The effects of continuous versus interrupted noise exposures on distortion product otoacoustic emissions in guinea pigs

Distortion product otoacoustic emissions (DPOAE) were measured serially in guinea pigs before and following 4-h exposures to a half-octave band of noise centered at 6 kHz, Stimulus parameters used to elicit the DPOAE were f(2)/f(1) = 1.26 and L(2) = L(1)-10. The 80 dB SPL exposures resulted in attenuation of emissions, which was maximal at the frequency one-half octave above the exposure when referenced to the f(2) stimulus, and which recovered back to baseline after 2 days. The 90 dB SPL exposures resulted in a permanent deficit in emissions elicited by high-frequency stimuli, as measured after 8 days of recovery. A statistically significant difference was also found between animals exposed continuously for 4 h versus animals given two 2-h exposures separated by a 1-h break. Measures of f(2)-f(1) and 3f(1)-2f(2) indicated that they were more sensitive than 2f(1)-f(2) to alterations in cochlear function after noise exposure.