Contralateral Acoustic Stimulation Research Articles

Effects of contralateral noise on envelope-following responses, auditory-nerve compound action potentials, and otoacoustic emissions measured simultaneously.

This study assessed whether the effects of contralateral acoustic stimulation (CAS) are consistent with eliciting the medial olivocochlear (MOC) reflex for measurements sensitive to outer hair cell (otoacoustic emissions, OAEs), auditory-nerve (AN; compound action potential, CAP), and brainstem/cortical (envelope-following response, EFR) function. The effects of CAS were evaluated for simultaneous measurement of OAEs, CAPs, and EFRs in participants with normal hearing. Clicks were presented at 40 or 98 Hz in three ipsilateral noise conditions (no noise, 45 dB SPL, and 55 dB SPL). For the no noise condition, CAS suppressed or enhanced EFR amplitudes for 40- and 98-Hz clicks, respectively, while CAS had no significant effect on CAP amplitudes. A follow-up experiment using slower rates (4.4-22.2 Hz) assessed whether this insignificant CAS effect on CAPs was from ipsilateral MOC stimulation or AN adaptation; however, CAS effects remained insignificant despite favorable signal-to-noise ratios. CAS-related enhancements of EFR and CAP amplitudes in ipsilateral noise were not observed, contrary to the anti-masking effect of the MOC reflex. EFR and OAE suppression from CAS were not significantly correlated. Thus, the effects of CAS on EFRs may not be solely mediated by the MOC reflex and may be partially mediated by higher auditory centers.

Measurement of distortion-product otoacoustic emissions at low frequency and effect of contralateral acoustic stimulation on its level

Measurement of distortion-product otoacoustic emissions (DPOAEs) is one of the functional tests for the outer hear cells in the cochlea. Since the sound levels of the DPOAEs are quite low, it is easy to be buried in noise especially in the low frequency range, and frequency analysis and time averaging are required to detect them. In this study, focusing on the frequency stability of two stimulus sounds and a most prominent DPOAE-component, we tried to reduce noise floor and shorten the measurement time by choosing an adequate time window length for averaging the sound pressure waveform in the ear canal and the number of the averaging. As a result, it has become possible to measure DPOAEs at the low frequencies around 300 Hz in a relatively short time. Using this method, the changes in the DPOAE level induced by contralateral acoustic stimulation, which are caused by medial olivocochlear reflex, were measured. Although some exceptions were observed, the DPOAE was suppressed with increasing the sound pressure of the contralateral stimulus, and the degree of suppression was greater for the lower-frequency DPOAEs.

The Magnitude of Contralateral Suppression of Otoacoustic Emissions Is Ear- and Age-Dependent

The maturation of the uncrossed medial olivocochlear (UMOC) efferent remains poorly documented to date. The UMOC efferent system allows listeners to not only detect but also to process, recognize, and discriminate auditory stimuli. Its fibers can be explored non-invasively by recording the effect of contralateral acoustic stimulation (CAS), resulting in a decrease in the amplitude of transient evoked otoacoustic emissions (TEOAE). The objective of the present cross-sectional study was to investigate how the effectiveness of this system varies with age in healthy subjects aged 8 years to adulthood. For this purpose, 120 right-handed native French-speaking subjects (57 females and 63 males) were divided into five age groups of 24 subjects each: 8y–10y, 10y–11y6m, 11y6m–13y, 13y–17y, and ≥18y. TEOAE amplitudes with and without CAS were recorded. The equivalent attenuation (EA) was calculated, corresponding to the change in TEOAE amplitude equivalent to the effect generated by CAS. General linear models were performed to control for the effect of ear, sex, and age on EA. No sex effect was found. A stronger EA was consistently found regardless of age group in the right ear compared to the left. In contrast to the right ear, for which, on average, EA remained constant across age groups, an increasingly weaker TEOAE suppression effect with age was found in the left ear, reinforcing the asymmetrical functioning of the UMOC efferent system in favor of the right ear in adulthood. Further studies are needed to investigate the lateralization of the UMOC efferent system and its changes over time in cases of atypical or reversed cortical asymmetries, especially in subjects with specific learning disorders.

