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 74 dB pSPL, distortion-product otoacoustic emissions (DPOAEs) at 65/45 dB SPL and pure-tone audiometry were used to detect noise-induced, inner ear 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.     

Potentiation of noise-induced hearing loss by amikacin in guinea pigs.

Noise and aminoglycosides initially attack cochlear outer hair cells (OHCs). Distortion product otoacoustic emissions (DPOAEs) are used for the early diagnosis of damage to OHCs. The effects of sub-damaging doses of amikacin, an aminoglycoside antibiotic agent, on noise-induced hearing loss (NIHL) were examined in guinea pigs. Animals were grouped by gender and exposed to broadband noise at 105 dB SPL for 12 h and/or injected i.m. with either amikacin (100 mg/kg/day) or saline for 10 days. Auditory brainstem response (ABR) thresholds, along with DPOAE amplitudes, were measured serially before and after noise exposure. DPOAE amplitudes decreased and ABR thresholds elevated immediately after noise exposure and then gradually recovered. At all frequencies, the emission amplitudes recovered completely to pre-exposure baseline values by 4 days after noise exposure. There was no effect of amikacin on either the ABR threshold or DPOAE amplitudes, in animals treated with amikacin only. However, amikacin significantly prolonged the effect of noise exposure on DPOAE amplitude but not on the noise-induced temporary threshold shift (TTS) of the ABR. In animals treated with a combination of noise and amikacin, significant changes in DPOAE amplitudes were still observed at 4 weeks after cessation of noise exposure. No gender difference in the responses to noise and/or amikacin could be demonstrated. The present findings indicate that even sub-damaging dosages of amikacin might impair recovery from NIHL in guinea pigs.     

The relationship between auditory threshold and evoked otoacoustic emissions

The aim of this study was to compare transiently evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) in normal hearing ears (n = 44) and ears with cochlear hearing loss (HL) to obtain defined data on qualitative and quantitative correlations. In addition, we wanted to determine the reliability with which a clinical examiner could predict a typical, idealized audiometric configuration from TEOAE measurements. In the hearing-impaired subjects (n = 149), a 50% reduction of OAE incidence was caused by a mean HL of 10.5 dB for TEOAE compared to 27 dB SPL for DPOAE. A 90% incidence reduction was found at a mean threshold elevation of 33 dB for TEOAE and 51 dB for DPOAE. Correlation between TEOAE amplitudes and HL was in general rather low (r = –0.1 to –0.5), while DPOAE amplitudes showed a slightly better correlation with HL (r = –0.3 to –0.6). In general, efforts to derive an audiogram from evoked OAE have been more promising for DPOAE than for TEOAE. However, our studies showed that approximately 40% of the ears with HL could be categorized correctly into one of five typical audiometric patterns from TEOAE measurements. Additionally, a cochlear HL in or near the medium frequency range was much more likely to cause a reduction in TEOAE than an isolated low- or high-frequency lesion. Accordingly, TEOAE were often preserved in ears with isolated HL in the high or low frequencies. Received: 7 May 1998 / Accepted: 25 September 1998     

不同环境对正常青年人诱发性耳声发射检测的影响

目的 研究正常青年人在隔音和非隔音环境下的瞬态诱发耳声发射（TEOAE）和畸变产物耳声发射（DPOAE）,探讨环境噪声对耳声发射的影响,为临床应用提供参考。方法 应用Capella耳声发射仪对正常听力青年人102耳分别在隔音和非隔音环境下记录DPOAE和TEOAE。结果 两种环境下DPOAE的幅值无显著差异,信噪比（S/N－ratio）、叠加次数、扫描时间有显著性差异;ＴＥＯＡＥ的幅值、信噪比、相关系数（Ｃorr)、叠加次数、扫描时间均有显著性差异;隔音和非隔音环境下的ＤＰＯＡＥ、ＴＥＯＡＥ的通过率有显著性差异。结论 环境噪声（５５－６５dBSpL)对ＤＰＯＡＥ幅值（除０.5kHz外）无明显影响,对ＴＥＯＡＥ有显著影响;在听力筛选时,尤其是在非隔音环境下应用ＤＰＯＡＥ较ＴＥＯＡＥ准确率高;不但具有频率特异性,且可明显降低假阳性率。     

Diplacusis, hearing threshold and otoacoustic emissions in an episode of sudden, unilateral cochlear hearing loss

Limited data are available on the relationship between diplacusis and otoacoustic emissions and sudden hearing threshold changes, and the detail of the mechanism underlying diplacusis is not well understood. Data are presented here from an intensively studied single episode of sudden, non-conductive, mild hearing loss with associated binaural diplacusis, probably due to a viral infection. Treatment with steroids was administered for 1 week. This paper examines the relationships between the hearing loss, diplacusis and otoacoustic emissions during recovery on a day-by-day basis. The hearing thresholds were elevated by up to 20 dB at 4kHz and upwards, and there was an interaural pitch difference up to 12% at 4 and 8 kHz. There was also a frequency-specific change in transient evoked otoacoustic emission (TEOAE) and distortion-product otoacoustic emission (DPOAE) level. DPOAE level was reduced by up to 20 dB. with the greatest change seen when a stimulus with a wide stimulus frequency ratio was used. Frequency shifts in the 2f2-fi DPOAE fine structure corresponded to changes in the diplacusis. Complete recovery to previous levels was observed for TEOAE, DPOAE and hearing threshold. The diplacusis recovered to within normal limits after 4 weeks. The frequency shift seen in the DPOAE fine structure did not quite resolve, suggesting a very slight permanent change. The time-courses of TEOAE. diplacusis and hearing threshold were significantly different: most notably, the hearing threshold was stable over a period when the diplacusis deteriorated. This suggests that the cochlear mechanisms involved in diplacusis, hearing threshold and OAE may not be identical.     

Effects of repeated "benign" noise exposures in young CBA mice: shedding light on age-related hearing loss

Temporary hearing threshold shift (TTS) resulting from a "benign" noise exposure can cause irreversible auditory nerve afferent terminal damage and retraction. While hearing thresholds and acute tissue injury recover within 1-2 weeks after a noise overexposure, it is not clear if multiple TTS noise exposures would result in cumulative damage even though sufficient TTS recovery time is provided. Here, we tested whether repeated TTS noise exposures affected permanent hearing thresholds and examined how that related to inner ear histopathology. Despite a peak 35-40 dB TTS 24 hours after each noise exposure, a double dose (2 weeks apart) of 100 dB noise (8-16 kHz) exposures to young (4-week-old) CBA mice resulted in no permanent threshold shifts (PTS) and abnormal distortion product otoacoustic emissions (DPOAE). However, although auditory brainstem response (ABR) thresholds recovered fully in once- and twice-exposed animals, the growth function of ABR wave 1( p-p ) amplitude (synchronized spiral ganglion cell activity) was significantly reduced to a similar extent, suggesting that damage resulting from a second dose of the exposure was not proportional to that observed after the initial exposure. Estimate of surviving inner hair cell afferent terminals using immunostaining of presynaptic ribbons revealed ribbon loss of ～ 40 % at the ～ 23 kHz region after the first round of noise exposure, but no additional loss of ribbons after the second exposure. In contrast, a third dose of the same noise exposure resulted in not only TTS, but also PTS even in regions where DPOAEs were not affected. The pattern of PTS seen was not entirely tonotopically related to the noise band used. Instead, it resembled more to that of age-related hearing loss, i.e., high frequency hearing impairment towards the base of the cochlea. Interestingly, after a 3rd dose of the noise exposure, additional loss of ribbons (another ≈ 25 %) was observed, suggesting a cumulative detrimental effect from individual "benign" noise exposures, which should result in a significant deficit in central temporal processing.     

