Transient-evoked otoacoustic emissions as a measure of noise-induced threshold shift

The Effect of Short-Term Noise Exposure on Audiometric Thresholds, Distortion Product Otoacoustic Emissions, and Electrocochleography

Purpose The purpose of the study was to examine the effect of short-term noise exposure on audiometric thresholds, distortion product otoacoustic emissions (DPOAEs), and electrocochleography (ECochG) as a function of ear and sex. Method Preexposure and postexposure measures of audiometric thresholds, DPOAEs, and ECochG indices were examined. Sixteen male and 16 female adults participated. Participants were exposed to a 2000-Hz narrowband noise presented at 105 dBA for 10 min. Results Following noise exposure, significantly ( p < .0001) larger auditory threshold differences were observed for left ears. Larger auditory threshold differences were also observed for 3000 and 4000 Hz versus 2000 and 6000 Hz. DPOAE absolute amplitude differences increased with decreasing L ₁, L ₂ level ( p < .0001). DPOAE absolute amplitude differences also significantly rose with increasing f₂ frequencies ( p < .0001). Females generally had larger DPOAE absolute amplitude differences than males ( p < .05). Summating potential amplitudes were significantly larger for female left ears following noise exposure ( p = .03). Left-ear summating potential/action potential amplitude ratios and summating potential/action potential area ratios were increased following noise exposure ( p < .05). Conclusions Utilizing a test battery to examine the effects of short-term noise exposure can reveal the functional status of different structures in the cochlea. There appears to be a susceptibility of the left ear to short-term loud noise exposure. Findings with respect to a sex susceptibility to short-term loud noise exposure were not strong, as sex differences were only observed for a subset of the conditions.

Changes in cochlear function related to acoustic stimulation of cervical vestibular evoked myogenic potential stimulation

Evaluation of cervical evoked myogenic potentials (c-VEMP) is commonly applied in clinical investigations of patients with suspected neurotological symptoms. Short intense acoustic stimulation of peak levels close to 130 dB SPL is required to elicit the responses. A recent publication on bilateral significant sensorineural hearing loss related to extensive VEMP stimulation motivates evaluations of immediate effects on hearing acuity related to the intense acoustic stimulation required to elicit c-VEMP responses. The aim of the current study was to investigate changes in DPOAE-levels and hearing thresholds in relation to c-VEMP testing in humans. More specifically, the current focus is on immediate changes in hearing thresholds and changes in DPOAE-levels at frequencies 0.5 octaves above the acoustic stimulation when applying shorter tone bursts than previously used. Hearing acuity before and immediately after exposure to c-VEMP stimulation was examined in 24 patients with normal hearing referred for neurotologic testing. The stimulation consisted of 192 tonebursts of 6 ms and was presented at 500 Hz and 130 dB peSPL. Békésy thresholds at 0.125-8 kHz and DPOAE I/O growth functions with stimulation at 0.75 and 3 kHz were used to assess c-VEMP related changes in hearing status. No significant deterioration in Békésy thresholds was detected. Significant reduction in DPOAE levels at 0.75 (0.5-1.35 dB) and 3 kHz (1.6-2.1 dB) was observed after c-VEMP stimulation without concomitant changes in cochlear compression. The results indicated that there was no immediate audiometric loss related to c-VEMP stimulation in the current group of patients. The significant reduction of DPOAE levels at a wider frequency range than previously described after the c-VEMP test could be related to the stimulation with shorter tone bursts. The results show that c-VEMP stimulation causes reduction in DPOAE-levels at several frequencies that corresponds to half the reductions in DPOAE levels reported after exposure to the maximally allowed occupational noise for an 8 h working day. Consequently, extended stimuli intensity or stimulation repetition with c-VEMP testing should be avoided to reduce the risk for noise-induced cochlear injury.

Hearing Conservation Program for Marching Band Members: A Risk for Noise-Induced Hearing Loss?

Purpose

To examine the risk for noise-induced hearing loss (NIHL) in university marching band members and to provide an overview of a hearing conservation program for a marching band.

