Sunday, December 13, 2009

Acoustics: Shattering glass with sound

I really enjoy Make Magazine (USA) for their many contributions to open source hardware development, but that is not the subject of this post. Instead, I'd like to point you to an excellent video they have up on their site from the MIT Department of Physics on breaking a wine glass with sound.

Law Enforcement: LRAD used for crowd control

The LRAD (Long Range Acoustic Device) was used for crowd control during a G-20 meeting in Pittsburg, USA in September 2009, according to this report.  For background on LRAD, see my previous post.

Human Auditory System: Learn echolocation

I came across (yet) another article on learning echolocation, this time by Wired (USA, popular technology magazine).  It is worth a read, if only for the observations, such as getting dry mouth from clicking too much.

For the record, I posted about this topic before to refute the contention that humans are learning to do this for the first time.

Tuesday, November 24, 2009

Admin: Word verification requirement for comments

Due to an overly burdensome and increasing amount of spam comments, I have turned on word verification for all submitted comments. I hope that this has not inconvenienced anyone.

Kind Regards,

Audio Forensics: Signal Processing helps unravel JFK Shooting evidence

IEEE (The Institute of Electrical and Electronic Engineers) has started a public video section on its web site it calls  I have been a member of IEEE since at least my graduate school days, as are many speech and forensic scientists, so if you are in either one or both of these fields and are not a member, I highly recommend that you check into it. (And in the spirit of full disclosure and in the hopes of avoiding investigation under who knows what new law is actually now or ever will be on the books about such things on the Internet - no, they didn't pay me to plug them as a professional organization!).

On to the subject of this post: has a fascinating video clip on the gunshot analysis performed by various experts on the recordings JFK assassination.

Hat Tip: Thanks Alex!

Friday, November 13, 2009

Human Auditory System: Foreign subtitles improve speech perception

Want to improve your ability to comprehend a second spoken language? One way is to watch foreign films and read the foreign language subtitles - not the English ones. Eurekalert reports on a recent study.

Human Auditory System: Newborn babies cry with mother's accent

MedGadget reports on a study by French and German scientists on accent that a newborn uses - conclusion: its mother's. It is well known that a person's hearing system begins functioning while still forming in the womb. I find it fascinating that it is also "training" the speech part of the system at the same time and that the interplay works so soon after birth.

Sunday, November 01, 2009

Audio Forensics: Pro Tools Snow Leopard Pre-Release

I don't use Pro Tools myself, but many audio forensics professionals do, so here is a breaking news item...

From Hitsquad Musician's News:

Pro Tools Prerelease now available for Mac OS X Snow Leopard
Avid/Digidesign is pleased to announce the immediate availability of a prerelease version of Pro Tools software that provides expanded Mac OS X 10.6.x Snow Leopard compatibility to Pro Tools 8 users.

Friday, October 23, 2009

Audio Forensics: Speech quality versus intelligibility

Engineering Technology Magazine (Institute of Engineering and Technology, UK) has a well written article concerning research by CLEAR (Center for Law Enforcement Audio Research) concerning the effect of noise reduction on intelligibility of evidentiary recordings and other audio in law enforcement situations.
... most speech-enhancement techniques improve sound quality at the expense of intelligibility, particularly when the signal-to-noise ratio (SNR) is very low. Closely related as they are, speech quality and intelligibility are not identical.
This is a classic trap that is easy for a novice to fall into.

Read it all.

(Hat tip: RH)

Wednesday, September 30, 2009

Human Hearing System: When an ear witness decides the case

The New York Times (USA) has an excellent article on human speech and hearing and how the vision system interacts with hearing.


Filtering: Video clip explains Auto-Tune software

Nova's ScienceNOW by PBS (Public Broadcasting Service, USA) has an informative video clip on Andy Hildebrand's pitch-correction software called Auto-Tune. This audio filtering technology is used by professionals to correct mis-sung notes both in the studio and during live performances. It has been compared to Photoshop for voices.


Saturday, September 26, 2009

Audio: Laser microphone patented reports on a new type of microphone designed and patented by David Schwartz. The principle behind the design involves a laser beam measuring the vibrations of smoke particles in a tube as they are deflected by sound. There are two interesting video clips on the page - one showing a demonstration of the second prototype and the other showing the components of the device.


Biometrics: FBI to migrate to multi-modal biometrics

COMPUTERWORLD reports on the FBI (Federal Bureau of Investigation, USA) announcement at the Biometric Consortium Conference that it will migrate from its IAFIS fingerprint database to a new multi-modal biometric database that will include DNA records, 3-D facial imaging, palm prints, and voice scans.

