Transient Evoked Otoacoustic Emissions Levels Research Articles

Twin study of neonatal transient-evoked otoacoustic emissions

Our knowledge of which physiological mechanisms shape transient evoked otoacoustic emissions (TEOAEs) is incomplete, although thousands of TEOAEs are recorded each day as part of universal newborn hearing-screening (UNHS). TEOAE heritability may explain some of the large TEOAE variability observed in neonates, and give insights into the TEOAE generators and modulators, and why TEOAEs are generally larger in females and right ears.The aim was to estimate TEOAE heritability and describe ear and sex effects in a consecutive subset of all twins that passed UNHS at the same occasion at two hospitals during a six-year period (more than 30 000 neonates screened in total). TEOAEs were studied and TEOAE level correlations compared in twin sets of same-sex (SS, 302 individual twins, 151 twin pairs) and opposite-sex (OS, 152 individual twins, 76 twin pairs). A mathematical model was used to estimate and compare monozygotic (MZ) and dizygotic (DZ) intra-twin pair TEOAE level correlations, based on the data from the SS and OS twin sets.For both SS and OS twin pairs TEOAE levels were significantly higher in right ears and females, compared to left ears and males, as previously demonstrated in young adult twins and large groups of neonates. Neonatal females in OS twin pairs did not demonstrate masculinized TEOAEs, as has been demonstrated for OAEs in young adult females in OS twin pairs. The within-twin pair TEOAE level correlations were higher for SS twin pairs than for OS twin pairs, whereas the within-pair correlation coefficients could not be distinguished from zero when twins were randomly paired. These results reflect heredity as a key factor in TEOAE level variability. Additionally, the estimated MZ within-twin pair TEOAE level correlations were higher than those for DZ twin pairs. The heritability estimates reached up to 100% TEOAE heritability, which is numerically larger than previous estimates of about 75% in young adult twins.

Otoacoustic emissions in neonates exposed to smoke during pregnancy

IntroductionThe toxic substances present in cigarette smoke can damage cochlea hair cells. This effect has been investigated by measuring otoacoustic emissions. ObjectiveTo investigate the impact of stimuli on otoacoustic emissions, comparing neonates with and without exposure to cigarette smoke during pregnancy. MethodsTransient-evoked otoacoustic emissions, evoked by a click stimulus, and distortion product otoacoustic emissions, evoked by two tones tests were conducted in both ears, using an Interacoustic TITAN device. The study included 105 neonates divided into two groups: a study group, comprising 47 neonates exposed to smoke during pregnancy; and a control group comprized of 58 neonates who were not exposed. All participants had normal neonatal hearing screening. ResultsNo statistical differences in distortion product otoacoustic emissions response levels were found between the groups. In the transient-evoked otoacoustic emissions tests lower response levels were observed in the study group than the control group in frequency band analysis of the right ear, with statistically significant differences in signals and signal-noise ratio (except at 1kHz). ConclusionThe impact of smoking exposure could be analyzed through transient-evoked otoacoustic emissions in neonates. The group effect of smoke exposure during pregnancy was evidenced by a reduction in transient-evoked otoacoustic emissions levels. This same effect was not observed for the analyses performed on distortion product otoacoustic emissions levels.

Study of cochlear function in neonates and infants with congenital hypothyroidism

ObjectiveTo investigate the signal amplitudes of transient evoked otoacoustic emissions (TEOAE) in neonates and infants diagnosed with congenital hypothyroidism (HC) and verify their association with clinical and laboratory aspects. MethodsA cross-sectional study with a convenience sample of 22 individuals with congenital hypothyroidism and a group of 22 individuals without the disease, neonates and infants, aged 0–12 months. The TEOAE amplitudes were evaluated in both groups and compared using the Mann-Whitney test. The existence of association between TEOAE amplitudes and clinical-laboratory variables was verified through the Spearman correlation coefficient. ResultsThere were no statistically significant differences between TEOAE amplitudes between the two groups. There was an association between the amplitudes of TEOAE and serum levels of thyroid stimulating hormone (TSH) and free thyroxine (T4) in the diagnostic test. ConclusionsThe existence of an association between serum levels of TSH and free T4 in the diagnostic test and the amplitudes of TEOAE suggests the influence of these hormones on the auditory function.

