Melville, New York, November 1, 2002
Sound is universal, from the first detectable signals of the Big Bang to the complex songs of whales. Sound plays an essential part in human history, from music to spoken language to the medical use of ultrasound.
Researchers from around the world will discuss the latest discoveries in sound at the First Pan-American/Iberian Meeting on Acoustics, which will take place from December 2-6, 2002 at the Fiesta Americana Grand Coral Beach Hotel in Cancun, Mexico. The meeting is jointly sponsored by the Acoustical Society of America, the Iberoamerican Federation of Acoustics and the Mexican Institute of Acoustics. Over 1000 papers will be presented.
In work that may lead to improved sterilization techniques, researchers will show that acoustic shock waves can be deadly to microorganisms under the right conditions. The reductions in kidney infections that often follow shock wave lithotripsy (a therapy that breaks up kidney stones with ultrasonic pulses) inspired Achim Loske of the Centro de Fisica y Technologia Avanzada (firstname.lastname@example.org) to study the effect of shock waves on E. coli, listeria, and salmonella bacteria. Loske found that conditions associated with shock waves could significantly reduce the viability of microorganisms (Paper 3aBB5). Small, acoustically generated bubbles, known as cavitation, dramatically improve the effect of disinfectants, according to researchers at Georgia State University and Georgia Tech. In recent studies, mild isopropyl-based disinfectants had little effect on bacterial cultures after exposures as long as 18 minutes. However, 90 percent of bacteria were killed after only a minute of exposure to mild disinfectants in combination with acoustic cavitation and high ambient pressures. The study may lead to more efficient and versatile sterilization; certain surgical instruments, for example, cannot currently withstand the high temperatures of common disinfecting equipment known as autoclaves (Kenneth Cunefare, email@example.com, 4pBB13).
Ancient pyramids, amphitheaters, and megaliths are often visually awesome structures. In recent years, researchers have discovered that many archeological sites are acoustically inspirational as well. Numerous talks on this subject will be presented at session 3aAA, which will be cochaired by David Lubman, firstname.lastname@example.org, who has done some notable work on the bird-chirp-like echoes in the Mayan pyramid Kulkulkan in Mexico. Rock walls, staircases, and chambers can produce complex echoes that make a handclap sound like galloping horses, or create eerie distortions in the sounds produced by instruments or voices. In some cases, unusual acoustics of natural spaces may explain why certain places became sacred to ancient peoples. In others, acoustical responses of manmade structures may have been intentional, perhaps built to add magic and mystery to a holy place. In either case, research suggests ancient peoples were much more in tune with architectural and natural acoustics than previously realized. Talks in session 3aAA explore the remarkable acoustical characteristics of a pre-Columbian amphitheater (papers 3aAA4, 3aAA5, 3aAA8, 3aAA9), the stairways of archeological sites such as Chichen Itza and Teotihuacan (3aAA6, 3aAA7), and megalithic chambers in Ireland (3aAA2), among other sites.
Using the ability of sound to levitate tiny liquid droplets, researchers at Lund University in Sweden have developed a miniaturized analysis system for studying living cells and biochemical reactions in submicroscopic drops. The researchers performed studies of single fat cells in 250-nanoliter droplets. They levitated the drops with sound, and added substances to the levitated droplet with specially developed dispensers. Adding molecules that bonded to the fat cells stimulated the decomposition of the fat cells, leading to fatty acid release and a consequent pH decrease of the surrounding solution. They easily followed pH change by using pH-dependent fluorescing molecules that were continuously monitored by fluorescence-imaging detection. The levitation approach could also be employed for observing how macromolecules such as proteins "nucleate" or coalesce, in ways that are not possible with standard crystallization techniques. As Staffan Nilsson of Lund (email@example.com) will describe, this technique could lead to ideas for optimizing the growth of medically or biologically important materials (2aPA3).
