Average thresholds in the 8 to 20 kHz range as a function of age

The sound-pressure thresholds at the extended high frequencies of 8-20 kHz were measured for 65 normal subjects aged between 10 and 69 years. The results are not unlike those obtained by previous investigators. The thresholds increased gradually as a function of frequency, except around 12 kHz and above 19 kHz, and also as a function of age. To clarify the connections between threshold, frequency and age, we introduced the regression lines for the threshold by analysing two ranges of frequencies (8-10 kHz and 14-19 kHz) and determining their slopes and intercepts. The regression line analysis reveals that the thresholds at 8-10 kHz tend to increase more at higher frequencies as subject age increased above 30 to 39 years, and those at 14-19 kHz increase translationally with increase of age. Our results did not contradict earlier reports on the pathological changes of the inner ear.