Cilostazol Effect on Amikacin-Induced Ototoxicity: An Experimental Study

Objectives: To find out the possible protective effect of cilostazol against amikacin-induced ototoxicity. Methods: This study was carried out on 24 adult male rats classified into 4 equal groups of 6 animals each. (1) The control group was administered saline (1 ml/day, p.o.) for 14 days. (2) The amikacin group was administered amikacin (200 mg/kg, i.m.) once daily for 14 days. (3) The cilostazol-amikacin (14 days) group was administered cilostazol (30 mg/kg, p.o.) once daily and amikacin (200 mg/kg, i.m.) once daily for 14 days. (4) The cilostazol (28 days)-amikacin (14 days) group was administered cilostazol (30 mg/kg, p.o.) once daily for 28 days and amikacin (200 mg/kg, i.m.) once daily for 14 days. Changes in the transient evoked otoacoustic emissions (TEOAEs) in the 4 groups were interpreted statistically. Results: No reported significant differences in TEOAE levels were detected between the groups at the start of the study. In all frequency bands, TEOAEs disappeared after amikacin treatment in the amikacin-alone group and remained absent in the amikacin-cilostazol (14 days) group, while TEOAEs reappeared in the amikacin-cilostazol (28 days) group. Conclusion: Cilostazol treatment for 28 days had a protective effect against amikacin-induced ototoxicity in rats.

Use of Otoacoustic Emissions (OAE) to detect sub-clinical inner ear damage in divers of the Indian Navy

BackgroundProfessional Divers are at a high risk of Sensorineural Hearing Impairment. Divers may sustain sub-clinical hearing loss that is not identified on pure tone audiometry (PTA). Otoacoustic Emissions (OAE) reflect the functional status of the Outer Hair Cells. OAE testing constitutes the only non-invasive means of objective cochlear investigation and may be a more sensitive measure than PTA in identifying sub-clinical hearing loss. MethodsThis cross-sectional study was performed to determine utility of Otoacoustic Emissions testing in detecting sub-clinical Inner Ear damage in divers of Indian Navy. Transient Evoked Otoacoustic Emissions (TEOAE) levels were measured in 50 audiologically asymptomatic ship divers of Indian Navy and compared with control group comprising of 50 normal hearing individuals. ResultsNo statistically significant differences were observed between the study and control group. Also no correlation was observed between diving years and TEOAE levels. There was no correlation greater than −0.49 between diving years and TEOAE SNR. ConclusionsWe concluded that TEOAE levels are not a sensitive tool in identifying ships divers without any history of noise exposure at risk for developing hearing loss.

Behçet Disease as a Cause of Hearing Loss: A Prospective, Placebo-Controlled Study of 29 Patients

We conducted a prospective, placebo-controlled study to determine the incidence and severity of inner ear involvement and hearing loss in patients with Behçet disease. Our study population was made up of 29 patients with Behçet disease and 28 healthy controls. Audiometric pure-tone thresholds and transient evoked otoacoustic emission (TEOAE) levels were determined in both groups. The main outcome measures were pure-tone audiometry (PTA) levels and TEOAE levels in the two groups. PTA detected a sensorineural hearing loss in 10 of the 29 patients (34.5%). The difference in audiometric findings between the two groups was statistically significant at 1, 2, 4, and 8 kHz (p ≤ 0.0498). A comparison of TEOAE levels revealed that the difference in sound-to-noise ratio between the two groups was not significant at 1, 1.5, 2, and 3 kHz, but it was significant in 4 kHz (p = 0.02), and the difference in reproducibility between the two groups was significant at 2 and 4 kHz (p ≤ 0.03). We conclude that all patients with Behçet disease should be screened for hearing impairment and subsequently treated if an impairment is discovered.

