Distortion product otoacoustic emission (DPOAE) input/output functions and the influence of the second DPOAE source.
Distortion product otoacoustic emissions (DPOAEs) at 2f1-f2 (f2/f1 = 1.2) have two components from different cochlear sources, i.e., a distortion component generated near f2 and a reflection component from the characteristic site of fDP. The interaction of the two sources may negatively affect the DPOAE input/output (I/O) functions that are used to predict either auditory thresholds or the compression characteristics of the basilar membrane. This study investigates the influence of the reflection component on DPOAE I/O functions in a frequency range for f2 from 1500 to 4500 Hz in steps of 18 Hz. A time windowing procedure is used to separate the components from the two DPOAE sources. With decreasing stimulus level, the relative contribution of the reflection component increases. I/O functions from the separated distortion component (DCOAE I/O functions) only show smooth changes in shape and slope with frequency, while "standard" DPOAE I/O functions show rapid changes between adjacent frequencies, indicating a strong influence from the interference with the second DPOAE source. A reduced variability for adjacent frequencies can be seen as well for prediction of hearing thresholds, when using DCOAE instead of DPOAE I/O functions.
Mauermann
Manfred
M
Medizinische Physik, Universität Oldenburg, D-26111 Oldenburg, Germany. manfred.mauermann@uni-oldenburg.de
Kollmeier
Birger
B
D000158:Acoustic Impedance Tests; D000328:Adult; D001309:Auditory Threshold; D003051:Cochlea / Q000502:physiology*; D006316:Hearing Loss, High-Frequency / Q000503:physiopathology; D006801:Humans; D008875:Middle Aged; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors