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.

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)

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.

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.

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.

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).

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)!

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.

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.

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.

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.