) has sponsored the development of a new, noise-immune stethoscope technology based on an ultrasonic transducer (article link).  The envisioned operational environments include not only battlefields, but also noisy civilian emergency situations such as helicopter air-evacuations, traffic accidents, sporting events, and the like.

The technology works on doppler shift, which is a frequency shift caused by movement - things moving away from you tend to stretch out their sound waves and things moving toward you tend to compress them, causing respective lowering and raising of the sound frequencies.  A practical example is when you hear an ambulance go by with its siren blaring.  At first the pitch (frequency) seems to go up (get higher) and then as it passes, it goes down.

Anyway, the article I linked to above (from the EMSResponder website) has a well written report. It is light on technical details, but it does a good job of pointing out advantages as well as potential problems

Friday, August 17, 2007

Indoor Acoustics: Restaurants and noise

I've recently begun following a blog called Cross-Spectrum/Acoustics - Sound, Vibration, and a Little Noise.  It has quite an interesting collection of links to articles on various topics on acoustics and noise, as the title implies, as well as good original content by the author.

On to the topic of this post.  One of the perennial challenges for forensic audio cleanup is to reduce the amount of interference on recordings made in bars, pubs, and restaurants.  In recent years, say the past ten, the amount of noise found in restaurants in the USA has risen dramatically thanks to a trend in restaurant design, which has resulted in an increase in the number of cases requiring forensic restoration and enhancement. Cross-Spectrum has a post with links to recent articles on the restaurant noise phenomenon.

"Restaurant noise" is a little too broad of a term in itself to describe the problem from a forensic standpoint, however.  Consider the different types of noises that may be found there:
  • music (instrumental and/or vocal; live or pre-recorded)
  • talking (speech; the cocktail party problem of too many voices blending together into babble)
  • dropped flatware (knives, forks)
  • clinking glassware
  • shouts (e.g. to get attention of wait staff)
  • resonance and reverberation
  • hum (fluorescent lighting)
Forensic audio practitioners will recognize lots of things about this list, for instance, impulsive noises (flatware, glassware, and shouts), broadband noise (talking), and harmonic noises (instrumental noise, hum and resonance).  Each of these types of noises is different and may require different treatment; however, one of these noises rises above the others in difficulty and that is talking (speech).  

Filtering out noise generally requires recognizing the noise signal as being somehow different from the desired signal, which is usually speech, in some domain we can measure it in (i.e. time, frequency, amplitude, or space) and then removing the noise using a filter implemented in the corresponding domain.  That process falls apart when the noise is speech itself - how do you tell the difference between interfering speech and desired speech on a mono, omni-directional recording made in an uncontrolled environment?  Therein lies the problem.  There are practical solutions, as well as impractical ones for that matter, but the best ones require prior-preparation.  Unfortunately, I'll have to leave this filtering discussion at this point as going in much deeper could lead to a book-length article!  (If you are interested in going in deeper, feel free to ask away in a comment or contact me directly using the email link found near the top-right of the page.)

As you can hopefully now appreciate, our job would be so much easier without this recent trend in designing restaurants, bars, and pubs to strengthen the cocktail party problem, hence my interest in the Cross-Spectrum posting.

Saturday, August 11, 2007

Human Auditory System: Using hearing test to predict SIDS

Dr. Daniel Rubens of Children's Hospital and Regional Medical Center in Seattle has announced a breakthrough in predicting and possibly even understanding SIDS (Sudden Infant Death Syndrome, also known as cot or crib death).  Using data from infant hearing tests, Dr. Rubens found a pattern where infants who later died of SIDS tested differently than normal infants.  

ScienceDaily has an article.

Acoustics: Detecting landmines with sound - cheaply

The trick to detecting landmines using sound is to do it before it goes "BANG", of course.  All attempts at humor aside, this is not an easy problem to do and gets harder (and less reliable) the cheaper you try to make the detection system.

The engineers at GIT (Georgia Institute of Technology) have been leaders in this research for a while.  They now claim to be able to reduce the cost of a landmine detection system that uses a low frequency sound wave to vibrate the landmines and a cheap microphone to detect the sound from the resulting movement of the mines.  New Scientist has a write-up.  Their paper is in the Journal of the Acoustical Society of America (JASA, July 2007)

Wednesday, August 01, 2007

Admin - Posting will be light

Due to many pressing work commitments, posting will be light during the next few weeks.  I'm saving up lots of material, so as soon as things slow down a bit (or I end up in an airport with a decent free or T-Mobile WiFi connection and some time to kill), I'll be back to posting in earnest.
Kind Regards,

Monday, July 09, 2007

Military: Digital Camouflage Continues to Catch on

Strategy Page has an article about how the Chinese are the latest to adopt digital camouflage patterns for their combat uniforms. Digital camouflage differs from traditional color blotch patterns in that it looks more "pixelized." The digital patterns hide the wearer better against human observers as well as, get this, night vision gear.

Saturday, July 07, 2007

Surveillance: Stop sign cameras

It is time to add a new type of "safety camera" to the list - a stop sign camera. The interesting thing about this system is that it detects if the car comes to a complete stop or not. Here is a brief news article about a deployment in California, USA.

Linguistics: Genetic component to tonal and atonal languages?

The Economist magazine (UK, center-left economics and news magazine) has an article on a statistical analysis by Dan Deidiu and Robert Ladd of the University of Edinburgh that shows a correlation between genetics and speaking a tonal or atonal language.
Aside: A tonal language is one where the pitch (tone) used when pronouncing a word changes its meaning.
Finding a correlation in itself is not surprising as most Asian languages are tonal. Where this study might lead, when combined with work by others, is to uncovering which came first - genetic differences that led to the development of tonal/atonal languages or language differences that became tied to genetics.

