Effect of combining batroxobin with acupuncture treatment on hearing recovery in patients with sudden sensorineural hearing loss.

BACKGROUND: The effect of batroxobin on hearing recovery in patients with Sudden Sensorineural Hearing Loss (SSNHL) is still controversial, and acupuncture shows auxiliary benefits for SSNHL. OBJECTIVES: To investigate the effectiveness of combining acupuncture with batroxobin therapy for patients with SSNHL. MATERIAL AND METHODS: One hundred and fifty-six patients with SSNHL were retrospectively enrolled in this study, and categorized into the control group (only batroxobin treatment) and observation group (batroxobin and acupuncture treatment). Pure Tone Audiograms (PTA) threshold and clinical outcomes of hearing recovery were compared. Logistic regression analysis was used to evaluate the association between hearing recovery and potential risk factors. RESULTS: Compared to the control group, the observation group had a higher overall effective rate (p = 0.006) and improvement in PTA threshold (p = 0.007). Among SSNHL patients with high-frequency and flat-type hearing loss, observation group demonstrated superior hearing recovery post-treatment compared to the control group (p < 0.05). Additionally, hearing recovery in patient with SSNHL were associated with SSNHL types, disease duration, neutrophil count and acupuncture (p < 0.05). CONCLUSIONS AND SIGNIFICANCE: Combining batroxobin and acupuncture treatments enhences the improvement of hearing recovery in SSNHL patients compared to only batroxobin treatments, especially high-frequency and flat-type hearing loss.

Pure tone audiogram classification using deep learning techniques.

OBJECTIVE: Pure tone audiometry has played a critical role in audiology as the initial diagnostic tool, offering vital insights for subsequent analyses. This study aims to develop a robust deep learning framework capable of accurately classifying audiograms across various commonly encountered tasks. DESIGN, SETTING, AND PARTICIPANTS: This single-centre retrospective study was conducted in accordance with the STROBE guidelines. A total of 12 518 audiograms were collected from 6259 patients aged between 4 and 96 years, who underwent pure tone audiometry testing between February 2018 and April 2022 at Tongji Hospital, Tongji Medical College, Wuhan, China. Three experienced audiologists independently annotated the audiograms, labelling the hearing loss in degrees, types and configurations of each audiogram. MAIN OUTCOME MEASURES: A deep learning framework was developed and utilised to classify audiograms across three tasks: determining the degrees of hearing loss, identifying the types of hearing loss, and categorising the configurations of audiograms. The classification performance was evaluated using four commonly used metrics: accuracy, precision, recall and F1-score. RESULTS: The deep learning method consistently outperformed alternative methods, including K-Nearest Neighbors, ExtraTrees, Random Forest, XGBoost, LightGBM, CatBoost and FastAI Net, across all three tasks. It achieved the highest accuracy rates, ranging from 96.75% to 99.85%. Precision values fell within the range of 88.93% to 98.41%, while recall values spanned from 89.25% to 98.38%. The F1-score also exhibited strong performance, ranging from 88.99% to 98.39%. CONCLUSIONS: This study demonstrated that a deep learning approach could accurately classify audiograms into their respective categories and could contribute to assisting doctors, particularly those lacking audiology expertise or experience, in better interpreting pure tone audiograms, enhancing diagnostic accuracy in primary care settings, and reducing the misdiagnosis rate of hearing conditions. In scenarios involving large-scale audiological data, the automated classification system could be used as a research tool to efficiently provide a comprehensive overview and statistical analysis. In the era of mobile audiometry, our deep learning framework can also help patients quickly and reliably understand their self-tested audiograms, potentially encouraging timely consultations with audiologists for further evaluation and intervention.

A history of occupational noise exposure is associated with steep-slope audiograms and poorer self-reported hearing-aid outcomes.

