Aging and middle ear function in rhesus monkeys (Macaca mulatta).

This study provided tympanometric data on rhesus monkeys (Macaca mulatta) and more support for this monkey as a good model for human peripheral auditory function. There have been few published reports concerning middle ear function in rhesus monkeys, and these experiments addressed that need. In the first experiment, peak acoustic admittance (Ytm) and ear-canal volume (Vea) were measured in 17 older adult monkeys and 16 younger adult monkeys. In the second experiment, middle ear resonance frequency was measured in eight younger adult monkeys and four older adult monkeys. Overall, peak Ytm, Vea, and resonance frequency were similar for monkeys and humans. Specifically, peak mean Ytm and mean Vea in monkeys were comparable to those values in human children. There was a trend for older monkeys to have decreased peak Ytm and Vea, but these trends did not reach statistical significance. There was a significant sex effect similar to what has been reported in humans. Male monkeys had larger peak Ytm values and larger Vea values compared with female monkeys regardless of age. Finally, there were no significant age or sex effects on resonance frequency.