Admin: Three strikes and you're out

This is just an administrative post to say that the reason my blogging has been lighter than usual is that my computer died, again. This is the third major malfunction in the ten or so months since I bought it. I have contacted Toshiba customer service and it appears that I will be allowed to return it without any hassles.

Sunday, June 17, 2007

Audio: Noise Canceling Headphone Review

The NY Times (US, center-left newspaper) has a review of noise canceling headphones just in time for the summer vacation air travel peak. Two entries joined Bose at the top of the list - Panasonic and Audio-Technica. They didn't surpass Bose (which is relatively hard to do in this market niche), but equaled it on performance and beat Bose on price (relatively easy to do!).

Things to note:
  1. Over-the-ear designs provide better noise cancellation.
  2. On-ear designs are smaller (and therefore take up less room in one's carry-on bag).
  3. The article didn't review in-ear earphones, which, in my opinion, offer better noise isolation than noise-canceling headphones and are much smaller, but suffer from not being as comfortable for extended use.
Why should audio forensic professionals be interested, other than just because they are often audiophiles to begin with? The answer is because of their sometimes challenging work environments. Simply put, all audio forensic filtering doesn't occur in pristine laboratory conditions. Then again, if you've ever spent time in many police audio "labs", you know they aren't always pristine in an audio (or any other) sense! I remember being invited into the lab of a federal level audio forensic examiner, which doubled as her office also, by the way. She opened the door and we squeezed into what was obviously a converted broom closet. Talk about resonances right in the speech band! Sigh...

But I digress. Audio filtering sometimes even has to be done in the field, which in urban environments can be quite noisy. So, as you can see, audio forensic examiners and audio technicians both can benefit from noise canceling and noise isolating headphones and earphones.

Wednesday, June 13, 2007

Biometrics: Implications of Pay by Voice commercial service

MIT's Technology Review has an article about the new Pay by Voice commercial service by a company called, surprisingly enough, Voice Pay. Now, I can imagine at least a couple of different general responses you, the reader, might have to this news. The first would be the semi-jaded, popular science devotee's reaction of "gee, that makes sense". The other would be the security-minded skeptic's reaction of "that's got to be so full of holes it will look like Swiss cheese."

Both responses are probably right in some sense, BUT, the devil is in the details, as they say. I'll point out the ones that seem the most obvious to me, without getting too technical.
  1. The system is based around mobile (or cell, for the US readers) phones, which implies more environmental noise than fixed line, compression effects (from coding the voice to use less bandwidth over the air), and possible hands-free use (which means even more noise and a different "sound" to the voice, which could confuse the voice recognition algorithm).
  2. Verifying someone's identity is easier than other recognition tasks (like picking someone out of a crowd). The system has been pre-trained on the person's characteristics and the system architecture is usually better controlled, for starters.
  3. This implementation of identity verification uses voice biometrics as well as call-back to the previously registered mobile number. This allows the fusion of two different types of data, although it is over the same "channel." If the shopping is done on-line, then there is not only multiple types of data, but also multiple channels that the data is passing over, which increases security.
  4. Fooling the system with a voice synthesizer might indeed be possible, but access to the potential victim's mobile phone would be required - as well as log-in details in some cases and 100% spoof rate could not be guaranteed.
  5. The company obviously didn't want to get into the issues surrounding false positive/negative rates and credit card security, but the truth of the matter is that the existing credit card system is not very secure in itself, but the losses to the credit card industry due to fraud are small enough compared to the profits that it isn't worth the effort to them to make it significantly more secure. (Note: Before anyone emails me about credit cards with chip and PIN, please consider just how big the credit card market is and how many traditional chipless cards are out there and will be for many years to come.) The company seems to be assuming that the same rules will apply here - if they succeed in getting into the market in a big way, their losses due to fraud will be easily written off.
There is much more that I could say here, but in the interest of not turning this into a paper by itself, I'll cut it off here. Feel free to email me or post a comment, though.

Optics: Liquid camera lens, no moving parts, now with zoom

New Scientist has an article on a different type of camera lens - it isn't made of glass or plastic, but instead uses the boundary of an oily liquid and water, which can be shaped by an electrical voltage to different amounts of curvature. Liquid lenses are used in some mass market products. The twist here is the ability to zoom. This latest research development still has some issues that need to be worked out if it is to supplant existing commercial technologies for the mass market (i.e. cheap, plastic lenses), but the principle seems to be sound. That bodes well for it finding at least a niche problem to solve.

Tuesday, June 05, 2007

Evidence: Courts feeling their ways through electronic discovery issues

The Economist (UK news and economics magazine; liberal in the classic sense) reports on how the judicial system is learning to deal with discovering evidence on mobile phones, computers, and other digital devices.

Video: Ultra-thin camera fits in shirt button and sees like an insect

MIT Technology Review has an article on an ultra-thin camera that uses a thin compound lens and image recognition software to try to see the way insects do.

Video: Using night vision gear to nab movie pirates

The Reuters Oddly Enough section has an article on how Malaysian cinema staff are catching people video taping new movies in the cinema (presumably to sell pirated copies of). How are they doing it? With night vision googles...

Brain science: Clues to roots of synaesthesia

The Economist (UK weekly news and economics magazine; liberal in the classic sense) has an article on a recent study by Romke Rouw and Steven Scholte of the University of Amsterdam into the biological mechanisms behind one form of the medical condition synaesthesia the causes one to see numbers and letters in color (or colour, as the British spell it).

