general, linguistics

speech perception, therapeutic ultrasound and detecting land mines

Today was the last day of my first meeting of the Acoustical Society of America. It was actually the 155th meeting of the society, and the 4th joint meeting with the Acoustical Society of Japan. Oh, and it was in Hawaii.

I have been a member of the ASA for several years now, and have read many articles in its journal, but I have not spent that much time reading journals outside of my subfield. There are 13 subfields at each meeting of the society, which also roughly correspond to different topics in the journal. I am most interested in the Speech Communication subfield, and spent the great majority of my time learning about all sorts of interesting research going on in that area. Even within Speech Communication, there is a great diversity. I saw some posters and presentations about lexical access, which I do, as well as posters on developing better cochlear implants, quite a few papers on automated speech recognition, some on clinical applications of phonetics, and a few on using ultrasound to track the movement of the tongue.

In addition to these talks, I also saw a couple in different fields. There were two plenary talks at the beginning of the conference – one Japanese person, and one American. The first plenary, by Masayuki Morimoto, covered a fairly wide range, from architectural acoustics to psychological acoustics. Ultimately, these two are very related. Acoustic engineers are interested in designing buildings with good acoustics, but ultimately, the definition of „good“ is dependent upon how humans perceive the acoustics of the space. He talked quite a bit about what types of parameters that one can measure, as opposed to parameters that cannot objectively be measured. Whether a person finds a space pleasing or not is very subjective. Whether a person finds a space ringy or deadening can be quantified though, and depending upon the space, one or the other might be desirable.

The second plenary, by Lawrence Crum, was on a completely different topic – therapeutic ultrasound. I had never really heard about this before. He gave a nice overview of how therapeutic ultrasound works, the history (first used in the 1950’s), and its applications. When we hear ultrasound, we usually think of imaging, and that is correct. Ultrasound imaging (or diagnostic ultrasound), shoots low power, low frequency sound waves into a medium, and registers the time it takes for the waves to bounce back. Objects at different angles and distances will take differing amounts of time to bounce back, and thus one can make an image. Therapeutic ultrasound uses high power, high frequency sound waves, and concentrates the waves at a particular point, much in the way one can use a magnifying glass to concentrate electromagnetic waves (e.g. sunlight) onto a piece of paper and catch it on fire. With very high power sound waves, one can do quite a bit of destruction. Destruction? Yes, destruction. One common application is for breaking up kidney stones — without surgery. Another is killing cancerous tissue, specifically for pancreatic cancer, which is a terrible sort of cancer. Another application is blood clotting (hemostasis).

Many acousticians are concerned about noise. Many speech communication people use noisy conditions to test hearing (including myself), and many are also concerned about trying to reduce noise pollution. I saw several talks about that. David Bowen gave a talk about how to perform acoustic audits for consumer products, mostly by isolating different parts of the product, such as the motor, or a fan, and using different tools to measure the amount of noise it produces. Then one can create a sound profile for the product, and try to reduce the noise through various methods. One example he gave was a copy machine. They swapped the metal chain with a composite chain, and perforated the aluminum frame inside, along with a few other modifications, to reduce the overall noise by about 8 decibels (remember that decibels are on a log scale, so that is actually a fairly large reduction).

One last small note. I did not attend any of these talks, but while reading through the abstract booklet, I noticed that there was a whole session on using acoustics to detect land mines. Talk about a diverse field. I am excited to learn more.