Stimulus-Frequency Otoacoustic Emission Suppression Tuning in Humans: Comparison to Behavioral Tuning

Abstract

As shown by the work of Kemp and Chum in 1980, stimulus-frequency otoacoustic emission suppression tuning curves (SFOAE STCs) have potential to objectively estimate behaviorally measured tuning curves. To date, this potential has not been tested. This study aims to do so by comparing SFOAE STCs and behavioral measures of tuning (simultaneous masking psychophysical tuning curves, PTCs) in 10 normal-hearing listeners for frequency ranges centered around 1,000 and 4,000 Hz at low probe levels. Additionally, SFOAE STCs were collected for varying conditions (probe level and suppression criterion) to identify the optimal parameters for comparison with behavioral data and to evaluate how these conditions affect the features of SFOAE STCs. SFOAE STCs qualitatively resembled PTCs: they demonstrated band-pass characteristics and asymmetric shapes with steeper high-frequency sides than low, but unlike PTCs they were consistently tuned to frequencies just above the probe frequency. When averaged across subjects the shapes of SFOAE STCs and PTCs showed agreement for most recording conditions, suggesting that PTCs are predominantly shaped by the frequency-selective filtering and suppressive effects of the cochlea. Individual SFOAE STCs often demonstrated irregular shapes (e.g., "double-tips"), particularly for the 1,000-Hz probe, which were not observed for the same subject's PTC. These results show the limited utility of SFOAE STCs to assess tuning in an individual.The irregularly shaped SFOAE STCs may be attributed to contributions from SFOAE sources distributed over a region of the basilar membrane extending beyond the probe characteristic place, as suggested by a repeatable pattern of SFOAE residual phase shifts observed in individual data.

Exploration of stimulus-frequency otoacoustic emission suppression tuning in hearing-impaired listeners

“…clear ear canals and normal appearance of the eardrum), and sensorineural hearing loss at 1 and/or 4 kHz in the ear chosen for testing (based on the degree of hearing loss or at random for symmetric hearing losses). The air-conduction hearing thresholds (in dB sound pressure level, SPL) were assessed with a modified Békésy tracking procedure at octave frequencies from 0.125–8 kHz (Lee et al, 2012; Charaziak et al, 2013). To assess the degree of hearing loss the listeners’ hearing thresholds in quiet were referenced to mean hearing thresholds of normally-hearing young adults (22–35 years old) measured with the same methods (Lee et al, 2012).…”

“…All measurements were carried out using the same equipment and procedures as described in detail elsewhere (Charaziak et al, 2013). In short, the listeners were seated comfortably inside a sound-attenuating booth with a tip of an OAE probe (Etymotic Research ER-10B+) placed in the ear canal.…”

“…due to hearing loss) at the individual level. Although we previously found a good agreement between average SFOAE STCs and PTCs in normally-hearing listeners, within an individual there was considerable variability in the degree of agreement (Charaziak et al, 2013). One interpretation of this result is that SFOAE STCs are not useful for predicting an individual’s frequency selectivity.…”

“…However, quantitative comparisons showed that commonly studied DPOAE STCs tend to indicate broader tuning (i.e. poorer frequency selectivity) than anticipated based on the behavioral tests, while SFOAE STC seem to agree better with behavioral estimates of tuning, at least in normally-hearing listeners (reviewed in Johnson et al, 2007; also see Keefe et al, 2008; Charaziak et al, 2013). Further support for the use of SFOAE STCs as a measure of frequency selectivity comes from a study in mice where SFOAE STCs were as sharply tuned as auditory nerve fiber tuning curves (Cheatham et al, 2011).…”

“…the tuning of cochlear filters that underlie frequency selectivity; Johnson et al, 2007). As a part of those attempts, in a previous study we assessed the applicability of stimulus-frequency (SF) OAEs to predict behaviorally assessed tuning in normally-hearing listeners (Charaziak et al, 2013). In this study, we aim to evaluate whether SFOAEs could reflect possible degradation of frequency selective filtering processes in cases of sensorineural hearing loss.…”