CLINICAL-SIGNIFICANCE OF PROBE-TONE FREQUENCY RATIO ON DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS

Parametric variations in the ratio of primary-tone frequencies were ex plored to optimize the amplitude of the 2f1-f2 distortion product otoa coustic emission for clinical purposes. Ten ears from 5 normally heari ng human subjects were examined with primary tones geometrically centr ed around the standard audiometric frequencies of 0.5, 1, 1.5, 2, 3, 4 , 6 and 8 kHz. The distortion product at the frequency 2f1-f2 (f1 < f2 ) was measured at six probe tone frequency ratios (f2:f1) varying betw een 1.15 and 1.40 using equal level primaries of 75 dB SPL. The result s showed that a single f2:f1 ratio between 1.20 and 1.25 provides a re asonable value for clinical use in that it optimizes the magnitude of the distortion product at 2f1-f2, provides for sufficient resolution i n the test frequency range, and is applicable to the standard clinical test frequencies.