Sound and Light Reflections

Computer Audio: Latest Audacity beta is released

2008-05-08T17:56:00.002-04:00

From the Audacity announcement:

The Audacity Team is pleased to announce the release of Audacity 1.3.5 (beta) for Windows, Mac and Linux/Unix. Changes include improvements and new features for recording, import/export and the user interface. Because it is a work in progress and does not yet come with complete documentation or translations into foreign languages, it is recommended for more advanced users. For all users, Audacity 1.2.6 is a stable release, complete and fully documented. You can have Audacity 1.2.6 and 1.3.5 installed on the same machine.

Enjoy!

Medical: Overview of Synesthesia

2008-05-03T06:08:00.002-04:00

Synesthesia is always a popular topic on this blog, judging by the number of hits it gets. In case you don't already know, synesthesia is a medical condition where the stimulation of one sense (such as smell) or cognitive pathway (such as interpreting numbers) gets merged with another sense or cognitive pathway. One commonly occurring example of synesthesia is the seeing of numbers with different colors. For an interesting and informative overview, see this write-up in Interesting Thing of The Day (ITOTD). Enjoy!

Image Forensics: Good Practices

2008-04-28T16:25:00.005-04:00

The Scientific Working Group on Imaging Technology (SWGIT) has released drafts of two new "good practices" documents for image forensics, titled "Best Practices for Forensic Photographic Comparison" and "Digital Imaging Technology Issues for the Courts".

These drafts, along with previously released good practices documents from SWGIT and other organizations, can be found on the IAI (International Association of Identification) website at this link.

(Hat Tip: MB)

Acoustics: Mosquito comes to the USA

2008-04-27T18:19:00.003-04:00

You might recall some of my previous posts (here and here) about the Mosquito tone - the high pitched tone that teenagers can hear but adults cannot. It was introduced as an anti-loitering feature in various European CCTV systems. The system operator could activate the annoying tone to drive away "hoodies" from the general area of a security camera in a mall, for example. Teenagers then exploited the technique against adults by making it into a ringtone for their cell (mobile) phones so that (adult) teachers could not hear the ring or text message notification in class.

The latest development is that the security implementation of the technology has undergone another evolutional generation and is being introduced into the US market. The company's Powerpoint presentation provides additional insight, even though one point it makes is entirely inaccurate - the latest version of the Mosquito system measures the ambient sound level and adjusts the level that it plays the annoying tone to be 5 dB (decibels) above the ambient, which, contrary to what the presentation claims, is not the same as being the level of a whisper. I think I understand what they were trying to get across with this point, but the way it is stated is inaccurate and misleading.

This is a controversial, yet ingenious use of technology and biology. We are sure to hear more about this in the weeks and months to come.

(Hat tip: boingboing)

History: FBI updates website in preparation for its centinial

2008-04-16T22:38:00.002-04:00

The United States Federal Bureau of Investigation (FBI) has updated its website in preparation for marking the one hundredth anniversary of its establishment on July 26th, 2008. They have added some fascinating articles on famous cases of forensic and historical interest. Enjoy!

(Hat tip to Government Computer News)

Forensic Education: Courses for young and old who are interested in forensic audio and video

2008-03-24T10:41:00.004-04:00

I've got two announcements regarding forensic education to pass along.

First off, the Department of Justice (USA) is funding Professor Rich Sanders, of the University of Colorado, Denver, to establish a new National Center for Audio/Video Forensics. The full university press release can be found here. It is scheduled to be up and running in the fall of 2009.

Second, the South Carolina Governor's School for Science and Mathematics (USA) runs its popular Summer Science Programs (SSP) every summer. SSP is a residential summer camp for rising 8th, 9th and 10th graders from across the state. The reason I mention it here is that I have been asked to teach two one-week runnings of a new course entitled A Mathematical Tour of Forensic Science. If you are interested, you can find out more on their website.

Update: I am informed by the director of the SSP that students from outside of South Carolina are also very welcome to participate.

Image Recognition: "Computer, where did I lay the keys?"

2008-03-17T21:50:00.002-04:00

The Daily Mail (UK tabloid newspaper) has a gadget article about Smart Goggles, a human wearable image recognition and recall system built into a set of glasses. The user trains the system by focusing its built-in camera on a series of objects, such as car keys, CDs, etc. while speaking the appropriate name of the object. Once trained sufficiently, the system automatically recognizes images it sees and stores the information for later retrieval, again by spoken word. The processor (computer) is worn on the user's back. The system was developed by Professor Kuniyoshi and colleagues at the University of Tokyo.

