听觉稳态诱发电位研究近展

听觉稳态诱发电位(SSEP)是由调制声信号引起的,反应相位与刺激信号的相位具有稳定关系的听觉诱发电位。它快速、无创、频率特异性好、与行为听阈相关性好、测试方法客观,结果判定客观。在调制频率>60Hz时,不受醒觉状态影响,是儿童特别是婴幼儿理想的听力损失定量诊断方法。多频SSEP在前者的基础上,双耳多个测试频率同时刺激,同时记录反应。不影响测试准确性,但大大提高了测试效率。     

Objective assessment of auditory thresholds in noise-induced hearing loss using steady-state evoked potentials

The purpose of this study is to evaluate whether steady-state evoked potential (SSEP) can be used for objective estimation of auditory thresholds in patients with noise-induced hearing loss (NIHL). Eleven subjects (22 ears) with a characteristic audiometric notch between 3000 and 6000 Hz participated in this study. Both pure-tone thresholds and SSEP thresholds were obtained for each ear of all subjects. The correlation of SSEP thresholds and pure-tone thresholds was assessed. The results show that SSEP thresholds predicted pure-tone thresholds with correlation coefficients (r) of 0.86, 0.92, 0.94 and 0.95 at 500, 1000, 2000 and 4000 Hz respectively. Typically, the SSEP thresholds overestimate the pure-tone thresholds by 10-20 dB, but they closely reflect the configuration of the audiogram. The strength of the relationship between SSEP and pure-tone thresholds increased with increasing frequency and increasing degree of hearing loss. In conclusion, SSEP can be used as a reliable and objective tool to assess auditory thresholds in patients with noise-induced hearing loss with high-frequency dips.     

感音神经性聋成人不同刺激声ASSR反应阈与纯音听阈的相关性分析

目的探讨调制声听性稳态反应(ASSR)、 CE-Chirp ASSR用于评估感音神经性聋成人客观听力的价值。方法对78例(131耳)感音神经性聋成人同时进行纯音听阈和调制声ASSR、 CE-Chirp ASSR测试,比较0.5~4 kHz各频率纯音听阈与调制声ASSR、CE-Chirp ASSR反应阈的相关性及差值。结果 0.5、1、2、4 kHz CE-Chirp ASSR反应阈与纯音听阈的相关系数(分别为0.77、0.73、0.80、0.88)均高于调制声ASSR反应阈与纯音听阈的相关系数(分别为0.64、0.61、0.78、0.84),调制声ASSR、CE-Chirp ASSR反应阈与纯音听阈均具有显著相关性(圴为P<0.01);0.5~4 kHz CE-Chirp ASSR反应阈和纯音听阈的差值(分别为8.09±4.74、10.76±5.86、7.44±7.95、6.11±9.14 dB)均明显小于调制声ASSR反应阈和纯音听阈间的差值(分别为14.31±6.38、13.85±6.25、17.17±6.29、13.58±4.35 dB),差异均有统计学意义(均为P<0.05)。结论 CE-Chirp ASSR快捷可靠,较调制声ASSR能更好地评估感音神经性聋成人的听力。     

chirp声诱发的听性稳态反应在新生儿和低月龄婴儿客观听力评估中的应用

目的探讨以线性调频脉冲音(chirp)为刺激声的听性稳态反应(auditory steady state response,AS-SR)(简称chirp-ASSR)的反应阈评估低月龄婴儿客观听力的可行性。方法对68例136耳6月龄及以下的双耳AABR筛查均通过的婴儿分别进行chirp-ASSR和短纯音诱发的听性脑干反应(tone burst evoked auditory brain-stem response,tbABR)检测,对反应阈和检测时间进行比较。结果①tbABR与chirp-ASSR在各个频率的反应阈相关性良好;②chirp-ASSR双耳检测时间(平均7分4秒)明显短于tbABR(平均21分6秒),可节省约66.51%的时间。结论 chirp-ASSR能快速评估低月龄婴幼儿的客观听力,结果可靠、稳定。     