Diplacusis,hearing threshold and otoacoustic emissions in an episode of sudden,unilateral cochlear hearing loss

Limited data are available on the relationship between diplacusis and otoacoustic emissions and sudden hearing threshold changes, and the detail of the mechanism underlying diplacusis is not well understood. Data are presented here from an intensively studied single episode of sudden, non-conductive, mild hearing loss with associated binaural diplacusis, probably due to a viral infection. Treatment with steroids was administered for 1 week. This paper examines the relationships between the hearing loss, diplacusis and oto-acoustic emissions during recovery on a day-by-day basis. The hearing thresholds were elevated by up to 20 dB at 4 kHz and upwards, and there was an interaural pitch difference up to 12% at 4 and 8 kHz. There was also a frequency-specific change in transient evoked otoacoustic emission ( TEOAE) and distortion-product otoacoustic emission (DPOAE) level. DPOAE level was reduced by up to 20 dB, with the greatest change seen when a stimulus with a wide stimulus frequency ratio was used. Frequency shifts in the 2f2 – f1 DPOAE fine structure corresponded to changes in the diplacusis. Complete recovery to previous levels was observed for TEOAE, DPOAE and hearing threshold. The diplacusis recovered to within normal limits after 4 weeks. The frequency shift seen in the DPOAE fine structure did not quite resolve, suggesting a very slight permanent change. The timecourses of TEOAE, diplacusis and hearing threshold were significantly different; most notably, the hearing threshold was stable over a period when the diplacusis deteriorated. This suggests that the cochlear mechanisms involved in diplacusis, hearing threshold and OAE may not be identical.     

Susceptibility of young adult and old rats to noise-induced hearing loss

This study was designed to test whether old rats show signs of presbyacusis and whether they would be either similarly or more or less susceptible to noise-induced hearing loss than young adult rats. Old (24 months) and young adult (3-4 months) Wistar rats were exposed to a broad-band noise of 113 dB SPL for a duration of 1 h (producing temporary threshold shifts) or 3 days (12 h noise/12 h quiet; permanent shifts). Auditory brainstem response (ABR), distortion product otoacoustic emissions (DPOAEs) and transient evoked otoacoustic emissions (TEOAEs) were measured before and after exposure. At the initial recording (before exposure), old rats demonstrated a small mean ABR threshold elevation, a reduction in amplitude of wave I (WI), a shortening of WI latency and a prolongation of the interpeak interval between WI and WIV, as compared to the young rats. The old rats also demonstrated a small DPOAE amplitude reduction and a reduction of peak-to-peak amplitude in the TEOAE response 2 ms after stimulus, but no reduction in TEOAE energy content between 2 and 4 kHz. These are signs of presbyacusis in the old rats. The noise exposures caused elevations in ABR threshold and reductions in DPOAE amplitude and TEOAE energy content that were similar in both the old and young rats. Their recovery from the noise-induced loss was also similar. Thus, the results of this study show that old and young adult rats, at least when considering clinically relevant intensities and durations of noise exposure, are equally susceptible to the effects of the exposure.     

Distortion-product otoacoustic emissions in humans with high frequency sensorineural hearing loss

Distortion-product otoacoustic emissions (DPOAEs) and pure-tone behavioral thresholds were compared in 20 ears with normal hearing and in 20 ears with high-frequency sensorineural hearing loss. The purpose was to determine if DPOAE amplitude is associated with pure-tone behavioral threshold. Comparison of results from the two groups of ears indicated that DPOAEs were reduced in amplitude or were absent in ears with high-frequency hearing loss. The differences occurred at frequencies above 1,500 Hz. Comparing results from 750 to 8,000 Hz within the same ear revealed a frequency-related correspondence of elevated behavioral threshold to reduced DPOAE amplitude. When behavioral thresholds were better than 20 dB HL, DPOAE amplitude was within the range (+/- 2 SDs) determined for the ears with normal hearing. When pure-tone threshold was greater than 50 dB HL, DPOAEs were absent or were significantly attenuated in 16/17 subjects (94%). The association of emission level with behavioral threshold level was variable when threshold was between these two extremes. Results imply that the measurement of DPOAEs has clinical potential as a means of detecting hearing loss by frequency.     