OBJECTIVE: To investigate the effects of previous occupational noise exposure in older adults with hearing loss on (1) audiometric configuration and acoustic reflex (AR) thresholds and (2) self-reported hearing abilities and hearing aid (HA) effectiveness. DESIGN: A prospective observational study. STUDY SAMPLE: The study included 1176 adults (≥60 years) with bilateral sensorineural hearing loss. Pure-tone audiometry, AR thresholds, and responses to the abbreviated version of the Speech, Spatial, and Qualities of Hearing Scale (SSQ12) and the International Outcome Inventory for Hearing Aids (IOI-HA) questionnaire were obtained, along with information about previous occupational noise exposure. RESULTS: Greater occupational noise exposure was associated with a higher prevalence of steeply sloping audiograms in men and women and a 0.32 (95% CI: -0.57; -0.06) scale points lower mean SSQ12 total score among noise-exposed men. AR thresholds did not show a significant relation to noise-exposure status, but hearing thresholds at a given frequency were related to elevated AR thresholds at the same frequency. CONCLUSIONS: A noise exposure history is linked to steeper audiograms in older adults with hearing loss as well as to poorer self-reported hearing abilities in noise-exposed men. More attention to older adults with previous noise exposure is warranted in hearing rehabilitation.

Predicting Atrophy of the Cochlear Stria Vascularis from the Shape of the Threshold Audiogram.

Several lines of evidence have suggested that steeply sloping audiometric losses are caused by hair cell degeneration, while flat audiometric losses are caused by strial atrophy, but this concept has never been rigorously tested in human specimens. Here, we systematically compare audiograms and cochlear histopathology in 160 human cases from the archival collection of celloidin-embedded temporal bones at the Massachusetts Eye and Ear. The dataset included 106 cases from a prior study of normal-aging ears, and an additional 54 cases selected by combing the database for flat audiograms. Audiogram shapes were classified algorithmically into five groups according to the relation between flatness (i.e., SD of hearing levels across all frequencies) and low-frequency pure-tone average (i.e., mean at 0.25, 0.5, and 1.0 kHz). Outer and inner hair cell losses, neural degeneration, and strial atrophy were all quantified as a function of cochlear location in each case. Results showed that strial atrophy was worse in the apical than the basal half of the cochlea and was worse in females than in males. The degree of strial atrophy was uncorrelated with audiogram flatness. Apical atrophy was correlated with low-frequency thresholds and basal atrophy with high-frequency thresholds, and the former correlation was higher. However, a multivariable regression with all histopathological measures as predictors and audiometric thresholds as the outcome showed that strial atrophy was a significant predictor of threshold shift only in the low-frequency region, and, even there, the contribution of outer hair cell damage was larger.SIGNIFICANCE STATEMENT Cochlear pathology can only be assessed postmortem; thus, human cochlear histopathology is critical to our understanding of the mechanisms of hearing loss. Dogma holds that relative damage to sensory cells, which transduce mechanical vibration into electrical signals, versus the stria vascularis, the cellular battery that powers transduction, can be inferred by the shape of the audiogram, that is, down-sloping (hair cell damage) versus flat (strial atrophy). Here we quantified hair cell and strial atrophy in 160 human specimens to show that it is the degree of low-frequency hearing loss, rather than the audiogram slope, that predicts strial atrophy. Results are critical to the design of clinical trials for hearing-loss therapeutics, as current drugs target only hair cell, not strial, regeneration.

Supporting-cell vs. hair-cell survival in the human cochlea: Implications for regenerative therapies.

Animal studies have shown that the supporting-cells surviving in the organ of Corti after cochlear insult can be transdifferentiated into hair cells as a treatment for sensorineural hearing loss. Clinical trials of small-molecule therapeutics have been undertaken, but little is known about how to predict the pattern and degree of supporting-cell survival based on audiogram, hearing loss etiology or any other metric obtainable pre-mortem. To address this, we systematically assessed supporting-cell and hair cell survival, as a function of cochlear location in 274 temporal bone cases from the archives at the Massachusetts Eye and Ear and compared the histopathology with the audiograms and hearing-loss etiologies. Results showed that supporting-cell survival was always significantly greater in the apical half than the basal half of the cochlea, that inner pillars were more robust than outer pillars or Deiters' cells, and that total replacement of all supporting cells with a flat epithelium was rare outside of the extreme basal 20% of the cochlea. Supporting cell survival in the basal half of the cochlea was better correlated with the slope of the audiogram than with the mean high-frequency threshold per se: i.e. survival was better with flatter audiograms than with steeply down-sloping audiograms. Cochlear regions with extensive hair cell loss and exceptional supporting cell survival were most common in cases with hearing loss due to ototoxic drugs. Such cases also tended to have less pathology in other functionally critical structures, i.e. spiral ganglion neurons and the stria vascularis.

A KCNQ4 c.546C>G Genetic Variant Associated with Late Onset Non-Syndromic Hearing Loss in a Taiwanese Population.