Computer Forensics: Cooling a hard drive to recover data on a broken hard drive

Here's a computer forensic trick I hadn't heard before - putting a broken hard drive into the freezer or refrigerator might "unstick" it.

Audio: Build your own noise canceling headphones

Headwize has the schematics and explanation.

Audio: Using ringtones to catch leopards

Want a convenient way to catch a leopard? Try using a ringtone of a cow mooing...

Brain Science: Infants are amazing learning machines

Live Science has the results of another study that highlights how fast and flexible learning is for an infant.

Monday, May 28, 2007

Admin: Limited posting

Posting will continue to be light due to heavy travel and work commitments. I am saving up material, though, so once I can get some free time, I'll be putting up several posts.
Kind Regards,

Sunday, May 13, 2007

Acoustics: Noise canceling windows

Here is a way to lessen the noise coming into your home or office from the outside - just integrate noise canceling technology into your windows. Tech Digest links to a Discovery News item on just such a technology in development. Sound proofing buildings is a technical challenge, particularly when they are near low frequency noise sources, like airports, rail lines, and highways/motorways. Low frequencies are harder to block as it take a lot of mass to absorb those sounds, compared to high frequency ones.

So, how are Thilo Bein, head of the business unit for energy, environment and health at Fraunhofer Institute for Structural Durability and System Reliability LBF in Darmstadt, Germany and his team doing it? Their solution is to use piezoelectric materials to vibrate the surface of the window glass so that it destructively interferes (i.e. cancels out) the noises trying to get through the glass, similar to how noise canceling headphones reduce the low frequency sounds on board an aircraft that try to get past the headphones and into the wearer's ears.

This is pretty neat idea which uses the strengths of noise canceling technology (which is good at reducing low frequency noises, but not so good at high frequencies) to solve a problem of our modern, urbanized and mechanized world.

Friday, May 11, 2007

Audio: Compare Headphone Measurements

The Headroom website allows you to build a customized graph comparing their measurements from testing many different headphones, including popular and professional over-the-ear, on-the-ear, in-the-ear (earbuds), and noise canceling models. This is a great tool for anyone serious about audio. I highly recommend it.

Acoustics: New British Sub Unveiled

The Telegraph (UK center-right newspaper) has an article on the unveiling of the Astute, a next generation, British Royal Navy nuclear submarine. Some of the 'factoids' mentioned in the article are very interesting - the nuclear power plant has the acoustic signature of a "torch" (British English for "flashlight"), it can detect the QE2 cruise liner leaving the harbor in New York all the way from the English Channel, and it uses a fiber optic "periscope" instead of the traditional kind. Enjoy!

Phone Forensics: Cell/Mobile Phone Forensics Recognized for What It Is

Wired has an article on Cell Phone ("Mobile Phone" for those unfamiliar with US English) Forensics that comes across as critical in tone, but, in my humble opinion, simply conveys the message that there is nothing magic about cell phone forensics - it is evidence and should be treated as such. That means establishing the chain of custody to preserve it and protect it from intentional and unintentional tampering.

The article makes a point about some software tools not having tamper protection built in. I know that this is a current issue regarding evidence, particularly digital evidence. However, the drive to ideally preserve evidence can be taken too far - real world practicalities must also be acknowledged and accommodated or else the evidential system, and therefore justice, will suffer in the end.
Aside: Please do not mistake my point - I am not against establishing standard operating procedures and best practices for preserving evidence, performing examinations, and the like. What I am against is establishing overly idealistic expectations that are not achievable in the real world across the myriad law enforcement and justice agencies. Put another way, I am for a reasonable balance that is biased toward continually improving the system over time.

The Wired article, at least to my reading, gives the impression that if a tool does not have built-in digital signature protection that it is somehow completely suspect. I don't think that is the case. There are ways to adjust operating procedures to accommodate this, such as MD5 hash generation software routines and proper (in the British sense of the word) evidence handling procedures. I think it is a good idea to have protection built-in, but that it is likewise a bad idea to automatically assume that if a tool that is used in an investigation doesn't have digital signature features built in that the evidence was likely tampered with. That sounds blindingly obvious when approached in this manner, but may not be so obvious to a jury or the general public.
To return to the main thrust of this post, cell phone data is not just any run of the mill evidence, it is "scientific evidence", so someone acting as an examiner needs to recover and analyze the data and then present the results. The article helpfully provides a link to a draft NIST (The National Institute of Standards and Technology, a US government agency) recommendation titled Guidelines on Cell Phone Forensics.

Phone forensics is a helpful tool and can provide valuable clues that would not be otherwise available. But like all scientific evidence, it must be handled, analyzed, and presented properly, and then taken into account along with other evidence, to be of use to investigators and the court.

Thursday, May 03, 2007

Admin: Does Toshiba have a lemon policy?

OK, I've learned patience over the years, but I'm coming to the end of mine. Since getting my Toshiba Satellite notebook back a week or so ago, I've been noticing an overheating problem. The first time or two I figured that I had blocked the bottom fan grill (speaking of which, is it coincidence that they now call them notebooks instead of laptops? Sitting one on your lap could easily block that grill and these modern processors do get hot.) Anyway, yesterday the fan started making some noise and then stopped. This will be the third time I've had to get this repaired in the approximately nine months I've had it.

Computer Audio and Video: Codec packs

Being able to play audio and video files, often years after they were originally created, has been a steadily growing problem for audio, video, and computer forensic examiners.

