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and natural. Physical measurements, such as A-weighted sound levels, provide only a partial characterization of an acoustical environment. To interpret noise annoyance or shape the subjective impression of a space, sociological and psycho- logical aspects must also be considered (Schulte-Fortkamp, 2002).
Work continues on improved noise control solutions. Examples of passive approaches currently being examined are the “drum silencer” to reduce the noise in ducts (Choy and Huang, 2002) and the absorption of noise using micro- perforated panels, the topic of a special session at the Spring 2006 ASA meeting in Providence. Active noise control, hav- ing moved beyond the initial hype, is now a mature field with an expanding number of applications. Noise reduction head- sets are now in common use on airplanes. An article by Kemp and Clark (2003) discusses how active control can reduce noise levels in a rocket fairing.
Thus, in the field of noise and its control, there has been steady progress on many fronts. There have been notable achievements for improved classroom acoustics, although continued efforts are required to achieve its widespread acceptance. But the world continues to be a noisy place. We’re not done yet.AT
References for further reading:
Beranek, L. L., and Lang, W.W. (2004). “The Acoustical Society of America’s contributions to the field of noise and its control,” in ASA at 75, edited by Henry E. Bass and William J. Cavanaugh (Acoustical Society of America, Melville, NY).
Choy, Y. S., and Huang, L. (2002). “Experimental studies of a drum- like silencer,” J. Acoust. Soc. Am. 112, 2026-2035.
Kemp, J. D., and Clark, R.L. (2003). “Noise reduction in a launch vehicle fairing using actively tuned loudspeakers,” J. Acoust. Soc. Am. 113, 1986-1994.
Lubman, D. (2005). “The classroom amplification challenge to ANSI S12.60-2002,” Acoustics Today 1(1), 33.
Nelson, P. B. (2005). “The ASA classroom acoustics effort,” Acoustics Today 1(1), 28-32.
Schulte-Fortkamp, B. (2002). “Soundscapes and living spaces: Sociological and psychological aspects concerning acoustical environments,” paper NOI-07-02 in Forum Acusticum Sevilla, posted at http://www.ia.csic.es/Sea/sevilla02/noi07002.pdf.
Michael R. Stinson is the past Chair of the Technical Committee on Noise and a Fellow of the ASA. He received B.Sc.(hon) and M.Sc. degrees in Physics from Simon Fraser University (Burnaby, BC) and his Ph.D. in Physics from Queen's University (Kingston, ON). In 1979, he joined the National Research Council of Canada where he is
currently leader
Acoustics and
Processing group.
research areas include the acoustics of the external and middle ear, sound propagation in porous materials, outdoor noise propagation, microphone arrays, and hearing aid feedback.
of the Signal His
Technical Committee on Noise 39