Saturday, August 29, 2009

Image Forensics: Seeing is NOT believing

Spectrum Magazine (by the Institute of Electrical and Electronic Engineers, or IEEE, USA) has an excellent overview article on detecting tampering in digital photographs by Professor Hany Farid (Dartmouth College, USA).


Monday, August 03, 2009

Human Auditory System: The Power of the Pentatonic Scale

Here is a link to a video of Bobby McFerrin (a famous jazz and a cappella musician) demonstrating the power of the pentatonic music scale at the World Science Festival 2009. Short and fascinating!


Friday, July 24, 2009

Admin: Posting will be light

Due to a continuing heavy travel schedule, posting will be light for a while.

Friday, June 12, 2009

Education: Yenka Light and Sound modeling software

I've been using Falstad's freeware Java applets for teaching acoustics and oscillation concepts in the classroom for years now. I recently decided to give Crocodile Clips' Yenka Light and Sound modeling software a try after some of my own children enjoyed using it in school. At first it was to take advantage of the free license for home use (yes, FREE). Now, however, I'm going to use it in classes thanks to the numerous models already built-in and even more content online. My favorite built-in model so far is "Speed of Sound" - which lets you add other media, such as vacuum, water, and wood, and see how the speed of sound changes and then interacts with the sound wave in air, assuming it exits the extra media at all - very cool!

Not to leave optics out, there are informative models for angles of reflection, refraction, mirrors, lenses, telescopes, and more. For instance, to show that the angle of incidence equals the angle of reflection, the student drags two protractors into the workspace and measures both angles as the (virtual) beam of light bounces off the mirror. Simple, but effective. Many more sophisticated models are available too, plus you can build your own and save them for later use (as an educator, I like that).

Yenka also covers more than the physics of sound and light - mathematics, chemistry, computers, electronics, and other packages are also available. I've tried the chemistry package with my boys. Being boys, they were particularly pleased with being able to experiment with (virtual) dangerous substances after having to suffer through the kid-safe chemistry sets sold in stores these days.

Crocodile Clips is based in the UK, so American and other visitors to their website may not understand the references to terminology used in the British education system. Luckily, the laws of physics do not change as a result of the software leaving the UK! Yenka is a free download for students to use at home. Use outside of the home requires buying a license, of course. Finally, it works on Mac and Windows operating systems.


Wednesday, April 29, 2009

Forensic Linguistics: Identify the language of a text

LangID is a new website that will identify the language of any text you can paste into its webpage or upload/tweet/email them with. This free service is based on the Google Ajax API (Application Programmer Interface) and currently identifies around 85 (human) languages with more being added. A list of the languages that it can identify can be found at this link.

(Hat tip: Good Morning Silicon Valley)

Thursday, April 16, 2009

Admin: Summer Science Program in Forensics

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. I'll be teaching two, one-week runnings of my course, A Mathematical Tour of Forensic Science, again this year. If you are interested, you can find out more on their website. I hope to see you there.

Thursday, March 12, 2009

Admin: Posting will be light

Due to a continuing, heavy travel schedule, posting will be light for a bit longer.

Thursday, February 19, 2009

Forensics: US National Academy of Sciences report is released

DNA evidence was the pebble in the pond, so to speak, for elevating the "science" in "forensic science" - the scientific rigor that has accompanied this new discipline of forensic science continues to ripple through all of the forensic disciplines and our legal system.  Of course, DNA evidence was not the only motivating factor, but I do contend that it was the most significant and that the mindset that accompanied its introduction also carried over the other disciplines.

The latest ripple was the release yesterday of a report by the US National Academy of Sciences titled "Strengthening Forensic Science in the United States: A Path Forward".  You can read it online or pre-order a print copy at this link.

One should keep in mind while listening to or reading press accounts of this report something that Robert Mueller (physicist, USA) once said, and I'll paraphrase: "Everything reported in broadcast or print media is generally correct, except, that is, for what they report on things that you are actually well versed in, which they invariably get wrong."  Such will likely be the case with reporting on this subject.

That being said, how I am interpreting the early press accounts of the report is that this report is another step in this process of bringing the scientific rigor applied to the introduction of DNA evidence into our legal system to all of the disciplines that were already here. In my opinion, this is a worthwhile endeavor.  However, we must all be wise enough to understand that we are humans and that any system we create will not be perfect, but if we design the system correctly then mechanisms will be included to minimize and weed out these natural errors while also minimizing the adverse affects on the ability of the system to perform its intended purpose.

