Reproducibility and short-term variability of transient evoked otoacoustic emissions

Short-Term Reliability of Different Methods of Contralateral Suppression of Transient Evoked Otoacoustic Emission in Children and Adults

Purpose This study aimed to investigate the reliability of 3 methods to measure contralateral suppression of transient evoked otoacoustic emissions (TEOAEs) in children and adults. Method Contralateral suppression of TEOAEs was measured in 14 adults and 14 children using 3 methods with and without contralateral acoustic stimulus (CAS). Method-I having "2 s on-off" and Method-II having "10 s on-off" interleaved presentation of white noise. Method-III used "continuous presentation of white noise". Test-retest reliability was checked in adults without removing the probe (same-probe recording) and reinserting the probe (different-probe recording) and in children using a different-probe recording. Results The absolute suppression amplitude of TEOAEs was higher for "continuous noise," followed by "10 s on-off" and "2 s on-off" CAS. There was no significant effect of age across the 2 probe recordings, 3 methods of TEOAEs with and without CAS, and for the absolute suppression amplitude. Also, in adults, there was no significant difference between same-probe and different-probe recordings across the 3 methods. High internal consistency was observed on Cronbach's alpha (α > .9) for the 3 methods and 2 probe recordings. High agreement and correlation between the recordings for all 3 methods were seen using Bland-Altman plots and Pearson product-moment correlation coefficient. Conclusion The study demonstrated that highly reliable contralateral suppression of TEOAE can be measured using the 3 methods in adults and children. However, continuous presentation of CAS resulted in greater TEOAE suppression amplitude compared to interleaved presentation of CAS; hence, the former is recommended.

Prenatal and postnatal serum PCB concentrations and cochlear function in children at 45 months of age

BACKGROUND

Some experimental and human data suggest that exposure to polychlorinated biphenyls (PCBs) may induce ototoxicity, though results of previous epidemiologic studies are mixed and generally focus on either prenatal or postnatal PCB concentrations exclusively.

OBJECTIVES

Our aim was to evaluate the association between pre- and postnatal PCB concentrations in relation to cochlear status, assessed by distortion product otoacoustic emissions (DPOAEs), and to further clarify the critical periods in development where cochlear status may be most susceptible to PCBs.

METHODS

A total of 351 children from a birth cohort in eastern Slovakia underwent otoacoustic testing at 45 months of age. Maternal pregnancy, cord, and child 6-, 16-, and 45-month blood samples were collected and analyzed for PCB concentrations. At 45 months of age, DPOAEs were assessed at 11 frequencies in both ears. Multivariate, generalized linear models were used to estimate the associations between PCB concentrations at different ages and DPOAEs, adjusting for potential confounders.

RESULTS

Maternal and cord PCB-153 concentrations were not associated with DPOAEs at 45 months. Higher postnatal PCB concentrations at 6-, 16-, and 45-months of age were associated with lower (poorer) DPOAE amplitudes. When all postnatal PCB exposures were considered as an area-under-the-curve metric, an increase in PCB-153 concentration from the 25th to the 75th percentile was associated with a 1.6-dB SPL (sound pressure level) decrease in DPOAE amplitude (95% CI: -2.6, -0.5; p = 0.003).

CONCLUSIONS

In this study, postnatal rather than maternal or cord PCB concentrations were associated with poorer performance on otoacoustic tests at age 45 months.

Masculinization of the mammalian cochlea

Otoacoustic emissions (OAEs) differ between the sexes in humans, rhesus and marmoset monkeys, and sheep. OAEs also are different in a number of special populations of humans. Those basic findings are reviewed and discussed in the context of possible prenatal-androgen effects on the auditory system. A parsimonious explanation for several outcomes is that prenatal exposure to high levels of androgens can weaken the cochlear amplifiers and thereby weaken otoacoustic emissions (OAEs). Prenatal androgen exposure apparently also can alter auditory evoked potentials (AEPs). Some non-hormonal factors possibly capable of producing sex and group differences are discussed, and some speculations are offered about specific cochlear structures that might differ between the two sexes.