Middle ear muscle and medial olivocochlear activity inferred from individual human ears via cochlear potentials.

The peripheral auditory system is influenced by the medial olivocochlear (MOC) and middle ear muscle (MEM) reflexes. When elicited by contralateral acoustic stimulation (CAS), these reflexes reduce cochlear amplification (MOC reflex) and limit low-frequency transmission through the middle ear (MEM reflex). The independent roles of these reflexes on auditory physiology and perception are difficult to distinguish. The amplitude of the cochlear microphonic (CM) is expected to increase or decrease when the MOC and MEM reflexes are elicited by CAS, respectively, which could lead to a straightforward interpretation of what reflex is dominant for a given CAS level. CM and ear canal sound pressure level (SPL) were measured for a 500 Hz, 90 dB SPL probe in the presence of contralateral broadband noise (CBBN) for levels ranging from 45-75 dB SPL. In most subjects, CM amplitude increased for CBBN levels of 45 and 55 dB SPL, while no change in ear canal SPL was observed, consistent with eliciting the MOC reflex. Conversely, CM amplitude decreased, and ear canal SPL increased in the presence of 65 and 75 dB SPL CBBN, consistent with eliciting the MEM reflex. A CM-based test of the MOC reflex may facilitate detection of MEM effects and the assessment of adults with cochlear hearing loss.

Evaluation of Auditory Functions in Patients with Psoriasis.

Our study aims to evaluate the functions of the middle and inner ear and the efferent auditory system in psoriasis. Hearing thresholds, resonance frequency, otoacoustic emission amplitudes with and without contralateral acoustic stimulation, contralateral suppression levels were evaluated in 35 psoriasis patients and 40 controls. The air-conduction hearing thresholds of the patients were significantly higher than the controls at 125, 250, 500, 1000, 2000, 4000, and 12,000Hz frequencies in the left ear, and 125, 250, 500, 1000, 2000, and 4000Hz frequencies in the right ear, and the bone-conduction hearing thresholds of the patients were found to be significantly higher than the controls at all frequencies in the left ear, and 250, 500, 1000 and 2000Hz in the right ear (p < 0.05). The resonance frequencies of patients were found to be significantly lower than the controls (p < 0.001). The emission amplitudes obtained with contralateral acoustic stimulation were significantly lower than without contralateral acoustic stimulation at 1kHz frequency in both groups (p < 0.01). There was no significant difference in contralateral suppression levels of the two groups (p > 0.05). Our findings indicate that middle ear mechanics can be affected by psoriasis. There was no significant difference between psoriasis patients and healthy controls in terms of efferent auditory functions. There was a significant difference at limited frequency in hearing thresholds and emission amplitudes between the groups.

Effect of Contralateral Acoustic Stimulation on Temporal Processing Abilities in Individuals with Normal Hearing.

The aim of the article was to compare the conditions of silent and contralateral noise on the temporal processing parameters. A total of 40 participants (20 males and 20 females) were enrolled in the study with a mean age of 21.7years, participants with normal hearing thresholds and no history of middle ear pathology were enrolled for the study. The temporal processing tests such as duration discrimination test, gap detection test, and temporal modulation transfer function tests were carried out in these 40 individuals in the two conditions of silent and contralateral noise using MATLAB. Statistical analysis was carried out using the SPSS version 25.0 were descriptive and inferential statistics were carried out. Data was normally distributed on the Shapiro-Wilk's test of normality due to which a paired t test was carried out to establish the nature of significance between the silent and contralateral noise condition. Results reveal the presence of significant difference (p < 0.01) between the groups for all the parameters of temporal resolution with contralateral noise condition performing better than silent condition for the parameters. There is a positive effect of the efferent auditory pathway on the temporal resolution parameters thus implying that speech perception in noise is improved in the presence of background noise for normal hearing individuals due to this effect.

