Temporary Threshold Shift in Hearing from Exposure to Different Noise Spectra at Equal dBA Level

The intent of this study was to determine whether sound‐level measurements in dBA could adequately depict harmfulness to hearing from exposures to noises differing widely in spectra. Each of 11 male listeners, aged 20–26 yr, were exposed on two separate occasions to three noises whose spectral slopes were −6, 0, and +6 dB per octave band. All such noises were presented for 30 min via an earphone at 100 dBA. Analyses of variance of the post‐exposure threshold data (corrected to 2 mm, TTS2) found insignificant differences due to the spectral variations for both test and retest conditions as averaged across audiometric frequencies 250–8000 Hz. Interactive effects between spectra and test frequencies were significant, the −6 and 0 dB spectral conditions causing relatively more TTS2 at frequencies below 3000 Hz, and the +6 dB spectrum more TTS2 at frequencies above 3000 Hz. Implication of results for noise‐hazard rating schemes using dBA measures are noted.