Temporary threshold shift from short-duration noise bursts.
Ear Hear 1975 1(1):4-10
The temporary threshold shift (TTS) caused by repeated short duration noise bursts lasting less than 1 second was studied. Eleven volunteers, aged 20 to 31 years, participated in the study. Each subject received a total of 21 separate noise exposures of 12.5, 50, 200, 800, and 3750 milliseconds (msec) duration. In the first experiment the different burst durations were employed at each of several noise on fractions, holding level and duration of exposure constant, in an effort to determine whether TTS produced by these intermittent noises followed the so called on fraction rule. The on fraction rule correctly predicted TTS for burst durations of 200msec and shorter for on fractions of 0.25 and greater. Exposures to noise with burst durations of 800 msec and greater produced less TTS than predicted. More than the predicted TTS was produced by noise bursts shorter than 200msec for the 0.125 on fraction, particularly for the 50msec burst duration. In the second experiment the subjects were exposed to low and high frequency octave bands of interrupted noise, each with a burst duration of 50 msec and off times ranging from 50 to 650msec. TTS increased markedly as a function of off time for noise off times greater than 150msec for the low frequency exposures, reaching a maximum at 550msec. For the high frequency noise this increase was not as marked.
NIOSH-Grant; Noise-induced-hearing-loss; Noise-exposure; Impulse-noise; Hearing-threshold; Sensory-thresholds; Humans
Otolaryngology U of Minnesota Box 461 Mayo Minneapolis, Minn 55455
Ear and Hearing
University of Minnesota Minneapolis, Minneapolis, Minnesota