豚鼠畸变产物耳声发射潜伏期的对侧抑制效应现象

目的 通过观察对侧抑制效应中畸变产物耳发射（distortion productotoacousticemissions,DPOAE)各指标的改变,探讨耳蜗生理机制及传出神经的调节机能。方法 12只健康杂色豚鼠分A、B2组,在对侧耳无声刺激及给予70dB SPL宽带噪声条件下,分别使用不同的原始纯音强度组合测定在f2＝2、4、6kHz时测试耳DPOAE之幅值及潜伏期。次日,A组动物背侧径路开放右耳听泡,圆窗膜给予60mmol/L卡因酸1μL,作用3h后拭去。给药后6h测试右耳无声刺激和给予70dB SPL宽带噪声刺激下,左耳的DPOAE幅值、潜伏期等指标。结果 ①用药前,A组对侧耳给声时以等强度原始音诱发的测试耳DPOAE各频率幅值与给声前基本无变化,而潜伏期显著延长;②用药前,B组对侧耳给声以差强度原始音（L2＝L1－10dB)诱发的测试耳DPOAE在2、4kHz的幅值与给声前相比有显著减小,潜伏期也显著延长;③A组用药后,对侧耳给声对测试耳DPOAE幅值和潜伏期均无显著影响。结论 潜伏期亦是对侧抑制研究中的敏感指标。对侧抑制效应在调制耳蜗转导机制中发挥负反馈作用。     

机械纺织工人畸变产物耳声发射的临床研究

目的研究畸变产物耳声发射(distortion product otoacoustic emissions,DPOAE)在监测和早期发现噪声性聋(noise induced hearingloss,NIHL)方面的应用价值。方法检测160名(285耳)机械纺织工人(其中噪声性聋组125例224耳,有噪声接触史但纯音听阈正常者为对照组,共35例61耳)和75名听力正常人(正常对照组)的鼓室导抗图、镫骨肌反射、纯音听阈及DPOAE,比较三组的DPOAE幅值和引出率。结果①噪声性聋组DPOAE幅值及引出率均较正常对照组明显下降(P<0.05);②对照组与正常对照组比较,对照组的DPOAE幅值在4kHz处、引出率在3~6kHz处明显下降(P<0.05);③随着接触噪声工龄的延长,DPOAE引出率逐渐下降(P<0.05)。结论DPOAE可以客观地监测和早期发现噪声性聋,较纯音测听更有意义。     

畸变产物耳声发射在军事噪声致爆震性聋早期监测中的作用

目的探讨畸变产物耳声发射(DPOAE)在军事噪声致爆震性聋早期监测中的作用。方法将听力正常的炮兵某部男性官兵88例(176耳)随机分成两组,每组44例(88耳),实验组参加火炮实弹射击训练,对照组未参加火炮实弹射击训练。对照组及实验组训练前后进行纯音测听及DPOAE测试,对两组结果进行比较分析。结果实验组训练后80耳中耳传导功能无障碍,其中13耳纯音听阈示感音神经性听力损失,DPOAE检查亦异常;67耳纯音听阈正常,其中15耳DPOAE幅值在4kHz处降低。与训练前、对照组比较,实验组训练后2、4及8kHz纯音听阈升高(P<0.05或P<0.01),以4kHz处升高最为明显;实验组训练后2、3、4、6及8kHzDPOAE幅值降低(P<0.05或P<0.01),其中以4kHz处降低最为明显。结论畸变产物耳声发射在军事噪声致爆震性聋早期监测中有一定应用价值,可对其防护、诊断和治疗提供指导和帮助。     

