Distortion Product Otoacoustic Emissions Research Articles

Prevailing Practices in Ototoxicity Monitoring in Individuals With Head and Neck Cancer Undergoing Radiotherapy and Chemoradiotherapy: A Scoping Review.

The aim of the current scoping review is to identify the studies reporting ototoxicity monitoring in individuals with head and neck cancer (HNC) undergoing radiation therapy and/or chemoradiation therapy across the world. The specific objectives were to identify and report the test protocol used, identify the most common timeline of follow-up, and identify barriers and facilitators influencing the implementation of the monitoring program. A comprehensive search was conducted across six electronic databases, including PubMed, Embase, Web of Science, Scopus, Google Scholar, and ProQuest. The scoping review method adhered to relevant guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews) and frameworks. The database search was carried out by two independent researchers, and studies were selected based on specific inclusion and exclusion criteria. This scoping review identified 13 studies that fulfilled the inclusion criteria of this study. Only one study reported findings from the perspective of ototoxicity monitoring. Another study explicitly mentioned that ototoxicity monitoring was a standard of care in their hospital. Only one study reported using the relevant guidelines for monitoring ototoxicity. Specialized tests such as high-frequency audiometry, distortion product otoacoustic emissions, and vestibular tests were rarely used. Ototoxicity monitoring was influenced by awareness-related factors, technical factors, treatment-related factors, and organizational factors. Research on ototoxicity monitoring programs is in its early stages, highlighting the need for standardized practices and multidisciplinary collaboration to enhance health care services for HNC patients. A standardized approach, improved awareness, and the incorporation of patient perspectives are crucial to enhancing ototoxicity monitoring in HNC patients.

Two new mouse alleles of Ocm and Slc26a5

The genes Ocm (encoding oncomodulin) and Slc26a5 (encoding prestin) are expressed strongly in outer hair cells and both are involved in deafness in mice. However, it is not clear if they influence the expression of each other. In this study, we characterise the auditory phenotype resulting from two new mouse alleles, Ocmtm1e and Slc26a5tm1Cre. Each mutation leads to absence of detectable mRNA transcribed from the mutant allele, but there was no evidence that oncomodulin regulates expression of prestin or vice versa. The two mutants show distinctive patterns of auditory dysfunction. Ocmtm1e homozygotes have normal auditory brainstem response thresholds at 4 weeks old followed by progressive hearing loss starting at high frequencies, while heterozygotes show largely normal thresholds until 6 months of age, when signs of worse thresholds are detected. In contrast, Slc26a5tm1Cre homozygotes have stable but raised thresholds across all frequencies tested, 3 to 42 kHz, at least from 4 to 8 weeks old, while heterozygotes have raised thresholds at high frequencies. Distortion product otoacoustic emissions and cochlear microphonics show deficits similar to auditory brainstem responses in both mutants, suggesting that the origin of hearing impairment is in the outer hair cells. Endocochlear potentials are normal in the two mutants. Scanning electron microscopy revealed normal development of hair cells in Ocmtm1e homozygotes but scattered outer hair cell loss even at 4 weeks old when thresholds appeared normal, indicating that there is not a direct relationship between numbers of outer hair cells present and auditory thresholds.

Speech intelligibility prediction based on a physiological model of the human ear and a hierarchical spiking neural network.

A speech intelligibility (SI) prediction model is proposed that includes an auditory preprocessing component based on the physiological anatomy and activity of the human ear, a hierarchical spiking neural network, and a decision back-end processing based on correlation analysis. The auditory preprocessing component effectively captures advanced physiological details of the auditory system, such as retrograde traveling waves, longitudinal coupling, and cochlear nonlinearity. The ability of the model to predict data from normal-hearing listeners under various additive noise conditions was considered. The predictions closely matched the experimental test data under all conditions. Furthermore, we developed a lumped mass model of a McGee stainless-steel piston with the middle-ear to study the recovery of individuals with otosclerosis. We show that the proposed SI model accurately simulates the effect of middle-ear intervention on SI. Consequently, the model establishes a model-based relationship between objective measures of human ear damage, like distortion product otoacoustic emissions, and speech perception. Moreover, the SI model can serve as a robust tool for optimizing parameters and for preoperative assessment of artificial stimuli, providing a valuable reference for clinical treatments of conductive hearing loss.