Wednesday, February 18, 2009

Phonetics: The Sounds of American English

Check out this educational page on the Sounds of American English from the University of Iowa (USA) - complete with cut-away animations of what is happening in the vocal tract and videos of the face during articulation.  My wife is probably tired of hearing me point out over the years that this is exactly what is missing from educational software for learning foreign languages.  Learning to properly articulate a sound element (phoneme) is so much easier if you know what the articulators (i.e. lips, tongue, jaw) are doing!  Well done.

Sunday, February 08, 2009

Photography: Automatic panning device for gigabit images

Engadget profiled the GigaPan Epic some time ago. The Epic is a robotic camera mount that holds your point-and-shoot digital camera and then automatically pans the visual scene, taking picture after picture (up to thousands, according to the manufacturer). Software is included that then automatically stiches the individual images into a single digital panoramic image. Very cool. The inventor used it at the recent inauguration to capture a panorama of the mall. Many more images can be found at a community page devoted to these images. Here is a link to the product page with more details (and the sales price).

Why would anyone need so many pixels in an image? Over the Christmas holidays, the pundits were telling us that no one needs more than, say, 6 megapixels in a camera. Two examples where more pixels are needed include when one needs to zoom in to get small details or when one requires very wide angle shots with good resolution (i.e. which is hard to do with a fisheye lens or a dome mirror).

A potential forensics application is crime scene photography, thanks not only to its functionality, but also its modest cost and compatibility with a wide range of digital cameras.


Image Restoration: iMovie Stabilization feature

Despite the best of intentions, I have not yet been able to get around to testing Apple's new iMovie video stabilization feature for the Mac OS (Operating System). I will, however, whet you appetite with a Macworld review I've come across that gives examples.


Friday, January 30, 2009

Audio Forensics: Solving a Beatles' chord mystery

Dalhousie University (Nova Scotia) math professor Jason Brown has apparently solved a musical "who-dunnit" - what was the opening chord of the Beatles' famous Hard Days Night? There was an agreed upon suspect - namely George Harrison - but what was the chord? No one could reproduce it, even knowing what guitars they used in performances.

Enter Professor Brown. The professor used tools well known to forensic audio examiners - an FFT (Fast Fourier Transform) to analyze the spectrum and logic. And what did he deduce? It appears that George Harrision had a little help from someone else - perhaps the Beatles' manager, George Martin - who simultaneously played the chord on a piano! So, in the spirit of the board game Clue (Cluedo, for you Brits), it was George AND George, in the recording studio, with a guitar AND piano. Mystery solved!

Here is an article to read more about it. And another one. Enjoy!

(Hat tip to D.E. - thanks!)

Computer Audio: Latest Audacity beta (1.3.7) is released

Audacity 1.3.7(beta) is available for download. This release primarily seems to consist of bug fixes, but they do say that they added support for DirectSound, which is a widely-used Windows(R) DirectX API (Application Programmer Interface). Here is the text from their announcement:

Audacity ( is a fast multi-track audio editor and recorder for Windows, Mac, and Linux/Unix.

The Audacity Team is pleased to announce the release of Audacity 1.3.7 (beta) for Windows, Mac and Linux/Unix. This is primarily a bug-fix release to significantly improve stability and usability, especially on Mac OS X, but includes some new features too.

Cross-Platform Bug Fixes include:

* Muting/soloing caused incorrect channel results in exported stereo files
* Fixes for Nyquist effects, Compressor and Noise Removal
* Fixed Export as WAV could be corrupted if overwriting to same file, and Export Multiple to uncompressed formats only produced 16-bit WAV
* MP3 and WMA now export correctly with all supported metadata

Platform-specific Bug Fixes include:
* Windows Vista: crash opening Preferences
* Mac OS X and Linux: fixes for spurious clipping, label typing, no shortcuts after running effects, and project rate when importing files
* Mac OS X only: fixes for inactive or corrupted menus and hidden dialogues, portable settings, and Command and Control shortcuts. Also FFmpeg installer now available.

New features/other improvements:
* F11 Full Screen mode, high-quality "Sliding Time Scale/Pitch Shift" effect, Audio Contrast Analyzer
* Windows: sound devices can now be opened using the more efficient DirectSound API
* Improved latency correction using fixed correction value

See for details.