Contralateral Suppression of Transient Otoacoustic Emissions and Sentence Recognition in Noise in Young Adults

One purported role of the medial olivocochlear (MOC) efferent system is to reduce the effects of masking noise. MOC system functioning can be evaluated noninvasively in humans through contralateral suppression of otoacoustic emissions. It has been suggested that the strength of the MOC efferent activity should be positively associated with listening performance in noise. The objective of the study was to further explore this notion by examining contralateral suppression of transient evoked otoacoustic emissions (TEOAEs) and sentence recognition in two noises with normal hearing young adults. A repeated measures multivariate quasi-experimental design was employed. Thirty-two normal hearing young adult females participated. Reception thresholds for sentences (RTSs) were determined monaurally and binaurally in quiet and in competing continuous and interrupted noises. Both noises had an identical power spectrum and differed only in their temporal continuity. "Release from masking" was computed by subtracting RTS signal-to-noise ratios in interrupted from continuous noise. TEOAEs were evoked with 80 dB peSPL click stimuli. To examine contralateral suppression, TEOAEs were evaluated with 60 dB peSPL click stimuli with and without a contralateral 65 dB SPL white noise suppressor. A binaural advantage was observed for RTSs in quiet and noise (p < .0001) while there was no difference between ears (p >.05). In noise, performance was superior in the interrupted noise (i.e., RTSs were lower vs. continuous noise; p < .0001). There were no statistically significant differences in TEOAE levels between ears (p >.05). There was also no significant difference in the amount of suppression between ears (p = .41). There were no significant correlations or predictive linear relations between the amount of TEOAE suppression and any indices of sentence recognition in noise (i.e., RTS signal-to-noise ratios and release from masking; p > .05). The findings are not consistent with the notion that increased medial olivocochlear efferent feedback, as assessed via contralateral suppression of TEOAEs, is associated with improved speech perception in continuous and interrupted noise.

Contralateral Suppression of Transient-Evoked Otoacoustic Emissions in Children With Sickle Cell Disease

In previous studies, otoacoustic emissions (OAEs) have been found to be larger in normal-hearing children with sickle cell disease (SCD). It was hypothesized that some dysfunction or reduction in the medial olivocochlear efferent suppression of outer hair cell activity was responsible for this phenomenon. To test this hypothesis, contralateral suppression of transient-evoked otoacoustic emissions (TEOAEs) was examined in children with and without SCD. Thirteen African American school-aged normal-hearing children with homozygous SCD and 13 age- and gender-matched control children participated. TEOAEs were obtained bilaterally with 80 dB peSPL nonlinear click stimuli. To examine contralateral suppression, TEOAEs were obtained with 60 dB peSPL linear click stimuli with and without a contralateral 65 dB SPL white noise suppressor. Overall and half-octave band TEOAE levels were found to be larger in children with SCD relative to the normal control children (p < 0.05), consistent with previous reports of increased OAE levels. There was no significant difference (p > 0.05) in the absolute or proportional amount of TEOAE suppression as a function of group and ear. There were also no significant correlations or linear predictive relationships between TEOAE suppression and TEOAE level for either ear or group (p > 0.05). These findings do not support the notion that increased OAE levels in children with SCD are a consequence of abnormal medial olivocochlear system function as assessed with contralateral suppression of TEOAEs.

Physical and Physiological Effects on Otoacoustic Emissions in Hypobaric Hypoxia

Tinnitus and dizziness are symptoms of acute mountain sickness. We investigated the mechanism by which high altitude (i.e. hypobaric hypoxia) affects inner ear function by measuring transient evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) under conditions of normobaric normoxia (1,013 hPa; 760 mm Hg) and hypobaric hypoxia (540 hPa; 405 mm Hg). The possibility that air pressure effects on the eustachian tube impacted our findings was excluded by the use of tympanograms. The nonphysiological effects of hypobaric hypoxia on TEOAE and DPOAE were also assessed using an ear simulator. Under conditions of hypobaric hypoxia, both TEOAE and DPOAE levels were reduced. The amount of reduction that occurred was approximately 4 dB in the total echo power and signal-to-noise ratio of the TEOAE, and in the 2f₁ – f₂ element level of the DPOAE. Stimulus levels that were measured using an ear simulator were also reduced by approximately 4 dB under conditions of hypobaric hypoxia. These results do not indicate that stimulus levels affected TEOAE and DPOAE levels because these levels were actually only slightly affected by changes in the stimulus level. Instead, this reduction was likely due to the nonphysiological hypobaric effects of the sound pressure emitted from the tympanic membrane. We conclude that the impact of hypobaric hypoxia on cochlear function was negligible up to pressures of 540 hPa.

