Figure 7.

Regression analyses were applied to parse the effects of age and audiometric status on distortion OAE compression threshold. (A-D) Significant correlations between age and compression threshold were present at four f₂ frequencies after the variance in audiometric thresholds (defined as a pure tone average, or PTA, of 0.5, 1 and 2 kHz) was controlled; the older the subject, the higher the compression threshold. However, this low-mid-frequency PTA does not capture the audiogram differences between younger and middle-aged ears; hence, a high-frequency audiometric PTA of 2, 4, and 8 kHz was applied and the regression repeated. (E, F) Significant correlations remained at two frequencies (f₂ = 2607 and 7394 Hz) after controlling for the variance accounted for by differences in high-frequency audiometric thresholds.