Method

Sound levels during band rehearsals were recorded and audiometric hearing thresholds and transient otoacoustic emission were measured over a 3-year period. Musician's earplugs and information about hearing loss were provided to the students. The hearing thresholds of other college students were tested as a partial control.

Results

There were no significant differences in hearing thresholds between the two groups. During initial testing, more marching band members showed apparent high-frequency notches than control students. Follow-up hearing tests in a subsequent year for the marching band members showed that almost all notches disappeared. Persistent standard threshold shift (STS) across tests was not observed in the band members.

Conclusion

Band members showed no evidence of STS or persistent notched audiograms. Because accepted procedures for measuring hearing showed a lack of precision in reliably detecting early NIHL in marching band members, it is recommended that signs of NIHL be sought in repeated measurements compared to baseline audiograms rather than in a single measure (a single notch). A hearing conservation program for this population is still recommended because of lengthy rehearsal times with high sound-level exposure during rehearsals.

The effect of impulse noise on distortion product otoacoustic emissions

The aim of this study was the evaluation of distortion product otoacoustic emissions (DPOAEs) before and after noise exposure from shooting, and the comparison of DPOAEs with pure-tone audiometry. Thirteen young male police officers were exposed to impulse noise from shooting, without using earplugs. Standard pure-tone audiometry, tympanometry, and DPOAEs were performed before exposure and at one hour post- and 24 hour post-exposure. In the one hour post-exposure testing mean pure-tone thresholds were elevated in the 1-8 kHz frequency zone and DPOAE levels were reduced at several frequencies. DPOAEs were more affected at 3 kHz or lower, whereas pure-tone thresholds were more affected at higher frequencies. After the final examination, non-significant partial shifts at high frequencies on both tests remained. Pure-tone audiometry was overall more sensitive, but DPOAEs provided additional information about the cochlear status of certain ears. These data suggest that besides behavioral testing, DPOAEs may play a role as a fast, objective, and easy to perform test for monitoring subjects exposed to impulse noise.

Detecting incipient inner-ear damage from impulse noise with otoacoustic emissions

Audiometric thresholds and otoacoustic emissions (OAEs) were measured in 285 U.S. Marine Corps recruits before and three weeks after exposure to impulse-noise sources from weapons' fire and simulated artillery, and in 32 non-noise-exposed controls. At pre-test, audiometric thresholds for all ears were <or=25 dB HL from 0.5 to 3 kHz and <or=30 dB HL at 4 kHz. Ears with low-level or absent OAEs at pre-test were more likely to be classified with significant threshold shifts (STSs) at post-test. A subgroup of 60 noise-exposed volunteers with complete data sets for both ears showed significant decreases in OAE amplitude but no change in audiometric thresholds. STSs and significant emission shifts (SESs) between 2 and 4 kHz in individual ears were identified using criteria based on the standard error of measurement from the control group. There was essentially no association between the occurrence of STS and SES. There were more SESs than STSs, and the group of SES ears had more STS ears than the group of no-SES ears. The increased sensitivity of OAEs in comparison to audiometric thresholds was shown in all analyses, and low-level OAEs indicate an increased risk of future hearing loss by as much as ninefold.

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.

Immediate and long-term effect of rifle blast noise on transient-evoked otoacoustic emissions

Firing noise of small-arms is characterized by a rapid change in pressure and a sharp peak in sound pressure level of 155-170 dB SPL. In the present study, we examined the behavior of transient-evoked otoacoustic emissions (TEOAE) of a group of soldiers exposed initially to the noise of small-arms fire during their basic training. The study included 15 soldiers and lasted 6 months. Measurements were performed before and immediately after two firing sessions, 2 weeks apart, and after 6 months. There was no significant difference between the audiograms that were measured prior to the noise exposure and those measured after 6 months. Wide-band TEOAE levels decreased over time, but the most significant decrease occurred between the two last sessions that were 5.5 months apart. No significant changes in TEOAE levels were observed before and immediately after exposure. However, at the high frequency range, an increase in TEOAE levels was observed in the third session relative to the previous one. During the 2 weeks after the first exposure, the soldiers were not exposed to noise. This TEOAE property might indicate the existence of a protective mechanism in the ear from traumatic harmful noise.