Ototoxic Effect of Nicotinamide Riboside.

We studied the function of the auditory system in Wistar rats after repeated intravenous administration of nicotinamide riboside (NR). The functional activity of the receptor and retrocochlear parts of the auditory system were assessed by recording short-latency auditory evoked potentials (SLAEPs) and distortion-product otoacoustic emissions (DPOAEs) at baseline, immediately after NR administration, and 1 and 2 months later. Repeated intravenous NR administration (cumulative dose of 2700 mg/kg) to Wistar rats has a detrimental impact on the structures within the cochlear section of the auditory system.

Therapeutic Function of Liraglutide for Mitigation of Blast-Induced Hearing Damage: An Initial Investigation in Animal Model of Chinchilla.

Auditory injuries induced by repeated exposures to blasts reduce the operational performance capability and the life quality of military personnel. The treatment for blast-induced progressive hearing damage is lacking. We have recently investigated the therapeutic function of liraglutide, a glucagon-like peptide-1 receptor agonist, to mitigate blast-induced hearing damage in the animal model of chinchilla, under different blast intensities, wearing earplugs (EPs) or not during blasts, and drug-treatment plan. The goal of this study was to investigate the therapeutical function of liraglutide by comparing the results obtained under different conditions. Previous studies on chinchillas from two under-blast ear conditions (EP/open), two blast plans (G1: 6 blasts at 3-5 psi or G2:3 blasts at 15-25 psi), and three treatment plans (blast control, pre-blast drug treatment, and post-blast drug treatment) were summarized. The auditory brainstem response (ABR), distortion product otoacoustic emission (DPOAE), and middle latency response (MLR) recorded within 14 days after the blasts were used. Statistical analysis was performed to evaluate the effect of liraglutide under different conditions. ABR threshold shifts indicated that the conditions of the EP and open ears were substantially different. Results from EP chinchillas indicated that the pre-blast treatment reduced the acute ABR threshold elevation on the day of blasts, and the significance of such an effect increased with the blast level. Liraglutide-treated open chinchillas showed lower ABR threshold shifts at the later stage of the experiment regardless of the blast levels. The DPOAE was less damaged after G2 blasts compared to G1 when pre-blast liraglutide was administrated. Lower post-blast MLR amplitudes were observed in the pre-blast treatment groups. This study indicated that the liraglutide mitigated the blast-induced auditory injuries. In EP ears, the pre-blast administration of liraglutide reduced the severity of blast-induced acute damage in ears with EP protection, especially under G2. In animals with open ears, the effect of liraglutide on the restoration of hearing increased with time. The liraglutide potentially benefits post-blast hearing through multiple approaches with different mechanics.

ELEKTROFIZJOLOGICZNE POMIARY UPOŚLEDZENIA SŁUCHU U NARAŻONYCH NA HAŁAS ŻOŁNIERZY ZE SŁUCHEM W NORMIE

IntroductionSome electrophysiological changes can occur in the auditory system in response to noise exposure with or without any permanent auditory threshold shift. The purpose of this study was to identify and measure cochlear function after noise exposure in individuals with normal hearing according to standard audiometric thresholds.Material and methodsPure tone audiometry (PTA) over the standard 0.250–8 kHz range and at 12 kHz, as well as distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) testing, were performed on 42 soldiers who had participated in combat. A control group of 40 participants underwent the same tests.ResultsIn the noise-exposed group, significantly poorer PTA thresholds were recorded at 12 kHz. DPOAE levels were significantly low only at 4 kHz. On ABR testing, both wave I and wave V demonstrated a significant decrease in amplitude and a significant increase in latency for the noise-exposed group.ConclusionsOur findings reveal that high levels of noise can not only damage outer hair cells but also cause changes at the level of the synapses (synaptopathy) which are not evident using standard PTA tests. However, electrophysiological methods can detect some changes in cochlear function.

Audiological profile of patients with type 2 diabetes mellitus.