Changes in Transient-Evoked Otoacoustic Emissions in the First Month of Life

Current Joint Committee on Infant Hearing guidelines recommend the use of transient-evoked otoacoustic emissions (TEOAEs) as a screening tool to identify hearing loss for newborns cared for in the well-baby nursery. Newborns who do not pass the TEOAE screen before leaving the hospital are typically rescreened as outpatients by 1 mo of age, at which time, approximately 50 to 70% pass screening criteria. To better understand why many infants are referred at initial screening but pass at the rescreening, more complete knowledge of developmental differences in the TEOAE levels, noise floor, or a combination of both for infants who pass and fail birth screening is needed. In addition, it has been shown that infants with occluding ear-canal debris are more likely to not pass TEOAE screening at the hospital than those without occluding ear-canal debris. This study explores whether changes in TEOAE levels in half-octave frequency bands are related to changes in ear-canal debris over the first month of life. Seventy-nine neonates from a well-baby nursery had their hearing screened before leaving the hospital and again at approximately 1 mo of age. All participants passed the follow-up screening. Overall TEOAE levels and levels in half-octave frequency bands centered at 1.5, 2, 3, and 4 kHz were measured. Judgments of ear-canal debris were made by otoscopy and were rated using one of three categories at both visits. TEOAE levels in infants significantly increased from birth to 1 mo of age across all frequencies tested, regardless of whether they passed or failed the screening at birth. The increase in TEOAE level was frequency dependent, with the greatest increases occurring in the highest frequency bands. No significant correlation between debris change and frequency-specific changes was found for either ear. Infants who failed the screening at birth but who subsequently passed at 1 mo of age had significantly lower TEOAE levels at the rescreening than did infants with passing TEOAE levels at birth. However, pass/fail status at birth was only a weak predictor of TEOAE levels at 1 mo of age. The increase in TEOAE levels during the first month of life is frequency dependent, with greater increases occurring at higher frequencies. Increased TEOAE levels were not associated with changes in ear-canal debris.

Changes in Transient-Evoked Otoacoustic Emission Levels with Negative Tympanometric Peak Pressure in Infants and Toddlers

Otoacoustic emission (OAE) testing is now a standard component of the diagnostic audiology protocol for infants and toddlers and is an excellent tool for detecting moderate-to-profound cochlear hearing loss. Detection of hearing loss is especially important in infants and toddlers. Unfortunately, middle-ear dysfunction has a high incidence in this age range and can confound interpretation of OAEs. The goal of the study was to determine how transient-evoked otoacoustic emission (TEOAE) and noise levels were different when tympanometric peak pressures (TPP) measured from tympanograms were normal versus negative in the same individual. Another goal was to determine how TEOAE screening pass rates using a priori pass criteria were affected on days when TPP was negative. TEOAE and noise levels were collected in 18 cases under 2 conditions: on a day when the tympanogram TPP was normal and on a day when the tympanogram TPP was negative. Data were collected from 11 children aged 3 to 39 mo, some of whom were tested more than once. Paired t tests were performed to determine whether there were changes in overall TEOAE and noise levels and TEOAE and noise levels analyzed into half-octave bands. A one-way ANOVA was performed on differences across half-octave bands to determine whether TPP affected TEOAE levels for some frequency bands more than others. Equality-of-proportion Z tests were run to determine whether there were significant differences in the percentage of "passes" on days when TPP was negative and TPP was normal. Mean TEOAE level was lower when TPP was negative, but noise levels did not change between the 2 conditions. Mean TEOAE levels were lower for all frequency bands from 1000 to 4000 Hz and no significant differences were found among the mean reduction across frequency bands. There were no significant differences in the percentage of passes between TEOAEs collected on days when TPP was normal and when TPP was negative. Mean data indicated that when tympanograms had negative TPP, TEOAE level was lower by approximately 4 dB across all frequency bands. However, this affected the pass rate in only 5% to 6% of cases. Although the number of participants in the current study was small, the data suggest that it is possible to measure TEOAEs in children with negative TPP. If emission-to-noise ratio is used to identify hearing loss in mid-to-high frequency bands, the majority of children will still have TEOAEs that meet clinical criteria, this providing the clinician with important information about cochlear status.

The effect of longitudinal noise exposure on behavioral audiograms and transient-evoked otoacoustic emissions

The ear vulnerability of a group of combat soldiers was tested. The study initially included 84 soldiers and lasted two years. The soldiers were exposed to the noise of small-arms fire. Measurements included transient-evoked otoacoustic emissions (TEOAE) and pure-tone audiometry. Measurements, initially performed prior to the soldiers’ basic training, were repeated several times during the study. In general, TEOAE levels (Em) decreased over time. About 57% of the ears developed a slight hearing loss (SHL) after two years of noise exposure. We define SHL as a threshold shift of 10 dB or greater, in at least at one of the audiometric frequencies 1000, 2000, 3000, 4000, or 6000 Hz. About 63% of the tested ears that had medium TEOAE level (1<Em<8 dB SPL) prior to the noise exposure, developed SHL. On the other hand, among the ears whose Em were either very low (Em≤1 dB SPL) or very high (Em≥8 dB SPL), less than 30% developed SHL. We suggest a prediction for ear vulnerability on the basis of Em prior to noise exposure.

Characteristics of normal newborn transient-evoked otoacoustic emissions: Ear asymmetries and sex effects

Transient-evoked otoacoustic emissions (TEOAEs) were recorded from more than 30000 newborns over a six year period. Analysis was performed on all the TEOAEs that passed the bedside universal hearing screen (n=60431), in order to characterize the normal properties of neonatal TEOAEs and to study ear and sex effects. Short recording times (median=33 s) were observed in combination with high entire TEOAE level (median=18.8 dB SPL for an 81.8 dB SPL peak stimulus), and high reproducibility (median=86%). Signal-to-noise ratio (S/N) of the TEOAE was highly frequency-dependent, being poorer at low frequencies. Prolonged averaging increased median reproducibility to 97%, but the minor S/N-improvement at low frequencies did not justify the longer test time. Highly significant mean lateral asymmetries (right >left) and sex differences (female >male) existed in entire TEOAE level, S/N TEOAE, and in half-octave frequency bands (700–4000 Hz). Mean lateral and sex entire TEOAE level differences were 1.1 dB and 1.3 dB, respectively. Stimulus levels were not affected by ear or sex. Hence, physiological differences at the level of organ of Corti were demonstrated in newborns.

Influence of leisure-time noise on outer hair cell activity in medical students

Noise exceeding a certain level can damage outer hair cells and thus cause hearing loss. In the past, noise-induced hearing loss was mainly caused by occupational noise. Leisure-time noise may be a promoting factor, particularly in young adults. The purpose of this study was to investigate whether transient evoked otoacoustic emissions (TEOAE) can be used to evaluate outer hair cell damage in young adults with no history of hearing complaints. The data obtained from the measurement of TEOAE were correlated with the participants' listening habits and exposure to leisure-time noise. Eighty-eight young adults (47 women, 41 men; age 22.9+/-2.9 years) were examined. TEOAE were measured using standard ILO 88 equipment. All participants had normal hearing (hearing thresholds better than 20 dB HL; frequency range 0.125-10 kHz). None of the participants suffered from permanent tinnitus. All participants answered a questionnaire concerning their listening habits. On average, the participants frequented a discotheque 1.4 times a month; 25% had never visited a discotheque, 35% visited once a month and 32% twice or three times a month. Sixteen per cent reported transient tinnitus after every visit to a discotheque and 58% after nearly every visit. Eight per cent suffered from transient hearing loss after every visit to a disco and 37% after nearly every visit. Three per cent (4%) reported tinnitus (nearly) every morning after visiting a discotheque. The TEOAE level was above 6 dB in all participants [9.2+/-3.6 dB (mean +/- SD)] and reproducibility was above 60% (90+/-9%). All values matched pass criteria for normal TEOAE under clinical conditions. However, TEOAE levels and reproducibility decreased significantly with an increased number of visits to discotheques. Outer hair cell damage could be measured using TEOAE in individuals exposed to leisure-time noise, although these individuals exhibited no measurable puretone hearing loss.

Mudanças das emissões otoacústicas por transientes na supressão contralateral em lactentes

It has been suggested that the function of the medial olivocochlear system (MOCS) can be evaluated by the suppression effect of the transient evoked otoacoustic emission (TEOAE). The competitive noise has an inhibitory effect on the functioning of the outer hair-cell, reducing the level of otoacoustic emissions. Despite the fact that there is no postnatal growth of the cochlea, middle ear growth and auditory processing development continue after birth. To analyze age-related changes of MOCS using the TEOAE suppression in healthy infants. 25 full-term infants with no risk factors for hearing loss were evaluated in two moments: at birth and at the age of six months. At both ages TEOAE were recorded in the "Quickscreen" mode, nonlinear stimulation at 78dB peSPL, for both ears, with and without contralateral noise presented at 60dB SPL. The data analyses, using ANOVA, revealed significant contralateral suppression of otoacoustic emissions in both groups, but the TEOAE levels and the amount of TEOAE contralateral suppression were smaller at six-month of age when compared to the neonatal period (p < 0.01). The TEOAE suppression effect for neonatals was 2.81dB (+/- 0.19dB) and at the age of six months was 1.41dB (+/- 0.29dB). The amount of TEOAE suppression decreased from birth to six months of age. The association between contralateral acoustic stimulation and a commercially available rapid TEOAE measurement system enables a non-invasive monitoring of the auditory efferent mechanism and seems to be clinically feasible to evaluate cochlear status and auditory efferent function development in infants at risk.

Reduced Medial Olivocochlear Bundle System Function in Children with Auditory Processing Disorders

A common complaint of children with auditory processing disorders (APD) is difficulty in understanding speech in the presence of background noise. Evidence from animal and human studies has suggested that the medial olivocochlear bundle (MOCB) may play a role in hearing in noise. The MOCB function can be evaluated by the suppression effect of the transient evoked otoacoustic emissions (TEOAE) in response to contralateral acoustic stimulation (CAS). The present study was conducted to investigate the suppression effect of TEOAE in APD children. The study groups comprised 15 APD children aged 8–13 years associated with learning disabilities and 15 controls matched for gender and age. The suppression effect of TEOAE was evaluated by comparing the TEOAE levels with and without CAS. A significantly reduced suppression effect of TEOAE was demonstrated in the APD group, when compared to the controls. In addition, higher TEOAE levels were found in the APD group, suggesting inherent reduced MOCB activity on the outer hair cells in APD children. These results imply that some APD children present low activity of the MOCB system, which may indicate a reduced auditory inhibitory function and affect their ability to hear in the presence of background noise.

Clinical Observations with Evoked Otoacoustic Emissions at Mayo Clinic

Clinical applications of transient evoked otoacoustic emission (TEOAE) measures began in 1989 at Mayo Clinic Rochester. Normative data indicates: a) greater TEOAE level for women and right ears beginning in the teen years, b) mean TEOAE levels remain relatively stable through the first seven decades of life, c) between subject EOAE level variability for normal hearing adults is high (up to about 30 dB) while within subject variability is low (about 4 dB), suggesting EOAEs should not be used to estimate pure-tone thresholds but are valuable in monitoring hearing status. Good frequency specificity of TEOAEs is demonstrated across high frequency hearing loss. Examples of TEOAEs in differential diagnosis are provided for cases of sudden hearing loss, auditory neuropathy and eighth nerve tumors including pre and post operative testing assessing changes in auditory function related to surgical procedures. Finally, our experience with TEOAEs in newborn hearing screening is described.

