Effects of background noise on earphone thresholds.

Real-ear attenuation at threshold (REAT) and monaural pure-tone thresholds were determined for normally hearing adults using a supra-aural, Audiocup, and insert earphone. The thresholds were obtained in quiet and in background noises approximating the maximum permissible ambient noise levels (MPANLs) allowed in an audiometric test room specified by ANSI S3.1-1991 and OSHA (1983). The supra-aural REAT was less than the Audiocup, which was less than the insert earphone. The mean threshold shifts were negligible regardless of earphone type in the ANSI noise and for the insert earphone in the OSHA noise. Thresholds can be obtained down to 0 dB HL in ANSI 1991 MPANLs using a supra-aural, Audiocup, or insert earphone and in OSHA MPANLs using an insert earphone. However, the OSHA MPANLs are too high and the REAT is too low for a supra-aural earphone and Audiocup for testing down to 0 dB HL.