Fluctuations in susceptibility to noise-induced temporary threshold shift as influenced by the menstrual cycle.

The relationship between the menstrual cycle and changes in HTL and in TTS (from exposure to "magenta" noise at 115 dBA for 10 min) was studied bidaily over 40 days in 9 normal-hearing (HTLs less than or equal to 15 db at .5-8 kc/s) aged from 20-30 years. All HTLs pre- and post-exposure were estimated from interrupted-tone, fixed-frequency Bekesy tracings. The analysis used was a technique developed to study such biological rhythms, a least-squares regression to a cosine function. An F ratio from the bivariate normal distribution was used to evaluate whether significant fluctuations across sessions occurred either in pre-exposure HTLs (2-8 kc/s) or in TTS (2,3,4, and 6 kc/s). No effects were frequency-dependent. For the pre-exposure HTLs 24 of 63 total measures showed a significant (p less than .05) fluctuation, ranging from 1.6 to 6.8 db. For the TTS data, 14 of 36 measures showed a significant fluctuation, ranging from 2.4 to 9.1 db. In general, pre-exposure HTLs were highest (poorer hearing) and TTS was least during menses.