Brainstem-evoked responses of guinea pigs exposed to high noise levels in utero.

Pregnant guinea pigs were exposed to loom room noise at 115 dB A for 7.5 hr/day for various periods during the last one-third of pregnancy. When the hearing of their offspring was tested by auditory brain stem-evoked response techniques at 6-dB intervals, peak IV latencies of exposed pups were found to be significantly longer than those of otherwise similar control pups. The latency differences corresponded to a 5-dB increase in stimulus at medium stimulus levels and 10-12 dB near threshold. The results indicate that it is possible for noise-induced loss to occur in utero in mammals whose auditory maturation process is complete, or nearly so, before birth.