Woodbury, New York, November 6, 1995
The Acoustical Society of America (ASA) will hold its 130th Meeting November 27-December 1, 1995 at Adam's Mark Hotel, St. Louis, Missouri. At the meeting over 580 papers will be delivered. With 7000 members, the ASA is the largest scientific organization in the United States devoted to acoustics.
Paleo-Ocean Acoustics Biological Effects of Lithotripsy Time-Reversed Sound in Solids A Brief History of Noise Ultrasound Mammography Those Annoying Computer Fans Ultrasound Scanners for Airplanes and Paper Straw as a Structural Component of Houses Steelpans Computational Aeroacoustics Making Music Hot Topics in Acoustics Acoustic Classification of Zooplankton Invisible Microbubbles 3D MRI Pictures of the Vocal Tract ATOC and Marine Mammals Underwater Explosion Shock Waves Studies of Voice New Developments in Loudspeaker Materials Building a Better Home Theater Detecting Objects Buried In Sand Recent Advances in Hearing Aids
Living creatures in the sea communicate primarily through sound. The absorption of sound limits the range and quality of ocean communication. How have the sound transmission properties of the ocean changed over the last 50 million years? Paleo-ocean acoustics explores the chemical and temperature changes in the ocean's history and how they may have affected ocean communication conditions. Paper 3aAO10 describes how the changing concentrations in such constituents as dissolved carbon dioxide could have changed the properties of ocean sound transmission.
Extracorporeal shock wave lithotripsy (ESWL) is a popular medical technique in which externally generated shock waves are sent through the body to break up kidney stones. However, internal bleeding and kidney damage can sometimes occur as a side effect of the procedure. In efforts to make lithotripsy safer, researchers at session 4aPA will describe investigations into the mechanisms that lead to the breakup of kidney stones and the factors that can cause bleeding and tissue damage.
Last year, scientists announced that they had developed a device that acts as a mirror for sound waves--if you say "acoustics" into the device it will zap a reversed sound wave right back into your mouth that sounds something like "scitsuoca." More than a neat toy, this device has potential applications in medical imaging and quality control. For example, shining ultrasound waves through the body to break up kidney stones causes some of the sound wave to reflect from the kidney stone. The device would take the reflected wave and create a sound wave that travels right back to the source, thereby sending additional energy to destroy the kidney stone. In a similar fashion, it could be used to pinpoint mechanical defects in planes and ships. Previous time-reversal mirrors worked only in air and other fluids. At the ASA meeting, researchers will describe the successful reversal of acoustic waves propagating in solid objects. This development may bring researchers closer to the goal of useful applications. (Paper 1pPA5)
Speakers will present a review of written accounts of noise pollution over the ages. The findings are not surprising. Noise pollution, the presenters write, has been "a major concern of urban living for more than 2000 years." Exponentially increasing publications of research papers in this century led to the development of international standards and measurement techniques, but the simultaneous increase in the types and locations of noise, combined with ways of reducing construction costs, has led the authors to conclude that "outdoor and neighbor noise may be worse than at any time in history." (2aAA1)
Ultrasound images of breast tissue can ideally reveal tumors as small as 4 or 5 millimeters in size. Producing such sharp images requires not only the proper ultrasound equipment, but also lots of computer time to generate high-resolution images from the data. Researchers have now refined an existing mathematical technique to reconstruct ultrasound images with better resolution at less computational cost. (1pPA1)
One example of airflow-induced noise can be found right on your desktop. Researchers have employed a system for reducing noise in computer fans and printer fans. Their system employs "active noise control" techniques, in which loudspeakers produce sound waves that cancel out noise. (2aNS4)
An important part of the aircraft inspection process is to check for corrosion in the fuselage, the main body of an aircraft. Paper 1pPA3 describes a portable ultrasound scanner that shines a focused ultrasonic beam on the fuselage, allowing much smaller patches of corrosion to be detected than with earlier techniques. This device has been employed in the Federal Aviation Administration's National Aging Aircraft Research Program. In paper 3aEA4, researchers describe a device that uses ultrasonic beams to test paper strength. Such a device could be useful to the paper industry, which does not currently have a noncontact quality control system.
Surely the Three Little Pigs and the Big Bad Wolf would never have anticipated that straw would make a comeback as a construction material. Primarily used as bedding for horses and cattle over the last few thousand years, straw is now increasingly being used in the American Southwest as an inexpensive, environmentally friendly construction component for houses, storage facilities, and restaurants. But appropriate use of straw in buildings requires an understanding of their acoustical properties. Measurements on the sound absorption of wheat and rye-grass straw bales will be presented for bales placed in different configurations. (2aAA6)
Session 5aMU is devoted to the musical acoustics of the steelpan. A tuned percussion instrument that originated in Trinidad, the steelpan is now played throughout the world in calypso, popular, jazz, and classical music. Paper 5aMU1 is devoted to the history of the steelpan, while papers 5aMU2 and 5aMU3 deal with the unique acoustics of this percussion instrument. The construction and tuning of steelpans is discussed in paper 5aMU4, and music of steelpans will be played as part of paper 5aMU5.
As part of ongoing efforts to control noise pollution in the skies, sophisticated computer models can now predict the noise produced by different jet and helicopter blade designs. Paper 2aNS1 describes the latest advances in this field of computational aeroacoustics.
A musical instrument is not merely an object that converts human gestures into audible sound. One can argue that a true musical instrument allows a performer to exquisitely control the properties of the sound being produced, for instance by producing a stable pitch and maintaining sustained tones. What are the serendipitous properties of the bowed string and the blown pipe that make them playable? Gabriel Weinreich of the University of Michigan provides some insights at a special tutorial (1eID1). Paper 4pMU8 describes a computer program that can pick out the pitch of individual notes and their duration, a step towards computer recognition and transcription of human-performed musical passages.
