Acoustics: Visualizing whale calls as art

NewScientist (science magazine, UK) has a fascinating set of images from Mark Fischer, who uses artistically manipulated wavelet transforms of the calls of marine mammals to create stunning artwork.
Enjoy!

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.

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 ieee.tv.  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: ieee.tv has a fascinating video clip on the gunshot analysis performed by various experts on the recordings JFK assassination.

Hat Tip: Thanks Alex!

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.

Enjoy!

Human Auditory System: Speech Intelligibility overview

A colleague pointed me to the following overview of speech intelligibility on the Sound & Video Contractor website. It was written for intelligibility during teleconferencing, but the information in it is directly applicable to audio forensics. Special attention should be paid to how reverberation and signal-to-noise ratio (SNR) affect intelligibility.

Enjoy!

Sonar: US submarines get acoustic signal processing upgrade

The US submarine fleet is undergoing an overhaul of its sonar signal processing systems. Defense Industry Daily has a short article.

Fun: Sew me the music

Gizmodo highlights a sewing machine by SOUNDS.BUTTER that stitches the time-amplitude waveform of the sound.

Human Auditory System: Artificial Cochlea

A next generation implementation of an artificial cochlea has been developed by researchers at the University of Michigan and Tufts University (both in the USA). The natural cochlea is the sea-shell-shaped structure in the human auditory system that is the final stage in the conversion of air pressure variations (a.k.a. sound waves) into neural impulses that convey the frequency and amplitude information information contained in the sound to the brain for interpretation.

EDN (USA technical magazine) has an article which contains more technical detail and pictures on the advance.

I should point out that this version of the artificial cochlea is not an exact replica in form factor (i.e. shape) or function of a natural cochlea. For instance, the artificial cochlea is planar in shape versus sea-shell-shaped; covers the frequency range of 4200 to 35,000 Hz versus the 20 to 20,000 Hz of the human ear; and isn't continually fine tuned by an external processor to focus on frequency bands of interest, like the human cochlea does when one is, for instance, one's brain is picking out a familiar voice in a cocktail party situation. I mention this not to detract from their excellent work, but instead to give you, curious reader, reasonable expectations as to its specifications and performance.

Acoustics: Listenging to nature

Using microphones to capture the sounds made by animals in their habitat, minus humans and their man-made sounds. These sounds are known as the "biophony" and are used to sense the quality and character of the animals' habitat. Wired has the story.

Author's comment: It's a good thing that animals don't have privacy rights in the USA (yet!), or these scientists would be in jail for unlawful surveillance activities!

(Via Cross-Spectrum Acoustics)

Fun: Top Ten Amazing Physics Videos

Wired has them. Enjoy!

Acoustics: Science of sound in the sea

Sound requires a medium, such as air, to travel in. Here is a link to a site dedicated to the case where the medium is water. The site belongs to the University of Rhode Island (USA) and it has plenty of information for educators and students about the science of sound and the animals that make underwater sounds, such as dolphins, whales, and fish. I particularly liked the recordings of the animal sounds.

PS. Thanks to C.S. for the link!

Acoustics: Acoustic cloaking

First there came visual cloaking of tanks, et al. Now, there is a design idea for an acoustic cloak - I should have seen it coming (pun intended)!

Acoustics: Mosquito comes to the USA

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)

Miscellaneous: More links

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

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

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

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.

Acoustics: Underwater acoustic modem

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.

Brain Science: Train your brain for multi-tasking

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

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)