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< or =1 dB SPL) or very high (Em> or =8 dB SPL), less than 30% developed SHL. We suggest a prediction for ear vulnerability on the basis of Em prior to noise exposure.

Hearing threshold shift measured by otoacoustic emissions after shooting noise exposure in soldiers using hearing protectors

OBJECTIVE

The aim of the study was to assess the influence of short-term impulse noise to temporary threshold shift in soldiers using hearing protectors.

STUDY DESIGN AND SETTING

The study included 80 subjects with correct tympanic membrane and thresholds measured by pure-tone audiometry less than 20 dB. There were two groups: 40 soldiers protected during shooting and 40 young males who didn't shoot. TEOAE were performed by ILO 292 Echoport Otodynamics device 3 to 5 minutes before shooting and 2 minutes and 1, 2, and 3 hours after shooting.

RESULTS

Short-term exposure to impulse noise generated by five gunshots from the rifle kbk AKMS hasn't induced temporary threshold shift of hearing for chosen frequencies in soldiers using hearing protectors. Spectral analysis for chosen frequencies revealed that measurement reproducibility, stimuli level, and probe stability appeared to be comparable and repeatable.

CONCLUSION

Our results show that the use of hearing protectors safeguarded against impulse noise.

SIGNIFICANCE

The use of earmuffs is strongly recommended because they seem to sufficiently attenuate shooting noise.

Low-level otoacoustic emissions may predict susceptibility to noise-induced hearing loss

In a longitudinal study with 338 volunteers, audiometric thresholds and otoacoustic emissions were measured before and after 6 months of noise exposure on an aircraft carrier. While the average amplitudes of the otoacoustic emissions decreased significantly, the average audiometric thresholds did not change. Furthermore, there were no significant correlations between changes in audiometric thresholds and changes in otoacoustic emissions. Changes in transient-evoked otoacoustic emissions and distortion-product otoacoustic emissions were moderately correlated. Eighteen ears acquired permanent audiometric threshold shifts. Only one-third of those ears showed significant otoacoustic emission shifts that mirrored their permanent threshold shifts. A Bayesian analysis indicated that permanent threshold shift status following a deployment was predicted by baseline low-level or absent otoacoustic emissions. The best predictor was transient-evoked otoacoustic emission amplitude in the 4-kHz half-octave frequency band, with risk increasing more than sixfold from approximately 3% to 20% as the emission amplitude decreased. It is possible that the otoacoustic emissions indicated noise-induced changes in the inner ear, undetected by audiometric tests. Otoacoustic emissions may therefore be a diagnostic predictor for noise-induced-hearing-loss risk.

A longitudinal study of changes in evoked otoacoustic emissions and pure-tone thresholds as measured in a hearing conservation program

Non-linear transient-evoked otoacoustic emissions (TEOAEs) at 74dB pSPL, distortion-product otoacoustic emissions (DPOAEs) at 65/45dB SPL and pure-tone audiometry were used to detect noise-induced, inner car changes in a longitudinal study. Repeated-measures ANOVAs were made on the Noise (n=69) and Quiet (n=42) groups. The Noise group's hearing thresholds increased by 1.2 dB and DPOAE amplitude decreased by -0.9 dB. For both groups, TEOAE amplitude decreased by approximately -0.6 dB. Eight of 12 ears with permanent threshold shift (PTS) and 10 of 13 ears with temporary threshold shift (TTS) showed TEOAE decrements or low baseline TEOAE amplitudes. Fewer TTS and PTS ears also showed DPOAE decrements, and there was never a DPOAE decrement without a corresponding TEOAE decrement or low TEOAE baseline. Some TTS ears showed permanent emission decrements. Although otoacoustic emissions show promise in detecting noise-induced inner ear changes, it is premature to use them in hearing conservation programs.

Noise in magnetic resonance imaging: no risk for sensorineural function but increased amplitude variability of otoacoustic emissions

OBJECTIVES

Objectives were to perform exact measurements of the noise exposure in a magnetic resonance imager and to investigate the effects of magnetic resonance imaging (MRI) noise on hearing sensitivity, which are still controversial, in a large number of patients.