Sex differences in distortion-product and transient-evoked otoacoustic emissions compared

Although several studies have documented the existence of sex differences in spontaneous otoacoustic emissions (SOAEs) and transient-evoked OAEs (TEOAEs) in humans, less has been published about sex differences in distortion-product OAEs (DPOAEs). Estimates of sex and ear differences were extracted from a data set of OAE measurements previously collected for other purposes. In accord with past findings, the sex differences for TEOAEs were substantial for both narrowband and wideband measures. By contrast, the sex differences for DPOAEs were about half the size of those for TEOAEs. In this sample, the ear differences were small for TEOAEs in both sexes and absent for DPOAEs. One implication is that the cochlear mechanisms underlying DPOAEs appear to be less susceptible to whatever influences are responsible for producing sex differences in TEOAEs and SOAEs in humans. We discuss the possibility that differences in the effective level of the stimuli may contribute to these outcomes.

Transient-evoked otoacoustic emissions in a group of professional singers who have normal pure-tone hearing thresholds

OBJECTIVES

The objective of this study was to determine whether transient-evoked otoacoustic emissions (TEOAEs) measured in a group of normal-hearing professional singers, who were frequently exposed to high-level sound during rehearsals and performances, differed from those measured in age- and gender-matched normal-hearing non-singers, who were at minimal risk of hearing loss resulting from excessive sound exposure or other risk factors.

DESIGN

Twenty-three normal-hearing singers (NH-Ss), 23 normal-hearing controls (NH-Cs), and 9 hearing-impaired singers (HI-Ss) were included. Pure-tone audiometry confirmed normal-hearing thresholds (>or=15 dB HL) at 0.5, 1.0, 2.0, 3.0, 4.0, 6.0, and 8.0 kHz in NH-Ss and NH-Cs, and confirmed mild, high frequency, sensorineural hearing loss in HI-Ss (HI-Ss were included only to estimate sensitivity and specificity values for preliminary pass or fail criteria that could be used to help identify NH-Ss at risk for music-induced hearing loss). TEOAEs were measured twice in all ears. TEOAE signal to noise ratio (S/N) and reproducibility were examined for the whole wave response, and for frequency bands centered at 1.0, 1.4, 2.0, 2.8, and 4.0 kHz.

RESULTS

Moderate to high correlations were found between test and retest TEOAE responses for the three groups. However, absolute test-retest differences revealed standard deviations that were two to three times larger than those reported previously, with the majority of the variability occurring for the 1.0 kHz band. As such, only the best TEOAE response (B-TEOAE) from the two measurements in each ear was used in further analyses, with data from the 1.0 kHz band excluded. With one exception, within-group comparisons of B-TEOAE S/N and reproducibility across ears and gender revealed no statistically significant differences for either NH-Ss or NH-Cs. The only significant within-group difference was between left and right ears of NH-C females for S/Ns measured in the 2.0 kHz band, where median responses from right ears were found to be higher than left ears. Across-group comparisons of B-TEOAEs revealed lower median S/N and reproducibility values for NH-Ss compared with NH-Cs for the whole wave response and 1.4 kHz band. For the 2.0 kHz band, reproducibility was similar for the normal-hearing groups but median S/N was found to be lower for NH-Ss. No significant differences in S/N or reproducibility were found between normal-hearing groups for the 2.8 and 4.0 kHz bands. Using data from NH-Cs and HI-Ss to establish sensitivity and specificity values for various TEOAE pass or fail criteria, six preliminary criteria were identified as having sensitivity and specificity values >or=90%. When these criteria were applied to NH-Ss, the number of NH-S ears passing ranged from 57% to 76%, depending on the criteria used to judge the NH-S ears, which translates into 24% to 43% of ears failing.

CONCLUSIONS

Although TEOAE responses were measurable in all singers with normal audiometric thresholds, responses were less robust than those of NH-Cs. The findings suggest that subtle cochlear dysfunction can be detected with TEOAE measurement in a subset of normal-hearing professional singers. Although preliminary, the study findings highlight the importance of pass or fail criterion choice on the number of ears that will be identified as "at risk" for music-induced hearing loss.

What Do Sex, Twins, Spotted Hyenas, ADHD, and Sexual Orientation Have in Common?

