Normal Hearing Thresholds Research Articles

Noise-induced hearing loss excess risk: indicators and criteria the problem of choosing

The optimal indicators and adequate criteria for the quantitative assessment of hearing loss excess risk with noise exposure above 80 dBA is urgently needed determination. The technology for calculating hearing thresholds according to the model of the third edition of the ISO 1999.3:2013 standard, depending on gender, age, length of service and noise exposure, based on MSExcell tables, for population percentiles 1÷99% in 1% steps has been developed. Rules for selecting optimal indicators and criteria for hearing loss for the early signs of hearing loss excess risk and the excess risk of occupational noise-induced hearing loss have been developed. The excess risk of hearing loss for men on the age, length of service and the level of noise exposure dependences are calculated. The optimal indicators and criteria for hearing loss to identify early signs of the effect of noise on the hearing organ and to calculate the excess risk of hearing loss when exposed to noise are identified. Calculated by the average binaural hearing threshold at frequencies of 0.5; 1.0; 2.0 and 3.0 kHz with an 30 dB assessment criterion excess risk most adequately solves the risk of occupational hearing loss determining problem. For the determine of early signs of hearing loss excess risk the average binaural threshold for hearing at frequencies of 4 and 6 kHz with an assessment criterion of 20 dB is useful better.

Cochlear and brainstem auditory responses in patients with generalized epilepsy - A cross-sectional study

Background: Epilepsy being a neurological disorder is characterized by excessive abnormal discharge in neurons of brain. Such abnormal activity rapidly engages many cortical and subcortical structures. As a result, this could influence auditory information processing of neuronal pathways in brainstem. Aims and Objectives: The objectives of the study were (1) To assess the cochlear responses transient evoked otoacoustic emissions (TEOAEs) in newly diagnosed drug-naive patients of epilepsy and (2) To assess the brainstem auditory evoked responses (ABR) in newly diagnosed drug-naive patients of epilepsy. Materials and Methods: The study was done in the department of audiology in a tertiary care institute. Three audiological tests, i.e., pure tone audiometry (PTA), auditory brainstem evoked responses (ABR), and TEOAEs were recorded on 30 patients in the age group of 15–45 years diagnosed with epilepsy and 30 age- and gender-matched controls. Results: All the participants chosen for the study were having normal hearing thresholds bilaterally as confirmed by PTA (air conduction thresholds below 25 dB HL across the audiometric frequencies of 250 Hz–8000 Hz). The absolute latency values of ABR were prolonged in patients of epilepsy (P < 0.05). The difference in interpeak latencies was found to be statistically non-significant. The amplitude values for waves III and V of ABR were reduced in epileptics (P < 0.05). The TEOAEs recorded in these patients of epilepsy showed no significant change in amplitude, noise floor, and signal-to-noise ratio. Conclusion: The findings of this study suggest that the epileptic patients have delayed absolute peak latencies and decreased amplitudes of waves III and V, indicating the possible involvement of lower brainstem due to seizure activity. However, this study also suggests that epileptic seizure is less likely to result in any alteration at the level of outer hair cells.

Calculation method for tonal audibility considering the effect of normal hearing thresholds

Calculation method for tonal audibility considering the effect of normal hearing thresholds

Hearing Impairment and Prevalence of Mild Cognitive Impairment in Japan: Baseline Data From the Aidai Cohort Study in Yawatahama and Uchiko.

Hearing impairment (HI) in midlife may increase the risk of dementia. However, epidemiological research on the association between HI and mild cognitive impairment (MCI) is very limited. The present cross-sectional study investigated the relationship between HI and MCI using baseline data from the Aidai Cohort Study. Study subjects were 995 Japanese adults aged 36 to 84 years. We used the audiometric definition of HI adopted by the World Health Organization, which identifies the speech-frequency pure-tone average hearing thresholds at 0.5, 1, 2, and 4 kHz tones. HI was defined as present when pure-tone average was >25 dB HL in the better hearing ear. MCI was defined as being present when a subject had a Japanese version of the Montreal Cognitive Assessment score of <26. Adjustment was made for age, sex, smoking status, alcohol consumption, leisure time physical activity, hypertension, dyslipidemia, diabetes mellitus, history of depression, body mass index, waist circumference, employment, education, and household income. Among the 995 study subjects, the prevalence values of HI and MCI were 24.3% and 44.5%, respectively. HI was independently positively associated with MCI: the multivariate-adjusted odds ratio (95% confidence interval) was 1.86 (1.32 to 2.62). HI was independently related to a higher prevalence of MCI in those aged 60 to 69 years and those aged 70 years or older: the multivariate-adjusted odds ratios (95% confidence intervals) were 1.64 (1.03 to 2.62) and 2.30 (1.04 to 5.27), respectively. HI may be associated with a higher prevalence of MCI.

