Effects on Threshold Sensitivity of Exposing the Normal Ear to Pure Tones and White Noise over Sensation Levels of 10 db to 100 db

By means of a modified Békésy Audiometer, with which it is possible to measure a temporary threshold shift (TTS) resulting from a sound exposure within a few seconds after termination of the stimulus, it was found that: (1) measurable shifts occur after 10 db sensation level (SL), 10 second exposures; (2) greater shifts occur for the exposure tone following 20 db SL one-minute exposures than comparable shifts following 80 db SL one-minute exposures; (3) at low intensity level exposures the greatest shift occurs for the exposure frequency. At progressively higher intensity level exposures a shift develops for frequencies progressively higher than the exposure frequency until at relatively high exposure intensity levels the maximum shift develops for frequencies from one-half to one octave above the exposure frequency; (4) low intensity level white noise exposures result in significant shifts for white noise but negligible shifts for pure tones. Relatively high intensity level white noise exposures result in significant shifts for both white noise and pure tones.