Talks at session 3pID will describe some of the latest advances in physiological acoustics, physical acoustics, and animal bioacoustics.
Sophisticated studies of humankind's impact on the ocean environment require a detailed knowledge of the population of important ocean organisms such as zooplankton, tiny animal organisms on the low end of the food chain. New sonar techniques allow for the distinction of three different types of plankton: gas-bearing, fluid-like and hard elastic-shelled. Preliminary results of these new techniques are encouraging, possibly enabling more advanced studies of zooplankton population than previously possible (2aAO6).
Ocean processes create huge amounts of bubbles too small for the naked eye to see. In the 1960s and 1970s, researchers detected immense numbers of coastal bubbles between 30 and 600 microns (millionths of a meter) in diameter. In the 1990s, acousticians are putting these bubbles to work, tracing important ocean properties. Noise from rainfall and underwater breaking waves can be ascribed to the creation of microbubbles and their radiation of sound. With this knowledge of microbubble behavior, the underwater sound of breaking waves can yield information on ocean wave height. The underwater sound of rainfall can reveal the range of rainfall drop sizes in real time. The information from rain noise can even describe the clouds from which the rain has fallen. (3aPAa1)
Decades of research in artificial speech production have produced little direct information on the shape of the vocal tract as it generates sound. Using magnetic resonance imaging (MRI), scientists have now produced 3-dimensional pictures of the vocal tract for a 29-year-old male subject pronouncing a variety of vowels and consonants. The information from these images was then applied to a speech synthesizer. These images, and results of the speech simulation, will be presented in paper 3aSC1. In research aiming to provide a better understanding of the vocal tract, paper 3aSC5 presents investigations of whether there is chaos associated with the pronounciation of a sustained vowel. Researchers have also developed a mathematical description of vocal vibrato, the back-and-forth variation in the pitch of a musical note. (4pMU3)
In efforts to monitor the global climate, the Acoustic Thermometry of Ocean Climate (ATOC) experiment will broadcast low-frequency sound waves over long distances in the ocean to measure ocean temperature and other quantities. Concerns have been raised that the sound waves in ATOC may have environmental impacts on marine life. In an effort to assess the impact of ATOC, paper 4aAB7 studies the hearing sensitivities of certain types of dolphins and small whales. The relative effect of the ATOC sound waves will be compared with effects from other sources of noise such as aircraft, pleasure craft, and whales.
Offshore oil workers typically dismantle temporary platform structures by detonating an underwater explosive. Such explosives generate shock waves which can have an impact on marine life and the surrounding environment. Acousticians modelling the blast waves have found that the wave pressure depends more sensitively on the explosive's weight and less on its depth below water than was previously assumed. Understanding these shock waves may help efforts to reduce the size of environmental impact of these explosive charges. (Paper 1aPA5)
Researchers in paper 3pSC1 will describe evidence for a high degree of similarity between the voices of members of the same family. Paper 3pSC2 investigates listener identification of African-American and Caucausian speakers, finding that Caucausian male speakers were most accurately identified by speakers who did not see them, while African-American females were least accurately identified. Paper 3pSC4 is an acoustic study of acted emotions in speech. A whole range of speakers delivered "unique" emotions (such as anger and joy) with vocal characteristics that were generally consistent from speaker to speaker, while "ambiguous" emotions (such as neutrality and nervousness) were delivered in quite different fashions depending upon the speakers.
The compact-disc revolution of the 1980s sparked the demand for speakers that can faithfully reproduce the clarity and range of digital audio. What are the new techniques that are allowing speakers to deliver the highs, lows, crashes and whispers that were once impossible to hear in a living room? Paper 1pEA1 describes the new materials and technologies for state-of-the-art speakers. For example, some speakers now have woofers (the part of the speaker that delivers low tones) that employ ferrofluids, fluids that change their flow properties in response to electric fields. Whereas traditional speakers vibrate in a rectilinear fashion, paper 1aEA5 describes a speaker that produces sound by vibrating in a rotary fashion. Such a design may have inherent advantages over traditional speakers.
Current home theater setups employ 5 or 6 speakers which act as distinct sound sources, compared to the simple two-speaker stereo systems of yesteryear. Paper 2aAA4 describes special design considerations for home stereo, such as the need for more absorptive walls, and careful placement of low-pitched loudspeakers.
Speakers at talk 5aPAa12 will describe a device that employs above-ground loudspeakers to generate sound waves that can be used to detect small objects buried in sand.
Hearing aids have come a long way in the last 30 years, because of improved components and also because scientists better understand what to do (and what not to do) when designing them. For instance, attempts to filter out background noise turned out to be a disaster, because valuable speech information was lost in the process. Paper 2aEA1 reviews the progress in hearing aids over the last several decades. Paper 2aEA2 describes the completely-in-the-canal (CIC) hearing aid, the smallest hearing aid available today. Paper 2aEA6 discusses micromachined silicon microphones for hearing aids.
Meeting abstracts may be viewed at the location http://asa.aip.org/abstracts.html for those with access to the Web. (Note: This link presently contains abstracts for the 131st meeting.)
For more information during the meeting, contact Elaine Moran (elaine@aip.org) at the ASA registration desk, 314-241-7400. For information before the meeting, contact Ben Stein at bstein@aip.acp.org or 301-209-3091. Return to 130th Meeting Archive Return to ASA Press Room