Page 63 - Summer 2015

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the exposure risk for the protected ear. The equivalent en- ergy method applies the impulse peak insertion loss metric to reduce the free-field exposure to account for the hearing protector. The model-based method applies a distributed- element acoustic representation of the hearing protector to account for transmission through the protector, vibration of the protector, and leakage around the protector. Although the new MIL-STD 1474E is an advance over assigning all protectors a 29-dB reduction, much more research needs to be conducted to validate the performance of hearing protec- tion models in the presence of high-level impulse noise.
Hearing protection is another area where TCN members have advanced our understanding of noise. Over the past several years, various manufacturers have developed fit- testing systems that are fast and accurate assessments of the attenuation an individual receives from his or her HPD. Through the collaboration of manufacturers, government laboratories, academia, and commercial testing laboratories, the American National Standards Institute (ANSI) S12 Ac- credited Standards Committee for Noise is developing the first standard test method for assessing the personal attenua- tion rating (PAR) of an HPD. Unlike the noise reduction rat- ing (NRR) that is published on the label of every protector, the PAR tells the user how well she/he has fit the product. Methods to measure PAR range from transmission loss mea- surements with probe tube microphones to psychoacoustic paradigms utilizing stimulus detection or loudness balance. The HPD fit-testing standard will standardize how the PAR is calculated and allow employers to determine whether their workers are adequately protected when exposed to po- tentially harmful noise.
Although the TCN is not one of the largest technical com- mittees within ASA, it is a strong and vibrant community that is focused on many interesting and important problems that affect our society. Many of these problems are interdis- ciplinary in nature, which leads to collaborations by mem- bers of the TCN with other subdisciplines within acoustics as well as with others outside the ASA. A quick look at the recipients of ASA awards who are members of the TCN re- veals a list of names of talented and respected acousticians who have contributed to the strength of the discipline and the strength of ASA (Richard Lyon, Keith Attenborough, Michael Stinson, and Gilles Daigle to name a few). There has also been a healthy influx of young talented members of the ASA to the TCN, ensuring that the future of the TCN looks to be bright indeed. It is a wonderful opportunity to associ- ate with all of the TCN members.
Disclaimer: The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention or the National Institute for Oc- cupational Safety and Health.
Biosketches
Scott Sommerfeldt is a Professor of Physics and dean of the College of Physical & Math- ematical Sciences at Brigham Young Univer- sity. He is the former chair of the Technical Committee on Noise and has an active re- search program focused on the areas of active noise control and energy-based acoustics.
William J. Murphy is a Captain in the
United States Public Health Service Com-
missioned Corps and is the coordinator
of the Hearing Loss Program for the Na-
tional Institute for Occupational Safety
and Health in Cincinnati. He is a Fellow
of the Acoustical Society of America, the
chair of the Technical Committee for Noise, and the former chair of the ASA’s ANSI S12 accredited standards committee on noise. He and his wife, Debbie, have three children. He enjoys music and teaching physics and computer program- ming for homeschooled students in Lawrenceburg, Indiana.
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