The otoacoustic emissions (OAEs) measured in a collection of special populations of humans and certain nonhuman species suggest that OAEs may provide a window into some processes of human prenatal development and sexual differentiation. For reasons that are unclear, OAEs appear to be highly sensitive to events occurring during prenatal development that seem to be related to the degree of exposure to androgens a fetus receives. The (largely circumstantial) evidence for a relationship between androgen exposure and OAE strength comes from a series of studies of twins, children with attention-deficit/hyperactivity disorder, people of differing sexual orientations, and spotted hyenas, among others. Some conclusions are bolstered by parallel studies using auditory evoked potentials (AEPs). OAEs and AEPs are simple, objective, noninvasive measures that appear to have potential as tools of value to researchers working on a wide variety of basic and applied topics beyond audition.

Sex differences in otoacoustic emissions measured in rhesus monkeys (Macaca mulatta)

Click-evoked otoacoustic emissions (CEOAEs) and distortion-product OAEs (DPOAEs) were measured in about 60 rhesus monkeys. CEOAE strength was substantially greater in females than in males, just as in humans. DPOAE strength was generally slightly stronger in females, just as in humans. In males, CEOAEs were weaker (more masculine) in the fall breeding season and in winter than in the summer. In females, CEOAEs were slightly stronger (more feminine) in the fall, when sex steroids are elevated in females (and males), than in the summer when rhesus monkeys are reproductively quiescent. Thus, the sex differences in CEOAEs were greater in the fall than in the summer. We presume that the seasonal fluctuations in OAEs reflect activational hormonal effects, while the basic sex differences in OAEs likely reflect organizational effects of prenatal androgen exposure. Some monkeys of both sexes had been treated with additional testosterone or the anti-androgen flutamide during prenatal development. In accord with expectations, prenatal androgen treatment weakened CEOAEs in females, and prenatal flutamide treatment strengthened CEOAEs in males. For DPOAEs, the differences between treated and untreated groups were mostly small and often inconsistent. Taken as a whole, the data from both rhesus monkeys and humans suggest that the linear, reflection-based mechanism of OAE production that underlies CEOAEs is more sensitive to prenatal androgenic processes than is the nonlinear distortion mechanism that underlies DPOAEs.

Temporal nonlinearity revealed by transient evoked otoacoustic emissions recorded to trains of multiple clicks

A series of detailed experiments is described that investigates how a transient evoked otoacoustic emission (TEOAE) recorded to one-click stimulus is affected by the presence of a variable number of preceding clicks presented over a range of interclick intervals (ICIs). Part of the rationale was to determine if the resulting nonlinear temporal interactions could help explain the amplitude reduction seen when TEOAEs are recorded at very high click rates, as when using maximum length sequence stimulation. Amongst the findings was that the presence of a preceding train of clicks could either suppress or enhance emission amplitude, depending on the number of clicks in the train and the ICI. Results also indicated that the duration of the click trains, rather than the ICI, was the important factor in yielding the most suppressed response and that this seemed to depend on stimulus level. The results recorded at two levels also suggested that the cochlear temporal nonlinearity being monitored was in part related to the nonlinear process that determines the compressive input/output function for stimulus level. It is hypothesised that nonlinear temporal overlap of vibration patterns on the basilar membrane may underlie much of the pattern of results.

Recent advances in the hearing assessment of children

The remarkable specificity and sensitivity of otoacoustic emissions (OAEs) in identifying cochlear dysfunction, and the speed and objectivity with which the test can be conducted has made the OAE procedure the 'standard-of-care' in pediatric audiology assessment. Together with the auditory brainstem responses (ABRs), the OAE procedure not only separates sensory from neural impairment, but also facilitates early audiologic diagnosis and management. This article describes some unique applications of the OAE procedure in the diagnosis, monitoring and treatment of auditory dysfunction.

Otoacoustic emissions in 28 young adults exposed to amplified music

Popular concern about widespread damage to the hearing from exposure to amplified music continues, although there has been little firm evidence of permanent effects in casual listeners. Measurement of transient evoked otoacoustic emissions (TEOAEs) provides a sensitive technique for testing outer hair cell (OHC) function, and was used in this study of 28 young adults aged 18-25 years, whose only significant source of noise exposure was loud music, to look for evidence of poorer cochlear function in those of greater exposure; they provided 27 right ears and 27 left ears suitable for measurement of TEOAE strength. Estimates of subjects' total noise dose were obtained from self-reports of the duration and intensity of their exposure to music and other sources of noise. Ears with greater exposure to loud music showed significantly weaker TEOAEs than less exposed ears in response to a 4 kHz tone burst, or in response to a saturating (82 dBSPL) click if the response was treated with a high-frequency bandpass filter (2-4 kHz) (p<0.05). Differences between more exposed and less exposed groups of ears were most marked in the 2 kHz half-octave band for right ears, and in the 2.8 kHz half-octave band for left ears. A hypothesis is proposed that weakness in TEOAEs as a result of exposure to loud music is seen first in the 2 kHz region of the emission spectrum, and later at higher frequencies; and that for a given amount of exposure, TEOAE weakness (or OHC damage) is more advanced in left ears than in right.