It isn't much of a stretch to see how these same concepts could be built into other video applications, such as CCTV systems, for instance. Don't be surprised if they don't work this into a future episode of CSI or similar television show (or the next James Bond movie, for that matter).

Optics: "Look Mom, no lens!"

2008-03-04T07:00:00.003-05:00

Similar to a child demonstrating how he can ride a bicycle without using his hands, now we have scientists taking pictures without a lens.

Upon reflection, it was a predictable next step. First we had the major advance of refocusing out-of-focus images by, in essence, building a correction lens, all in software. This is what allowed NASA (the USA space agency) to correct some of the Hubble Space Telescope images after it was put into orbit with an out-of-focus optical chain.

But it one can simulate a lens well enough to correct an image, even if imperfectly, why not replace the real lens with a simulated one and focus the unfocused image received by the (lens-less) sensor? That is what the team at Argonne National Laboratory (Illinois, USA) is working on. Of course, simulations are rarely, if ever, as good as the real thing in all aspects, but if for their particular problem (X-ray imaging) the simulated lens is better than their real one, then they will have improved the imaging system and advanced the state of the art yet again.

Forensics: Track where someone has been by analyzing their hair

2008-02-29T22:25:00.003-05:00

The Economist magazine (UK) has a short article on how forensic analysis of the chemical composition of a suspect's hair can be used to determine where he has been.

Miscellaneous: More links

2008-02-25T23:12:00.007-05:00

Working for a living interferes with blogging - Responsibility is such a cruel mistress.

As you can probably figure out from the intro, I have to give you my sincerest apologies, but work is leaving no time for thoughtful comments or analysis, so here are the links to the raw material that I hoped to turn into interesting posts:

Talk to the machine (Strategy Page)

Listening in with the council's lie detectors (Times Online; hat tip to A.F.)

Music Special: Five great auditory illusions (New Scientist)

Astronomy Technology Brings Nanoparticle Probes Into Sharper Focus (Science Daily)

Wanted: RAM's help in solving crimes (New Scientist) (a YouTube video explaining the attack can be found here)

Snakes Locate Prey Through Vibration Waves (Science Daily)

The 'non-lethal' flashlight (New Scientist Blogs)

Car Camera Recorder Pro: Video of Everything in Your Car's Path (TechnoRide)

Abuse of Auto-Tune (Cross Spectrum)

Justice Grants will Fund Research at CU-Denver (Business Journal)

FBI wants palm prints, eye scans, tattoos (CNN)

Enjoy! I hope to be back with more in-depth blogging soon.

Indoor Acoustics: Noise in Restaurants

2008-02-18T15:50:00.002-05:00

Alexandra Gill writing in the Globe and Mail (Canadian newspaper) has an excellent article about noise in restaurants. Here is a taste (sorry for the pun):

So how loud is too loud?

The ideal sound level for normal conversation is 55 to 65 decibels. When the ambient noise rises to about 70 decibels, you have to raise your voice to be heard. At 75 decibels, conversation is difficult. Above 85 decibels, prolonged exposure - more than eight hours - can permanently damage your hearing.

While restaurant noise levels aren't a threat to hearing loss, "they are certainly an issue for communication. Many, if not most, restaurants have noise levels that are too high for comfortable conversation," says Christine Harrison, an occupational audiologist with the Workers Compensation Board of British Columbia.

I recommend reading the entire article. Enjoy.

Human Auditory System: Echolocation Technique for the Blind is Rediscovered

2008-02-18T10:28:00.006-05:00

Perhaps I should have entitled this post "Everything Old is New Again" instead. The Sunday Times of London (UK, center-left newspaper) ran an article recently on how blind British school children are being taught a "pioneering" technique using echoes to help them navigate - just like bats do. The article even mentions Dan Kish and the YouTube video of him riding bicycles on city streets to show that the technique works. Great stuff!

The only problem is that this technique is not new to mankind. It has been used by humans since at least the 1800s, as evidenced by historical accounts of James Holman, nicknamed the "Blind Traveler" for his use of echolocation to travel the world.

Just in case I've lost you by immediately launching into correcting a historic inaccuracy, I will explain what human echolocation is. Simply put, it is the technique of using sound bouncing off of an object (i.e. echoes) to sense where the object is. Blind people have been taught this technique for years, hence the metal tip on the end of the traditional "white cane" used by many blind people over the years to tap the ground as they walked. The technique seems to have decreased in popularity since the widespread introduction of seeing-eye dogs (Note: this is an educated guess based on my own understanding of history, so if I'm wrong, please feel free to correct me!).

Despite the errors in the article and YouTube video, I am excited that this technique is being reintroduced for the benefit of those with impaired vision.