Extended high‐frequency audiometry in patients with acoustic trauma

Objectives: The aim of this study was to examine extended high‐frequency (EHF) hearing in patients with acoustic trauma. Design: A prospective, case–control study in a group of soldiers with acoustic trauma caused by shooting practice during basic training. Setting: Tertiary referral centre. Participants: A total of 39 young soldiers hospitalized for hearing loss and tinnitus following exposure to weapon impulse noise were studied. Conventional audiometry in the frequency range 0.25–8 kHz and EHF audiometry in the frequency range 9–20 kHz were performed, both on admittance and before discharge. Thirty healthy recruits of similar age and sex were used as controls. Main outcome measures: Pure‐tone threshold changes documented by conventional and EHF audiometry. Results: The most significant differences in pure‐tone thresholds on initial testing were found in the frequency range 0.25–11.2 kHz, and especially in the 4–8 kHz region. Reduction in thresholds across most frequencies was observed after treatment, although recovery was partial in most cases. Conclusions: The EHF audiometry adds no significant additional information to conventional pure‐tone audiometry in assessing and monitoring noise‐induced hearing loss.     

短纯音及切迹噪声掩蔽的短纯音ABR用于儿童听力评估的研究

目的研究儿童短纯音（tone burst）及同侧切迹噪声（notched noise）掩蔽短纯音诱发的ABR反应阈,与短声诱发的听性脑干反应（click-evoked auditory brainstem response,c-ABR）以及40Hz听觉事件相关电位（40Hz Auditory Event Related Potentials,40Hz AERP）反应阈的关系,以评价这些测试方法在儿童听力评估中的应用价值。方法应用SmartEP听觉诱发电位仪在29例（53耳）儿童（男18例,女11例,年龄2月-8岁）中测试短声ABR、短纯音ABR、两种不同强度切迹噪声掩蔽短纯音诱发的ABR（分别定义为c-ABR、tb-ABR、amtb-ABR和bmtb-ABR）及40Hz AERP。结果（1）fb-ABR、amtb-ABR、bmtb-ABR在2kHz、4kHz两个频率的反应阈与c-ABR的反应阈接近,反应阈之间有较好的相关性;（2）tb-ABR、amtb-ABR、bmtb-ABR的反应阈与40Hz AERP的反应阈在0.5、1、2、4kHz各个频率均接近并有较好的相关性。结论使用短纯音及同侧切迹噪声掩蔽短纯音诱发的ABR的反应阈预测儿童的纯音行为听阈是可行的。     

Prediction of hearing thresholds: comparison of cortical evoked response audiometry and auditory steady state response audiometry techniques

The present study evaluated how well auditory steady state response (ASSR) and tone burst cortical evoked response audiometry (CERA) thresholds predict behavioral thresholds in the same participants. A total of 63 ears were evaluated. For ASSR testing, 100% amplitude modulated and 10% frequency modulated tone stimuli at a modulation frequency of 40Hz were used. Behavioral thresholds were closer to CERA thresholds than ASSR thresholds. ASSR and CERA thresholds were closer to behavioral thresholds at higher frequencies than at lower frequencies. Although predictions based on CERA thresholds are slightly more accurate than ASSR thresholds, the differences may not be clinically significant, particularly when the degree of individual variations is considered. Prediction of hearing thresholds became more accurate when hearing loss increased. Due to variations in prediction across participants, a single correction factor cannot be used. Other factors must be considered in selecting whether to use CERA or ASSR in predicting behavioral thresholds.     

Prediction of hearing thresholds: Comparison of cortical evoked response audiometry and auditory steady state response audiometry techniques

The present study evaluated how well auditory steady state response (ASSR) and tone burst cortical evoked response audiometry (CERA) thresholds predict behavioral thresholds in the same participants. A total of 63 ears were evaluated. For ASSR testing, 100% amplitude modulated and 10% frequency modulated tone stimuli at a modulation frequency of 40Hz were used. Behavioral thresholds were closer to CERA thresholds than ASSR thresholds. ASSR and CERA thresholds were closer to behavioral thresholds at higher frequencies than at lower frequencies. Although predictions based on CERA thresholds are slightly more accurate than ASSR thresholds, the differences may not be clinically significant, particularly when the degree of individual variations is considered. Prediction of hearing thresholds became more accurate when hearing loss increased. Due to variations in prediction across participants, a single correction factor cannot be used. Other factors must be considered in selecting whether to use CERA or ASSR in predicting behavioral thresholds.     

Tone-evoked brainstem responses and auditory steady state responses to 40hz and 80hz amplitude modulated stimuli with different frequencies — a comparative study

Abstract  Tone burst evoked auditory brainstem responses and auditory steady state responses with 40 or > 80 Hz modulation can be used to determine frequency specific threshold. Aim  The present study was taken up to check for the efficacy of estimating hearing thresholds by tone burst ABR and ASSR. The frequency effect (low, mid and high) on estimating the threshold was also focused upon. Methods  20 normal hearing adults (40 ears) in the age range of 16 to 30 years participated in the study. The pure tone audiometry and immittance was initially done. Subsequently, tone-burst ABR, 80Hz ASSR and 40Hz ASSR to estimate the threshold with three frequencies 500Hz (low), 2000Hz (mid) and 4000Hz (high) was done. The data was analyzed statistically using pair sample t-test. Results  ASSR threshold for 80Hz and 40Hz was almost comparable. ASSR was superior to estimate the threshold than tone-burst ABR. For the low frequency the discrepancy between the behavioral threshold and frequency-specific evoked audiometry was more when compared to mid and high frequency. Conclusion  Present study showed that steady-state responses were efficient means of threshold detection than visual detection of ABR wave-V. In awake adult subjects, 40Hz and 80Hz amplitude modulated produced similar results. For the threshold estimation ASSR was better than tone-burst ABR.     

听觉中枢功能状态对老年感音神经性听障患者听力语言康复的影响

目的探究听觉中枢功能状态对老年感音神经性听障患者听力语言康复的影响。方法选取我院2018年1月~2020年8月诊治的老年感音神经性听障患者109例,分别进行纯音测听、助听听阈测试、皮层听觉诱发电位测试及言语识别测试。以55 dB声压级(sound pressure level,SPL)下皮层听觉诱发电位P1是否全部引出波形分为A组(引出波形,n=47)和B组(未引出波形,n=62);比较两组患者纯音测听、助听听阈结果和言语识别率,分析助听听阈与听觉诱发电位P1波潜伏期、幅值的相关性。结果A组患者纯音听阈显著高于B组(P<0.05);A组在低频、中频、高频的助听听阈值均显著低于B组(P<0.05)。配戴助听器后两组患者的言语识别率均增加,且A组显著高于B组(P<0.05)。P1波幅值随着刺激强度增强逐渐降低,助听听阈随着引出P1的刺激强度增强逐渐提高。助听听阈与幅值呈显著负相关(P<0.05),与P1波潜伏期无相关性(P>0.05)。结论皮层听觉诱发电位与助听听阈测试结果具有相关性。     

Using multi-stimulus auditory steady state response to predict hearing thresholds in high-risk infants

The purpose of this study was to investigate whether multi-stimulus auditory steady-state responses were capable of estimating hearing thresholds in high-risk infants. A retrospective chart review study. Three tertiary referral centers. Infants born between January 2004 and December 2006 who met the criteria for risk factors of congenital hearing loss were enrolled in the study. While under sedation, the multi-stimulus auditory steady-state response was used to determine multi-channel auditory steady-state response thresholds for high-risk infants younger than 13 months. Conditioned play audiometry was then applied to these children at 23–48 months of age to obtain pure tone audiograms. Auditory steady-state response thresholds and pure tone thresholds were then compared. A total of 249 high-risk infants were enrolled in the study. 39 infants were lost during follow-up. The remaining 216 infants completed both examinations. The Pearson correlation coefficients (r) between the ASSR levels and pure tone thresholds were 0.88, 0.94, 0.94 and 0.97 at 500, 1,000, 2,000 and 4,000 Hz, respectively. The strength of the relationship between the auditory steady-state responses and pure tone thresholds increased with more severe degrees of hearing loss and higher frequencies. We conclude that initial multichannel ASSR thresholds measured under sedation are highly correlated with pure tone thresholds obtained 2 or 3 years later. ASSR can be used to predict the frequency-specific hearing thresholds of high-risk infants and can provide information for early hearing intervention.     

Otoakustische Emissionen, Hirnstammpotentiale, Tonschwellengehör und Sprachverständlichkeit bei auditorischer Neuropathie

The combined findings of "normal evoked otoacoustic emissions (EOAE) and absent or markedly disturbed auditory evoked potentials from the brainstem and/or cortex" has been named auditory neuropathy in the English literature. The pure tone thresholds in these patients range from mild to severe loss. The loss of speech comprehension is out of proportion in comparison to the pure tone threshold elevation. This combination of findings suggests that cochlear function and in particular outer hair cell function, is normal in these patients but also suggests that the inner hair cell / VIII nerve functional unit is abnormal. Disruption in neural synchrony has previously been postulated as a reasonable explanation for the absent auditory brainstem response while otoacoustic emissions are preserved. Because the long-latency auditory evoked potentials, not having the stringent synchrony requirements of the ABR, may also be missing, the term synchrony - disruption may be somewhat misleading. The literature about auditory neuropathy is reviewed here: We now know that a set of salient features distinguishes these patients from the majority of patients with sensorineural hearing loss or other described syndromes. The symptoms defining auditory neuropathy are mild, moderate or severe elevation of auditory thresholds to pure tone stimuli by air and bone conduction, absent to severely abnormal ABRs to high level stimuli, present otoacoustic emissions (that do not suppress with contralateral noise), word recognition ability poorer than expected from the pure tone hearing loss configuration (in cases with mild to moderate hearing threshold elevation) and absent acoustic reflexes to both ipsilateral and contralateral tones. The entire set of findings, consistently seen in these patients, supports the importance of the crosscheck principle in diagnostic evaluation especially in children with delayed and/or impaired language acquisition. It is of ponderous importance that this disorder is not being confused with sensory hearing loss.     

听神经病的听功能状态分析

目的 :探讨听神经病的听功能状态及病损部位。方法 :分析 6 5例听神经病患者的临床资料、纯音测听、声导抗测试、听性脑干反应 (ABR)、4 0Hz听觉相关电位及OAE检查结果。结果 :听神经病的低频听力损失源于蜗后的传入、传出神经及听性脑干受损 ,表现为声反射、传出抑制、ABR异常及诱发性OAE与纯音听阈不呈平行关系 ,与之相对应 ,低频区的外毛细胞处于失抑制的超常活动状态 ,表现为低频区SOAE增强、TEOAE反应幅值及DPOAE幅值升高 ;听神经病的高频听力损失源于耳蜗的外毛细胞损害 ,表现为高频区DPOAE幅值与纯音听阈呈一致性下降 ;听神经病的中频听力损失最轻或接近正常 ,表现为 2kHz附近的纯音听阈和DPOAE幅值均接近于正常。结论 :听神经病的传入、传出系统及耳蜗水平均有不同程度的功能障碍 ,其病损部位主要在耳蜗传入、传出神经 ,向上可侵及脑干 ,向下可侵及耳蜗     

Noise‐induced hearing loss is exacerbated by long‐term smoking

Objective: To analyse the influence of long‐term smoking on the hearing threshold of individuals subjected to occupational noise exposure. Design: Prospective observational cohort study. Setting: Occupational health examination of noise‐exposed employees in the brick manufacturing industry. Participants: A study group of long‐term smokers (n = 30) and a control group of non‐smokers (n = 58) were identified from a population of 227 male noise‐exposed employees. Individuals of both groups were employed for 10 years or more at a single brick manufacturing plant. Data on noise exposure, smoking habits, medical and otological history were collected and standard pure tone audiometry was obtained. Exclusion criteria included asymmetrical or conductive hearing loss, uncontrolled systemic illnesses, history of head injury, chronic middle ear pathology or major ear operations. Main outcome measure: Pure tone audiometry. Results: Both groups had similar mean age and total duration of occupational noise exposure. The median age‐corrected hearing thresholds at 3 and 4 kHz in the smokers group were significantly higher (～7dB) than those in the non‐smokers group. No statistical difference in the hearing thresholds between both groups was found in any other tested frequency (0.5, 1, 2, 6 and 8 kHz). Conclusion: Long‐term smokers with occupational noise exposure may, on the basis of this limited study, have a higher risk of developing permanent hearing loss at 3 and 4 kHz when compared with non‐smokers with a similar occupational history.     

Human auditory steady state responses: effects of intensity and frequency

Human auditory steady state responses were recorded in 41 normal subjects and 22 patients with hearing loss. The effect of intensity on the responses at different tonal frequencies was assessed using the sweep technique. The amplitude of the responses increases and the phase delay decreases with increasing intensity. Both the amplitude and the phase delay are smaller for high frequency tone bursts. Notched noise decreases the amplitude of the response by a factor of two but does not affect the phase of the responses. Thresholds were estimated in waking subjects using two techniques: intensity sweeps analyzed by linear regressions, and fixed intensities analyzed by Hotelling's T2 test. Frequency-specific thresholds obtained with notched noise were less variable and more accurate with the fixed intensity technique. In patients with sensorineural hearing loss the amplitude increased more with increasing intensity above threshold than in patients with conductive hearing loss.     

Notched-noise-BERA: methods and diagnostic use

BACKGROUND: As Picton demonstrated with case reports in 1978, thresholds of click-evoked potentials do not match to pure tone thresholds if hearing loss differs across the test frequencies. Thus, he developed a stimulation with brief tone pips masked by a notched noise that over the years became the standard method for frequency specific threshold estimation. Currently, new technologies like auditory steady-state responses and Chirp-evoked potentials promise to overcome some disadvantages of the NN-BERA. METHODS: Thus, a systematic review about the NN-BERA was needed to further compare the competitive technologies. Literature research was performed according to the present guidelines for evidence based medicine. It was found that a meta-analysis with data pooling was impossible because of massive discrepancies of methods and subjects across the retrieved publications. RESULTS: The differences of means between pure tone thresholds and NN-BERA-thresholds were up to 12 dB. Standard deviations were 2 to 16 dB and generally higher at 0.5 und 1 kHz compared to 2 and 4 kHz. Correlations were r = 0.84 to r = 0.97. CONCLUSIONS: The NN-BERA faces a growing competition by auditory steady state potentials, chirp-evoked potentials, and distortion product otoacoustic emissions but serves still as the standard for an objective threshold estimation since it's accuracy is well evaluated and the interpretation is independent from statistical tests which accuracy is not sufficiently evaluated at present.     

Simultaneous Acquisition of 80 Hz ASSRs and ABRs From Quasi ASSRs for Threshold Estimation

OBJECTIVES:: Both 80 Hz auditory steady state responses (ASSRs) and tone burst auditory brainstem responses (ABRs) have been shown to provide reasonable estimates of the behavioral thresholds. Although ASSRs provide statistically objective estimates that can be easily automated by computers, they present no information for the neurophysiological interpretation of the results. ABRs, on the other hand, do not provide easily automated information and usually need expert interpretation of the recorded waveforms. A recently developed continuous loop averaging deconvolution algorithm offers an alternative solution by acquiring slightly jittered 80 Hz quasi auditory steady state responses (QASSRs), thus enabling the acquisition of both recordings simultaneously. The purpose of this study is to investigate a specially developed 80 Hz QASSR paradigm for simultaneous acquisition for both responses for threshold detection purposes. DESIGN:: Sixteen ears from eight adults with normal hearing were tested. Amplitude modulated QASSRs were obtained using slightly jittered temporal sequences of tone bursts presented at a mean rate of 78.125 Hz. Four carrier frequencies (500, 1000, 2000, and 4000 Hz) at several stimulus intensity levels were monaurally presented and QASSRs to 128 sweeps blocks were recorded. The ABRs were extracted using the CLAD algorithm. Wave V was visually identified and analyzed in the time domain as in everyday clinical practice. In addition, statistically objective ?MP computation method was used to automatically detect ABR threshold as well. The QASSRs were analyzed in the frequency domain and magnitudes, phase delays, and thresholds were obtained. Phasor (polar plot) diagrams were constructed. QASSR and ABR hearing thresholds were obtained and compared with behavioral thresholds. RESULTS:: Study reveals that the QASSR method provides accurate objective estimation of the audiometric thresholds from extracted ASSRs and latency/amplitude information from extracted ABRs. The largest mean threshold difference for QASSR was within 5 dB for all carrier frequencies including 500 Hz. For auditory threshold estimation in adults with normal hearing, the Hotelling's T-Square test in four dimensions in the frequency domain was more accurate than the ?MP or visual ABR threshold detection in the time domain. CONCLUSIONS:: Simultaneously recorded ASSR and ABR from QASSRs provide accurate and effective method for frequency-specific hearing threshold estimation with neurophysiological information in adults with normal hearing. Further research is required for hearing-impaired adults, newborns, and infants.     

成人感音神经性聋的听觉稳态反应反应阈与纯音听阈

目的探讨成人感音神经性聋的听觉稳态反应（auditory steady-state responses,ASSR）反应阈与纯音听阈的关系。方法选择中国医科大学附属一院耳鼻咽喉科门诊感音神经性聋的成人患者,分别进行纯音听力测试、ASSR检查,比较ASSR在0.5、1、2、4 kHz频率处的反应阈与纯音听阈的相关性及按听力损失程度比较两者的差值。结果 ASSR反应阈与纯音听阈在各频率处的相关系数分别为0.840、0.905、0.886、0.924;随着感音神经性听力损失的加重二者的差值明显缩小。随着频率的增加,两者的差值明显缩小。结论成人感音神经性聋ASSR反应阈与纯音听阈有显著相关性,随着听力损失的加重,ASSR反应阈愈接近纯音听阈,ASSR作为成人感音神经性聋听力定量诊断的客观方法有很大的临床应用价值。     

Hypoacusis among the Polar Eskimos of northwest Greenland

Audiological tests were conducted on 188 Polar Eskimos (75 males and 43 females) in small, remote, nonindustrialized settlements of Northwest Greenland. Most males of this small Eskimo tribe hunt regularly for food using rifles and shotguns. The means of the pure tone hearing thresholds indicated that 77% of the males in the population sample had a hearing loss (greater than 25 dB HL) in the high frequency range (above 2,000 Hz), in one or both ears. Also, 73% of the males had bilateral hearing losses (greater than 25 dB HL), and 73% had hearing thresholds greater than or equal to dB in one or both ears. A high frequency hearing loss was found in 46% of the males of the younger age groups (less than or equal to 40 years), mainly in the 3,000 to 8,000 Hz range, with the mean loss gradually extending to 2,000 and 1,000 Hz, and increasing in severity with age. The mean pure tone thresholds of 6- to 60-year-old female Polar Eskimos (who do not hunt with firearms) were generally within normal limits over the entire audiometric frequency range for the younger groups, and increased with age to the mild hearing loss range. Among the females, 35% had a hearing loss (less than 25dB HL) in the high frequency range (above 2,000 Hz) in one or both ears, and 21% had thresholds of greater than or equal to 50 dB in one or both ears. Conductive hearing losses in the low frequency range were not widespread among the males or females of this survey. The findings of this study suggest: (1) The high incidence of age-related hearing loss among the Polar Eskimo males is the result of frequent exposure to high intensity, impulse firearm noise, which is the major source of noise for this population, in an otherwise "noise-free" environment. (2) The primary noise-induced permanent threshold shift among Polar Eskimo hunters occurs in the age range of 10-40 years, and increases slowly thereafter, mainly as a result of continual noise exposure and presbyacusis. It is recommended that ear protectors and a comprehensive hearing conservation/rehabilitation program be provided for the Polar Eskimo population at once in order to prevent further hearing impairment and to rehabilitate those persons presently suffering from hearing loss.     

Some static characteristics of the stapedial muscle reflex

The stapedial muscle reflex was investigated in a group of normal and sensorineural ears. Pure tones of 250, 500, 1 000, 2 000, and 4 000 Hz, 600 Hz bandwidth narrow-band noise centered at 500, 1 000, 2 000, and 4 000 Hz and modified wide-band noise were utilized as reflex producing stimuli. All stimuli were presented through either of 2 prototype reflex-indicator systems generating probe tones of 625 and 800 Hz developed in the Audiology Department of Sahlgren's Hospital, or a Madsen ZO-70 electro-acoustic impedance meter generating a probe tone of 220 Hz. Reflex thresholds for pure tones and noise stimuli were determined with the prototype system delivering a probe tone of 800 Hz for normal and sensorineural ears. the average reflex threshold for pure tone stimuli approximated 85 dB hearing level for normal ears and 86 dB for the ears showing a sensorineural hearing loss. No differences were found for an ascending or descending approah to threshold or by measuring reflex response for changes in amplitude or amplitude phase. The hearing level limits for normal reflex response found in this study for pure tones between 250 and 4 000 Hz ranged from a lower limit of 75 dB to an upper limit of 95 dB. Comparison of reflex thresholds for 500 and 4 000 Hz for the 3 reflex-indicator systems resulted in most sensitive thresholds for the 220 Hz probe tone system (82.5 dB) and least sensitive thresholds for the 625 Hz probe tone system (88.0 dB). Narrowband and white noise stimuli produced reflex thresholds approximately 15 dB more sensitive than for pure tones. As was true for pure tones, aspproaching threshold from above or below, or measuring reflex response as change in amplitude or amplitude phase showed no difference. Altered middle ear pressure by Valsalva and Toynbee maneuvers in normal ears elevated reflex thresholds as much as 20 dB for pressure changes exceeding ±50 mm water pressure. Studies of reflex growth for pure tone stimuli increasing or decreasing in intensity shows a steeper response pattern for normal ears than those with sensorineural hearing loss and more shallow response for both grops at 4 000 Hz than for lower frequencies. An abnormally flat reflex growth rate may be of diagnostic significance.