Wednesday, January 28, 2009

Image Recognition: Facial recognition feature in iPhoto

I installed Apple's iPhoto '09 last night to test how the face recognition feature (called "Faces", of all things) worked. There are nearly 4,000 photos in my personal library, so I left it running overnight while it went through the database and, I assume, ran its face detection algorithm. I then decided to run a test. I manually identified the same person in two different photographs and had iPhoto go out and locate matches, which is its next step in its learning process - the user next needs to confirm or not confirm the identity of each one of the identifications it produces.

So how did it do at the end of this first step? Surprisingly well is the answer, particularly for a consumer-grade product. The raw numbers were 72 correct and 16 incorrect at this first step, but that doesn't tell the whole story. In the instances where it was incorrect, all but three were confused with family members (which admittedly is the most likely confusion outcome since for all pictures with faces in the database, generally at least one is a family member). In addition, it also correctly chose pictures where only one eye was visible, where the age was significantly different, and where there were different emotions clearly visible on the faces. It also did not seem to have a problem with different compression levels, low resolution (including one that was very granulated), face paint, under-exposure, black-and-white, scans (of printed pictures), and color. Finally, it made only one error out of 86 pictures in correctly detecting and locating the face.

So, even though this was not a properly constructed test, the results were more than impressive enough to warrant looking at it further for professional use in some applications.

PS. This is not a product review, per se, but I should say that my experience with this just-released version was not all positive. Namely, it was horribly slow during the step where one has to select a picture, go into the Faces mode, and then type in the subject's name. Each entry took two to three minutes to accomplish, so I saw the "spinning beach ball" that Mac OS-X uses to let you know it is busy quite a lot. Hopefully this bug will get corrected and patched quickly.

Tuesday, January 27, 2009

Evidence: Listen to the raw audio evidence

If you would care to listen to the audio and read the transcripts of the Governor Blagojevich (IL, USA) wiretaps, here is the link.

Image Recognition: Facial and license plate recognition news items

There are two on-line news articles related to image recognition that I would like to bring to your attention.

The first news article is about law enforcement in Tacoma, Washington, USA using a facial recognition package to match 16 years worth of prisoner mug shots with pictures taken by ATM (Automated Teller Machines) in a forgery and theft investigation to generate the lead needed to solve the case.

The second news article is from New Orleans, Louisiana, USA where local law enforcement used a license-plate recognition system to make 20 arrests and recover 23 stolen vehicles and license plates in a 25 day period.

The common thread here is, of course, automatic image recognition. These software algorithms have come a long way in the last decade. However, one should understand that the conditions are partially or completely controlled in both of these applications - i.e. distance, lighting, exposure, aspect (turned toward the camera), and (possibly) compression all fall within acceptable boundaries. In addition, with the license plate recognition problem, the character set and fonts were known in advance. The controlled conditions and a priori knowledge significantly increase the accuracy of the results tremendously and the chances of a successful investigation and prosecution.

(Hat-tip to JUSTNETNews, USA - I highly recommend this free service of the National Law Enforcement and Corrections Technology Center, or NLECTC, which is part of the National Institute of Justice, USA)

Saturday, January 17, 2009

Photoshop: Most blatant Photoshopped covers

I met a graphics artist today whose job is to "Photoshop" pictures for advertisements. We got to comparing stories and she mentioned an incident involving Kate Winslet, the actress, where her legs were slimmed a bit too drastically and caused a stir. Well, before long we were pulling out my MacBook and Googling for that and other instances of "Photoshopped" covers. Here is the best link we found.


Legal: Recording conversations in the USA

Michael Flynn's podcast, Legal Lad's Quick and Dirty Tips for a More Lawful Life, gives an excellent overview of the legalities of making an audio recording of someone in the USA when you are not a government agency performing lawful surveillance. When is it legal and when is it not? The short answer is: it depends - on whether there was a reasonable expectation of privacy, what state the conversation takes place in, and whether all parties being recorded gave consent.

For instance, if one is having a loud conversation on the street (a public place), how can one expect privacy from being overheard? If one can be overheard, how can he then complain that a record (or recording) was made of what he said? An example from daily life, that we can all probably identify with, is the standard phrase we hear when we dial technical support or customer service - "All calls are recorded for quality assurance." In other words - "We're recording you - you've been warned". By being advised and not hanging up, you will likely been seen as having given implied consent.

Legal Lad, being a lawyer as well as having good communication skills, gives a more thorough and educational overview of this subject.


Sunday, January 04, 2009

Careers: Profile of a Court Reporter

The Wall Street Journal (center-right financial newspaper, USA) has an informative profile of court reporting as a career option. One point from the article that caught my eye was that while training takes only two years and salaries are attractive (at least in the USA), one must learn to type at 225 words a minute with 97% accuracy!