AMBIENT NOISE-LEVELS IN INDUSTRIAL AUDIOMETRIC TEST ROOMS

In 1983 the Occupational Safety and Health Administration (OSHA) speci fied maximum permissible ambient noise levels (MPANLs) that would allo w valid hearing threshold measurements in an audiometric test room. Ho wever ambient noise sound pressure levels (SPLs) in rooms used for ind ustrial hearing tests are unknown. The present study reports octave ba nd (125 to 8000 Hz) ambient noise SPLs measured in 490 single-walled p refabricated audiometric test rooms located in industrial settings tha t were obtained from eight sources. The ambient noise SPLs were highes t in the lower frequencies and decreased as frequency increased. All 4 90 rooms met the OSHA MPANLs. Fortunately, the ambient noise SPLs were considerably lower than the OSHA MPANLs, since previous research has demonstrated that hearing thresholds cannot be obtained down to 0-dB H L in a test room having ambient noise levels equal to the OSHA MPANLs. In fact, 33%, or 162 of the 490 test rooms, met the more stringent MP ANLs recently specified by the American National Standards Institute ( ANSI) for industrial hearing testing. Given that the OSHA MPANLs are t oo high and that the test room ambient noise SPLs were considerably le ss than the OSHA MPANLs, that authors recommend that the OSHA MPANLs b e revised to the more stringent ANSI 1991 MPANLs so that hearing thres holds for baseline and annual audiograms can be measured down to 0-dB HL.