Of course, video examiners encounter this almost daily if they are dealing with security digital video recorder (DVR) files because of the proprietary codecs (which is short for COder DECoder, and is the software program that converts video to and from a particular digital file format) used by manufacturers of the systems to lock users into their brands.

Even for those who do not process security DVR every day, things have been getting worse. Part of this is due to changes in the latest Windows Media Player where Microsoft removed one of the popular codecs previously used to encode/decode AVI files. Many people are under the impression that AVI is uncompressed and either doesn't need a codec or only has one universal codec. This is far from the truth. AVI, like WAV, is a very flexible format and it supports the use of almost any audio or video codec. To play the file, you have to have the correct codec - period. No codec, no playback - it is that simple.

I was faced with this problem just recently due to the Microsoft changes. The files were uncompressed AVI and would not play on three different machines, even though they played back correctly only two months before. A bit of digging found the cause. The solution ended up being to download an audio/video codec pack. I used the free one found here, but there are others out on the Internet also.

You can imagine how this can be a problem for law enforcement where evidence may need to be archived for up to 25 years and still be able to played back. All it takes is one automatic update and the ability to playback can cease. This is why I recommend to my students that they always include a copy of a freeware player that will play back the media as part of the archived evidence.

Wednesday, May 02, 2007

Surveillance: Debate over CCTV cameras - adding audio and concealing cameras

The Daily Telegraph (UK, center-right newspaper) has an article about a political debate in the UK over whether microphones should be added to CCTV camera installations and whether there should be CCTV cameras that were no obvious displayed or, in other words, hidden.

This has to be a quick posting - unfortunately I don't have time for a fully researched and referenced article, but I'd like to point out a few things from completely different aspects.

The first is from a policy angle. According to the article, the UK has about 4.5 million CCTV cameras. Most of these camera systems are not run by governmental bodies but instead by companies and the like, if I understand things correctly. (It should be noted that the British public supports the use of CCTV)

Adding microphones to CCTV installations brings up the issue of whether non-governmental entities would be allowed to "eavesdrop".
Aside: For purposes of this post, by the term "eavesdrop" I mean listening to conversations which are thought to be private.
Just having a microphone with a camera does not mean that it will be possible to understand individual conversations or even that any collected speech can be listened to or understood by the CCTV operators. For instance, sound captured by microphones can be automatically analyzed (i.e. by a computer) to detect alerting sounds such as gunshots (which are uncommon in most of the UK due to gun control laws), screams or threatening tones of speech. A system could be designed such that the human operator has no access to the audio itself, but is instead only alerted by a text message or other indicator.

To summarize my points from the policy perspective, the act of installing a microphone does not necessarily imply that peoples' conversations are going to be bugged and there are some benefits to be had that do not involve any significant 'invasion of privacy' issues, assuming said system is designed properly. A final policy point is that having private companies collecting conversational speech or installing concealed CCTV in public places raises lots of privacy issues (obviously!). The former seems open to serious abuse unless it is heavily and closely regulated (like the police are). I'm withholding judgment on the latter - there just wasn't enough information in this article for me to form an opinion yet as I don't understand what problem is to be addressed and the perceived benefit.

Although I covered some technical issues while addressing policy, there are a few more points to make from that aspect also. The first is that simply mounting a single omni-directional microphone, no matter how sensitive, up on a pole with a CCTV camera is not going to necessarily pick up conversational speech, as any sound engineer can tell you. What is going to be recorded from way up there by an omni mic during busy times? A cocktail party-like blend of sounds, gunshots, sirens, shouts and other loud sounds is about all that will be heard on the microphone output in real urban scenarios. So, my question is what the microphones are supposed to be for? There are obvious benefits that could be derived, but not without cost and technical implications. It seems to me that there is some need here for some consultations with experts knowledgeable about audio, filtering, and the like before this goes too far.

Anyway, that is all for the moment. Please feel free to comment, but please understand that I wrote this very quickly so I was not able to address all the issues that are raised by the political debate. Nothing is implied by my leaving anything out.

Tuesday, May 01, 2007

Audio: Musical score "hidden" on Rosslyn Chapel arches for 600 years

The Daily Telegraph (UK, center-right newspaper) has an article on a musical score found encoded on the arches of Rosslyn Chapel (yes, the one from the Dan Brown novel, Freemasonry, et al). What convinced me that this wasn't just another Da Vinci Code styled, publicity-seeking attempt was listening to the motet it transcribed. Why would I have been skeptical? Oh, just that in addition to being found in the chapel associated with the Holy Grail, it also involved Chladni patterns, cubes, and an ex-RAF (Royal Air Force) codebreaker.

Monday, April 30, 2007

Audio: Combination noise isolating earbud and in-ear microphone

The Raw Feed has a description and picture of a new cell phone earbud with built-in microphone by Japan's Nap Enterprise Co. They claim 30 dB noise reduction (passive, not active like noise-canceling earbuds and headphones). Because the microphone pickup is in the ear canal and isolated from the outside world by the wearer's head and the earbud itself, the speech picked up by the microphone should be much, much quieter. I look forward to hearing an audio sample! If anyone comes across one, please point me to it.

Admin: New layout completed

It is done (finally). Enjoy!

Admin: New layout to blog

I am in the middle of upgrading to Blogger's new Layouts feature so that I can add widgets to the blog. Please bear with me. The customizations I've made (such as the links list) have all been cleared away and will take some time to add back in. Regardless, the blog is functional and new posts and comments are still going up.

