Assessment of cochlear effects and extra-auditory disorders in male rats exposed repetitively to low noise.

BACKGROUND: The noise is considered as a factor of environmental stress, causing a wide range of health effects such as acoustic, cardiovascular, nervous and endocrine systems. PURPOSE: The present study was conducted to examine the affects of repeated exposure to noise on the peripheral auditory system, adrenal gland and heart tissue. METHOD: The White strain rats "Wistar" were exposed to chronic and repetitive exposure noise at two different intensity levels of 70 and 85dB (A). The noise level was generated by the Audacity® software to an octave-band noise (8616 kHz). The sound exposure duration was 6 hr/day, 5 days per week for 3 months. Quantitative and qualitative investigations were performed by using electron microscopy. The ganglion neuron counting was examined via light microscopy. RESULTS: The results show that exposure to sound intensities 70 and 85 dB (A) for long periods, lead to changes in the morphological structure of the cochlea (inner ear), adrenal cortex and cardiac tissue which involve cell disruption which over time can lead to pathological effects. CONCLUSION: This study provides morphological evidence that repetitive exposure noise at moderate sound levels to 70 and 85 dB (A) induces changes in the peripheral auditory system, the adrenal cortex and heart tissue.