Clinical presentation is heterogeneous for autosomal dominant nonsyndromic hearing loss (ADNSHL). Variants of KCNQ4 gene is a common genetic factor of ADNSHL. Few studies have investigated the association between hearing impairment and the variant c.546C>G of KCNQ4. Here, we investigated the phenotype and clinical manifestations of the KCNQ4 variant. Study subjects were selected from the participants of the Taiwan Precision Medicine Initiative. In total, we enrolled 12 individuals with KCNQ4 c.546C>G carriers and 107 non-carriers, and performed pure tone audiometry (PTA) test and phenome-wide association (PheWAS) analysis for the patients. We found that c.546C>G variant was related to an increased risk of hearing loss. All patients with c.546C>G variant were aged >65 years and had sensorineural and high frequency hearing loss. Of these patients, a third (66.7%) showed moderate and progressive hearing loss, 41.7% complained of tinnitus and 16.7% complained of vertigo. Additionally, we found a significant association between KCNQ4 c.546C>G variant, aortic aneurysm, fracture of lower limb and polyneuropathy in diabetes. KCNQ4 c.546C>G is likely a potentially pathogenic variant of ADNSHL in the elderly population. Genetic counseling, annual audiogram and early assistive listening device intervention are highly recommended to prevent profound hearing impairment in this patient group.

Hearing sensitivity: An underlying mechanism for niche differentiation in gleaning bats.

Tropical ecosystems are known for high species diversity. Adaptations permitting niche differentiation enable species to coexist. Historically, research focused primarily on morphological and behavioral adaptations for foraging, roosting, and other basic ecological factors. Another important factor, however, is differences in sensory capabilities. So far, studies mainly have focused on the output of behavioral strategies of predators and their prey preference. Understanding the coexistence of different foraging strategies, however, requires understanding underlying cognitive and neural mechanisms. In this study, we investigate hearing in bats and how it shapes bat species coexistence. We present the hearing thresholds and echolocation calls of 12 different gleaning bats from the ecologically diverse Phyllostomid family. We measured their auditory brainstem responses to assess their hearing sensitivity. The audiograms of these species had similar overall shapes but differed substantially for frequencies below 9 kHz and in the frequency range of their echolocation calls. Our results suggest that differences among bats in hearing abilities contribute to the diversity in foraging strategies of gleaning bats. We argue that differences in auditory sensitivity could be important mechanisms shaping diversity in sensory niches and coexistence of species.

The accuracy of standard audiometric hearing level thresholds in pediatric patients.

OBJECTIVES: Standard audiograms provide decibels Hearing Level (dB HL) thresholds, which are referenced to normative values specified in decibels Sound Pressure Level in an acoustic coupler. Due to variability in external ear acoustics, the actual sound levels reaching the eardrum can vary across individuals. The real-ear to coupler difference (RECD) is a frequency-specific measurement of the difference between sound levels measured at the eardrum and in a coupler. Here, we compare the standard audiogram dB HL levels to RECD corrected hearing thresholds (dB RECHL) in children. METHODS: Children who underwent standard audiometric and RECD testing were included. The dB RECHL was established and the differences between dB HL and dB RECHL (threshold error) was calculated. A threshold error >5 dB was considered significant. RESULTS: A total of 166 children were included (mean age 12 years). Overall, 14% had normal hearing, 52% had conductive hearing loss and 27% had sensorineural hearing loss. Hearing threshold levels were overestimated by the standard audiogram compared to dB RECHL, at all frequencies (250-6000 Hz). In the lower frequencies and at 6000 Hz, 33-59% of patients were overestimated, with a threshold error up to 25 dB. In the mid frequencies, 33% were overestimated with a similar threshold error. CONCLUSION: Standard audiogram thresholds overestimated hearing levels in children which may have clinical implications. This problem can be addressed by correcting thresholds with RECD. More studies are needed to assess the effect of correcting thresholds on hearing outcomes in children.

A Preliminary Study Investigating the Association Between Hearing Acuity and a Screening Cognitive Tool.

OBJECTIVES: Studies in cognitive aging demonstrated inconsistent association between hearing and cognition in older adults. Furthermore, it is still unclear if hearing loss at high frequencies, which is the earliest to be affected, is associated with cognitive functioning. This study aimed to determine the association between global cognitive status and pure tone average (PTA) at 0.5, 1, and 2 kHz (PTA low) and PTA at 4 and 8 kHz (PTA high). METHODS: This study involved 307 adults aged 60 years and older. Participants had their hearing and cognition measured using pure tone audiometry and Mini Mental State Examination (MMSE), respectively. RESULTS: Pure tone average (low) accounted for significant but minimal amount of variance in measure of MMSE. Multiple regression analyses were also performed on normal and impaired hearing cohorts and cohorts with younger (60-69 years) and older (≥70 years) groups. The results revealed a significant relationship between PTA (low) and MMSE only in the younger age group. In contrast, no significant relationship was found between PTA (high) and cognition in any of the cohorts. CONCLUSION: Pure tone average (low) is significantly but minimally related to measure of general cognitive status. Similar relationship is not observed between high-frequency hearing and cognition. Further research using a more comprehensive cognitive test battery is needed to confirm the lack of association between high-frequency hearing and cognition.

Cochlear Implantation in Siblings With Refsum's Disease.

OBJECTIVES: Whether the origin of severe hearing loss in Refsum's syndrome is caused by cochlear impairment or retrocochlear degeneration remains unclear. This case report aims to investigate hearing performance before and after cochlear implantation to shed light on this question. Also, identification of new mutations causing Refsum's syndrome would be helpful in generating additional means of diagnosis. METHODS: A family of 4 individuals was subjected to genetic testing. Two siblings (56 and 61 years old) suffered from severe hearing and vision loss and received bilateral cochlear implants. Genetic analysis, audiological outcome, and clinical examinations were performed. RESULTS: One new mutation in the PHYH gene (c.768del63bp) causing Refsum's disease was found. Preoperative distortion product otoacoustic emissions (DPAOEs) were absent. Postoperative speech perception in Freiburger speech test was 100% for bisyllabic words and 85% (patient No. 1) and 65% (patient No. 2), respectively, for monosyllabic words. Five years after implantation, speech perception remained stable for bisyllabic words but showed decreasing capabilities for monosyllabic words. DISCUSSION: A new mutation causing Refsum's disease is presented. Cochlear implantation in case of severe hearing loss leads to an improvement in speech perception and should be recommended for patients with Refsum's disease, especially when the hearing loss is combined with a severe loss of vision. Decrease of speech perception in the long-term follow-up could indicate an additional retrocochlear degeneration.

Occupational noise exposure, hearing loss, and notched audiograms in the HUNT Nord-Trøndelag hearing loss study, 1996-1998.

OBJECTIVES/HYPOTHESIS: To study the prevalence and usefulness of audiometric notches in the diagnosis of noise-induced hearing loss (NIHL). STUDY DESIGN: Audiograms and data on noise exposure from 23,297 men and 26,477 women, aged 20 to 101 years, from the Nord-Trøndelag Hearing Loss Study, 1996-1998. METHODS: The prevalence of four types of audiometric notches (Coles, Hoffman, Wilson) and 4 kHz notch were computed in relation to occupational noise exposure, age, sex, and report of recurrent ear infections. RESULTS: The prevalence of notches in the 3 to 6 kHz range (Wilson, Hoffman, and Coles) ranged from 50% to 60% in subjects without occupational noise exposure, and 60% to 70% in the most occupationally noise-exposed men. The differences were statistically significant only for bilateral notches. For 4 kHz notches, the prevalence varied from 25% in occupationally nonexposed to 35% in the most occupationally exposed men, and the differences were statistically significant for both bilateral and unilateral notches. For women, the prevalence of notches was lower than in men, especially for 4 kHz notches, and the differences between occupationally noise exposed and nonexposed were smaller. Recreational exposure to high music was not associated with notched audiograms. CONCLUSIONS: The detection of bilateral notches and unilateral 4 kHz notches is of some value in diagnosing NIHL, especially in men. LEVEL OF EVIDENCE: 4 Laryngoscope, 127:1442-1450, 2017.

Should obtaining a preoperative audiogram before tympanostomy tube placement be used as a quality metric? A survey of pediatric otolaryngologists.

INTRODUCTION: Obtaining a preoperative audiogram prior to tympanostomy tube placement is recommended by the American Academy of Otolaryngology-Head and Neck Surgery clinical practice guideline (CPG): Tympanostomy tubes in Children, and this process measure is also used as a quality metric by payers. However, whether audiograms should be mandated in cases of tube placement for both chronic otitis media with effusion (COME) and recurrent acute otitis media (RAOM) is controversial. The objective of this study is to determine reports of practice patterns of pediatric otolaryngologists regarding obtaining audiograms before and after tympanostomy tube placement and opinions regarding utility of CPGs and use of this process measure as a quality metric. METHODS: A 16-question cross-sectional survey of American Society of Pediatric Otolaryngology (ASPO) members was conducted. Per ASPO policy, no repeated requests or other enhanced response techniques were permitted. Independent t-tests for proportions were used to compare responses. RESULTS: 127 pediatric otolaryngologists completed the survey (response rate 26.9%). Nearly 70% of respondents reported being in practice for >10 years. 74% of respondents reported obtaining preoperative audiograms "always" or "most of the time" for COME, vs. 56.7% for RAOM (p < 0.0001). 76% agreed that obtaining a preoperative audiogram was representative of high quality for COME, vs. 52% for RAOM (p < 0.0001). 12% of respondents "completely agreed" that compliance with all aspects of CPGs represented high quality, while 68.8% responded that they somewhat agreed. CONCLUSION: There is no consensus among pediatric otolaryngologists regarding the necessity of a preoperative audiogram in tympanostomy tube placement, especially for RAOM. Further evidence demonstrating the benefit of preoperative audiogram obtainment should be developed prior to inclusion as a guideline recommendation and as a quality metric.

Peripheral Hearing Structures in Fishes: Diversity and Sensitivity of Catfishes and Cichlids.

Fishes have evolved an astonishing diversity of peripheral (accessory/ancillary) auditory structures to improve hearing based on their ability to transmit oscillations of gas bladder walls to the inner ears. So far it is unclear to what degree the size of the bladder and the linkage to the ear affect hearing in fishes. An interfamilial study in catfishes revealed that families which possess large, single swim bladders and one to four Weberian ossicles were more sensitive at higher frequencies (≥1 kHz) than families which have small, paired, and encapsulated bladders and one to two ossicles. An intrafamilial investigation in thorny catfishes (family Doradidae) revealed that small differences in bladder morphology did not affect hearing similarly. Members of the cichlid family possess an even larger variation in peripheral auditory structures than catfishes. The linkage between the swim bladder and ear can either be present via anterior extensions of the bladder or be completely absent (in contrast to catfishes). Representatives having large bladders with extensions had the best sensitivities. Cichlids lacking extensions had lower sensitivities above 0.3 kHz. Species with a vestigial swim bladder exhibited a smaller hearing bandwidth than those with larger swim bladder (maximum frequency: 0.7 kHz vs. 3 kHz). Catfishes and cichlids reveal that larger gas bladders and more pronounced connections between the swim bladder and the inner ear result in improved hearing at higher frequencies. The lack of a connection between a large bladder and the inner ear does not necessarily result in a smaller detectable frequency range.

Audioprofile Surfaces: The 21st Century Audiogram.

OBJECTIVE: To present audiometric data in 3 dimensions by considering age as an addition dimension. METHODS: Audioprofile surfaces (APSs) were fitted to a set of audiograms by plotting each measurement of an audiogram as an independent point in 3 dimensions with the x, y, and z axes representing frequency, hearing loss in dB, and age, respectively. RESULTS: Using the Java-based APS viewer as a standalone application, APSs were pre-computed for 34 loci. By selecting APSs for the appropriate genetic locus, a clinician can compare this APS-generated average surface to a specific patient's audiogram. CONCLUSION: Audioprofile surfaces provide an easily interpreted visual representation of a person's hearing acuity relative to others with the same genetic cause of hearing loss. Audioprofile surfaces will support the generation and testing of sophisticated hypotheses to further refine our understanding of the biology of hearing.

Hearing loss in shipyard employees.

BACKGROUND: Noise-induced hearing loss (NIHL) is one of the most prevalent occupational illnesses, with a higher incidence in the heavy industry. OBJECTIVES OF THE STUDY: The aim of this study is to investigate the prevalence of NIHL in Greece and explore its correlations with other job and individual-related factors. MATERIALS AND METHODS: Questionnaires were administered, and audiograms were conducted to 757 employees of a shipyard company in Greece, both white- and blue-collar, during the period 2006-2009. A modification of the 1979' equation of the American Academy of Otolaryngology was used to calculate hearing loss. Statistical analysis was conducted by means of the SPSS v. 17. RESULTS: A 27.1% of the employees were hearing handicap. Hearing loss was correlated with age, past medical history of ear disease (Meniere's disease, acoustic neuroma, otosclerosis) or injury, hyperlipidemia, job title and level of education. A few questions on subjective hearing ability and symptoms showed strong discriminatory power of hearing pathology. CONCLUSIONS: The results of this study emphasize the burden of disease in the shipyard industry, and the need for continuous monitoring, implementation of preventive measures and hearing conservation programs.

Ontogenetic investigation of underwater hearing capabilities in loggerhead sea turtles (Caretta caretta) using a dual testing approach.

Sea turtles reside in different acoustic environments with each life history stage and may have different hearing capacity throughout ontogeny. For this study, two independent yet complementary techniques for hearing assessment, i.e. behavioral and electrophysiological audiometry, were employed to (1) measure hearing in post-hatchling and juvenile loggerhead sea turtles Caretta caretta (19-62 cm straight carapace length) to determine whether these migratory turtles exhibit an ontogenetic shift in underwater auditory detection and (2) evaluate whether hearing frequency range and threshold sensitivity are consistent in behavioral and electrophysiological tests. Behavioral trials first required training turtles to respond to known frequencies, a multi-stage, time-intensive process, and then recording their behavior when they were presented with sound stimuli from an underwater speaker using a two-response forced-choice paradigm. Electrophysiological experiments involved submerging restrained, fully conscious turtles just below the air-water interface and recording auditory evoked potentials (AEPs) when sound stimuli were presented using an underwater speaker. No significant differences in behavior-derived auditory thresholds or AEP-derived auditory thresholds were detected between post-hatchling and juvenile sea turtles. While hearing frequency range (50-1000/1100 Hz) and highest sensitivity (100-400 Hz) were consistent in audiograms pooled by size class for both behavior and AEP experiments, both post-hatchlings and juveniles had significantly higher AEP-derived than behavior-derived auditory thresholds, indicating that behavioral assessment is a more sensitive testing approach. The results from this study suggest that post-hatchling and juvenile loggerhead sea turtles are low-frequency specialists, exhibiting little differences in threshold sensitivity and frequency bandwidth despite residence in acoustically distinct environments throughout ontogeny.

Aquatic acoustic metrics interface utility for underwater sound monitoring and analysis.

Fishes and marine mammals may suffer a range of potential effects from exposure to intense underwater sound generated by anthropogenic activities such as pile driving, shipping, sonars, and underwater blasting. Several underwater sound recording (USR) devices have been built to acquire samples of the underwater sound generated by anthropogenic activities. Software becomes indispensable for processing and analyzing the audio files recorded by these USRs. In this paper, we provide a detailed description of a new software package, the Aquatic Acoustic Metrics Interface (AAMI), specifically designed for analysis of underwater sound recordings to provide data in metrics that facilitate evaluation of the potential impacts of the sound on aquatic animals. In addition to the basic functions, such as loading and editing audio files recorded by USRs and batch processing of sound files, the software utilizes recording system calibration data to compute important parameters in physical units. The software also facilitates comparison of the noise sound sample metrics with biological measures such as audiograms of the sensitivity of aquatic animals to the sound, integrating various components into a single analytical frame. The features of the AAMI software are discussed, and several case studies are presented to illustrate its functionality.

Functional morphology of the inner ear and underwater audiograms of Proteus anguinus (Amphibia, Urodela).

Octavolateral sensory organs (auditory and lateral line organs) of cave salamander Proteus anguinus are highly differentiated. In the saccular macula of the inner ear the complex pattern of hair cell orientation and the large otoconial mass enable particle displacement direction detection. Additionally, the same organ, through air cavities within the body, enables detection of underwater sound pressure changes thus acting as a hearing organ. The cavities in the lungs and mouth of Proteus are a resonators that transmit underwater sound pressure to the inner ear. Behaviourally determined audiograms indicate hearing sensitivity of 60 dB (rel. 1 µPa) at frequencies between 1 and 10 kHz. The hearing frequency range was between 10 Hz and 10 kHz. The hearing sensitivities of depigmented Proteus and black Proteus were compared. The highest sensitivities of the depigmented animals (N=4) were at frequencies 1.3-1.7 kHz and it was 2 kHz in black animals (N=1). Excellent underwater hearing abilities of Proteus are sensory adaptations to cave habitat.