A new study provides a fascinating example of how one organism uses ultrasound in its environment as a counterattack strategy against a predator. Praying mantises have a unique way of hearing. The dragonlike insects have one ear, located in the middle of their chest, that "hears" ultrasound. This comes in handy while they are avoiding bats. The only problem is that praying mantises can't tell the direction from which the bat is coming. Now, University of Maryland psychologist David D. Yager (firstname.lastname@example.org) has found that ultrasound stimulates the praying mantises to perform some quick thinking and complicated maneuvers to avoid bats. Such responses require the central nervous system (CNS) to work overtime. By implanting an electrode on a praying mantis, Jeffrey Triblehorn (Yager's student) was able to measure CNS activity during a bat attack. The CNS was active during the bat's cries when it first began to strike the mantis, but right before the mantis was captured, the electrode measured no CNS activity. Yager suspects that the CNS activity stops as soon as the CNS triggers the mantises' fight-or-flight response. This might also prevent sensory overload to the mantis (3aAB8).
Recent efforts to establish standards for classroom acoustics in the US are based on the realization that noise levels can have a dramatic influence on learning and behavior in children. Exterior play areas are also vital to childhood socialization, informal learning, and environmental awareness. David Lubman (email@example.com) will discuss the benefits of thoughtfully designed educational soundscapes in paper 5aNSb4, with a look at both classroom acoustic standards and novel sonic playgrounds that include sound-focusing structures and transmission channels to stimulate learning, increase sonic awareness, and enhance the enjoyment that children gain from their surroundings.
In efforts that can lead to new kinds of sound insulation, researchers have experimentally demonstrated a new structure called a "tunable phononic band-gap material." Analogous to semiconductors which allow the passage of electrons only within a discrete band of energies, or "photonic crystals" which reject the passage of light over a specific frequency range or gap, a phononic bandgap material can reflect acoustic signals in some frequency ranges, leading to a high level of the sound attenuation. C\151cile Goffaux (firstname.lastname@example.org) and colleagues at the Facult\151s Universitaires Notre-Dame de la Paix in Belgium have fashioned an array of square steel rods that can be turned in order to alter the excluded sound frequencies. Centering their attention upon the practical acoustic range of around 500-1000 Hz, the Belgian researchers believe their system would be able to greatly reduce the noise of certain heat exchangers and air pumps, such as one finds at symphony halls (2pSAb3; background article, Physical Review B, 15 August 2001).
To properly monitor the global climate, and develop reliable climate models, scientists need accurate measurements of rainfall over the world's oceans. Rainfall is an important component of water, heat, momentum and gas transfer between the oceans and atmosphere. But rainfall measurements have been generally unavailable in oceanic regions. After many years of research on the physics of sound production by raindrop splashes, scientists have come up with an acoustic technique for counting rainfall simply by listening to the sound generated by the raindrops splashing on the ocean surface. Since 1999, scientists have been testing "acoustic rain gauges" (ARGs) at sea---and the results have been promising. The University of Washington's Barry Ma (email@example.com) will present 70 months' worth of acoustic data on ocean rainfall, and compare the measurements to other techniques such as satellite-based methods. Among the long-range goals of this project are to provide much-needed rainfall data for global climate models, and to develop the technology so that it could be deployed on a wide variety of ocean-measurement platforms worldwide (2pAO9).
South American dance traditions combine influences from Native American, African, and European cultures. Presenting examples of musical instruments from each of these traditions, Paul Wheeler of Utah State University will describe examples such as the panpipe, from Native American traditions in the Andes Mountains; the berimau, a musical bow used in Brazilian dance; and the bandoneon, an accordion-style German instrument most famous for its use in the tango from Argentina (2pMUb1). Beatriz Ilari of McGill University in Canada (firstname.lastname@example.org) will describe the instruments of Brazilian capoeira, a unique martial art form of Afro-Brazilian origin that combines elements of dance, music, fight, and ritual (2pMUb2). Utah State's Paul Wheeler will present studies of the Brazilian cuica, a drum of African origin that is played in ensembles during the famous Carnival parade in Rio de Janeiro (2pMUb3). Pablo Majilis of the University of Montreal (email@example.com) will discuss the instruments of the different forms of samba, with an emphasis on percussion instruments (2pMUb4) At the end of the session, audience members will have the opportunity to try some of the instruments on hand.
A new microscope design uses sound, not light, to investigate materials. At session 1pBB, Joie Jones of UC-Irvine (firstname.lastname@example.org) will discuss acoustic microscopy, a burgeoning technique that could provide new kinds of medically useful information on biological tissue (1pBB1). Unlike optical microscopy of biological specimens, no staining of tissue is necessary. In the technique, an ultrasound probe makes contact with a tissue sample; researchers then build up an image of the specimen based on how the tissue responds to the ultrasound. Unlike many other microscopy techniques, acoustical microscopy can be performed on living tissue, and even inside the body, with the use of small ultrasound devices. Although the resolution of acoustical microscopy is ultimately limited to the cell level, rather than the molecular level (its maximum resolution is about 0.1 microns, about a hundredth of the width of a red blood cell), it can provide unique information on a biological tissue's physical and mechanical properties, such as Alzheimer's plaques, for example. Also, it can yield quick information on things such as the pathology of skin biopsies, long before other techniques provide information. Yoshifumi Saijo of Tohoku University (email@example.com) and Antonius F. W. van der Steen (firstname.lastname@example.org) of the Erasmus Medical Center in the Netherlands will report on applications of acoustical microscopy to cardiology (1pBB3 and 1pBB4).
CORAL REEF BIOACOUSTICS With their ability to support millions of biological species, coral reefs are one of the most fragile-and important--ecosystems on the planet. Session 1pAB is devoted to acoustical methods for studying biological organisms in the limestone coral structures made by living organisms. Russell E. Brainard of the NOAA Fisheries Honolulu Laboratory and his colleagues will a project to assess, monitor, and protect the coral reef ecosystems of the U.S. Pacific Islands (1pAB12). Limited resources and the large distances between the Pacific Islands prevent constant monitoring of the coral reefs in the islands. However, their project aims to monitor these ecosystems and develop warning systems that can alert scientists to large changes in the reefs or potential threats to them.
Frogs make up some of the acoustically richest species on the planet. Researchers at session 2pAB will announce a host of new discoveries on frog communication. When competing for the attention of a female cricket frog, male cricket frogs change the timing, rate, and length of their mating calls. University of Texas at Austin researchers (Walter Wilczynski, email@example.com, a psychologist, and Michael Ryan, firstname.lastname@example.org, a biologist) found that male frogs took their cues from the timing of other competing male calls instead of the rate or length of the call. When the frogs heard a more aggressive call, they increased their emphasis on the timing of their calls. Wilczynski and Ryan also found that female cricket frogs are attracted to more aggressive calls (2pAB4). In nature, female gray tree frogs will sit near calling mates for many minutes before approaching a male, but in laboratory-based tests, females approached their mate in less than 30 seconds when exposed to calls broadcast by a loudspeaker. What is the difference between "natural" calls and broadcasted ones? Joshua Schwartz (Jschwartz2@pace.edu), a biologist at Pace University, decided to broadcast varied male frog calls (long and short calls) to measure the female's preference and waiting times in nature. Schwartz found that female frogs preferred long calls and that they "waited" an average time of about 2 minutes before approaching a male (2pAB10).
At session 4aNS, researchers will present advances in reducing noise inside airplanes. Buzz-saw noise is sound from engine rotation that passengers hear especially during takeoff and climb. David H. Reed of Boeing (email@example.com) will describe significant recent success in suppressing cabin buzz-saw noise, by strategic placement of acoustic linings in the engine inlet (4aNS5). Gopal Mathur, also at Boeing, will discuss advances in active noise-reduction techniques, in which a loudspeaker produces sound that cancels out noise in an aircraft cabin. Mathur will also discuss a technique, called active structural acoustic control (ASAC), for applying forces directly to the fuselage to eliminate vibrations that produce cabin noise (4aNS1). Gary Gibbs of NASA Langley will discuss real-time, adaptive technology for reducing noise and vibration inside airplanes (4aNS2).