Contralateral suppression of transient evoked otoacoustic emissions in adults: A normative study

Whilst otoacoustic emission (OAE) testing has proved to be valuable in revealing information about cochlear outer hair cell integrity, it does not provide insight into the afferent and efferent pathways once the stimulus has reached neural receptors. This information can be obtained objectively through contralateral acoustic stimulation (CAS) suppression. However, obtaining normative data is essential in the implementation of such tests. The primary aim was to undertake a small pilot study to collect the CAS suppression across a predefined frequency range in order to provide a preliminary normative data set to be used with the newly developed transient evoked otoacoustic emission (TEOAE)-CAS module (PATH MEDICAL, Germering, Germany). Secondary aims included the analysis of the relationships between left and right CAS suppression, between male and female CAS suppression and between TEOAE signal-to-noise ratio (SNR) and CAS suppression. The purpose of this study was to determine preliminary normative data for contralateral TEOAE suppression from 40 normal ears of 20 healthy young adults (10 males and 10 females). Subjects were recruited using purposive sampling. The CAS suppression responses were obtained automatically by means of the data-collection protocol on the device used. From the data obtained, correlations between TEOAE SNR and CAS suppression were made using Pearson's correlation coefficient. The data were statistically processed to form a normative database which possesses the potential of serving as a basis for further research aimed at determining the utility of CAS suppression testing when evaluating ear pathology. A mean CAS suppression of 0.8 decibels (dB) (0.61 SD) was obtained. There was no statistically significant relationship between TEOAE SNR and CAS suppression. There was no significant suppression difference in terms of laterality of ears or gender. Normative values for CAS suppression of TEOAEs in a group of normal-hearing individuals were obtained using the newly developed TEOAE-CAS module (PATH MEDICAL, Germering, Germany). The availability of normative data for contralateral TEOAE suppression using the studied module allows for it to become commercially available, which will enable researchers and audiologists to perform this measurement in different populations in the evaluation of ear pathology.

Detection of middle-ear muscle reflex activation using changes in otoacoustic emission stimulus amplitude versus absorbance: an initial investigation

Objectives The medial olivocochlear reflex (MOCR) reduces cochlear amplifier gain, which may be beneficial for hearing in noise. Additionally, measurement of the MOCR may be diagnostically useful in the audiology clinic. The MOCR can be measured as the change in transient-evoked otoacoustic emission (TEOAE) amplitude without versus with contralateral acoustic stimulation (CAS). However, CAS can activate the middle-ear muscle reflex (MEMR) which can confound the MOCR results. MEMR activation has been assessed using changes in TEOAE stimulus amplitude without versus with CAS. As an initial investigation, the current study compared detection of MEMR activation using changes in TEOAE stimulus amplitude to changes in wideband absorbance. Methods In 26 normal-hearing participants, the MEMR was measured as the change in absorbance and as the change in TEOAE stimulus amplitude without and with CAS. Percentile critical differences were developed from the test-retest measurements. Measures of agreement between MEMR detection methods were computed. Results CAS resulted in a larger number of participants exceeding the 95th percentile critical difference for absorbance compared to TEOAE stimulus amplitude (22 versus 1). Agreement between methods was low. Conclusion Initial results indicated that MEMR was detectable in a larger number of participants when using absorbance compared to TEOAE stimulus amplitude. However, future work could better equate the two methods and include measurement of MEMR thresholds to determine optimal methods for detecting MEMR activation during MOCR assessments.