自发性耳声发射与耳蜗传出调控的关系探讨

OBJECTIVE: To study the relationship between spontaneous otoacoustic emissions(SOAE) and efferent control of cochlea and their clinical significance. METHODS: SOAE, transient evoked otoacoustic emissions (TEOAE), distortion product otoacoustic emissions (DPOAE) and contralateral white noise (60 dB SPL) suppression of TEOAE and DPOAE experiments were conducted in 312 ears of 95 patients with retrocochlear impairment and/or MOCS dysfunction and 64 normal young adults. RESULTS: MOCS dysfunction was shown in 126 ears of 65 patients (130 ears) with auditory neuropathy, 2 ears of 2 patients with unilateral acoustic neuroma, 4 ears of 2 patients with hyperacusis, 14 ears of 26 patients(48 ears) with normal hearing level in unilateral or bilateral tinnitus. Stronger EOAE could be recorded in total 146 ears with MOCS dysfunction at any pure tone hearing level. SOAE could be recorded in 126 of 146 ears (86.3%) with MOCS dysfunction and 44 of 128 ears (34.3%) with normal hearing. SOAE of ears with MOCS dysfunction was mainly at frequencies from 0.693 to 3.055 kHz and SOAE of normal ears was at frequencies from 1.135 to 2.746 kHz. Average value of maximum amplitude of SOAE spectrum (-3.4 +/- 6.4) dB SPL was significantly greater than that in normal ears (-6.8 +/- 7.8) dB SPL (P < 0.01). The major frequency range of SOAE (0.693-3.055 kHz) in MOCS dysfunction ears was essentially consistent with that of efferent suppression in normal ears (0.7-3 kHz). CONCLUSION: The modulation of the cochlear active mechanisms by MOCS mainly presents in the low- and mid-frequency regions, these frequencies correspond to the frequency range of SOAE. Stronger SOAE indicates pathophysiological significance. There is a clear clinical relationship between SOAE and the efferent modulation of the cochlea.     

Age dependence of otoacoustic emissions: the loss of amplitude is primarily caused by age-related hearing loss and not by aging alone

The amplitude of otoacoustic emissions (OAE) is known to decrease with increasing age, but it is still unclear whether this is due to aging alone or to age-related hearing loss. This study describes the exploration of a large database (5,142 patients from 0.4 to 89.8 years) collected in a routine clinical testing. Reliable pure tone audiograms, transitory evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) recordings were available from 5,424 ears without conductive loss, acute sudden deafness or retrocochlear disorder. From this database, group 1 with behavioral thresholds of 10 dB HL or better at all frequencies from 1 to 4 kHz and group 2 with age-accordant thresholds after ISO 7029 were formed. In both groups, the OAE amplitude decreased with increasing age, but in group 1, the effect was significant only for DPOAE recorded at 3 and 4 kHz. In group 2, the loss of amplitude was steeper and highly significant for TEOAE as well as DPOAE at all frequencies, but most pronounced at high frequencies. These findings support the hypothesis that the reduction of OAE amplitude with increasing age is primarily caused by age-linked hearing loss and not by aging alone.     

Influence of sympathetic fibers on noise-induced hearing loss in the chinchilla

The influence of the sympathetic efferent fibers on cochlear susceptibility to noise-induced hearing loss is still an open question. In the current study, we explore the effects of unilateral and bilateral Superior Cervical Ganglion (SCG) ablation in the chinchilla on hearing loss from noise exposure, as measured with inferior colliculus (IC) evoked potentials, distortion product otoacoustic emissions (DPOAE), and outer hair cell (OHC) loss. The SCG was isolated at the level of the bifurcation of the carotid artery and removed unilaterally in 15 chinchillas. Another eight chinchillas underwent bilateral ablation. Twelve animals were employed as sham controls. Noise exposure was a 4kHz octave band noise for 1h at 110dB SPL. Results showed improved recovery of DPOAE amplitudes after noise exposure in ears that underwent SCGectomy, as well as lower evoked potential threshold shifts relative to sham controls. Effects of SCGectomy on OHC loss were small. Results of the study suggest that sympathetic fibers do exert some influence on susceptibility to noise, but the influence may not be a major one.     

