Archive for the ‘Technical’ Category

Sight of sound

Your eardrum converts the motion of the air into something you can hear, but what if everything around you could work the same way? In a recent TED Talk, MIT researcher Abe Davis demonstrates cutting edge research into extracting audio from silent video of everyday objects exposed to sound. Using high-speed video equipment and even a consumer-level camera, he extracts intelligible music and speech just by watching a nearby houseplant or a snack bag—the proverbial “fly on the wall”. Acknowledging the surveillance possibilities (which were already feasible using lasers), the research pushes beyond audio to expose the natural modal movement of an object by simply ensonifying it and recording what happens, allowing one to push, pull, and shake something virtually without ever touching it.

This sound is on fire

Many aspects of a firefighter’s work are not quite like the movies, and locating each other is one of them, according to a recent story from KUT News in Texas.  Visibility is poor or nonexistent in a real fire, so firefighters often have to rely on sound rather than vision.  A Personal Alert Safety System (PASS) is a device that emits a loud audible alarm if the wearer stops moving for more than a few seconds, allowing colleagues to come to the rescue.  Researchers at the University of Texas at Austin are working on ways to improve this system, which despite saving many lives doesn’t always work as well as it could.

For starters, an active fireground is a loud, noisy place, from things like sirens, power tools, engines, and the fire itself.  But beyond that, heat can do funny things to sound—hotter and colder parts of a room make sound travel faster or slower, and these changes in the speed of sound can actually bend sound waves that would otherwise travel in a straight line.  (Similar effects occur outdoors when the air temperature varies with height, such as being able to hear campers far away across a lake that cools the air.)  This heat refraction can wreak havoc with audibility and locating the source of a PASS beacon.  The current UT research will provide valuable insight into the sensory environment within a fire scene, and how compensation might be made for some of these acoustic challenges.

 

Did you hear that meteor?

This past weekend, the Perseid meteor shower reached its peak overnight between Sunday and Monday.  With a little patience and clear skies, the electromagnetic radiation in the visible spectrum that meteors release is easily seen.  But did you know that meteors also release very low frequency radio waves, below 30 kilohertz? According to livescience, going back hundreds if not thousands of years, people have claimed to hear sounds of meteors as they raced across the sky.  The very low frequency radio waves travel at the speed of light (not at the speed of sound) and arrive at the same time observers see a meteor passing overhead.  However, the radio waves need a transducer to could create a sound that is audible to people. This phenomenon is known as electrophonics, and in order to study it further, physicist Colin Keay created sounds in ordinary objects by exposing them to very low frequency radiation in a laboratory. Lightweight, membrane-like objects such as aluminum foil, foliage, thin wires, even dry frizzy hair produced sounds that were easily heard.

2012 Geminid Meteor Over Texas

Never having heard this before, we thought we would head out to Long Island to try and hear it for ourselves. We saw and heard a few things…First, there are quite a few sky-watchers in New York, which unfortunately meant that second, people noise and car stereos are louder than the sound from meteors.  Also, being by the beach, the sound of the ocean waves were also louder than the meteors.  Even if we couldn’t hear them this time, and although there were a few passing clouds, meteor showers still create a wondrous sight.  We will just have to make plans to go somewhere a bit quieter next time.

 

New York Noise

After over two years of work, we are glad to say that the final report for our project Wind Turbine-Related Noise in Western New York has been published.  Funded by the New York State Energy Research and Development Authority (NYSERDA) and the Electric Power Research Institute (EPRI), and co-produced with EPRI and Colden Corporation, the study presents a detailed and long-term look at noise levels and resident satisfaction near a modern, utility-scale wind power facility in Wyoming County, NY.

Wind Turbines

The findings of the study fill a gap in the available wind turbine noise research specific to New York State, and include a separate Syracuse University policy paper with specific and actionable advice for a non-technical public policy audience.  Both the Final Report (13-03) and the Policy Paper (13-03b) can be found at the NYSERDA R&D site, and we plan to present the project at the Wind Turbine Noise 2013 conference this August in Denver, Colorado.

A new record

Putting a new spin on the long-playing vinyl record, an editor at Instructables has devised a new method for producing LP records using a rapid prototyping “3D printer”.  Working directly from a digital audio file, Amanda Ghassaei uses the waveform profile to create a 3D computer model of the familiar LP groove, which is then built up in physical form by a UV-cured resin printer.

Despite the cutting-edge 16-micron resolution of the printer, the end result is rather crude, with a frequency response and audio quality as yet far beneath a typical analog vinyl record.  The all-digital noise introduced by the discrete print (in time, aliasing, and in amplitude, quantization) is also harsh compared with the traditional “warm” analog distortion sought after by vinyl enthusiasts and audiophiles.  Even so, one could foresee a niche market for one-off, just-in-time pressing of records to keep alive long out-of-print material (or new material that might be in limited demand).  Even though this can be accomplished with .mp3 files or CD-R discs, sometimes there’s simply nothing like setting needle to vinyl!

[via Wired]

Drop-less droplets

In a setup that’s equal parts science and Harry Potter, scientists at Argonne National Laboratory acoustically levitate liquids in midair to further critical pharmaceutical reasearch. Using a technology originally developed by NASA to simulate microgravity conditions, the pharmaceutical droplets are suspended in midair using standing waves of inaudible ultrasound generated by small speakers above and below.

By suspending a drug this way—free from any container or other physical contact—scientists can study its various forms and the ways it might be absorbed by the body. Not to mention putting on a pretty cool show in the process!