Fluctuations of Otoacoustic Emissions and Medial Olivocochlear Reflexes: Tracking One Subject over a Year

The purpose of the study was to measure the variability of transiently evoked otoacoustic emissions (TEOAEs) and the medial olivocochlear reflex (MOCR) over a long period of time in one person. TEOAEs with and without contralateral acoustic stimulation (CAS) by white noise were measured, from which MOCR strength could be derived as either a dB or % change. In this longitudinal case study, measurements were performed on the right and left ears of a young, normally hearing adult female once a week for 1 year. The results showed that TEOAE level and MOCR strength fluctuated over the year but tended to remain close to a baseline level, with standard deviations of around 0.5 dB and 0.05 dB, respectively. The TEOAE latencies at frequencies from 1 to 4 kHz were relatively stable, with maximum changes ranging from 0.5 ms for the 1 kHz band to 0.08 ms for the 4 kHz band. TEOAE levels and MOCR strengths were strongly and negatively correlated, meaning that the higher the TEOAE level, the lower the MOCR. Additionally, comparison of fluctuations between the ears revealed positive correlation, i.e., the higher the TEOAE level or MOCR in one ear, the higher in the second ear.

Evaluation of the efferent auditory system in COVID-19 adult patients

Background The short- and long-term effects of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on the medial olivocochlear reflex and outer hair cells in the cochlea remain largely unclear. Aims The aim of this study was to investigate the efferent auditory system effects in adult patients with COVID-19. Materials and methods The study included 18–50 years old 44 volunteers: 26 individuals (52 ears) with COVID-19 in the study group and 18 healthy individuals (36 ears) in the control group. Otolaryngological examination, immitancemetric evaluation, distortion product otoacoustic emission (DPOAE), contralateral acoustic stimulation with DPOAE, audiometric evaluation, and high frequency audiometric evaluation were performed in all individuals participating in the study. Results In our study, patients with COVID-19 had significantly lower DPOAE results with or without broadband noise at only 6 kHz frequency and contralateral suppression results at all frequencies compared to healthy individuals. A statistically significant difference was found between the study and control groups according to whether the participants had a response in the high frequency audiometry at 12 and 16 kHz frequencies. Conclusions COVID-19 affects many systems in the body. As a result of the findings obtained in the present study, it is shown that the auditory efferent system may also be affected.

Easy and Hard Auditory Tasks Distinguished by Otoacoustic Emissions and Event-related Potentials: Insights into Efferent System Activity

The medial olivocochlear (MOC) system is thought to be responsible for modulation of peripheral hearing through descending (efferent) pathways. This study investigates the connection between peripheral hearing function and auditory attention tasks of different degrees of difficulty. Peripheral hearing function was evaluated by analyzing the amount of change in otoacoustic emissions (OAEs) by contralateral acoustic stimulation (CAS), a well-known effect of the MOC system. Simultaneously, levels of attention were evaluated by event-related potentials (ERPs). The ERPs showed clear differences in processing tasks of different difficulty, but paradoxically there was no difference in the amount of OAE change brought about by CAS. There was also no effect on OAE latency, nor was there any difference in noise level or number of rejected trials. However, we observed that the changes in OAEs by CAS for easy and hard tasks were correlated with the magnitude of the P3 wave in the ERP. This suggests there might be some sort of mutual compensation mechanism – presently unknown – between periphery and cortex.

The Reliability of Contralateral Suppression of Otoacoustic Emissions Is Greater in Women than in Men.

The aim of this study was to compare the reliability of the medial olivocochlear reflex (MOCR) between men and women. The strength of the MOCR was measured in terms of the suppression of transiently evoked otoacoustic emissions (TEOAEs) by contralateral acoustic stimulation (CAS). The difference between TEOAEs with and without CAS (white noise) was calculated as raw decibel TEOAE suppression as well as normalized TEOAE suppression expressed in percent. In each subject, sets of measurements were performed twice. Reliability was evaluated by calculating the intraclass correlation coefficient, the standard error of measurement, and the minimum detectable change (MDC). The study included 40 normally hearing subjects (20 men; 20 women). The estimates of MOCR for both genders were similar. Nevertheless, the reliability of the MOCR was poorer in men, with an MDC around twice that of women. This can be only partially attributed to slightly lower signal-to-noise ratios (SNRs) in men, since we used strict procedures calling for high SNRs (around 20 dB on average). Furthermore, even when we compared subgroups with similar SNRs, there was still lower MOCR reliability in men.

