ASA 124th Meeting New Orleans 1992 October

4pPPa9. Normal hearing levels for noise-reducing earphone types.

Tom Frank

Donna M. Magistro

Dept. of Commun. Disord., Penn State Univ., 5-A Moore Bldg., University Park, PA 16802

This study determined normal hearing levels (HLs) and intrasubject threshold reliability for supra-aural earphones housed in noise-reducing enclosures. Monaural thresholds were obtained for 25 normally hearing adults from 500 to 6000 Hz over four trials separated by 1 but no more than 7 days using a typical supra-aural (TDH-49P) and four supra-aural (TDH-39 or 49P) earphones housed in an Auraldome, Audiomate, Madsen, and Audiocup noise-reducing enclosure. The output of the supra-aural and each supra-aural earphone normally housed in a noise-reducing enclosure was measured on a NBS 9A coupler so that the thresholds could be referenced to normal threshold sound-pressure levels (SPLs) re: ANSI S3.6-1989. Within each trial the thresholds approximated 0 dB HL for each earphone type at each frequency except for the Audiomate where thresholds were elevated by as much as 28 dB at 500 and 10 dB at 1000 Hz. Further, the Audiocup and Auraldome thresholds were consistently lower than the typical supra-aural earphone. Between trials the thresholds were consistent (reliable) for each earphone type. Implications regarding reference threshold SPLs for supra-aural earphones housed in noise-reducing enclosures, threshold reliability, and use in industrial hearing testing programs will be discussed.