Effect of anesthesia on transient evoked otoacoustic emissions in humans: a comparison between propofol and isoflurane

The influence of general anesthesia (GA) on auditory brainstem responses (ABRs) has been widely studied in humans whereas few studies have been devoted as yet to its effect on cochlear micromechanical properties. This study was aimed at evaluating: (1) the effect of GA on transient evoked otoacoustic emissions (TEOAEs) in humans (n=10), and (2) to compare the effects induced by two different anesthetic agents: propofol (n=5) and isoflurane (n=5). The TEOAEs were continuously monitored together with hemodynamic patterns describing various measures of blood pressure. (1) The GA induced a decrease in TEOAE amplitude and TEOAE amplitude was significantly correlated with the hemodynamic patterns. (2) Both anesthetic agents were responsible for a decrease in TEOAE during the first 20 min of recording. Under propofol, TEOAE amplitude increased after 20 min whereas under isoflurane TEOAEs continued to decrease. Under propofol, TEOAE amplitude was correlated with blood pressure changes in a highly significant manner, whereas under isoflurane TEOAE levels were completely independent of such hemodynamic patterns. These results infer that (1) the GA induced a decrease in TEOAE amplitude, and that (2) TEOAE changes induced by propofol could depend on the concomitant hemodynamic changes whereas isoflurane could be responsible for TEOAE changes depending on both, hemodynamic changes and its own pharmacological properties.

Contralateral transient evoked otoacoustic emissions following acoustic neuroma surgery

This study aimed to evaluate the effect of acoustic neuroma surgery on the contralateral cochlear function using transient evoked otoacoustic emissions (TEOAEs) and to test whether changes in TEOAEs differ according to the type of surgical approach. Forty four patients were included in this study. TEOAEs were recorded in both ears one day before (D0) and one month after surgery (D30). At D30, 20.5% of the patients showed an increase, 22.7% showed a decrease in contralateral TEOAEs amplitude and 56.8% remained stable. In the ear ipsilateral to the neuroma, TEOAE amplitude was significantly lower at D0 in the "increased" group compared to the "decreased" one. In the contralateral ear, TEOAE amplitude was significantly lower at D0 and D30 in the "increased" group compared to the "decreased" one and at D0 compared to the "stable" one. According to the surgical approach the patients were divided into two groups: a Translabyrinthine (TL) group (56.8% patients), and a retrosigmoid (RS) group (43.2% patients). The percentage of patients who presented an "increase" in TEOAEs amplitude in the contralateral ear was higher in the RS group (31.5) compared to the TL one (12%). The PTA lost at D0 was significantly higher in the TL group compared to the RS group. The TEOAE amplitude was significantly higher at D0 in both ipsi- and contralateral ears in the TL group compared to the RS one. These results suggest that acoustic neuroma removal is responsible for changes in contralateral TEOAEs. It can be hypothesized that changes in the efferent fibers secondary to surgery could partly explain these results.

Transient evoked otoacoustic emissions recorder using maximum length sequences as a function of stimulus rate and level

OBJECTIVE

The recently developed technique of recording transient evoked otoacoustic emissions (TEOAEs) using clicks presented according to maximum length sequences (MLSs) enables very high stimulation rates to be used. The aim of this study was to provide normative data on the relationship between TEOAEs recorded conventionally (at 40 clicks/sec) and those recorded using the MLS technique (at 11 maximum rates between 100 and 5000 clicks/sec) to establish a baseline for future clinical studies.

DESIGN

TEOAEs were recorded at 12 rates from 12 normally hearing adult ears at click levels decreasing in 5 dB steps from 68 dB peSPL.

RESULTS

The morphology of the waveforms and the pattern of the input/output functions with latency were similar for conventional and MLS TEOAEs. The only major difference between TEOAEs recorded at the different rates was in their absolute amplitude. As the click rate was increased from 40 clicks/sec there was a reduction in amplitude that reached a near asymptote at approximately 1500 clicks/sec. When expressed as a percentage reduction in amplitude compared with that recorded at 40 clicks/sec, this MLS "rate effect" was independent of stimulus level over all but the lowest test level (38 dB peSPL SPL).

CONCLUSION

Over a wide range of amplitudes of conventionally recorded TEOAEs (21 to 450 microPa for the 9 to 13 msec section of the otoacoustic emission), the mechanism involved in the MLS rate effect seems to act in a way that reduces the amplitude by an almost constant proportion, whatever its original size.

Individual differences and the reliability of 2F1-F2 distortion-product otoacoustic emissions: effects of time-of-day, stimulus variables, and gender

Distortion product otoacoustic emissions (DPOAEs) measured from the ear canal can be a sensitive tool to detect changes in cochlear function over time. However, if multiple-measurement procedures are to be useful clinically, testing needs to be reliable and sources of variability within individuals should be known. Herein, the influence of time-of-day (TOD), stimulus frequency, stimulus sound pressure level (SPL), and gender were evaluated on 2f1-f2 DPOAE amplitude in 16 adult volunteers with normal hearing. The effects of oral temperature and resting-pulse rate were also assessed. This study demonstrated a TOD main effect, with a period approximating one cycle-per-day. The magnitude of this effect averaged less than one dB and was not dependent on stimulus (frequency or SPL) or participant variables (gender, oral temperature, or resting-pulse rate), nor was it synchronized to a particular point-in-time. Stimulus level and gender effects on DPOAEs across frequency were also observed. Using generalizability theory (GT), DP iso-level/frequency profiles (DPILFPs) were found to be reliable measures within-subjects over a contiguous 24-hour time period. Significant and reliable between-subject differences were also documented. This study demonstrates the influence of stimulus and participant variables, quantifies the within-subject reliability over a 24-hour time period, and confirms that significant and reliable between-subject differences exist on DPOAEs across frequency, SPL, and gender.

Transient evoked otoacoustic emissions in nonsurgical ear

Several studies have reported contralateral hearing deficits following ear surgery. This study aimed to evaluate changes in micromechanical cochlear properties which could occur in the contralateral ear following ear surgery, using transient evoked otoacoustic emission (TEOAE) recording. Surgery involved tympanic membrane surgery in 13 cases and middle ear surgery in 16 cases. TEOAEs were recorded and compared for contralateral ears before (day 1: D1) and after (day 2: D2) ear surgery. Two patients failed to show a TEOAE reproductibility > 75%, and were excluded from the study, thus reducing the number of patients to 27. Results were compared to those of a control group of 12 normal hearing subjects, recorded in similar conditions also on day one (D1) and day two (D2). The difference between D1 and D2 was not significant in either group. Pre/postsurgery variations in TEOAE amplitude for the patient group were negatively and significantly correlated with the corresponding preoperative levels in that the greater the presurgical TEOAE level, the larger the decrease in postoperative level. Compared to the variation confidence intervals in the control group, TEOAE amplitude remained stable in 15 patients, increased in four and decreased in eight. These three groups of patients differed only regarding preoperative TEOAE amplitude values, which were significantly greater in the group which presented a decrease in TEOAE amplitude than in the others. Increase in TEOAE amplitude was more frequent after tympanic membrane surgery. On the other hand, TEOAE amplitude decrease was more frequent after middle ear surgery, and is significant compared to the tympanic membrane surgery results. The results show that cochlear micromechanical properties may be reduced in the ear contralateral to surgery and that this decrease depends on the severity of the surgical procedures in the operated ear, such as drilling or opening of the oval window.

Effects of noise and exercise on distortion product otoacoustic emissions

The effect of physical exercise on both distortion product otoacoustic emissions (DPOAE), and on the temporary effects of noise on human cochlear function was examined. Changes in DPOAEs were compared to changes in behavioural thresholds and the possible relation between contralateral suppression of DPOAEs and susceptibility to noise exposure was investigated. Békésy audiometry, tympanometry and DPOAEs were measured in 8 subjects on 3 separate occasions: before and after noise exposure; before and after exercise at 60% of maximal oxygen uptake (VO2max); and before and after a combination of noise exposure and exercise, all of 10 min duration. Noise exposure was third-octave band noise of 102 dB SPL centered at 2 kHz. The magnitude of the effect of noise exposure on DPOAE amplitude averaged in the 2-4 kHz range was comparable but weakly correlated to the magnitude of the temporary threshold shift (TTS) measured as the change in Békésy threshold at 3 kHz. There was no effect of physical exercise without noise exposure on either the Békésy threshold or the DPOAE amplitude. Physical exercise significantly increased the noise-induced TTS and the effect of noise exposure on DPOAE amplitude. A positive correlation was found between the temporary effect of noise exposure and the contralateral suppression effect on DPOAE amplitude.