畸变产物耳声发射与纯音听阈间测试频率的相关性研究

目的探讨畸变产物耳声发射(DPOAE)测值与纯音听阈值之间的相关性，阐明DPOAE测试频率(f0)与纯音听阈测试频率之间的对应关系。方法选正常听力人20倒(40耳)，蜗性聋病人100例(179耳)进行纯音听阈和DPOAE测试。用相关分析的统计方法计算出DPOAE测值与纯音听阈值之间的相关系数。结果DPOAE测值与纯音听阈值之间有负相关关系。f0为0．5、0．75、1．0．1．5、2．0、3．0、4．0、6．0、8．0kHz时的DPOAE测值与测试频率分别为1．0、1．0、1．0、2．0．3．0、3．0、4．0、6．0、8．0kHz时的纯音听阈值之间有相对最大的负相关系数。f0为0．5、0.75、1．0、1．5、2．0、3．0、4．0、6．0、8．0kHz时所对应的量相关纯音听阈测试频率分别为0．75、1．0、1．5、2．0、2．5、3．5、5．0、6．0、8．0kHz。结论DPOAE测值与纯音听阈值之间有负相关关系，且DPOAE测试频率与纯音听阈测试频率间存在一定的对应关系。     

煤矿井下噪声暴露工人畸变产物耳声发射检测

目的探讨畸变产物耳声发射（DPOAE）在监测及早期发现噪声性聋方面的价值。方法对73例142耳耳科正常人（对照组）和78例154耳煤矿井下噪声暴露工人（实验组,其中纯音听力正常组45例90耳,纯音听力异常组33例64耳）,行DPOAE0.5～16kHz检测,两组结果进行比较。结果实验组DPOAE幅值在3.0、4.0、6.0、11.2kHz处下降明显,与对照组比较差异有显著意义（P〈0.05）;而在12.5、14.0、16.0kHz频率两组差异无显著意义（P〉0.05）。纯音听力正常与异常的实验组分别与对照组比较,DPOAE幅值变化趋势相同,纯音听力正常与异常的实验组在3.0、4.0、6.0、11.2kHz处均下降,分别与对照组比较差异有显著意义（P〈0.05）;在11.2kHz处纯音听力异常的实验组下降更显著（P〈0.01）;实验组DPOAE引出率均下降,与对照组比较差异有显著意义（P〈0.05）。结论 DPOAE检查可用于噪声性聋的早期诊断和监测。     

硫辛酸对纯音听力损失前畸变产物耳声发射异常的作用及意义

目的观察脉冲噪声致纯音听力损失前畸变产物耳声发射（DPOAE）异常的自然转归及硫辛酸对其转归的影响。方法纯音听阈正常、DPOAE异常者26例（41耳）,随机分为对照组和治疗组,每组各13例。治疗组给予硫辛酸600mg/日静滴治疗,对照组给予安慰剂治疗,治疗后第2、4、6、8、10天,分别进行纯音听阈及DPOAE检查。结果治疗前两组各对应频率的纯音听阈及DPOAE幅值均无显著差别,DPOAE异常频率主要发生在3、4、6、8kHz。经过治疗后,两组的纯音听阈无明显变化,对照组异常频率的DPOAE的幅值自第8天开始,显著大于治疗前。治疗组异常频率的幅值自第4天开始显著大于治疗前。从治疗后第4天,治疗组异常频率的幅值显著高于对照组对应时间和频率的幅值。结论人耳对脉冲噪声致纯音听力损失前DPOAE幅值异常有一定的自行修复能力,硫辛酸对其恢复有明显的促进作用,提示硫辛酸对爆震性聋有预防作用。     

耳蜗性聋的畸变产物耳声发射测试

目的：通过畸变产物耳声发射(DPOAE)测试耳蜗性聋的敏感性、特异性和符合率来评估其测试效能。方法：测试听力正常人86耳和耳蜗性聋98耳的DPOAE，其1～6kHz各个频率的幅值与对应频率的电测听纯音听阈相比较，用所得到患耳蜗性聋敏感性和特异性值作受试者作业特征曲线。并计算其面积。其面积值并不因为DPOAE用于区别听力正常与否的取值标准不同而发生变化。用所得到的面积值来判断DPOAE的测试效能。结果：1～6kHz从低到高各个频率对应的受试者特征曲线面积分别为0．677，0．777，0．818，0．890，0．873。结论：DPOAE可以作为测试耳蜗性聋的一种频率特异性的客观方法。     

畸变产物耳声发射对耳蜗性聋和耳蜗后性聋的鉴别诊断意义

目的 探讨畸变产物耳声发射（DPOAE）鉴别诊断耳蜗性聋和耳蜗后性聋的意义。方法 采用ILO96耳动态分析仪对49例耳蜗性聋和4例耳蜗后性聋进行DPOAE测试。结果 耳蜗性聋组的DPOAE图显示出DPOAE幅值随纯音听阈的升高有不同程度的下降,并显示出很好的频率特异性,当纯音听阈＞50dBHL时,DPOAE消失。耳蜗后性聋组的DPOAE图显示出的DPOAE幅值变化不明显,仍在正常范围,与纯音听阈长吭程度缺乏相对应关系。结论 DPOAE是一种有效的辅助性鉴别诊断耳蜗性聋和耳蜗后性聋的方法。     

不同原因内耳损伤下畸变产物耳声发射的改变

目的研究不同原因内耳损伤下畸变产物耳声发射(distortion product otoacoustic emissions,DPOAE)改变的特点.方法对耳科正常人、噪声暴露工人和应用顺铂化疗的妇科肿瘤患者进行DPOAE(0.5～16 kHz)、常频纯音测听(0.5～8 kHz)及扩展高频测听(9～16 kHz)检查.对DPOAE幅值与纯音听阈进行比较分析.结果在噪声性和顺铂耳毒性损伤下,常频DPOAE表现为3～6 kHz幅值降低,早于对应常频纯音听阈变化.扩展高频DPOAE幅值均有下降,但频率区域不同,噪声组只在11.2 kHz处下降明显,其他频率变化不大,尤其是12.5 kHz、14 kHz、16 kHz三个频率几无变化;药物组除16 kHz外各频率均幅值下降.结论常频DPOAE比常频纯音测听和扩展高频DPOAE敏感,因此,在噪声、顺铂等引起的耳蜗性听力损害的早期监测中,优于常频纯音测听和扩展高频DPOAE.     

畸变产物耳声发射与纯音听阈间测试频率的相关性研究

目的:探讨畸变产物耳声发射(OPOAE)测值与纯音听阈值之间的相关性,阐明DPOAE测试频率(f0)与纯音听阈测试频率之间的对应关系。方法:选正常听力人20例(40耳),蜗性聋病人100例 (179耳)进行纯音听阈和DPOAE测试。用相关分析的统计方法计算出DPOAE测值与纯音听阈值之间的相关系数。结果:DPOAE测值与纯音听阈值之间有负相关关系。f0为0．5、0．75、1．0、1．5、 2．0、3．0、4．0、6．0、8．0kHz时的DPOAE测值与测试频率分别为 1．0、1．0、1．0、2．0、3．0、3．0、4．0、6．0、8．0kHz时的纯音听阈值之间有相对最大的负相关系数。f0为0．5、0．75、1．0、1．5、 2．0、3．0、4．0、6．0、8．0kHz时所对应的最相关纯音听阈测试频率分别为0．75、1．0、1．5、2．0、2．5、3．5、5．0、6．0、8．0kHz。结论:DPOAE测值与纯音听阈值之间有负相关关系,且DPOAE测试频率与纯音听阈测试频率间存在一定的对应关系。图1表3参6     

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.     

畸变产物耳声发射在唇腭裂婴幼儿听力检查中的应用

目的探讨唇腭裂婴幼儿畸变产物耳声发射（distortion product otoacoustic emission,DPOAE）的特点,并将其与听性脑干反应（auditory brainstem response,ABR）阂值检查的结果加以对照,以探讨DPOAE在这类患儿听力检查中的应用价值。方法DPOAE检查63例（126耳）,年龄2个月-42个月,平均11.83个月。其中单纯腭裂组（以下简称腭裂组）23例（46耳）,腭裂并发唇裂及牙槽裂组（以下简称唇腭裂组）30例（60耳）,单纯唇裂组（以下简称唇裂组）10例（20耳）,每耳均检查8个频率,若2-5kHz4个频点有≥3个频点通过即为该耳通过。在上述患儿中,ABR阈值检查腭裂组17例（34耳）,唇腭裂组10例（20耳）,唇裂组6例（12耳）,以能重复引出V波的最小刺激强度为ABR阈值。结果DPOAE检查：腭裂组通过7耳,未通过39耳,通过率为15.22％;唇腭裂组通过6耳,未通过54耳,通过率为10.00％;唇裂组通过18耳,未通过2耳,通过率为90％。统计分析腭裂组与唇腭裂组无显著差异,而腭裂组与唇裂组,唇腭裂组与唇裂组均有显著差异。ABR阈值检查统计分析结果与DPOAE一致。将各组DPOAE通过率与ABR正常率进行比较,腭裂组及唇腭裂组中二者无差异（P〉0.05）,虽然唇裂组中二者有差异（P〈0.05）,但唇裂组ABR阈值反应的听力下降较轻（均≤50dB nHL）。从总体趋势上说,DPOAE与ABR阈值检查在检测的结果上是一致的。结论唇腭裂患儿DPOAE和ABR检测结果一致,与ABR相比,DPOAE具有快速、简便、易实施等特点,因此DPOAE可以作为唇腭裂婴幼儿听力检查的手段,但仍需进一步结合ABR及其他相关的听力检查,以明确听力损害的程度和类型。     

Detection of hearing loss using 2f2-f1 and 2f1-f2 distortion-product otoacoustic emissions.

Although many distortion-product otoacoustic emissions (DPOAEs) may be measured in the ear canal in response to 2 pure tone stimuli, the majority of clinical studies have focused exclusively on the DPOAE at the frequency 2f1-f2. This study investigated another DPOAE, 2f2-f1, in an attempt to determine the following: (a) the optimal stimulus parameters for its clinical measurement and (b) its utility in differentiating between normal-hearing and hearing-impaired ears at low-to-mid frequencies (相似文献   

Correlation of transiently evoked to distortion-product otoacoustic emission measures in healthy children

OBJECTIVE: Transiently evoked (TEOAEs) and distortion-product otoacoustic emissions at the 2f1-f2 frequency (DPOAEs) are being used as a clinical tool for diagnosis of peripheral auditory pathology. Because both tests are fast and non-invasive, they may be an excellent method for hearing screening in infants and children. The purpose of this study was to compare the TEOAE and DPOAE measures obtained in a group of healthy children. METHODS: Sixty-six school-aged children with normal hearing were included in the study. Subjects with recent otologic disease or abnormal tympanograms were excluded. TEOAEs and DPOAEs were performed using a DP Echoport ILO 292 Otodynamics analyzer connected to a portable personal computer. Correlation between TEOAE amplitudes and DPOAE levels was estimated. RESULTS: Correlation between TEOAE amplitudes and DPOAE levels was highly significant across all measured frequencies. Correlation was more significant at the middle frequencies than at the low and high frequencies. CONCLUSIONS: Although frequency specific information may be obtained by both tests, most reliable results were obtained at the middle frequencies. TEOAE values were more prominent at low frequencies, whereas DPOAEs were more effective at high frequencies. Both methods are reliable, objective, fast and useful tests of the cochlear status and should be included in the standard audiological diagnostic work-up of children.     

