Near equivalence of human click-evoked and stimulus-frequency otoacoustic emissions

Abstract

Otoacoustic emissions (OAEs) evoked by broadband clicks and by single tones are widely regarded as originating via different mechanisms within the cochlea. Whereas the properties of stimulus-frequency OAEs (SFOAEs) evoked by tones are consistent with an origin via linear mechanisms involving coherent wave scattering by preexisting perturbations in the mechanics, OAEs evoked by broadband clicks (CEOAEs) have been suggested to originate via nonlinear interactions among the different frequency components of the stimulus (e.g., intermodulation distortion). The experiments reported here test for bandwidth-dependent differences in mechanisms of OAE generation. Click-evoked and stimulus-frequency OAE input/output transfer functions were obtained and compared as a function of stimulus frequency and intensity. At low and moderate intensities human CEOAE and SFOAE transfer functions are nearly identical. When stimulus intensity is measured in "bandwidth-compensated" sound-pressure level (cSPL), CEOAE and SFOAE transfer functions have equivalent growth functions at fixed frequency and equivalent spectral characteristics at fixed intensity. This equivalence suggests that CEOAEs and SFOAEs are generated by the same mechanism. Although CEOAEs and SFOAEs are known by different names because of the different stimuli used to evoke them, the two OAE "types" are evidently best understood as members of the same emission family.

Using Stimulus Frequency Emissions to Characterize Cochlear Function in Mice

“…SFOAE magnitude was estimated using the suppression method [3,21], i.e., a suppressor only slightly lower in frequency than the probe was also presented at 75 dB. In this approach, the SFOAE is defined as the vector difference between the canal pressure at probe frequency measured with and without the suppressor, which is assumed to reduce/eliminate the SFOAE [11]. FIGURE 2.…”

Delays and Growth Rates of Multiple TEOAE Components

“…TEOAEs, in a manner similar to SFOAEs, are thought to be generated by a coherent reflection mechanism located near the peak of the traveling wave [6]. TEOAE peaks occurring early in time, however, must be generated from a different place and/or by a different mechanism.…”

“…In humans, SFOAEs and TEOAEs are believed to be generated by place-fixed coherent reflection, at least at low stimulus levels [6,8]. At higher stimulus levels, it is possible that TEOAEs may have a distortion component [4,13,14].…”

Basal Contributions to Short-Latency Transient-Evoked Otoacoustic Emission Components

“…Generation of the LL component likely occurs at the tonotopic place, presumably through linear coherent reflection (LCR; Zweig and Shera 1995;Shera and Guinan 1999;Kalluri and Shera 2007a). (In this paper, the term "tonotopic place" refers to the place of maximum basilar membrane, BM, vibration for low-level stimuli.)…”