Over 1,000 papers will be presented at the meeting of ASA, the largest scientific organization in the United States devoted to acoustics, with over 7,000 members worldwide.

Here are some highlights from among the many papers being given at the meeting. Full abstracts of the papers mentioned below can be viewed by typing in the last name of the author or the appropriate paper code at the ASA Meeting Abstracts database.

(The first number of the paper code indicates the day of the talk, with "1" denoting Monday, "2" denoting Tuesday, and so on, up to "5" for Friday.)

Concert Halls And The First 80 Milliseconds

In a concert, the sound that goes directly from musical instruments to a listener's ear only gives part of the acoustical experience: The reflections of the sound from the various surfaces in the hall are greatly important. Conventional wisdom dictates that the most important reflections for determining sound quality of a concert hall occur in the first 80 milliseconds (thousandths of a second) after the direct sound.

John Bradley of the National Research Council of Canada will discuss why these early reflections have been considered so critical.(1pAA1)

Tor Halmrast of Statsbygg, a government building consultant in Norway, points out that reflections produce colorations in the sound which might be used for desirable effects in various instruments and registers of sound. (1pAA7)

Acoustical consultant Richard H. Talaske will cite numerous building spaces in which most of the sound one hears is a reflection, rather than direct sound; surprisingly, good speech intelligibility can sometimes be achieved in these cases, when much of the sound that one hears is a reflection. (1pAA9)

Session 2aAAa will contain over 100 poster presentations, each devoted to a different concert hall around the world, from Chicago to Kuala Lumpur, Malaysia. At session 4aAA, attendees will embark on a walking tour to three notable Chicago theaters: the Auditorium Theater, the Oriental Theater and the Goodman Theater. A technical discussion will take place at each stop.

Sonochemistry Products From Single Bubbles

Using simple laboratory equipment, scientists can focus sound waves into a tiny space and convert it into a pulse of light. In a process known as sonoluminescence, researchers aim ultrasound waves at a water tank to create bubbles which collapse and release a flash of light.

In a closely related process, known as sonochemistry, the collapsing bubbles perform chemical tasks such as breaking down hazardous chemicals to simpler, nonhazardous molecules and creating nanometer-scale biomaterials.

Sometimes sonoluminescence and sonochemistry happen together, but the difficulties of observing the collapsing bubbles makes the details of each process very difficult to elucidate. Now, Yuri Didenko and Kenneth Suslick of the University of Illinois at Urbana-Champaign have studied sonoluminescence in a single bubble and measured, for the first time, yields of hydroxl (OH) molecules and nitrite ions. Such information can help researchers understand the nature of cavitation (bubble formation) and the origin of single bubble sonoluminescence. (2aPAa4)

Number Sequences For Physics, Engineering And Art

Sequences of numbers are not just abstract mathematics; they have unexpected and practical uses in many areas of science and engineering, including acoustics. Foremost among these, according to Manfred R. Schroeder of the University of Goettingen, are maximum-length sequences, which are essentially semi-random sequences of pulses.

Schroeder will explain how such pulses can help measure concert hall acoustics, the general theory of relativity (by measuring radar echoes from planets), the travel times of deep-ocean sound waves (for monitoring ocean temperature), and improving synthetic speech and the sounds associated with computer music. (3aSP1)

Other talks at the session will concentrate upon the application of number sequences to architectural acoustics (3aSP2) and sound-based pollution monitoring in the atmosphere. (3aSP10).

Maxwell's Acoustics

One of the greatest physicists of all time, nineteenth-century Scottish physicist James Clerk Maxwell, is known mainly for developing the equations that united electricity and magnetism into a single framework, which still provides many important applications in electronics and other areas.

Much less known are Maxwell's important contributions to acoustics, some of which will be brought to light at the ASA meeting by Philip Marston of Washington State University.

In the kinetic theory of gases, which explained gas behavior in terms of atoms and molecules, Maxwell stated that he intended to address propagation of sound. He never published this in his subsequent papers, but he did examine the relationship between the speed of sound and an average or "root mean square" speed of atoms and molecules in gases.

This was communicated to a colleague who published this result in a subsequent manuscript. Marston has also found some less-known contributions of Maxwell, who refereed the manuscripts of journals which published the papers of many world-class acousticians. Some manuscripts became classics in the field. He also suggested the title for Lord Rayleigh's widely known tome, "The Theory of Sound." (4aPA1)

(Editor's Note: These descriptions were prepared by Ben Stein, Rory McGee and James Riordon of the American Institute of Physics in cooperation with the Acoustical Society of America. UniSci is pleased to have been allowed to utilize them.)

[Contact: Ben Stein]

24-May-2001