Temporary Threshold Shift Produced by Exposure to High-Frequency Noise

The temporary threshold shift at two minutes (TTS2) produced by exposure to high-frequency noise has been measured in a group having normal hearing. The noise source was filtered white noise. Peak frequencies used were at 16, 19, and 28 kilohertz (kilocycles per second). Sound pressure levels ranged from 85 to 100 dB. Eleven different combinations of spectra and sound pressure levels were tested. The results indicate that significant TTS2 can be produced at 6000 hertz by high-frequency noise at 100-dB over-all sound pressure level if the noise source contains lower-frequency components in the 10- to 12-kilohertz range which are below 80-dB sound pressure level. Noise at this same level without the lower-frequency components appears to improve hearing temporarily. The need for more definitive studies is indicated.