Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Animal Science (Animal, Dairy, and Poultry Sciences)

First Advisor

John K. Cullen, Jr


Prior exposure to moderate-level acoustic stimulation (conditioning) can reduce and/or prevent the deleterious effects of subsequent higher level exposures (Canlon et al., 1988; Campo et al., 1991). Both continuous and interrupted schedules of moderate-level noise have been used as conditioning exposures, and both schedules have been effective in providing protection against subsequent noise trauma. However, there is evidence to suggest that continuous noise exposures are more damaging to the cochlea than interrupted exposures of equal acoustic energy (Bohne et al., 1985, 1987), and moderate-level continuous and interrupted noise exposures differ in the pattern of auditory sensitivity change that they produce over time (Carder and Miller, 1972; Miller et al., 1963). A question arises as to whether there are differences in the amount of protection afforded by prior conditioning of the auditory system with moderate-level continuous or interrupted noise. The purpose of this study was to test the hypothesis that differences exist in the amount of protection provided by prior sound conditioning with continuous vs. interrupted, moderate-level noise. Differences were determined by monitoring the changes that occurred in distortion product otoacoustic emission amplitude growth functions subsequent to a traumatizing noise exposure in guinea pigs which had been conditioned with either continuous or interrupted noise of equal acoustic energy. Results suggest that there are significant differences in the degree of protection provided by prior sound conditioning with the continuous and interrupted schedules of moderate-level noise used in this study. Specifically, the interrupted conditioning protocol appears to afford some degree of protection against the damaging effects of the traumatizing noise exposure. However, the frequency region that is protected is limited to frequencies above the noise exposure band. Conversely, there is a lack of any consistent and sizable protective effect found across the entire test frequency range for the continuous sound conditioning protocol. Given the disparate findings of this and other studies, it appears that the protective role of sound conditioning with moderate-level noise is not a straightforward phenomenon and is highly dependent on the noise exposure conditions, animal species, and response measurements studied.