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Volume 106, Issue 3, September 1999
- PHYSIOLOGICAL ACOUSTICS 
106(1999); http://dx.doi.org/10.1121/1.427145View Description Hide Description
Most published data comparing the amplitudes of transient evoked otoacoustic emissions (TEOAEs) and bi-tonally evoked otoacoustic emissions (DPOAEs) indicate a low level of correlation, raising the question to what extent do the two responses share the same relationship with hearing function. However, DPOAE intensities are sensitive to stimulus parameters and comparisons with TEOAE have mostly been made with the specific range of DPOAE parameters found to optimize DP output level. To determine if other DPOAE stimulus parameter domains give closer correspondence between TEOAE and DPOAE characteristics, and DPOAE intensity and phase measurements were made across a sample 1/2-octave frequency range centered on 2 kHz in nine normally hearing subjects using a wide range of stimulus parameter configurations. The DP fine structure was resolved by detailed measurements and the mean DP levels were compared to those in the corresponding frequency range from TEOAE measurements obtained with the same probe fitting. The closest relationships between TEOAE and DPOAE amplitude were obtained with the smallest DPOAE stimulus frequency ratios and with lower DPOAE stimulus levels. For these conditions, the DPOAE intensity for individuals in this subject group could be predicted from TEOAE with a standard deviation of 1 dB, similar to the test–retest difference. The DPOAE phase versus frequency gradients for fixed corresponded closely with phase gradients in TEOAE data when a small DP primary stimulus frequency ratio was used. They differed markedly at wider frequency ratios. In contrast, DP phase agreement with TEOAE was good for all stimulus parameters, where measurable. These data suggest that the detailed mechanism of TEOAE and all DPOAEs is very similar when close stimulus tones are used to stimulate DP's. Significant divergence exists with the DP with the wider stimulus ratios typically employed for clinical testing. The reasons are discussed.