Phase-dependent suppression of transient evoked and distortion product otoacoustic emissions by a low-frequency tone.
The subjective recording of the masked threshold of short acoustical stimuli with a loud tone of 30 Hz (phase audiogram) has been used for the clinical diagnosis of endolymphatic hydrops (EH). In normally-hearing subjects, a marked modulation of the threshold was found, depending on the phase of the low-frequency tone. A very small dependence was found in patients with Menière's disease, due to the micromechanical changes in the basilar membrane (BM). The same phase relationship becomes apparent in low-frequency suppression of otoacoustic emissions. The amplitudes of TEOAEs are controlled by the phase-dependent displacement of the BM. The suppressed TEOAEs have to be measured separately in each phase relationship. During recording of suppressed DPOAEs, the low-frequency suppressor is permanently superimposed on the pair of primary tones. After time averaging and a moving short-time FFT, the spectral values of the DPOAEs are obtained depending on the phase of the low-frequency tone. Modulation depends also on the masker level, the levels of the primary tones, and on their frequency range. The method of low-frequency suppressed DPOAEs is an objective method to diagnose EH and could be a useful tool in human inner ear research.
Scholz
G
G
ENT Department, Charité, Campus Virchow-Klinikum der Humboldt Universität zu Berlin, Germany.
Mrowinski
D
D
Hensel
J
J
D000161:Acoustic Stimulation / Q000379:methods*; D001301:Audiometry, Pure-Tone / Q000379:methods; D001309:Auditory Threshold / Q000502:physiology; D001489:Basilar Membrane / Q000503:physiopathology; D001696:Biomechanical Phenomena; D006309:Hearing / Q000502:physiology; D006801:Humans; D008575:Meniere Disease / Q000175:diagnosis / Q000503:physiopathology; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D010470:Perceptual Masking; D012720:Severity of Illness Index