One widget that I've already added is the one for subscribing to feeds (found at the top right). It is also now easier to browse the archives (found at the lower right).

Kind Regards,

Sunday, April 29, 2007

Evidence: New procedure to improve accuracy of witness recollections

BBC Focus Magazine has an article about a technique, called self-administered interview (SAI), that is said to improve the accuracy of witness recall by 42 percent.

Under current UK police procedure, there is apparently a two step process for interviewing a witness - first a brief (summary) interview and then a more detailed one. The proposed procedure instead makes the initial process much more intensive and has the witness record as many details as possible using a questionnaire. The work is by Dr Lorraine Hope (University of Portsmouth, UK) and other researchers at University of Abertay and Florida International University.

In contrast to what the current common perception of what crime scene investigation can accomplish is, in reality there are a large number of crimes where the crucial evidence is testimony by an eye, or ear, witness. This makes accurate recollection extremely important, particularly since detailed memory does degrade rapidly with time in most people and eye/ear witness testimony, as currently "managed", is at least occasionally later found to be erroneous.

Additional Link: The Daily Telegraph (UK, center-right newspaper) also has a write-up with a few more details.

Computer Audio: Audition 3 in the works and an audio forensics wish list

First it was a rumor and now it is confirmed - Adobe Audition 3 is in development and Adobe plans to announce more about it later this year. A search of their web site didn't yield any additional details but there is a post on Hart Shafer's blog (Hart's Audition) that confirms it and mentions that it is on a different schedule than the rest of their Creative Suite. Hart Shafer is the product manager for Adobe's studio products, which includes Audition.

Admittedly, audio forensics is a small, niche market away from their core customer base, but if we are lucky, our needs will overlap the needs of their studio customers and a fine product will become even more useful to us. From a forensics point of view, here are the things that I have on my wish list:
  • Improve support for working with multi-channel WAV files that are not intended for surround sound, including easy trimming of multiple channels and saving, for starters.
  • Speed up loading of large multi-channel files
  • Improve the spectrogram interface to allow easy and accurate display and analysis of specific frequencies.
  • Include an option to decrease the streamlining (in other words, an "option to allow more options")
If you have anything to add to the list, just email me (link found on right side, near the top - don't forget to remove the anti-spam text!) or post a comment.

Wednesday, April 25, 2007

Bird songs and urban noise

You may have seen the fascinating nature videos of wild birds mimicking various man-made noises like cell/mobile phone ring tones, chainsaws, and the like. Now comes a study into another way that birds have adapted to living around mankind - singing at night to be heard further since it is quieter. A news article can be found here.

Sunday, April 22, 2007

Security: The weakest link

Q.- What high tech hacker tools are needed to steal $25 million of diamonds from behind all the layers of a bank's security system?

A. - Chocolates and charm.

The hacker community calls this "social engineering."

Biometrics: Gait recognition accuracy rates in controlled conditions

Researchers at the University of Southampton (UK) reported a 100% accuracy rate for verifying the identity of individuals by automatically analyzing the way they walk. IT Week (a UK information technology magazine) has some details.

Based on the IT Week article, it appeared to me that all the tests were conducted under controlled conditions. Visually-based biometric techniques generally require good lighting conditions (i.e. proper exposure of the image) and resolution. They also require that the features needed for recognition are not occluded.

Why would one need gait recognition when face recognition already exists? Some obvious advantages are that gait recognition doesn't require that the face is oriented toward the camera and the image resolution requirements are not as high. But if the conditions are controlled anyway, why can't the person be required to be close to and facing the camera?

A couple of questions that come to mind are 1) how much less the spatial resolution can be and 2) how robust it is to image compression (e.g. MPEG-4)? These could give the technique additional advantages.

One final observation I should make is that, as with all biometric techniques, being able to fuse the results of more than one technique improves the system accuracy and robustness. That alone could justify the inclusion of the technique in fielded systems.

Back to blogging

I would not recommend the particular Toshiba Satellite notebook that I have - two major warranty repairs in nine months, one to replace a bad display and a motherboard replacement. I do have many good things to say about the repair shop that I used for the motherboard replacement (Topaz Support). I am keen on them not just out of relief to have my notebook back, but because they were all the things that the last shop wasn't - helpful, efficient, communicative (they called me to give me status updates, not the other way around), and professional.

On the technical side, I was surprised to find that it seemed to work significantly faster than before. I haven't investigated why, but I wonder if it is because they updated the BIOS to the most recent version.

Monday, April 09, 2007

Admin: Cause and Effect

Cause - a dead computer (no signs of life at all...)

Effect - limited posting.

This particular computer (a Toshiba Satellite) is now on its second warranty repair in the nine months since I bought it. I hope to be back blogging soon.

Kind Regards,

Monday, March 19, 2007

Indoor Acoustics: Study of 40 Churches

Wired has a short write-up about research into church acoustics. The researchers used dummy heads with binaural microphones as well as separate soundfield microphones to make their recordings. A book is due to be published next month (April 2007) documenting their first round of results. The title is Worship, Acoustics and Architecture.

Sunday, March 18, 2007

Sonification: The Sound of Traffic

Wired has an article about a neat little Java application called Sound of Traffic that lets you 'listen' to TCP/IP traffic.

By the way, this process of converting non-speech data into sound in order to convey information is called sonification and it is a very interesting on-going area of research, particularly for helping the vision-impaired, but also for other things such as gaining insight into or simply entertainment from networking traffic.