The role of the medial olivocochlear reflex in psychophysical masking and intensity resolution in humans: a review.

This review addresses the putative role of the medial olivocochlear (MOC) reflex in psychophysical masking and intensity resolution in humans. A framework for interpreting psychophysical results in terms of the expected influence of the MOC reflex is introduced. This framework is used to review the effects of a precursor or contralateral acoustic stimulation on 1) simultaneous masking of brief tones, 2) behavioral estimates of cochlear gain and frequency resolution in forward masking, 3) the buildup and decay of forward masking, and 4) measures of intensity resolution. Support, or lack thereof, for a role of the MOC reflex in psychophysical perception is discussed in terms of studies on estimates of MOC strength from otoacoustic emissions and the effects of resection of the olivocochlear bundle in patients with vestibular neurectomy. Novel, innovative approaches are needed to resolve the dissatisfying conclusion that current results are unable to definitively confirm or refute the role of the MOC reflex in masking and intensity resolution.

Short-Term Test-Retest Reliability of Contralateral Suppression of Click-Evoked Otoacoustic Emissions in Normal-Hearing Subjects.

Purpose The objective of the current study was to investigate the short-term test-retest reliability of contralateral suppression (CS) of click-evoked otoacoustic emissions (CEOAEs) using commercially available otoacoustic emission equipment. Method Twenty-three young normal-hearing subjects were tested. An otoscopic evaluation, admittance measures, pure-tone audiometry, measurements of CEOAEs without and with contralateral acoustic stimulation (CAS) to determine CS were performed at baseline (n = 23), an immediate retest without and with refitting of the probe (only CS of CEOAEs; n = 11), and a retest after 1 week (n = 23) were performed. Test-retest reliability parameters were determined on CEOAE response amplitudes without and with CAS, and on raw and normalized CS indices between baseline and the other test moments. Results Repeated-measures analysis of variance indicated no random or systematic changes in CEOAE response amplitudes without and with CAS, and in raw and normalized CS indices between the test moments. Moderate-to-high intraclass correlation coefficients with mostly high significant between-subjects variability between baseline and each consecutive test moment were found for CEOAE response amplitude without and with CAS, and for the raw and normalized CS indices. Other reliability parameters deteriorated between CEOAE response amplitudes with CAS as compared to without CAS, between baseline and retest with probe refitting, and after 1 week, as well as for frequency-specific raw and normalized CS indices as compared to global CS indices. Conclusions There was considerable variability in raw and normalized CS indices as measured using CEOAEs with CAS using commercially available otoacoustic emission equipment. More research is needed to optimize the measurement of CS of CEOAEs and to reduce influencing factors, as well as to make generalization of test-retest reliability data possible.

Evaluation of the Contralateral Acoustic Stimulation Test After Audiological Examination of the Central Auditory System in Individuals with Normal Hearing

The aim of our study was to evaluate the contralateral acoustic stimulation tests of central auditory system after audiological examination of individuals with normal hearing. In this context, a number of criteria were considered for the determination of individuals with normal hearing. Normal hearing provides the ability to live independently in the social environment of an individual, and the level of hearing is considered necessary for enabling communication with the environment. A total of 15 individuals were included in our study. In all individuals, five different frequencies were obtained compared to the threshold for both ears. The frequencies were 1000 Hz, 1414 Hz, 2000 Hz, 2828 Hz and 4000 Hz; and the suppression thresholds were also measured. After audiological tests were performed for our study, the same measurements were repeated. Looking at the results of the study, a statistically significant difference was found between the measurement results for right and left ears in individuals with normal hearing (P&lt;0.05). Result: In order to see the suppressive effect, the integrity of the neural structures must be preserved starting from the medial nucleus of the superior olivary complex and reaching the OHCs. According to the results obtained in our study, we can conclude that MOCR is active, and the central nervous system is not impaired after the audiological evaluation. However, it is thought that a further study should be conducted with a larger sample group in order to obtain more specific results. Keywords: Contralateral suppression, normal hearing, otoacoustic emissions DOI: 10.7176/JHMN/87-06 Publication date: March 31 st 2021