Noise: Thoughts on quieting a lab

2008-02-17T08:48:00.002-05:00

This AP (Associated Press) article about new products on the market for quieting home environments got me thinking about my experiences quieting a few laboratories and what I learned along the way. Here are my thoughts, arranged in no particular order:

The frequency of the noise matters. High frequency noises can be reduced or eliminated by light-weight materials such as fiberglass, curtains, carpet, and rubber seals (e.g. around doors). Reducing low frequency noise requires MASS; in other words, it takes heavy materials to absorb the large amounts of sound energy contained in low frequency noise, such as from machinery, engines, air handlers, and the like.
Solid-core doors can make a big difference in the amount of sound coming from the hallway (or leaking out into it, for that matter) and cause little, if any, disruption to the work environment when used to replace existing hollow-core doors. Most doors that come standard in home and office environments are hollow in the middle and therefore don't absorb low frequency sounds very well at all.
If the room has a drop (also called a "false") ceiling, then replacing the standard ceiling tiles with acoustic ones can make a significant difference and is minimally disruptive.
Wall and door treatments, such as barium-loaded vinyl hangings and acoustic panels, offer the benefit of being able to be installed to an existing room without requiring tearing down the walls, but installing them may require significant effort and it will almost certainly be quite disruptive to the existing workspace (think about shelves and such that are on the walls).
If you have hollow walls (e.g. gypsum board on stud), then blowing insulation into the wall cavity can reduce middle and high frequency noises without being too disruptive.
If full-scale remodeling is an option, consider adding an extra layer of gypsum board or other massive material to the walls. If you go this route, then you should advise the workers to install the boards so that the seams (between boards) of the new layer do not over-lap the seams of the underlying layer. Of course, there may be complications with window and door frames fitting the non-standard thickness of the walls, but a competent carpenter can solve those issues.
Speaking of windows, if the building is located in an area where the external noise (e.g. vehicular traffic or aircraft) is an issue, then it will likely make things much simpler if you pick a room without a window for your lab in order to avoid having to acoustically shield it. Likewise, locating away from internal noise sources, such as elevators and air-handlers, is also a good idea where possible.
Quieting noises in your lab itself is also a good idea. Computer workstations and other electronic equipment fans are the usual culprits here. A variety of options now exist for quieting computers ranging from low-noise replacement fans to liquid cooling systems that can be added to existing computers.
If the acoustic environment is so poor that you need to go beyond the simpler of the measures listed above, then consider getting professional help (i.e. a consultant who specializes in this area) to evaluate the situation and recommend appropriate steps.
Choosing a room that isn't a strict rectangular box can be a good idea as it can mean significantly less resonance.

As I said above, my comments are based on my own personal experience on quieting existing rooms. I did not mention options that I am not personally experienced with, such as bass traps. Finally, I have not addressed anechoic chambers or designing sound studios as that is outside of the scope of this post.

Biometrics: Finger vein scanners being deployed

2008-02-03T06:43:00.000-05:00

The use of various biometric technologies to identify individuals as a routine matter of daily life has been slow to catch on, thus far at least. Perhaps it is because there is insufficient demand, perhaps it costs too much (relative to the perceived benefits), or perhaps there are drawbacks with the technologies that have been fielded to implement it to this point.

As far as industry addressing possible technology drawbacks of the equipment, the Guardian (UK, left-wing newspaper) reports that Hitachi has started fielding a new type of biometric technology - finger vein scanners. Finger vein scanners differ from finger print scanners in that they are reportedly more difficult to fool. The principle of operation in similar to the blood oxygenation sensors commonly used in medical settings - i.e. shining a light onto (into) the skin of the finger which is absorbed by the hemoglobin in the capillaries, thereby allowing the imaging sensor to "take a picture" of the capillary pattern. These patterns are reportedly unique to an individual, just like finger prints. Of course, it all depends in how you implement the matching algorithm, but that is another issue - for more, see the Journal of Forensic Identification paper on errors in fingerprint examination.

Whether the scanners address the cost issue I mentioned above remains to be seen. For more details, including one disturbinging case of how a gang got around a finger print scanner to steal an automobile, you can check out the Guardian article.

Optics: How camera lenses are made

2008-01-31T19:39:00.000-05:00

YouTube has a fascinating video segment on how camera lenses are made.

(Hat tip: Gizmodo)

Acoustics: Underwater acoustic modem

2008-01-31T19:18:00.000-05:00

An Israeli start-up, Sea-Eye Underwater Ltd., has developed an underwater acoustic modem that is fast enough to transmit real-time video. The reported range of the modem is 100-200 meters (1 meter = 1 yard, approximately).