Video Filtering: IBM Research on Automatic Face Masking and Privacy

IBM has been moving into the video surveillance services market as of late. Now comes word on some of its research into technologies that might support that. They are not the first to work on automatic face masking but it is the first time I've seen this privacy angle to it - automatically detect, track, and mask (i.e. blur) all faces on an incoming video stream and then selectively unmask as required to identify someone. I've worked with this regularly over the last ten years, so I know that it is a very challenging problem to do reliably, particularly with "real", not laboratory, video.

Human Hearing System: Subliminal Feedback Cure for Obsessive Gaming

Via Good Morning Silicon Valley.

Language: Prediction of the extinction of Manchu and half the world's other languages

Here is an article on the extinction of languages over at the New York Times.

Courtroom: Accreditation of Forensic Expert Witnesses & Daubert in UK

The issues of introducing accreditation for forensic expert witnesses and Daubert hearings have again been raised in the UK, this time in response to recent acquittals (where both sides had expert witnesses that disagreed) and the conviction of Gene Morrison on 20 counts of deceptively representing himself as a forensic expert with academic qualifications.

Several interesting things are discussed in this article (which basically reads like an opinion piece), including Daubert, whether a case should proceed when there is a serious dispute over forensic evidence, registration and accreditation of forensic expert witnesses, and the effect of privatizing forensic science service organizations.

(Hat Tip: TimesOnline, UK)

Friday, March 16, 2007

Human Visual System: Everything you know about the genetics of eye color is wrong

It turns out that the explanation behind what color (or colors, in rare cases) your eyes are is a lot more complicated than what I learned in school.

(Hat tip: GeekPress)

Courtroom: Jury Selection in USA

Psychology Today has an article on jury selection and who both sides use consultants to help decide who to excuse.

(Hat tip: Arts & Letters Daily, by way of GeekPress)

Friday, March 09, 2007

Biometrics: Biometric passport with RFID is hacked remotely

A regular reader pointed me to the Daily Mail (a UK tabloid) article describing how they had a security expert "hack" one of the new biometric passports with an electronic Radio Frequency IDentification (RFID) microchip to extract all of the digital data. They arranged to simulate intercepting the passport being mailed from the government to the citizen. Because the passport had this RFID chip, it could be remotely interrogated, they were able to do this without even opening the postal envelope containing the passport. Of course, the data was encrypted, so then the security expert had to break that (and he succeeded). The only apriori information he needed was the citizen's date of birth, which he obtained through searching the Internet. The entire process took four days, but in the end, he was able to recover all of the passport's digital data, which even included the citizen's digital picture.

It seems pretty obvious that they either didn't bother to do a proper independent security analysis before they developed and deployed the system or the managers discounted the results of any one that was done. Because of that lapse, now it seems that they need to rethink their encryption scheme at the very least. When they do, it might make sense to add some type of limit to the number of times a passport can be interrogated with an incorrect password, either in a certain time window or an accumulated number over the life cycle of the passport.

Computer Audio & Video: Windows Vista changes how audio and video are handled

Howstuffworks has the best summary of Windows Vista as related to audio and video rendering that I've read thus far. The highlights are:
  • The graphics and audio drivers will run in user mode instead of kernal mode so that errors with either will not cause 'Blue Screens of Death.'
  • Vista supports DirectX 9 but is really built around DirectX 10.
  • DirectX previously did not require graphics hardware to support many DirectX capabilities; now, however, only three features are optional.
  • Finally, the sound volume coming from each application can be separately controlled.
There is even more interesting information about Vista in the article for those who are interested.

Computer Forensics: The Real World of Computer Forensics

Here is the link to an account by Keith Jones of three criminal and civil cases involving computer forensics. Mr. Jones is a computer forensics expert witness (with whom I have no relationship).

(Source: Information Week's Optimize Magazine)

Forensic Photography: Retrieving color of ancient textiles

Eurekalert summarizes work by Chirstel Baldia and Kathryn Jakes (both at Ohio State University) that used forensic photography techniques to determine the original color of textiles recovered from Ohio's Seip burial mounds which are about 1600 years old.

Thursday, February 22, 2007

How many megapixels do our eyes have?

BBC Focus Magazine has a regular Q&A section, which, unfortunately, they do not publish on the Internet. The March 2007 edition has a reader's question - "How many megapixels do our eyes have?"

Their answer approaches the question from multiple angles. I won't quote the entire response here, but some of the interesting "factoids" are:
  • comparing the number of sensing elements - the eye has 5 million cones (the color receptors) and 100 million rods (the monochrome contrast receptors) which give a human the equivalent of two 105MP (MegaPixel) video cameras (because we have two eyes).
  • comparing spatial resolution over the eye's field of view - we have the equivalent of 576MP.
(Source: BBC Focus Magazine)

Sunday, February 11, 2007

Hey, someone changed my system beep!

I could have just as easily titled this post "Much Ado about Nothing", but it wouldn't have been as informative. PC Magazine does a good job dissecting the various weaknesses of the "flaw" in Microsoft Vista security which would allow an audio-based attack.

Ultrathin folded telephoto lens

Engineers at the University of California San Diego have created a folded lens by machining reflective surfaces into a optical crystal. this technology has the potential to shrink lens assemblies, which would be beneficial to lots of devices, such as cameras and night vision gear. However, this is still early stage research and hurdles remain - such as its inherent narrow depth of field. That being said, there are ways around that problem that might work for selected applications where thickness is more important than length (where I imagine that additional lenses with different focal lengths could be positioned on a rotating disk or similar arrangement to be employed as needs changed) or post-processing power consumption.