South Africa shows a high prevalence of type 2 diabetes with reported association with auditory dysfunction. To describe the audiological profile of adults with this metabolic condition. Employing a descriptive research design, 35 individuals with type 2 diabetes, selected through purposive sampling, underwent a basic audiological assessment in addition to extended high-frequency (EHF) audiometry, distortion product otoacoustic emissions (DPOAE) testing and neurological auditory brainstem response (ABR) test. This study revealed a 31.4% prevalence of hearing loss with 81.8% being sensorineural in nature. Poor hearing thresholds were observed at 16 kHz (n= 19; 54.3%), 18 kHz (n= 24; 68.6%) and 20 kHz (n= 30; 85.7%) in the right ear and at 16 kHz (n= 20; 57.1%), 18 kHz (n= 24; 68.6%) and 20 kHz (n= 30; 85.7%) in the left ear. Absent DPOAEs were observed at 6 kHz (n= 20; 51.7%) and 8 kHz (n= 24; 68.6%) in the right ear and at 6 kHz (n= 17; 48.6%) and 8 kHz (n= 29; 82.9%) in the left ear, possibly indicating that type 2 diabetes specifically targets higher frequency hearing. The ABR results revealed a delayed absolute latency of wave III bilaterally (right ear -69%; left ear - 51%), suggesting an impact of this metabolic disease on retro-cochlear pathways. Hearing loss should be recognised as a comorbidity accompanying type 2 diabetes, which indicates the need for routine comprehensive audiological assessments to facilitate early detection and intervention.Contribution:The present findings have implications for audiology clinical protocols; diabetes related health policies and patient education.

A longitudinal study investigating the effects of noise exposure on behavioural, electrophysiological and self-report measures of hearing in musicians with normal audiometric thresholds

Musicians are at risk of hearing loss and tinnitus due to regular exposure to high levels of noise. This level of risk may have been underestimated previously since damage to the auditory system, such as cochlear synaptopathy, may not be easily detectable using standard clinical measures. Most previous research investigating hearing loss in musicians has involved cross-sectional study designs that may capture only a snapshot of hearing health in relation to noise exposure. The aim of this study was to investigate the effects of cumulative noise exposure on behavioural, electrophysiological, and self-report indices of hearing damage in early-career musicians and non-musicians with normal hearing over a 2-year period. Participants completed an annual test battery consisting of pure tone audiometry, extended high-frequency hearing thresholds, distortion product otoacoustic emissions (DPOAEs), speech perception in noise, auditory brainstem responses, and self-report measures of tinnitus, hyperacusis, and hearing in background noise. Participants also completed the Noise Exposure Structured Interview to estimate cumulative noise exposure across the study period. Linear mixed models assessed changes over time. The longitudinal analysis comprised 64 early-career musicians (female n = 34; age range at T0 = 18–26 years) and 30 non-musicians (female n = 20; age range at T0 = 18–27 years). There were few longitudinal changes as a result of musicianship. Small improvements over time in some measures may be attributable to a practice/test-retest effect. Some measures (e.g., DPOAE indices of outer hair cell function) were associated with noise exposure at each time point, but did not show a significant change over time. A small proportion of participants reported a worsening of their tinnitus symptoms, which participants attributed to noise exposure, or not using hearing protection. Future longitudinal studies should attempt to capture the effects of noise exposure over a longer period, taken at several time points, for a precise measure of how hearing changes over time. Hearing conservation programmes for “at risk” individuals should closely monitor DPOAEs to detect early signs of noise-induced hearing loss when audiometric thresholds are clinically normal.

Resistance to age-related hearing loss in the echolocating big brown bat ( Eptesicus fuscus ).

Hearing mediates many behaviors critical for survival in echolocating bats, including foraging and navigation. Most mammals are susceptible to progressive age-related hearing loss; however, the evolution of biosonar, which requires the ability to hear low-intensity echoes from outgoing sonar signals, may have selected against the development of hearing deficits in echolocating bats. Although many echolocating bats exhibit exceptional longevity and rely on acoustic behaviors for survival to old age, relatively little is known about the aging bat auditory system. In this study, we used DNA methylation to estimate the ages of wild-caught big brown bats ( Eptesicus fuscus ) and measured hearing sensitivity in young and aging bats using auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). We found no evidence for hearing deficits in aging bats, demonstrated by comparable thresholds and similar ABR wave and DPOAE amplitudes across age groups. We additionally found no significant histological evidence for cochlear aging, with similar hair cell counts, afferent, and efferent innervation patterns in young and aging bats. Here we demonstrate that big brown bats show minimal evidence for age-related loss of peripheral hearing sensitivity and therefore represent informative models for investigating mechanisms that may preserve hearing function over a long lifetime.