EETimes has the story.

Image Forensics: An overview

2008-01-21T17:17:00.000-05:00

I recently purchased and read the excellent book, Photoshop CS3 for Forensic Professionals, by George Reis and can highly recommend it. Today I came across an overview of image forensics written by him and thought I'd share it with you. The overview article, in an issue of MacTech, can be found here. Enjoy!

Forensics: Name that codec in one note

2008-01-20T23:00:00.000-05:00

Sometimes I feel that I lose track of the founding purpose of this blog - which is to educate people in a non-commercial way about audio and video forensics. In that spirit, I will let the non-specialists among you in on a current trick of the trade - namely, G-Spot. G-Spot is often the first thing a video forensics professional turns to when a piece of digital surveillance video evidence won't play on the laboratory's workstation.

G-Spot is a software application developed by Steve Greengerg to identify what codec is needed to play a video file. Given the plethora of low-cost digital video recorder (DVR) security systems on the market, many, if not most, with their own proprietary codecs, G-Spot can be a life saver. Here is a link to a review of the application (Note: there is some sexual innuendo, but I did not find it to be overly crude).

Now you know what drives many video examiners to distraction every day and what they turn to for the answer.

Brain Science: Train your brain for multi-tasking

2008-01-20T22:44:00.000-05:00

As reported by John Tierney of the New York Times (center-left news media, USA), researchers at Wake Forest University and University of North Carolina Greensboro (both in the USA), there may be something to the "Train your brain" fad, at least if you are musical conductor:

The researchers used functional magnetic resonance imaging to map the brains of musical conductors and non-musicians who tried to distinguish musical tones while also being shown visual images. The scans showed that non-musicians had to turn off more of their visual sense than the conductors did in order to focus on the task. One of the researchers, Dr. Hodges, director of the Music Research Institute at UNC-Greensboro, says there are two possible interpretations of the results:

One is that the brains of musicians are wired this way, and that’s why they became musicians. The other is that they train their brains for rewiring. Because conductors have to be able to hear a bad note, then identify who did it, perhaps they rewire their brains to combine their visual and auditory senses. An experienced conductor has trained day after day, year after year, to let their brains pick up various signals from their senses.

The article is quite good and highly worth reading through.

Miscellaneous: List of links Part 2

2008-01-10T21:09:00.000-05:00

How the brain makes a whole out of parts

Use your iPhone to get the name of a song using "Listen"

Humans ARE actually better with one sense than most mammals (namely, fine sound frequency sensitivity)

Adobe Photoshop Elements 6 for Mac is about to be released (and it includes some very neat features for a consumer-grade product, such as Guided Editing and Photomerge)

Telephone companies cancel FBI wire taps over unpaid bills (Not to be a cynic and nothing in particular against The Register, other news outlets, or governmental bodies, but don't be surprised if this hasn't been overblown a bit for political or news making purposes.)

Create professional 3D photographic images in your office

LANL researchers develop low power MRI system (LANL = Los Alamos National Laboratory, USA)

Miscellaneous - List of links for audio geeks

2008-01-10T16:40:00.000-05:00

Too much work PLUS too few mentally productive hours EQUALS a list of links without any in-depth analysis. Sorry about that, but I hope to return to blogging more seriously soon. Until then, enjoy these:

Stereo from a single box (Blumlein was an audio genius. If you are an audiophile, I suggest you read a biography on him sometime.)

How the iPhone blew up the wireless industry

Acoustic superlens could mean finer ultrasound scans

Ultra-thin digital voice recorder

Noise reduction technology for cell/mobile phones (Note that the sales spiel uses words like "crystal" and "pristine" but you can clearly hear artifacting at low levels. Not trying to be overly critical, but couldn't they have let the results speak for themselves without the spin?)

Human Auditory System: Mosquito test your hearing

2007-12-30T08:26:00.000-05:00

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.

Noise Cancellation: Quieting an aircraft

2007-12-27T22:45:00.000-05:00

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

2007-12-27T14:51:00.000-05:00

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

2007-12-27T11:50:00.000-05:00

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

Beautiful and average not the same

Seven medical myths

One person in 1,000 has synaesthesia

The influence of color on taste perception

Hacking your internal clock

The foreign patent money trap

What your iPhone knows about you

FBI unveils a $1B biometrics initiative

Angry populace burning British security cameras

How extra pounds boost your risk of cancer (sorry, but I couldn't find a free on-line version with graphics included, but if you have full access to the newsletter or the New England Journal of Medicine, they are stunningly impressive)

And to end on a brighter note:

2007 foot-in-mouth awards