Ventriloquists, like the renowned Edgar Bergen, can't actually throw their voices. Instead, they give the impression that sound is coming from a dummy, such as Bergen's wooden friend Mortimer Snerd, by moving the dummy's mouth in time with words that the ventriloquist speaks. Bergen could speak with minimal lip movement, and as a result audiences tended to associate Bergen's voice with Snerd's moving mouth. Researchers studying ventriloquism in the past showed that increasing the distance between a voice's actual source and its apparent source reduces the realism of the illusion. Now researchers from Tilburg University in the Netherlands have found that the features on the dummy's face are also important. In paper 2aPP6, Ilja Frissen (I.H.E.Frissen@kub.nl) will discuss a series of tests that monitored the perceptions of subjects presented with vocal sounds paired with images of faces that either had their features arranged normally or had their features scrambled to varying degrees. The work can provide insights beyond ventriloquism, offering clues to cognitive function by revealing how people combine visual and acoustical signals to perceive speech.
The Cancun meeting will feature presentations on a wide range of musical instruments. Stephanie Weisser of the Free University of Brussels (firstname.lastname@example.org) will discuss the bagana, a big Ethiopian lyre with ten strings that is played with the voice for prayer and meditation (1pMU8). Didier Demolin of the Free University of Brussels (email@example.com) will talk about a wooden Congo instrument called the Ekonda scraper, which accompanies the remarkably complex polyphonic vocal harmonies of singers in that region (1pMU9). Presenting a multi-disciplinary investigation that starts at archaeological sites in Scotland and Ireland and ends up in the hands of musicians, Murray Campbell of the University of Edinburgh will describe reconstructed versions of ancient Celtic horns, their sounds, and their possible role in ancient times (4pAAa2). Roberto Velazquez Cabrera will discuss Yaxchilan's whistles, ancient Mayan clay whistles that have the shape of frogs and sound like frogs when played (4pAAb3). Other papers in session 4pAAb will discuss lost Mayan instruments and the acoustics of musical instruments from other pre-Columbian cultures in the Americas.
Open-plan office environments are becoming increasingly common around the world, but they can often be very noisy and distracting environments. Minimizing noise and outside speech can help enhance a worker's job satisfaction and performance. Researchers at session 1pAAa will present studies and solutions for maximizing speech privacy in both open- and closed-office environments. Yong Ma Ma of the University of Calgary and colleagues point out that traditional measures of speech privacy in an office assume that English or a Western language is spoken; their study investigates how the use of different languages may greatly influence the speech privacy conditions in an office (4aAAa4). Flavia F. Nogueira of the Federal Univ. of Santa Catarina in Brazil and colleagues will present a computer simulation of 64 workstations in an open plan office, in efforts to investigate the factors that influence speech privacy (5pAAb1).
For hotel guests, a quiet room would seemingly be a minimum requirement for a satisfying stay, but blocking out noise is far from guaranteed, even in the very best hotel facilities. Five-star hotels, with their wide range of facilities such as ballrooms and shopping areas, often face significant challenges in ensuring the quiet rooms that their guests may expect. One- and two-star hotels, which often have very different designs, face acoustical dilemmas of their own. Melvin Saunders of the Dallas consulting firm Pelton Marsh Kinsella (firstname.lastname@example.org) will discuss major sources of noise in each of these hotel types, and suggest techniques and methods to produce acoustically successful hotel projects (1pAAb1). Hotel guests usually worry about television noise and conversations from adjoining rooms, but another significant source of noise is "structure-borne" sound, coming from such places as mechanical rooms, laundry rooms and the like. Acoustical consultant George Paul Wilson will discuss guidelines for reducing this noise (1pAAb2). Perhaps one of the most prevalent kinds of hotel noise is the low-frequency thumps of footfalls on both carpeted and hard-surface floors. While this problem has eluded solution for a long time, John LoVerde of Veneklasen Associates in California will describe new ways of modifying existing hotel construction that suggest "there may be practical solutions to this longstanding problem" (1pAAb3).
Other sessions at the meeting include: guitar acoustics; Pan-American noise standards; automatic speech recognition; development of acoustics programs in Latin America; music buildings in Latin America; studies of speech and hearing; global monitoring using infrasound; hearing protection; environmental noise planning and legislation.
These items were prepared by James Riordon, Ben Stein, Emilie Lorditch, and Phil Schewe of the American Institute of Physics in cooperation with the Acoustical Society of America.
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