The relationship between distortion product otoacoustic emissions and audiometric thresholds in the extended high-frequency range.

Distortion product otoacoustic emissions (DPOAEs) and behavioral audiometry are routinely used for hearing screening and assessment. These measures provide related information about hearing status as both are sensitive to cochlear pathologies. However, DPOAE testing is quicker and does not require a behavioral response. Despite these practical advantages, DPOAE testing is often limited to screening only low and mid- frequencies. Variation in ear canal acoustics across ears and probe placements has resulted in less reliable measurements of DPOAEs near 4 kHz and above where standing waves commonly occur. Stimulus calibration in forward pressure level and responses in emitted pressure level can reduce measurement variability. Using these calibrations, this study assessed the correlation between audiometry and DPOAEs in the extended high frequencies where stimulus calibrations and responses are most susceptible to the effect of standing waves. Behavioral thresholds and DPOAE amplitudes were negatively correlated, and DPOAE amplitudes in emitted pressure level accounted for twice as much variance as amplitudes in sound pressure level. Both measures were correlated with age. These data show that with appropriate calibration methods, extended high-frequency DPOAEs are sensitive to differences in audiometric thresholds and highlight the need to consider calibration techniques in clinical and research applications of DPOAEs.

Exploring the Influence of Extended High-Frequency Hearing on Cochlear Functioning at Lower Frequencies.

Diminished basal cochlear function, as indicated by elevated hearing thresholds in the extended high frequencies (EHFs), has been associated with lower levels of click-evoked and distortion-product otoacoustic emissions measured at lower frequencies. However, stimulus-frequency otoacoustic emissions (SFOAEs) at low-probe levels are reflection-source emissions that do not share the same generation mechanism as distortion-source emissions. The primary objective of the present study was to examine the influence of hearing thresholds in the EHFs on SFOAEs measured at lower frequencies. SFOAEs were recorded from both ears in 45 individuals with normal hearing thresholds in the conventional audiometric frequencies (0.25-8 kHz). Hearing thresholds were also measured at EHFs (10, 12.5, and 16 kHz). SFOAE magnitudes and signal-to-noise ratios (SNRs) were averaged across 1, 2, and 4 kHz probe frequencies and also averaged for high-probe frequencies (2 and 4 kHz). SFOAE magnitudes and SNRs were significantly higher for ears with better EHF hearing relative to poorer EHF hearing, categorized based on the median split. In addition, hearing in the EHFs significantly contributed to the variance in all SFOAE measures, except for the high-frequency SFOAE magnitudes model. However, hearing thresholds at the probe frequencies did not significantly contribute to the variance in SFOAEs. The study findings suggest that alterations in the basal cochlea, as revealed by EHF hearing thresholds, could be associated with diminished cochlear functioning in relatively apical regions, shown by SFOAEs at lower frequencies, in individuals with normal audiograms. These findings underscore the significance of considering EHF thresholds in audiological evaluations, as alterations in these frequencies may reflect broader cochlear health status.

Pulsed DPOAEs in serial measurements : Combined analysis paradigm of simultaneously occurring changes in hearing thresholds and DPOAEs.