The effect of noise bandwidth on the contralateral suppression of transient evoked otoacoustic emissions

The purpose of this study was to determine whether the bandwidth or loudness of a contralateral stimulus is the most important factor in evoking suppression of transient evoked otoacoustic emissions (TEOAEs). TEOAEs were measured in both ears of 10 women in quiet and in the presence of one of three contralateral noise bands; narrow band (NB), wide band (WB) and equalized (EQ), all centered at 2000 Hz. The NB (100 Hz bandwidth) and WB (2200 Hz bandwidth) noises were presented at 60 dB SPL. The SPL of the EQ (100 Hz bandwidth) noise was adjusted such that it was equal in loudness to the WB noise as determined using a psychoacoustic procedure. Only the WB noise was associated with a significant reduction of TEOAE levels. It is believed that this effect occurred because the WB noise has greater effective energy representation across frequency on the basilar membrane as it may receive more gain from the action of the cochlear amplifier. Results of the present study indicate that noise bandwidth is the most important factor in the contralateral suppression of TEOAEs.

Identification of neonatal hearing impairment: transient evoked otoacoustic emissions during the perinatal period.

1) To describe transient evoked otoacoustic emission (TEOAE) levels, noise levels and signal to noise ratios (SNRs) for a range of frequency bands in three groups of neonates who were tested as a part of the Identification of Neonatal Hearing Impairment multi-center consortium project. 2) To describe the relations between these TEOAE measurements and age, test environment, baby state, and test time. TEOAEs were measured in 4478 graduates of neonatal intensive care units (NICUs), 353 well babies with at least one risk indicator, and 2348 well babies without risk factors. TEOAE and noise levels were measured for frequency bands centered at 1.0, 1.5, 2.0, 3.0, and 4.0 kHz for a click stimulus level of 80 dB SPL. For those ears not meeting "passing" stopping criteria at 80 dB pSPL, a level of 86 dB pSPL was included. Measurement-based stopping rules were used such that a test did not terminate unless the response revealed a criterion SNR in four out of five frequency bands or no response occurred after a preset number of averages. Baby state, test environment, and other test factors were captured at the time of test. TEOAE levels, noise levels and SNRs were similar for NICU graduates, well babies with risk factors and well babies without risk factors. There were no consistent differences in response quality as a function of test environment, i.e., private room, unit, open crib, nonworking isolette, or working isolette. Noise level varied little across risk group, test environment, or infant state other than crying, suggesting that the primary source of noise in TEOAE measurements is infant noise. The most significant effect on response quality was center frequency. Responses were difficult to measure in the half-octave band centered at 1.0 kHz, compared with higher frequencies. Reliable responses were measured routinely at frequencies of 1.5 kHz and higher. TEOAEs are easily measured in both NICU graduates and well babies with and without risk factors for hearing loss in a wide variety of test environments. Given the difficulties encountered in making reliable measurements for a frequency band centered at 1.0 kHz, its inclusion in a screening program may not be justified.

Transient-Evoked Otoacoustic Emissions in a Representative Population Sample Aged 18 to 25 Years: Emisiones otoacüAsticas evocadas por transitorios en una muestra representativa de población con edades entre 18 y 25 años

Transient-evoked otoacoustic emissions (TEOAEs) were obtained from 688 ears of a group of 345 young adults aged 18 to 25 years, using the Otodynamics ILO88 in the standard, non-linear mode. Normative data for TEOAEs obtained from 186 otologically normal (ON) ears are presented. In 5 ON ears, there was no recordable response, despite hearing threshold levels better than 20 dB. The main factors affecting the TEOAE level were (1) gender, where females had larger responses on average than males; (2) tym-panometric measures, where ears with entirely normal tympanometric measures had larger responses than those with minor tympanometric abnormalities; (3) click stimulus intensity measured in the ear canal, which correlated positively with TEOAE level; and (4) hearing threshold level at 0.5 kHz, which correlated negatively with amplitude. There was also a small effect of social noise exposure in the 2-kHz region of the TEOAE, where the response was lower in those subjects exposed to significant social noise.