Acoustic reflex growth in the aging adult.

Growth in amplitude of the acoustic reflex to filtered noise and tones of 500, 1000, and 2000 Hz was measured with an aural acoustic-admittance meter in 30 persons between the ages of 20 and 79 years. Although thresholds of the acoustic reflex did not vary significantly across the age range of the subject sample, the rate of growth in amplitude decreased linearly with increase in age decade. Given information on the aging of structures in the acoustic reflex pathway, the growth data are interpreted tentatively to mean that the contractual capacity of the stapedius muscle is diminished in older ears.