High-frequency hearing influences lower-frequency distortion-product otoacoustic emissions

OBJECTIVES: The primary goal of this study was to test the ability of 2f1-f2 distortion-product otoacoustic emissions (DPOAEs) to detect reduced cochlear function in the presence of normal behavioral sensitivity. DESIGN: A prospective study was performed in normal-hearing young adults using simple and complex regression analyses to clarify the relationship between ultra-high frequency (UHF) hearing and DPOAE levels at lower frequencies, as well as the influence of hearing levels for frequencies within the conventional test range and subject age on this association. METHODS: Average DPOAE levels between 4 to 8 kHz, which were elicited by equilevel primary tones of low to moderate levels, were measured as level-frequency functions, or distortion-product (DP) grams, and related to the mean UHF hearing levels from 11.2 to 20 kHz. The median hearing level for the UHF hearing was used to separate subjects into good and poor UHF hearers. This distinction was then used to compare DPOAE levels from 4 to 8 kHz for the 2 groups to determine if UHF hearing status influenced DPOAE levels at lower frequencies. RESULTS: Simple regression analysis revealed that the 4-to 8-kHz DPOAE levels were significantly correlated with the pure-tone average (PTA) from 11.2 to 20 kHz. However, the PTA for 4 and 8 kHz was also significantly correlated with the PTA for UHF hearing. Further multiple regression analyses revealed that UHF hearing significantly and uniquely accounted for approximately 14% of the variance in DPOAE levels from 4 to 8 kHz for most of the primary-tone level combinations. In contrast, neither the PTA for the conventional hearing range nor subject age contributed significantly to the DPOAE variance. CONCLUSIONS: The findings suggest that UHF hearing influences DPOAEs at significantly lower frequencies because emissions are sensitive to subtle changes in outer hair cells not yet detected by pure-tone thresholds in this region or because alterations in the basal cochlea affect the generation of lower-frequency DPOAEs originating from more apical cochlear regions.     

Intra- and intersubject variability of acoustically evoked otoacoustic emissions. II. Distortion product otoacoustic emissions]

BACKGROUND: Distortion product otoacoustic emissions (DPOAEs) are evoked by simultaneously stimulating the cochlea with two tones. The DPOAE with the highest amplitude (at the frequency 2f1-f2) is usually used for routine audiological evaluation. Any interpretation of DPOAEs in a clinical setting must consider their intra- and intersubject variability. METHODS: DPOAE measurements were performed in 36 normally hearing adults in three weekly test sessions. Each ear was tested twice per session, and the results were statistically analyzed. RESULTS: All test candidates had measurable DPOAEs. Statistically significant differences in absolute DPOAE amplitudes were neither found between two measurements at the same day, nor at weekly intervals, nor between right and left ear of the same candidate. Absolute DPOAE amplitudes in women were significantly higher in the 2-6 kHz range whereas they presented with significantly lower amplitudes below 2 kHz when compared to men. CONCLUSIONS: The present results indicate that monitoring of the inner ear status can be reliably performed using DPOAE measurements. Change in DPOAE amplitudes effectively indicate changes in the cochlear function with high sensitivity. Compared to TEOAE measurements, DPOAEs offer a higher frequency resolution in a broader frequency band and thus more detailed information about the cochlear condition.     

High frequency distortion product otoacoustic emissions in children with and without middle ear dysfunction

OBJECTIVE: Distortion product otoacoustic emissions (DPOAEs) (9-16kHz) are a useful measure of the function of the cochlea, which may be damaged by ototoxic drugs during anticancer chemotherapy. As children undergoing chemotherapy may also have middle ear problems, it is necessary to know if middle ear problems would have a confounding effect on the ability of DPOAEs to assess cochlear function in the extend high frequency region (9-16kHz). The present study aimed to investigate the effect of middle ear dysfunction on DPOAEs in the extended high frequency region in young children. METHODS: The sample was comprised of 100 ears of 50 school-aged children (21 boys and 29 girls) with a mean age of 6.3 years (S.D.=0.5; range 5.3-7.3). Otoscopy, pure tone hearing screening, tympanometry, acoustic reflexes and DPOAEs for both the conventional and extended high frequencies were administered to each child under typical school screening conditions. Participants were classified into one of three groups based on immittance (tympanometry and acoustic reflex) results. They included a "pass immittance" group, a "fail immittance" group and an "undetermined" group (with a pass in either tympanometry or acoustic reflexes, but not both). DPOAE amplitudes and signal-to-noise ratios (SNRs) were measured and compared across the three groups of participants. RESULTS: The fail immittance group showed significantly smaller DPOAE amplitudes and SNRs when compared to the other two groups at frequencies ranging from 1 to 9.5kHz and at 13kHz, but not at 10, 11, 12 and 14kHz. There was no significant difference in DPOAE results between the pass immittance and undetermined groups. CONCLUSIONS: Despite the adverse effects of middle ear dysfunction, its effect on DPOAEs in the extended high frequency region was not as severe as that in the lower frequency region. Hence, assessment of cochlear function in children with a middle ear lesion in the extended high frequencies using DPOAEs should be made with caution.     

The clinical use of oto-acoustic emissions of cochlear distortion products

Otoacoustic emissions of cochlear distortion products (DPOAEs) were measured in normally hearing and hearing-impaired human ears. A total of 133 subjects (231 ears) were tested. Two puretone stimuli f1 and f2 were delivered to a sound probe fixed in the outer ear canal. The frequencies of the two primaries were chosen so that their geometric mean represented pure-tone audiometric frequencies. The otoacoustic emission was measured at the distortion product frequency 2f1-f2 by spectral averaging. For 199 ears, the levels of the primaries were 73 dBHL for L1 and 67 dBHL for L2. Statistical analysis was carried out in 77 ears of 46 subjects with normal hearing (average hearing levels at pure-tone audiometric thresholds less than or equal to 10 dBHL) and 36 ears of 25 subjects exhibiting near-normal hearing (average hearing levels at pure-tone audiometric thresholds less than or equal to 20 dBHL). The mean DPOAE amplitudes were similar in these two groups of ears. In 111 of these 113 ears (98.2%), DPOAEs were detected at three or more of the six tested frequencies between 1 and 6 kHz. DPOAEs were measured in more than 75% of ears at each frequency between 1-6 kHz and in more than 86% between 1-4 kHz. Eighty-six hearing-impaired ears of 44 subjects with sensorineural hearing loss formed the patient group. A highly significant correlation between pure-tone audiometric thresholds and DPOAE amplitudes was demonstrated in the frequency range of 1-4 kHz. Percentiles of DPOAE amplitudes were calculated in 22 ears with a mean pure-tone threshold less than or equal to 5 dBHL and in 12 specially selected pathological ears.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Distortion product otoacoustic emissions show exceptional resistance to noise exposure in MOLF/Ei mice

Baseline distortion-product otoacoustic emissions (DPOAEs) at several primary-tone levels were compared between naive 2- to 3-month old inbred CBA/CaJ (CBA) and wild-derived MOLF/Ei (MOLF) mice. Only minor DPOAE differences were noted between the two strains and these differences were not systematic across frequency or test levels. These emission findings were consistent with earlier results on auditory brainstem response thresholds reported by others [Zheng et al., Hear. Res. 130 (1999) 94-107] thus suggesting that both CBA and MOLF strains have normal hearing. Subsequent episodes of over-exposure to a 105-dB SPL, octave-band noise centered at 10 kHz for 8 h revealed that MOLF DPOAEs were exceptionally resistant to the adverse aftereffects of excessive noise exposure as compared to CBA mice. Unlike the noise-exposure resistant inbred 129/SvEvTac strain, which has reduced baseline DPOAE levels especially at high frequencies, MOLF mice have normal DPOAEs making the interpretation of noise-exposure effects more straightforward.