Influence of noise exposure on antioxidant system and TEOAEs in rabbits

Noise exposure may cause hearing loss. The precise mechanism leading to cochlear damage in acoustic trauma is not known. Eight rabbits were used in this study. Transient evoked otoacoustic emissions (TEOAEs) were recorded in all animals and blood malondialdehyde (MDA) and glutathione (GSH) levels were determined. All rabbits were then exposed to 100 dB SPL broadband noise for 1 h. TEOAEs were recorded again and blood MDA and GSH levels determined following noise exposure. The reproducibility scores of the TEOAE measurements were found to be significantly lower (P < 0.01), whereas the amplitudes and signal-to-noise values of emissions decreased (P > 0.01) in rabbits exposed to noise. The TEOAE energies were poor at 4 kHz. During this threshold shift, GSH blood levels decreased and MDA levels increased, indicating that there is a close relationship between noise-induced hearing loss and the antioxidant system. These findings indicate that TEOAE recording is an excellent test for detecting effects of noise on hearing. Received: 29 September 2000 / Accepted: 15 June 2001     

Monitoring noise susceptibility: sensitivity of otoacoustic emissions and subjective audiometry

The capacity of different audiological methods to detect a high noise susceptibility was examined in 20 normally hearing and 26 especially noise-susceptible subjects. The latter were selected from 422 soldiers in field studies: they had shown a temporary threshold shift (TTS) in pure tone audiometry (PTA) after regular training with firearms. In laboratory experiments, the TTS-positive soldiers were re-examined using greatly reduced sound intensities, which caused no TTS in a control subject group. Before and after acoustic stimulation, different subjective (PTA, high frequency audiometry (HFA), upper limit of hearing (ULH)) and objective (transiently evoked otoacoustic emissions (TEOAE), distortion products (DPOAE)) audiological tests were performed. After exposure to low impact noise in the laboratory, in both PTA and HFA, a TTS was observed in 11.5% (N = 3) of the noise-susceptible group (compared to 0% in the control group). In the TTS-positive group, deterioration of the ULH occurred in 28% (N = 7) (compared to 15% (N = 3) in the control group). An ULH improvement occurred in only one subject (3.8%) (compared to 25% (N = 5) in the control group). Significant alterations of click-evoked OAE-amplitudes were found in 26.9% (N = 7) of the selected groups, whereas stable emissions were observed in all but one subject (5%) of the control group. However, DPOAE alterations were seen in 19.2% (N = 5) of the TTS-positive soldiers but also in 25% (N = 5) of the control group. These results suggest that TEOAE provides a more sensitive and more objective method of detecting a subtle noise-induced disturbance of cochlear function than do PTA or DPOAE.     

Clinical investigation on spontaneous otoacoustic emission (SOAE) in 447 ears

OBJECTIVES: It is known that spontaneous otoacoustic emission (SOAE) is often observed in normal hearing ears, but concrete clinical application of SOAE test has been rarely reported, compared with transiently evoked otoacoustic emission (TEOAE) and distortion product otoacoustic emission (DPOAE) tests. In addition, there have been a variety of opinions concerning laterality of SOAE, and influence of gender and hearing on SOAE. The reason for this may be that each report has the small number of subjects and lacks in statistical power. Therefore, in the present study, SOAE, TEOAE and DPOAE were measured in 447 ears of subjects at various ages with different hearing level, and statistical analysis was performed to investigate the clinical significance of SOAE. MATERIALS AND METHODS: The subjects were 447 ears in 268 patients (268 ears in females, and 179 ears in males). The age of subjects ranged from 0 to 75 years (mean: 30.8 years), and there were 222 left and 225 right ears. The subjects of schoolchildren or older (414 ears) received pure-tone audiometry, and infants (33 ears) received auditory brain-stem response (ABR). SOAE and TEOAE were measured using ILO88 (Otodynamics, Version 4.20). DPOAE was measured using ILO92 (Otodynamics, Version 1.32). RESULTS: Incidence of SOAE and the number of SOAE per ear were high in the subjects at age of 50 years or younger, in those with hearing level of not more than 30 dB, in the right ear, and in females. Incidence of SOAE in the whole of normal hearing ears was approximately 38%, but the ears with SOAE had almost normal hearing of not more than 30 dB. CONCLUSIONS: SOAE is useful for objective hearing assessment. Moreover, SOAE sometimes appeared in the ears in which TEOAE or DPOAE could not be confirmed, and it might be useful for definite diagnosis of disease state to measure SOAE in addition to TEOAE or DPOAE.     