Correlation and Reliability of Behavioral and Otoacoustic-Emission Estimates of Contralateral Medial Olivocochlear Reflex Strength in Humans.

The roles of the medial olivocochlear reflex (MOCR) in human hearing have been widely investigated but remain controversial. We reason that this may be because the effects of MOCR activation on cochlear mechanical responses can be assessed only indirectly in healthy humans, and the different methods used to assess those effects possibly yield different and/or unreliable estimates. One aim of this study was to investigate the correlation between three methods often employed to assess the strength of MOCR activation by contralateral acoustic stimulation (CAS). We measured tone detection thresholds (N = 28), click-evoked otoacoustic emission (CEOAE) input/output (I/O) curves (N = 18), and distortion-product otoacoustic emission (DPOAE) I/O curves (N = 18) for various test frequencies in the presence and the absence of CAS (broadband noise of 60 dB SPL). As expected, CAS worsened tone detection thresholds, suppressed CEOAEs and DPOAEs, and horizontally shifted CEOAE and DPOAE I/O curves to higher levels. However, the CAS effect on tone detection thresholds was not correlated with the horizontal shift of CEOAE or DPOAE I/O curves, and the CAS-induced CEOAE suppression was not correlated with DPOAE suppression. Only the horizontal shifts of CEOAE and DPOAE I/O functions were correlated with each other at 1.5, 2, and 3 kHz. A second aim was to investigate which of the methods is more reliable. The test–retest variability of the CAS effect was high overall but smallest for tone detection thresholds and CEOAEs, suggesting that their use should be prioritized over the use of DPOAEs. Many factors not related with the MOCR, including the limited parametric space studied, the low resolution of the I/O curves, and the reduced numbers of observations due to data exclusion likely contributed to the weak correlations and the large test–retest variability noted. These findings can help us understand the inconsistencies among past studies and improve our understanding of the functional significance of the MOCR.

Contralateral suppression of transient evoked otoacoustic emissions in children with phonological disorder.

BackgroundPerception of acoustic details in the speech signal is important for speech sound development. The medial olivocochlear pathway, a part of the auditory efferent system, plays a role in stimulus-related control of the cochlea. One clinical tool to evaluate the medial olivocochlear activity, which is thought to improve speech perception in noise, is the suppression of otoacoustic emissions.AimsThis study investigated the suppression of transient evoked otoacoustic emissions in children with phonological disorder in comparison with that in typically developing controls.Study DesignCase-control study.MethodsA total of 23 children with phonological disorder (aged 5–10 years) and 21 age- and sex-matched controls (P > 0.05) participated in the study. Participants had pure-tone thresholds ≤ 15 dB hearing loss and normal middle ear functions. Transient evoked otoacoustic emissions with and without contralateral acoustic stimulation were measured.ResultsAlthough the mean transient evoked otoacoustic emissions suppressions were lower in the group with phonological disorder than in the controls, these differences were not statistically significant (P > 0.05). No left/right ear asymmetry of transient evoked otoacoustic emissions suppression was detected in either of the groups (P > 0.05).ConclusionChildren with phonological disorder did not show alterations in medial olivocochlear functioning in the medial olivocochlear activity as measured by the contralateral suppression of transient evoked otoacoustic emissions.

