Reconciling the origin of the transient evoked ototacoustic emission in humans

Abstract

A pervasive theme in the literature for the transient evoked otoacoustic emission (TEOAE) measured from the human ear canal has been one of the emission arising solely (or largely) from a single, place-fixed mechanism. Here TEOAEs are reported measured in the absence of significant stimulus contamination at stimulus onset, providing for the identification of a TEOAE response beginning within the time window that is typically removed by windowing. Contrary to previous studies, it was found that in humans, as has previously been found in guinea pig, the TEOAE appears to arise from two generation mechanisms, the relative contributions of these two mechanisms being time and stimulus-level dependent. The method of windowing the earliest part of the ear canal measurement to remove stimulus artifact removes part of the TEOAE i.e., much of the component arising from a nonlinear generation mechanism. This reconciliation of TEOAE origin is consistent with all OAEs in mammals arising in a stimulus-level dependent manner from two mechanisms of generation, one linear, one nonlinear, as suggested by Shera and Guinan [J. Acoust. Soc. Am. 105, 782-798 (1999)].

A mechanism for simultaneous suppression of tone burst-evoked otoacoustic emissions

“…This states that, even at high stimulus levels, the main source of TEOAEs is linear coherent reflection of stimulus-evoked travelling waves off place-fixed perturbations in cochlear mechanics (e.g. Shera, 2004;Kalluri and Shera, 2007;Sisto and Moleti, 2008;Withnell et al, 2008). This view is compatible with the concept of "generator channels" tonotopically distributed along the BM, within which TEOAE components at a particular frequency are generated locally (i.e.…”

“…less than approximately 2 ms post-stimulus onset (e.g. Siegel et al, 2005;Notaro et al, 2007;Withnell et al, 2008), they will be removed from the response waveform as a consequence of discarding early waveform segments dominated by unwanted stimulus 5 ringing. It is therefore unlikely that basal-source TEOAE components play a significant role in simultaneous suppression of TBOAEs.…”

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

“…Basal generation of SL TEOAE components is broadly consistent with the hypothesis that the components are generated through intermodulation distortion induced by cochlear interactions between different-frequency components in the evoking-stimulus' bandwidth (Withnell and Yates 1998;Withnell and McKinley 2005;Withnell et al 2008;Goodman et al 2009;Moleti et al 2012). However, if generated through intermodulation distortion, SL contributions to the OAE would be expected to decrease as the spectral bandwidth of the evoking stimulus decreases-recent work has failed to show such an effect Lewis and Goodman 2014).…”

“…This relationship was of interest as it provides an empirical test of the hypothesis that shorter-latency components are generated basal to longer-latency components of similar frequency (Withnell et al 2008;Goodman et al 2011;Moleti et al 2013). In light of recent work demonstrating that SL components depend on the active cochlear elements at locations basal to those of the LL component (Moleti et al 2014), a two-tone suppression paradigm was used to examine the extent of those contributions.…”

“…(In this paper, the term "tonotopic place" refers to the place of maximum basilar membrane, BM, vibration for low-level stimuli.) The generation mechanism and place of the SL components are less certain, with both intermodulation distortion and basal coherent reflection being hypothesized (Withnell and McKinley 2005;Withnell et al 2008;Goodman et al 2009Goodman et al , 2011Moleti et al 2012;Moleti et al 2013). The latencies of the SL components imply generation basal to the tonotopic place; however, the basal-extent of such contributions is unclear.…”