Abstract
Currently used threshold audiograms fail to detect the early stages of noise-induced hearing impairment. Threshold shifts may reach 10 to 15 dB before the impairment is detected. Loudness difference limen and critical band phenomena may provide an earlier and more sensitive test for such hearing impairment. Data is reported which shows that the difference limen shift (DLS) due to noise persists longer than temporary threshold shift (TTS). These findings suggest that DLS may be a more feasible tool for industrial use than either TTS or monitoring audiometry.