The work has been published in Applied Optics (February 1st, 2007)

(Hat tip and image source: PhysOrg)

Security holograms relatively easy to copy

The Daily Irrelevant has a post on the rise in counterfeiting of security holograms, which are found on everything from credit cards to whiskey bottles these days. Reportedly, the cost of the equipment to make a copy is in the range of only $2,500 USD, which, given the illegal profits to be made, is insignificant. Interesting reading.

Saturday, February 10, 2007

Facial composite study results

According to a recently released study, facial composite systems used by police do not produce very good likenesses - not even good enough for people to correctly identify celebrities. The systems they studied were ones the police use to "build" (or composite) a face by having the eye witness select from a large collection of eyes, ears, noses, etc. EurekAlert reports that
According to authors, these poor results are not deficiencies in the software per se but instead a mismatch between how we remember faces and how composites are produced. "Numerous lines of evidence converge on the view that faces are generally processed, stored and retrieved at a holistic level rather than at the level of individual facial features." Ultimately the psychological process of remembering faces may include more complex representations such as multidimensional similarity to other faces or relative sizes and distances of features and so on that are not readily retrieved by memory nor utilized by facial composite software.
The authors go on to recommend whole face, or "looks like", methods instead of the existing "parts" based methods (e.g. eyes and ears) as a way to get better results. "Looks like" systems have produced good results in previous studies, as I recall, so maybe they are on to something.

The study was published in Current Directions in Psychological Science (February 2007 issue).

Saturday, February 03, 2007

Noise map of Great Britain

The Telegraph (a center-right newspaper in the UK) has published a noise map of Great Britain that was compiled from traffic noise levels by Deepak Prasher, professor of audiology at University College London. I can not recall ever seeing such a map, but it is fascinating to not only note the absolute levels on particular places (especially the sites where you need ear plugs to get a good night's sleep) but also to compare different areas.

Training your mind and dyslexia

One of my favorite radio programs is the excellent Science Friday, which is broadcast on NPR (National Public Radio) in the USA. A recent edition talked about the plasticity of the human brain and included some interesting statements about research into treatments for dyslexia. I had not heard of the studies linking dyslexia to hearing difficulties - not vision processing difficulties as one might assume. You can find an MP3 download at the link above.

Clarification: I should have said "linking dyslexia to auditory processing difficulties" or something similar, not "hearing difficulties", which was too ambiguous. I should have also said "not only vision processing difficulties", as some theories of the roots of dyslexia still focus on vision processing (for instance, the so called magnocellular theory).

The root causes of dyslexia are not fully understood and serious research is ongoing. I suggest the following Nature article (Franck Ramus, 2001) for an overview.

I would also like to say "thank you" to the readers who pointed out my misstatement and the ensuing discussions in the comments. If you are just now coming across this post, I recommend reading the comments to catch up.

Military gunshot detectors

Strategy Page has a brief overview of the current state of gunshot detectors used by the US military. It talks about both all-acoustic and acoustic-infrared systems. Enjoy.

Thursday, February 01, 2007

Image blurring of sensitive information

First, the attention grabbing bit - using traditional digital image blurring techniques may not be effective in all cases. The title of the article from which this post derives is "Why blurring sensitive information is a bad idea".

Why? With statistical techniques, it may be possible to extract some of the original image details were. Now for the complicating details. First, it wasn't shown with a real case - it was simulated. Second, although one could probably deduce this from the article, traditional digital blurring is in all likelihood very effective against information with high spatial frequencies (i.e. images with lots of changes, like pictures of faces not taken at a close distance). The problem MIGHT occur with blurring data with mostly low frequency content, like large sized numbers, such as on an image of the check used in the article.

Nonetheless, it is a very interesting piece of work. I look forward to someone showing this work against "real data".

Hubble is hobbled

This is widely reported, but I still think it is important enough not to pass without mentioning - the Hubble Space Telescope has been hit by another fault, this time from an electricalshort. To summarize the the most probable outcome, it will probably lose two of its three"camera channels", leaving it with only the Solar Blind Channel (which is sensitive to ultravioletwavelengths). To read more, here is the New Scientist Space article.

Tuesday, January 23, 2007

Artistic image from camera obscura

Abelardo Morell creates works of art from camera obscura images. Here is one that I came across on the Daily Irrelevant. Note the long exposure times - 8 hours! Why? Because the camera obscura images are faint and it takes a long exposure time to correctly expose the film/imager for his purposes.

Monday, January 22, 2007

Bomber detection and tracking using gait recognition and radar

MIT's Technology Review has an article on CounterBomber and the gait recognition technology by Rama Chellappa (University of Maryland, USA) which underlies it.

(Hat tip: GeekPress)

A blogger moves on

Christian Beckner, founder of the excellent blog Homeland Security Watch, is moving on to a new job with the Democratic staff of the Senate Homeland Security and Governmental Affairs Committee (HSGAC). Mr. Beckner has done a remarkable job on his blog and his contributions there will be missed. He has been recruiting a team of people to take over his blog, so if you are interested in joining, you might want to surf on over there. I wish him the best of luck in his new position.

Saturday, January 20, 2007

Another cell phone study

No strong associations between low levels of cell (mobile) phone use and cancer have been discovered thus far. However, from what I understand, the past studies have not shown this conclusively for all cases. This is not surprising - remember that there are many, many variables involved and they all have to be investigated properly before being able to authoritatively claim that there is no association at all.