STUDY DESIGN

Prospective trial.

METHODS

Acoustic noise during seven different MRI sequences was measured using a custom-made microphone containing no ferromagnetic parts. In 244 ears of 126 patients, pure-tone audiometry was performed once before and once after MRI noise, and distortion product otoacoustic emissions were measured once before and three times after MRI.

RESULTS

The sound pressure level (SPL) at the patient's ear (with consideration of the sound-damping effect of the head support) ranged from 79.5 to 86.5 dB (A), depending on the MRI sequence, with brief sound pressure peaks up to 120 dB SPL. No significant incidence of temporary threshold shift and no reduction of mean distortion product otoacoustic emission amplitude were apparent. However, a significant increase in distortion product otoacoustic emission amplitude variability after noise exposure with equal distribution of increased and decreased amplitudes was observed. This variability showed a maximum at 15 minutes after noise, as demonstrated by continuous measurements.

CONCLUSIONS

First, MRI noise does not impose a risk to hearing function under the measurement condition of a sound-damping head support or ear protectors. Second, a subtle effect is demonstrated by increased distortion product otoacoustic emission amplitude variability. Third, the increased otoacoustic emission amplitude variability is an audiometric parameter that is extremely sensitive to effects of acoustic stimulation, indicating more discrete changes in cochlear activity than pure-tone audiometry or otoacoustic emission amplitude reduction. A shift of the operation point (OP) of the outer hair cell (OHC) between basilar membrane and tectorial membrane is suggested as underlying cause.

Use of ABR threshold and OAEs in detection of noise induced hearing loss

OBJECTIVE

To determine which measure is the most sensitive to noise induced hearing loss (NIHL): auditory nerve brainstem response (ABR), distortion product otoacoustic emission (DPOAE) or transient evoked otoacoustic emission (TEOAE), and how to assess possible changes in these responses.

SUBJECTS & METHODS

Four groups of rats were exposed to various durations of 113 dB SPL broadband noise: 5 or 10 minutes (temporary changes in cochlear function), and 3 or 4 hours (permanent changes). Group means and data from individual animals were compared before and after exposure.

RESULTS

Mean group DPOAE amplitude reduction showed no clear advantage over mean ABR threshold elevation in detection of temporary and permanent NIHL. Data from individual rats, however, indicated a clinical advantage for DPOAEs in detecting slight temporary, but not permanent, changes. TEOAEs were more sensitive in detecting changes in individual rats than as a group measure.

CONCLUSIONS

TEOAE and DPOAE monitoring may improve detection of NIHL, though it should be used in conjunction with audiometric threshold monitoring.

Otoacoustic emissions in the general adult population of Nord-Trøndelag, Norway: II. Effects of noise, head injuries, and ear infections

Otoacoustic emissions (OAEs) have been suggested as a sensitive measure of cochlear function with the potential for preclinical detection of damage. The present work assesses the risk for decreased OAEs associated with occupational and leisure noise, head injuries and recurrent ear infections. The predictive power of the environmental factors on different OAE values is compared with the prediction of conventional pure-tone hearing thresholds (PTTs). The analyses are based on data from 5072 adult subjects comprising a subsample of the 51975 subjects from the Nord-Trøndelag Hearing Loss Study. The subjects participated in a general health screening, including an examination of pure-tone audiometry, transient OAEs and distortion-product OAEs, and completed a questionnaire regarding history of noise exposure and ear disease. The predictions of OAEs and PTTs were analysed using regression analysis for various sex and age groups (20-44 years, 45-64 years, > or = 65 years). The fraction of the variance explained by exposure was generally moderate (0-4%, varying with age, sex, and type of measurement). Males showed moderate effects of work noise, impulse noise and ear infection, while ear infection was the only significant predictor in females. There were no effects of music noise and head injuries. The effect of exposure on OAEs that remained after controlling for PTTs was small and similar to the effect of exposure on PTTs that remained after controlling for OAEs.