Oxidative Stress as a Risk Factor for Hearing Changes in HIV-positive Normal Listeners

OBJECTIVES:Human immunodeficiency virus-positive (HIV+) individuals can experience a decrease in antioxidants. Such deficiency can make inner ear cells and synapses more vulnerable to oxidative stress, resulting in auditory alterations, even in the presence of normal thresholds. This study aims to compare the audiological findings of HIV+ patients (with and without exposure to anti-retroviral treatment) to those of healthy individuals.METHODS:This was a cross-sectional observational study, comprising 42 normal-hearing adults divided into the Control Group (CG), without HIV; Group I (GI), HIV+, without exposure to the highly active anti-retroviral therapy (HAART); Group II (GII), HIV+, with exposure to HAART. All participants underwent conventional audiometry (0.25-8 kHz), high-frequency audiometry (9-20 kHz), transient evoked otoacoustic emissions (TEOAEs), efferent auditory pathway’s inhibitory effect assessment, brainstem auditory evoked potentials (BAEPs), and cognitive potential (P300).RESULTS:In the comparison of the hearing thresholds between the groups, there was a statistically significant difference for most of the frequencies assessed (GII presented hearing thresholds significantly poor when compared with other groups). The presence of TEOAE and the inhibitory effect was also verified in a significantly higher number of individuals in the CG than in the other groups. As for the BAEP, there was a statistically significant difference for the interpeak intervals I-V (GII showed higher values when compared with CG). For P300, there were no statistically significant differences.CONCLUSION:Normal-hearing HIV+ individuals (with and without exposure to HAART) presented with poor performance in the audiological procedures, suggesting the presence of auditory alterations even in the presence of normal-hearing thresholds.

Scandcleft Project Trial 2-Comparison of Speech Outcome in 1- and 2-Stage Palatal Closure in 5-Year-Olds With UCLP.

To investigate in-depth speech results in the Scandcleft Trial 2 with comparisons between surgical protocols and centers and with benchmarks from peers without cleft palate. A prospective randomized clinical trial. Two Swedish and one Finnish Cleft Palate center. One hundred twelve participants were 5-years-old born with unilateral cleft lip and palate randomized to either lip repair and soft palate closure at 4 months and hard palate closure at 12 months or lip repair at 3 to 4 months (Arm A), or a closure of both the soft and hard palate at 12 months (Arm C). A composite measure dichotomized into velopharyngeal competency (VPC) or velopharyngeal incompetency (VPI), overall assessment of velopharyngeal function (VPC-Rate), percentage of consonants correct (PCC score), and consonant errors. In addition, number of speech therapy visits, average hearing thresholds, and secondary surgeries were documented to assess burden of treatment. Across the trial, 53.5% demonstrated VPC and 46.5% VPI with no significant differences between arms or centers. In total, 27% reached age-appropriate PCC scores with no statistically significant difference between the arms. The Finnish center had significantly higher PCC scores, the Swedish centers had higher percentages of oral consonant errors. Number of speech therapy visits was significantly higher in the Finnish center. At age 5, poor speech outcomes with some differences between participating centers were seen but could not be attributed to surgical protocol. As one center had very few participants, the results from that center should be interpreted with caution.

Influence of Visual Deprivation on Auditory Spectral Resolution, Temporal Resolution, and Speech Perception.

We evaluated whether blind subjects have advantages in auditory spectral resolution, temporal resolution, and speech perception in noise compared with sighted subjects. We also compared psychoacoustic performance between early blind (EB) subjects and late blind (LB) subjects. Nineteen EB subjects, 16 LB subjects, and 20 sighted individuals were enrolled. All subjects were right-handed with normal and symmetric hearing thresholds and without cognitive impairments. Three psychoacoustic measurements of the subjects’ right ears were performed via an inserted earphone to determine spectral-ripple discrimination (SRD), temporal modulation detection (TMD), and speech recognition threshold (SRT) in noisy conditions. Acoustic change complex (ACC) responses were recorded during passive listening to standard ripple-inverted ripple stimuli. EB subjects exhibited better SRD than did LB (p = 0.020) and sighted (p = 0.003) subjects. TMD was better in EB (p < 0.001) and LB (p = 0.007) subjects compared with sighted subjects. SRD was positively correlated with the duration of blindness (r = 0.386, p = 0.024). Acoustic change complex data for ripple noise change at the Cz and Fz electrodes showed trends toward significant correlations with the behavioral results. In conclusion, compared with sighted subjects, EB subjects showed advantages in terms of auditory spectral and temporal resolution, while LB subjects showed an advantage in temporal resolution exclusively. These findings suggest that it might take longer for auditory spectral resolution to functionally enhance following visual deprivation compared to temporal resolution. Alternatively, a critical period of very young age may be required for auditory spectral resolution to improve following visual deprivation.

Cochlear Dead Regions in Sporadic Unilateral Vestibular Schwannomas Using the Threshold-Equalizing Noise Test

Background: Vestibular schwannoma (VS) is a benign intracranial neoplasm originating in the Schwann cells of the vestibular nerve. Despite its origin, the most common symptom is sensorineural hearing loss which is presented in more than 90% of patients. The underlying pathophysiology of this hearing loss has not been fully understood. Objective: To assess the in vivo function of cochlear inner hair cells and spiral ganglion neurons in VS, cochlear dead regions (DRs) were evaluated via the threshold-equalizing noise (TEN) test in untreated VS patients. Method: Untreated patients diagnosed with sporadic unilateral VS and normal contralesional hearing were enrolled from July 2011 to June 2016. Audiometric evaluation including TEN tests were performed. Based on the magnetic resonance findings, characteristics of individual tumors were assessed. Results: The average pure-tone threshold (word recognition score [WRS]) of 23 enrolled patients was 42.7 dB (76.1%). Nineteen DRs (11.8% of 161 tested frequencies) were found in 8 patients (34.8% of enrolled cases). Among the intracanalicular (IAC) tumors, 6 out of 10 ears (60%) carried DRs, while 2 of 13 (15.4%) showed DRs among the cerebellopontine angle (CPA) lesions (p = 0.039). Pure-tone thresholds and WRS were not different between the two groups. Logistic regression analysis showed that the tumor location, IAC versus CPA, was significantly associated with DRs (p = 0.041, Nagelkerke R² = 0.471), whereas age, sex, tumor size, distance from the tumor to the cochlea, T2-weighted hypointensity on the MRI and pure-tone thresholds showed no significance. Conclusions: Cochlear DRs are detected in hearing losses associated with unilateral sporadic VS using the TEN test. Individual DRs were detected variously in high, mid, or low frequencies. In our preliminary data, IAC tumors showed a higher number of DRs than CPA tumors despite similar average hearing thresholds. Further studies including longitudinal follow-up of hearing as well as change in DRs may provide useful information about VS patients.

Association of Dietary Factors with Presence and Severity of Tinnitus in Korean Adults with Normal Hearing

Tinnitus is the perception of sound regardless of the external sound stimulus and have been focused about various risk factors in recent researches. The aim of this cross-sectional study was to investigate the nutritional risk factors for tinnitus with normal hearing in the general population by examining data from the Fifth Korea National Health and Nutrition Examination Survey (KNHANES). A total of 12,658 people were enrolled in Fifth KNHANES 2010-2012. We divided the subjects into two groups: tinnitus group and no tinnitus group, with a normal hearing threshold (< 25 dB). We analyzed the survey questionnaires for data on tinnitus, quality of life (QoL), and nutritional intake. The group with tinnitus and normal hearing accounted for 17.8% (n=2,249) of the total population. The QoL scores, including those for depression, pain, anxiety, and daily activity were significantly worse in the group with tinnitus than those in the normal group. The nutritional intake in the tinnitus group was generally low. A regression analysis revealed that a low salt intake was an important risk factor for the development of tinnitus in adults with normal hearing (OR=1.19, p=0.008). Mineral intake may affect the occurrence of tinnitus. In particular, lifestyle associated with low salt intake may be a risk factor for the development of tinnitus.

The association between subcortical and cortical fMRI and lifetime noise exposure in listeners with normal hearing thresholds

In animal models, exposure to high noise levels can cause permanent damage to hair-cell synapses (cochlear synaptopathy) for high-threshold auditory nerve fibers without affecting sensitivity to quiet sounds. This has been confirmed in several mammalian species, but the hypothesis that lifetime noise exposure affects auditory function in humans with normal audiometric thresholds remains unconfirmed and current evidence from human electrophysiology is contradictory. Here we report the auditory brainstem response (ABR), and both transient (stimulus onset and offset) and sustained functional magnetic resonance imaging (fMRI) responses throughout the human central auditory pathway across lifetime noise exposure. Healthy young individuals aged 25–40 years were recruited into high (n = 32) and low (n = 30) lifetime noise exposure groups, stratified for age, and balanced for audiometric threshold up to 16 kHz fMRI demonstrated robust broadband noise-related activity throughout the auditory pathway (cochlear nucleus, superior olivary complex, nucleus of the lateral lemniscus, inferior colliculus, medial geniculate body and auditory cortex). fMRI responses in the auditory pathway to broadband noise onset were significantly enhanced in the high noise exposure group relative to the low exposure group, differences in sustained fMRI responses did not reach significance, and no significant group differences were found in the click-evoked ABR. Exploratory analyses found no significant relationships between the neural responses and self-reported tinnitus or reduced sound-level tolerance (symptoms associated with synaptopathy). In summary, although a small effect, these fMRI results suggest that lifetime noise exposure may be associated with central hyperactivity in young adults with normal hearing thresholds.

Temporal cues from visual information benefit speech perception in noise

Speech perception in noise is a challenge for older adults and listeners with hearing loss. It is also challenging for a subset of listeners with normal hearing thresholds. One way to improve performance in noisy settings is to provide visual information of the talker. The current study examines what aspects of this visual input are necessary to receive an audio-visual benefit. To test the hypothesis that a visual analogue of the speech amplitude envelope aids speech comprehension, speech sentences in babble noises, with or without visual stimuli, were presented to listeners. In this case, the visual analogue was a sphere that varies based on normal, mismatched, and reversed relation to the amplitude envelope of the speech signal. Even when the audio-visual correlation is reversed (higher amplitude = smaller volumes), a significant improvement in speech perception in the auditory-visual condition versus the audio-only condition was gained even though no visual representation of phonetic information was available. These results provide strong evidence that the amplitude envelope can be inferred from visual displays and can be integrated online in speech perception. This study has implications for potential technological enhancements to speech perception with hearing devices – in particular, the integration of a non-auditory signal.

Individual differences in the attentional modulation of the human auditory brainstem response to speech inform on speech-in-noise deficits

People with normal hearing thresholds can nonetheless have difficulty with understanding speech in noisy backgrounds. The origins of such supra-threshold hearing deficits remain largely unclear. Previously we showed that the auditory brainstem response to running speech is modulated by selective attention, evidencing a subcortical mechanism that contributes to speech-in-noise comprehension. We observed, however, significant variation in the magnitude of the brainstem’s attentional modulation between the different volunteers. Here we show that this variability relates to the ability of the subjects to understand speech in background noise. In particular, we assessed 43 young human volunteers with normal hearing thresholds for their speech-in-noise comprehension. We also recorded their auditory brainstem responses to running speech when selectively attending to one of two competing voices. To control for potential peripheral hearing deficits, and in particular for cochlear synaptopathy, we further assessed noise exposure, the temporal sensitivity threshold, the middle-ear muscle reflex, and the auditory-brainstem response to clicks in various levels of background noise. These tests did not show evidence for cochlear synaptopathy amongst the volunteers. Furthermore, we found that only the attentional modulation of the brainstem response to speech was significantly related to speech-in-noise comprehension. Our results therefore evidence an impact of top-down modulation of brainstem activity on the variability in speech-in-noise comprehension amongst the subjects.

Individuals with normal hearing thresholds differ in their use of fine timing cues to identify consonants in noise

Individuals with normal hearing thresholds differ in their use of fine timing cues to identify consonants in noise

Assessment of Hearing Aids Outcomes for Patients With Hearing Loss

Background: Age-related hearing loss is a vital problem that impacts daily living including communication, socialization, and wellbeing. To be fitted with appropriate hearing aids can certainly improve quality of life. Therefore, it is essential to develop a set of indicators that will be used to measure hearing aids outcomes.&#x0D; Objectives: To determine the effectiveness of hearing-aid outcomes and to examine common hearing aid problems.&#x0D; Methods: A retrospective analysis of medical records of 634 patients receiving hearing aids services at Ramathibodi Hospital from July 2015 to June 2016, was performed. Data were collected using a data collection form and were examined by conducting descriptive analysis and paired t tests. Common hearing aid problems were analyzed using qualitative content analysis.&#x0D; Results: Of 634 patients receiving hearing aids services, the average hearing thresholds and speech recognition scores among with and without hearing aids, across a range of hearing loss, were statistically significant (P &lt; .01). Patients’ satisfaction on hospital services, and on hearing aids were 4.64 and 4.34, respectively. Common hearing aid problems were communication strategy, hearing aid manipulation, and routine maintenance of hearing aids and/or ear molds.&#x0D; Conclusions: Patients receiving hearing aids services from Ramathibodi Hospital reported better speech sound hearing and communication. They were satisfied with hospital services and hearing aids on defined indicators.

Auditory temporal acuity improves with age in the male mouse auditory thalamus: A role for perineuronal nets?

The ability to perceive and interpret environmental sound accurately is conserved across many species and is fundamental for understanding communication via vocalizations. Auditory acuity and temporally controlled neuronal firing underpin this ability. Deterioration in neuronal firing precision likely contributes to poorer hearing performance, yet the role of neural processing by key nuclei in the central auditory pathways is not fully understood. Here, we record from the auditory thalamus (medial geniculate body [MGB]) of young and middle-aged, normally hearing male CBA/Ca mice. We report changes in temporal processing of auditory stimuli, with neurons recorded from ventral and medial MGB subdivisions of older animals more likely to synchronize to rapid temporally varying stimuli. MGB subdivisions also showed increased probability of neuronal firing and shorter response latencies to clicks in older animals. Histological investigation of neuronal extracellular specializations, perineuronal nets (PNNs) and axonal coats, in the MGB identified greater organization of PNNs around MGB neurons and the presence of axonal coats within older animals. This supports the observation that neural responses recorded from ventral and medial MGB of older mice were more likely to synchronize to temporally varying stimuli presented at faster repetition rates than those recorded from young adult animals. These changes are observed in animals with normal hearing thresholds, confirming that neural processing differs between the MGB subdivisions and such processing is associated with age-related changes to PNNs. Understanding these age-related changes and how they occur have important implications for the design of effective therapeutic interventions to improve speech intelligibility into later life.

Adults who report difficulty hearing speech in noise: an exploration of experiences, impacts and coping strategies

Objective: Listening difficulties in noise are common, even in those with clinically normal hearing. There is a suggestion that subjective assessment of hearing difficulties may be more closely associated with listening effort and fatigue rather than objective measures of hearing and/or speech perception. The aim of this study was to better understand these perceptual deficits and experiences of this population.Design: An exploratory survey was distributed to participants with self-reported listening-in-noise difficulties. The primary aim of the survey was to gather information about challenging listening environments, its impact, and preferred rehabilitation strategies. Secondly, responses were compared to their performance on behavioural tasks.Study sample: Fifty adults aged 33–55 (22 females, with normal or near-normal hearing thresholds), completed the survey, and 45 of these performed behavioural tasks.Results: Background noise with conversational content was the most common source of hearing difficulties. Participants expended higher concentration and attention when communicating in noise, and correlations with previously published behavioural data was reported. Social impacts varied, few had sought treatment, and respondents preferred training over devices.Conclusions: Insights gained may provide clinicians and researchers with an understanding of the situations, impacts and non-auditory factors associated with listening-in-noise difficulties, and preferred rehabilitation for these clients.

Speech Perception in Noise With Formant Enhancement for Older Listeners

Purpose Degraded speech intelligibility in background noise is a common complaint of listeners with hearing loss. The purpose of the current study is to explore whether 2nd formant (F2) enhancement improves speech perception in noise for older listeners with hearing impairment (HI) and normal hearing (NH). Method Target words (e.g., color and digit) were selected and presented based on the paradigm of the coordinate response measure corpus. Speech recognition thresholds with original and F2-enhanced speech in 2- and 6-talker babble were examined for older listeners with NH and HI. Results The thresholds for both the NH and HI groups improved for enhanced speech signals primarily in 2-talker babble, but not in 6-talker babble. The F2 enhancement benefits did not correlate significantly with listeners' age and their average hearing thresholds in most listening conditions. However, speech intelligibility index values increased significantly with F2 enhancement in babble for listeners with HI, but not for NH listeners. Conclusions Speech sounds with F2 enhancement may improve listeners' speech perception in 2-talker babble, possibly due to a greater amount of speech information available in temporally modulated noise or a better capacity to separate speech signals from background babble.

The relationship between hearing loss and insomnia for patients with tinnitus

Objective: It is possible that tinnitus, hearing loss and insomnia are all linked to oxidative stress. If so, there should be a relationship between insomnia and hearing loss among patients with tinnitus. The aim of this study was to assess the relationship between insomnia and hearing thresholds for patients with tinnitus.Design: This was a retrospective study.Study sample: Data were gathered from records of 1066 consecutive patients (≥18 years old) with tinnitus who were seen in an audiology clinic in the UK.Results: Seventy percent of patients experienced some form of insomnia as measured via the Insomnia Severity Index (ISI). Thirty eight percent of patients had hearing loss. Regression models showed that the average hearing threshold across ears and frequencies (0.5–4 kHz), adjusted for age and gender, did not predict ISI scores: regression coefficient (b) = 0.02 (95% confidence interval, CI: –0.013 to 0.05, p = 0.25). Moreover, the ISI scores did not predict the severity of hearing loss: b = 0.07 (95% CI: –0.05 to 0.18, p = 0.25).Conclusion: The data do not support the idea that high levels of oxidative stress, which are associated with insomnia, have a strong influence on hearing loss among patients with tinnitus.

Behavioral evaluation of auditory function abnormalities in adult rats with normal hearing thresholds that were exposed to noise during early development

Noise-exposed rat pups provide a model of early deprivation of sensory input to the central auditory system, allowing the study of developmental neuroplasticity. Our previous results have demonstrated that a brief exposure of rats to broadband noise (125 dB SPL 8 min, 14th postnatal day) at the onset of hearing resulted in an altered intensity perception and frequency discrimination in adulthood despite normal hearing thresholds. In this study, we assessed the gap-detection ability and possible presence of tinnitus- and hyperacusis-like behavior in adult rats after the same neonatal acoustic trauma, using measurements of the acoustic startle response (ASR) in quiet and noisy environments and its prepulse inhibition by gaps in noise (gap-PPI). A significant deficit in the ability to detect gap was observed in the exposed rats when 55 dB SPL broadband noise was used as background. An increase of noise intensity to 65–75 dB SPL led to strengthening of the gap-PPI in exposed animals, which approached the gap-PPI values of control animals at these levels. Behavioral signs of tinnitus (gap detection deficits in 10 kHz narrow band noise) were found in 25% of exposed rats. An increased sensitivity to continuous noise was manifested in all exposed rats by suppression of the ASR at significantly lower background noise levels than in the controls. This effect was particularly pronounced in rats with tinnitus-like behavior. Our results indicate that neonatal acoustic trauma, producing only a transient threshold shift, may produce permanent abnormalities in suprathreshold auditory functions and the development of tinnitus and hyperacusis-like behavior.

Early Diagnosis of Hearing Loss in Patients Under Methadone Maintenance Treatment.

Background and Objective: Methadone maintenance treatment (MMT) as the most effective treatment for opioid addictions could induce both reversible and permanent hearing loss. Therefore, early detection of methadone-induced hearing loss is necessary to prevent irreversible cochlear damage. The present study aims to identify the early onset of hearing loss in patients who underwent MMT and to compare them with the age and gender matched normal hearing peers.Methods: This was an analytic cross-sectional study conducted on patients (n = 27 males; age range: 18–53 years old) who received 3 months MMT course (MMT group) and a control group consisting of age and gender matched healthy individuals (n = 27 males). Before MMT, all patients underwent conventional audiometry (250–8,000 Hz) and those with normal hearing threshold participated into the study. One month after MMT termination, the patients were assessed for possible hearing loss using conventional pure tone audiometry (PTA), extended high frequency (EHF) audiometry, and distortion product otoacoustic emissions (DPOAEs).Results: Our results demonstrated that the mean EHF thresholds in the MMT patients were significantly greater than the age- and gender-matched healthy controls across all frequencies (p < 0.001). However, there was no statistically significant difference in conventional PTA thresholds between both groups (p > 0.05). DPOAE amplitudes significantly reduced at higher frequencies (3,000–8,000 Hz) in the MMT group, compared to the healthy control group. In contrast to the conventional PTA audiometry, the EHF and DPOAE assessments identified hearing impairments in 11 (40.74%), and 14 (51.85%) of the MMT patients, respectively. The main mechanisms proposed for methadone induced hearing loss are cochlear ischemia following vasospasm or vasculitis, direct effect of opioids on opioid receptors present in cochlear stria vascularis of inner ear, blood-labyrinth selective transport of opioidproteins and receptors, and genetic polymorphism and mutations.Conclusion: The EHF and DPOAE tests have the potential to detect earlier changes in auditory function than conventional frequency audiometry in the MMT patients.