This Times (UK) article gives a brief summary of some past findings and tells of a new study that will focus on long term users. The interest from an audio perspective is some evidence that prolonged use holding the cell phone to the ear (instead of using an wired ear bud or handsfree) may be associated with acoustic neuroma brain tumors.

From my own personal experience, I believe that I can objectively claim to perceive a significant difference, after approximately ten minutes of use, between having my mobile phone with the phone pressed against my ear and using it in handsfree mode away from my ear. This does not say that I am going to get cancer, but it does contradict, at least in my isolated case, the written claims that mobile phone use could not possibly affect human tissue in any perceivable manner.

This is a controversial area of research and, in my opinion, requires careful study and careful reporting to balance convenience, health, and other issues properly.

Tuesday, January 16, 2007

Brain study show rapid link formation between sound and action

Science Daily reports on an article published in the journal Society for Neuroscience on an fMRI study into how the brain reacts to sounds that are produced by specific actions. The researchers taught subjects with no musical training how to play a song and then used the fMRI imager to see how their brains reacted to the sounds played back. Interestingly enough, the subjects' brains activated the same regions involved in actually playing the notes.

Although not addressed in the report, it makes one wonder if this plays a role in learning speech...

Monday, January 15, 2007

Beyond Nielsen ratings - now with audio

Imagine getting a free cell phone, but instead of being forced to listen to advertising in exchange for your free-ride, it listens to you instead. That's right. Every so often, it records the activity going on around you and then uses a computer algorithm to create a "signature" from those sounds passes that signature back to a processing center, where another algorithm compares that signature to its master database to recognize what media type and "program" you are listening to - be it a music CD, TV/radio program, Muzak, rock concert, or whatever. Your data is then compiled with many others' to create media ratings. By only passing a signature and not the raw audio itself, no actual conversations get eavesdropped on - which would be illegal in many places.

In this age of TiVO, iPod, and other time- and/or location-shifting devices to allow viewers and listeners to consume media when and where it is convenient, traditional ways of measuring and estimating ratings are not as effective - hence the market's experimentation with this type of technology.

If you are interested in reading more, one company that is selling such a service is IMMI (Integrated Media Measurement Inc). There is a link on their home page to a Wall Street Journal review of several companies doing similar things.

(Hat Tip: Bruce Schneier's CRYPTO-GRAM email newsletter, January 17, 2007 edition)

Murder captured by surveillance camera

ABC News has the details.

Saturday, January 06, 2007

January's surprise - Comet McNaught (C/2006 P1)

Sky and Telescope has a guide to observing this bright, but only recently discovered, comet. Unfortunately, it is staying very low in the night sky. Stargazers in the northern temperate latitudes will have the best luck, as long as seeing is good.

(Author's note: See the comments for another link with more information.)

National Security musical chairs in USA

Larry Johnson over at the No Quarter blog has an interesting take on the musical chairs going on in Washington, D.C. (WDC) in the upper levels of the national security community. Mr. Johnson (formerly with CIA as well as Department of State's Office of Counter Terrorism, according to his bio) writes a fairly "hardball" styled blog, which in my opinion suits this type of subject (i.e. bureaucratic/political gossip).

With the creation of the Director of National Intelligence and the shifts in power (i.e. budgets and authority) toward the military during the last ten years or so, there have been very real and significant changes in the US national security community. When you add the issues caused by the Iraq War, the War on Terrorism, and the merger of multiple organizations to form the Department of Homeland Security, it will be many years before things involving security, intelligence, and defense run smoothly again in WDC.

Noise cancelling earbuds for operational environments

Taking out the ambient drone of an aircraft is one thing (a fairly simple thing, processing-wise) but taking out impulsive noises is another. Strategy Page has an article on a company that is trying to do this for the military guys with a (not quite shipping yet) product called QuietOps (by Silynx).

Lawyers and scientific evidence

For a very unflattering take on how little many lawyers currently know about forensic science and scientific evidence, check out this news article from Perth (Australia). I don't know how accurate this is but it is an interesting read.

(Hat tip: Forensic News Blog)

Duke University Lacrosse Team Case

As I lived in the Raleigh-Durham (NC, USA) area for some years during my time with DAC (Digital Audio Corporation) and while founding Signalscape, I have an interest in the happenings around that charming and dynamic part of the USA. For these personal reasons, in addition to the obvious professional ones, I have been following the case brought by DA Nifong against members of the Duke Lacrosse Team and its spiral downward into near farce. There have been significant questions about the evidence, as well as the timing and conduct of the DA, from the beginning and things have only gotten worse as time has passed.

That is a long introduction to get around to saying that thanks to a reader of this blog, I can tell you about a well-written blog devoted to the above case.

Bad guys blog

US News and World Report (a center-right weekly news magazine) has a very informative blog that I am checking regularly. It should be interesting for anyone following terrorism or crime.

Wednesday, January 03, 2007

Latest implementation of micro-stress detector for voice - Skype

Geekpress has an amusing article on the "Kiskkish lie detector", a third-party add-on to Skype 3.0. Regular readers of this blog will know of my opinion on voice stress analysis masquerading as lie detection.

13 photographs that changed the world

Most people of my age will recognize these famous photographs, but not know the stories behind them. This article gives both.

(Note: I came across site during my holiday surfing, but can't remember how I got there now so I can't give proper credit.)

Stupid Crime Tricks of 2006

Sorry for the lapse in my posting during the Christmas holidays. To make up for it, I offer this post to start your New Year off with a smile: The Fresno (California) Bee's humorous round-up of real stupid crime tricks from this year past.

Happy New Year!
Keith McElveen