Correlations among evoked potential thresholds, distortion product otoacoustic emissions and hair cell loss following various noise exposures in the chinchilla

Changes in cubic distortion product otoacoustic emissions (ΔDPOAEs), evoked potential threshold shifts (TSs) and outer hair cell (OHC) losses were measured in a population of 95 noise-exposed chinchillas. Each animal was exposed to one of 23 different noises in an asymptotic threshold shift (ATS) producing paradigm or an interrupted noise paradigm which typically produced a toughening effect. Noises were narrow band (400 Hz) impacts with center frequencies of 0.5, 1.0, 2.0, 4.0 or 8.0 kHz presented 1 impact/s at peak SPLs of 109, 115, 121 or 127 dB. The duration of the exposures was 24 h/day for 5 days (ATS paradigm) or 6 h/day for 20 days (toughening paradigm). Based on a linear regression analysis of individual subject and group mean data, correlations among the following dependent variables were made: ΔDPOAEs, ATS, toughening or TS recovery (TS_r), permanent threshold shift (PTS) and OHC loss. Correlations among these metrics were generally highest for DPOAE primary frequency levels, L₁=L₂=70 dB. Correlation between ΔDPOAE and TS_r was typically low, while a considerably higher correlation was found between ΔDPOAE and ATS. Correlations among the permanent measures of noise-induced effects, i.e. for ΔDPOAE/PTS and ΔDPOAE/OHC loss were typically poor when there was only a small or a moderate noise-induced effect (PTS<25 dB and ΔDPOAE<20 dB). However, for PTS<25 dB the correlation between PTS and OHC loss was considerably better than the correlation between ΔDPOAE and OHC loss. For more severe noise-induced changes there was generally a good correspondence between OHC loss, PTS and ΔDPOAE metrics.     

瞬态诱发耳声发射检测职业性听力损伤的可行性研究

目的 :探讨瞬态诱发耳声发射 (TEOAE)检测职业性听力损伤的可行性及临床应用价值。方法 :选择 90例 (180耳 )噪声暴露工人为实验总组 ,按噪声暴露时间长短又分为 1、2、3组 ;另选 11例 (2 2耳 )正常听力青年人作为对照组 ,行纯音听阈和TEOAE测试。结果 :各实验组纯音听阈值明显高于对照组 ,TEOAE总重复率、幅值和信噪比及各频段重复率、幅值和信噪比明显低于对照组 (P <0 .0 5或P <0 .0 1)。实验 1、2、3组间比较 ,随着噪声接触时间的增加 ,各频率点纯音听阈提高 ,TEOAE总重复率、幅值和信噪比及各频段重复率、幅值和信噪比变小 ,在 2 .5 0～ 3.5 0kHz和 3.5 0～ 4 .5 0kHz频段最明显。结论 :用TEOAE检测职业性听力损伤是可行的 ,有临床应用价值 ,最敏感频段为 2 .5 0～ 3.5 0kHz和 3.5 0～ 4 .5 0kHz频段。     