No Change in Medial Olivocochlear Efferent Activity during an Auditory or Visual Task: Dual Evidence from Otoacoustic Emissions and Event-Related Potentials.

The medial olivocochlear (MOC) system is thought to be responsible for modulation of peripheral hearing through descending (efferent) pathways. This study investigated the connection between peripheral hearing function and conscious attention during two different modality tasks, auditory and visual. Peripheral hearing function was evaluated by analyzing the amount of suppression of otoacoustic emissions (OAEs) by contralateral acoustic stimulation (CAS), a well-known effect of the MOC. Simultaneously, attention was evaluated by event-related potentials (ERPs). Although the ERPs showed clear differences in processing of auditory and visual tasks, there were no differences in the levels of OAE suppression. We also analyzed OAEs for the highest magnitude resonant mode signal detected by the matching pursuit method, but again did not find a significant effect of task, and no difference in noise level or number of rejected trials. However, for auditory tasks, the amplitude of the P3 cognitive wave negatively correlated with the level of OAE suppression. We conclude that there seems to be no change in MOC function when performing different modality tasks, although the cortex still remains able to modulate some aspects of MOC activity.

Efferent-induced shifts in synchronized-spontaneous-otoacoustic-emission magnitude and frequency.

Synchronized-spontaneous otoacoustic emissions (SSOAEs) present as slow-decaying emission energy that persists after the transient-evoked otoacoustic emission (TEOAE). SSOAEs possess high amplitudes and signal-to-noise ratios, making them potentially ideal candidates to assay the medial-olivocochlear reflex (MOCR). The current work quantified MOCR-induced changes to SSOAEs over a 36-dB stimulus level range and compared MOCR effects between TEOAE- and SSOAE-based assays. Otoacoustic emissions were evoked using band limited clicks from 52 to 88 dB peak sound pressure level (pSPL) with and without contralateral-acoustic stimulation (CAS) in 25 normal-hearing, female adults. The CAS was 50-dB sound pressure level (SPL) broadband noise and served to activate the MOCR. The number of SSOAEs increased with the stimulus level through approximately 70 dB pSPL. The presentation of CAS resulted in fewer SSOAEs. SSOAEs exhibited compressive growth and approached saturation for stimulus levels of 70 dB pSPL. The primary effects of CAS were a reduction in the SSOAE magnitude and an upward shift in the SSOAE frequency. These changes were not strongly affected by the stimulus level. Time-domain analysis of the SSOAE revealed an increase in the CAS-induced magnitude shift during the decay portion of the SSOAE. Compared to CAS-induced TEOAE magnitude shifts, SSOAE magnitude shifts were typically 2-3 dB larger. Findings support SSOAEs as a means to assay the MOCR.

Reliability of contralateral suppression of otoacoustic emissions in children

Objective The purpose of the study was to determine the reliability in children of the medial olivocochlear reflex when measured as decibels of suppression of transiently evoked otoacoustic emissions (TEOAEs) by contralateral acoustic stimulation (CAS). Design TEOAEs with and without CAS (white noise) were measured. In each subject, measurements were performed twice. Of particular interest was the suppression of TEOAEs by CAS and its reliability. Reliability was evaluated by calculating the standard error of measurement (SEM) and minimum detectable change (MDC). Study sample Fifty-one normally hearing girls aged 3–6 years. Results The average global TEOAE suppression was around 0.6 dB. The highest reliability was for global values, with SEM of 0.2 dB and MDC of ±0.55 dB for the standard 2.5–20 ms recording window and slightly higher values for an 8–18 ms window. The worst reliability in the studied group was for the 1 kHz half-octave frequency band. Additionally, ears without spontaneous otoacoustic emissions had higher suppression levels than those with, but they also had lower signal-to-noise ratios, which may limit their clinical utility. Conclusions The current study shows that, under the studied paradigm, TEOAE suppression does not have satisfactory reliability since MDC was similar to the level of suppression.