Transient evoked otoacoustic emissions as screening for hearing losses at the school for military training

The present study was designed to investigate the applicability of transient evoked otoacoustic emissions (TEOAEs) as a method of screening for hearing losses among recruits attending obligatory military service. TEOAEs, tympanometry and puretone audiometry were recorded in 95 male recruits. Sixty-one recruits were tested after a 2-month period of gunfire exposure in order to document any permanent change in cochlear function. Screening by pure-tone audiometry showed an unexpectedly high prevalence of hearing losses > 20 dBHL, probably due to technical reasons. Thresholds were corrected using lower thresholds obtained at the end of service or by ENT specialists. The accuracy with which normal and impaired ears could be identified with TEOAEs analysed in frequency bands was determined by decision theory. Impairment was defined as mean hearing thresholds > or = 30 dBHL averaged from three neighbouring frequencies. Adequate accuracy was obtained in the middle frequencies. Further improvement of the technique is needed before it can be deemed suitable for detecting hearing losses at low and high frequencies. TEOAEs are quicker to measure and offer greater objectivity than pure-tone audiometry. A small decrease in TEOAE level was found after the training period. The TEOAEs were highly repeatable and had a higher sensitivity than pure-tone audiometry to detection of small changes in cochlear function under conditions normally found when testing recruits.

Transient-evoked otoacoustic emissions. Helpful tool in the detection of pseudohypacusis

The object of the present study was to demonstrate the use of TEOAEs for diagnosing pseudohypacusis. Thirty-four patients were investigated for suspected pseudohypacusis based on the case history and clinical and audiological findings. TEOAEs confirmed the diagnosis in all cases except four patients with a pre-existing organic hearing loss exceeding 25-30 dB HL. All the remaining 30 patients showed normal TEOAE responses except four of the ears in which final assessment revealed hearing threshold lower than 30 dB in the middle frequency region. The method can be time-saving when performed at the first consultation. With its element of surprise, the patient can be confronted with the existence of a functional hearing loss. This frequently results in marked threshold improvement on repeat pure-tone audiometry.

The influence of spontaneous otoacoustic emissions on the amplitude of transient-evoked emissions

The aim of the study was to analyse whether the presence of spontaneous otoacoustic emissions (SOAEs) in a group of normal-hearing adults is related to larger transient evoked otoacoustic emission (TEOAE) amplitudes when compared to a similar adult population without SOAEs. Twenty-four normal-hearing subjects participated in the investigation. They were selected to form two groups of 12, one containing only subjects with measurable spontaneous emissions, the other of members who had no measurable spontaneous emissions. Each group comprised 7 males and 5 females. TEOAEs were recorded in both linear and non-linear mode, and equivalent sound pressure levels in different octave frequency bands were calculated. For each frequency band, the comparison of the equivalent sound pressure levels in the two selected groups showed statistically significant differences. Therefore, when normative TEOAE data were collected with the purpose of establishing a normative reference for the assessment of cochlear hearing loss, it is mandatory to search for and, when pertinent, to compensate for the presence of SOAEs.

Temporary threshold shift and otoacoustic emissions after industrial noise exposure

The objective of the present study was to investigate whether employees in a noise-exposed environment developed changes in cochlear function as manifested by elevation of pure-tone threshold and/or reduction in transient evoked otoacoustic emission (TEOAE) amplitude. Pure-tone air-conduction audiometry, otoacoustic emissions (OAEs) and tympanometry were recorded in 13 healthy employees on three consecutive days both before and after 7 h of noise exposure. Employees exposed to an industrial noise level of 85-90 dBA developed significant pure-tone air-conduction threshold elevation at 4 and 6 kHz. A significant reduction of the TEOAE amplitude was found. There was no correlation between temporary threshold shift (TTS) and TEOAE reduction.