Otoacoustic emissions in ears with hearing loss

Fifty ears of 37 patients demonstrating several common types of hearing impairment were examined for the presence of spontaneous and evoked otoacoustic emissions to investigate the relationship of acoustic emissions to hearing pathology. Of the 50 ears, 44 exhibited various degrees of sensorineural hearing loss. Evoked otoacoustic emissions to clicks were detected in 34 of 35 sensorineural hearing loss ears with a subjective click threshold less than 55 dB SPL (25 dB nHL). None of nine ears with sensorineural hearing impairment and a subjective click threshold greater than 55 dB SPL demonstrated click-evoked emissions. Spectral analyses revealed that the constituent frequency components of evoked emissions were always within the frequency range where audiometric thresholds were less than 35 dB HL, and in the majority (94%) of cases, thresholds were less than 25 dB HL. In ears with relatively well-preserved hearing within the frequency range of click or 1.5-kHz toneburst stimuli, the basic features of evoked emissions were similar to those described for normal ears. Similarly, for ears demonstrating spontaneous otoacoustic emissions, estimated audiometric thresholds at the emitted frequencies were always less than 20 dB HL. The influence of the type of otologic pathology on acoustic emissions was studied in a subset of ears exhibiting typical high-frequency hearing losses. Ears with a noise-induced impairment showed a significant reduction in the incidence of both spontaneous emissions and spectral peaks in evoked emissions that was not evident in ears with similar patterns of hearing loss caused by other factors.     

Changes in otoacoustic emissions and high-frequency hearing thresholds in children and adolescents

With the aim of characterizing the loss of high frequency hearing sensitivity in children, hearing thresholds and otoacoustic emissions were measured in a group of 126 normal hearing children and adolescents aged from 6 to 25 years. The subjects were divided into four 5-year age groups. Hearing thresholds over a range of 125 Hz-12.5 kHz were similar in all age groups, the average hearing threshold at 16 kHz was significantly elevated in the oldest age group. The response values of transiently evoked otoacoustic emissions (TEOAEs) significantly declined with age; the decline was negatively correlated with the hearing loss at 16 kHz. Significantly larger TEOAE responses and average distortion-product otoacoustic emission (DPOAE) values at 6.3 kHz were present in the youngest group in comparison with the other three older groups. Spontaneous otoacoustic emissions (SOAEs) were present in 70.8% of the children (in either one or both ears) with the greatest prevalence in the 11-20-year-old subjects. In the 21-25-year-old group, the hearing loss at 16 kHz was significantly smaller in ears with SOAEs than in ears without SOAEs. The results demonstrate that the increase in the high frequency hearing threshold at 16 kHz, which starts at ages over 20 years, is correlated with a decrease in the TEOAE responses at middle frequencies.     

Protective effect of a purified polyphenolic extract from Ecklonia cava against noise-induced hearing loss: Prevention of temporary threshold shift

ObjectiveNoise is one of the most common causes of hearing loss. Approximately 16% of American teenagers (12–19 years) have hearing loss caused by loud noise. The implication of noise-induced hearing loss (NIHL) in teenagers has received increasing attention. Although temporary threshold shift (TTS), a type of NIHL, is a transient hearing loss, it can accelerate age-related hearing loss. Reactive oxygen species are a primary cause of TTS. As the polyphenols from Ecklonia cava are known to have potent antioxidant effects, we investigated the protective effects of a purified polyphenolic extract of Ecklonia cava (PPEE) against TTS in mice.MethodsThe radical-scavenging activity of PPEE was evaluated using the 1,1-diphenyl-2-picrylhydrazyl assay. The PPEE + Noise and Saline + Noise groups were administered intraperitoneal PPEE (100 mg/kg) and saline, respectively, for 5 days before exposure to noise at 100 dB SPL for 60 min. Hearing ability was assessed following noise exposure using auditory brainstem responses and distortion product otoacoustic emissions.ResultsPPEE exhibited significant radical scavenging activity. The ABR threshold shifts 1 day after exposure to noise at 16 kHz and 1, 7, and 14 days after exposure to noise at 32 kHz, were significantly less in the PPEE + Noise than in the Saline + Noise group. One day after noise exposure, mice in the PPEE + Noise group showed a significant degree of protection in relation to their DPOAE level at f2, 17, and 28 kHz.ConclusionsThese findings suggest that PPEE may be a potential preventive agent against TTS. In addition, as a food ingredient approved by the United States Food and Drug Administration, PPEE may be administered to those who are exposed to noise inevitably with little likelihood of adverse effects, thereby contributing to the prevention of TTS.