Suppression of tone burst evoked otoacoustic emissions in relation to frequency separation.
Tone burst evoked otoacoustic emissions (TBEOAEs) were measured for two tone bursts presented separately and as a two-tone burst complex to examine the linearity of TBEOAE generators for different frequency separations of the stimuli. The stimuli were: (a) tone bursts of 5-ms duration and center frequencies of 1, 1.5, 2 and 3 kHz; (b) complex stimuli with the 1-kHz tone burst combined digitally with each of the other specified tone bursts. Signals were delivered at 70 dB SPL using a non-linear processing method and at 60 dB SPL using a linear method to 21 ears of normally hearing adults. Spectra of TBEOAEs obtained with single-tone bursts were superimposed (composite) and compared to those of the two-tone burst complex. A close correspondence between the composite and complex spectra was present in all ears. However, the components on the higher-frequency slope of the 1-kHz spectral peak were reduced in the complex spectra obtained with a frequency separation of 0.5 kHz when compared to the corresponding composite spectra. The reduction was greater at a stimulus level of 70 dB SPL than with 60 dB SPL. The effect was smaller for a frequency separation of 1 kHz, and almost absent for the tone burst separation of 2 kHz. Thus, suppression leads to weak non-linear frequency superposition for higher-level, closely spaced stimuli.
Yoshikawa
H
H
Department of Otorhinolaryngology, Juntendo University School of Medicine, Hongo, Tokyo, Japan.
Smurzynski
J
J
Probst
R
R
D000161:Acoustic Stimulation / Q000379:methods; D000293:Adolescent; D000328:Adult; D003051:Cochlea / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology