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Hearing protector labeling for active noise reduction devices.

Authors
Murphy-WJ; Franks-JR; Behar-A
Source
J Acoust Soc Am 2004 Oct; 116(4):2595
NIOSHTIC No.
20045254
Abstract
The US EPA regulation 40 CFR part 211b does not specify how to label hearing protectors that use active noise reduction(ANR). Real-ear attenuation at threshold (REAT) measurements are appropriate for testing the passive noise reduction performance of the earmuff. The contribution of ANR to the overall attenuation must be measured either with an acoustic test fixture (ATF) or using the microphone in real ear (MIRE) technique. ATFs must adequately mimic the coupling of the protector with either the skin of the ear canal or the side of the head, as well as provide sufficient attenuation to eliminate effects of bone conduction. The MIRE technique uses a miniature microphone positioned in the ear canal either at the entrance or at the tympanic membrane, and can be used to measure the insertion loss between the occluded and unoccluded conditions for both the passive and active modes of the protector. ATF and MIRE measurements made for several protectors demonstrate effective performance below 1000 Hz. This paper will examine methods for combining ATF and MIRE measurements with REAT to develop effective and informative rating for the ANR class of hearing protectors.
Keywords
Laboratory-testing; Impulse-noise; Acoustical-materials; Acoustical-measurements; Acoustics; Shock-waves; Sound; Sound-analyzers; Sound-propagation; Ear-protection; Ear-protectors; Hearing-protection; Noise-analysis; Noise-levels; Noise-sources
Contact
William J. Murphy, Hearing Loss Prevention Team, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 1090 Tusculum Ave., Mailstop C-27, Cincinnati, OH 45226-1998
CODEN
JASMAN
Publication Date
20041001
Document Type
Abstract
Email Address
wjm4@cdc.gov
Fiscal Year
2005
NTIS Accession No.
NTIS Price
Identifying No.
M102014
Issue of Publication
4
ISSN
0001-4966
NIOSH Division
DART
Source Name
Journal of the Acoustical Society of America
State
OH; IN; AL
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