To date, there is no consensus on how to standardize the assessment of ototoxicity in serial measurements. For the diagnosis of damage to the cochlear amplifier, measurement methods are required that have the highest possible test-retest reliability and validity for detecting persistent damage. Estimated distortion-product thresholds (LEDPT) based on short-pulse distortion-product otoacoustic emission (DPOAE) level maps use individually optimal DPOAE stimulus levels and allow reliable quantitative estimation of cochlea-related hearing loss. Hearing thresholds were estimated objectively using LEDPT and subjectively using modified Békésy tracking audiometry (LTA). Recordings were performed seven times within threemonths at 14frequencies (f2 = 1-14 kHz) in 20ears (PTA4 (0.5-4 kHz) < 20 dB HL). Reconstruction of the DPOAE growth behavior as afunction of the stimulus levels L1, L2 was performed on the basis of 21DPOAE amplitudes. Anumerical fit of anonlinear mathematical function to the three-dimensional DPOAE growth function yielded LEDPT for each stimulus frequency. For the combined analysis, probability distributions of hearing thresholds (LTA, LEDPT), DPOAE levels (LDP), and combinations thereof were determined. LTA and LEDPT each exhibited atest-retest reliability with amedian of absolute differences (AD) of 3.2 dB and 3.3 dB, respectively. Combining LEDPT, LDP, and LTA into asingle parameter yielded asignificantly smaller median AD of 2.0 dB. It is expected that an analysis paradigm based on acombination of LEDPT, suprathreshold LDP, and fine-structure-reduced LTA would achieve higher test performance (sensitivity and specificity), allowing reliable detection of pathological or regenerative changes in the outer hair cells.

Re-evaluating the scoring criteria of the Interacoustics Sera Neonatal Hearing Screener

Abstract Introduction: Newborn hearing screeners via otoacoustic emissions (OAEs) have become the standard in audiological clinical practice. Despite the application of OAE protocols for more than 3 decades, there has been no consensus on the standardization of the recorded responses. Usually, manufacturers based the scoring criteria of the OAE responses on small scale samples and in many cases on data published in the literature. Since there are no standards in the OAE probe construction, the resulted OAE responses are quite different between OAE screeners. The project evaluated the scoring criteria used in the Interacoustics Sera OAE screener. Methods: Eight hundred and eleven infants were initially screened by the Accuscreen OAE screener for a Pass or a Fail outcome. Seven hundred and ninety-two infants resulted as Pass were re-evaluated with the Sera transient-evoked OAE (TEOAE) and distortion-product OAE (DPOAE) protocols. Results: In terms of screening efficiency, the DPOAE protocol performed better, showing results very similar to the Accuscreen performance (Fail %: 2.4 vs. 2.3). The data showed that the recordings of the TEOAE responses were more prone to noise corruption. Using 10th percentile normative distribution values, DPOAE-optimized scoring criteria were estimated as 3.1, 7.9, 9.9, and 8.9 dB for the tested frequencies of 2.0, 3.0, 4.0, and 5.0 kHz. Unfortunately, the TEOAE signal-to-noise (S/N) data resulted as too noisy (despite relatively large TEOAE responses); therefore, the TEOAE responses were considered as scoring criteria candidates. The latter were estimated as 4.61, 6.35, 7, 1 and 3, 35 dB at 1.4, 2.0, 2.8, 4.0 kHz. Conclusion: It is possible to improve the screening efficiency of the DPOAE Sera protocol using optimized scoring criteria, aiming the correct identification of at least 90% of all normal hearing subjects. The Sera TEOAE protocol needs further investigation to identify the source of the noise, which lowers significantly the reported S/N ratios. The collected OAE data confirm that there are differences among the responses obtained by various screeners; therefore, an OAE probe standardization is necessary.

Exposure to Noise or Music in Clinical Trials: A Scoping Review on Ethical and Methodological Considerations.

Use of noise or music in experimental human studies requires balancing the need to avoid subjecting participants to potentially harmful noise levels while still reaching levels that will produce a measurable change in the primary outcome. Several methodological and ethical aspects must be considered. This study aims to summarize ethical and methodological aspects, and reported outcomes, of previously published experimental paradigms using loud noise/music. Four databases (Medline, Central, Web of Science, and Scopus) and two trials registries (Clinicaltrials.gov and EU Clinical Trials) were searched. Extracted items had the details of author and year of publication, study design and purpose, population, setting timeline and material, selected battery test, and effect of noise/music on participants' hearing. Thirty-four studies were included. Exposure safety considerations were reported in five studies. Eleven studies assessing hearing loss used white or narrow-band noise [(NBN (0.5-4 kHz), up to 115 dBA, duration range: 3'-24 hours)], and 10 used pop music (up to 106 dBA, duration range: 10'-4 hours). Experimental setting varied significantly. Temporary thresholds shift (TTS) and reduction in distortion product otoacoustic emissions were found at 1-8 kHz, with maximum average TTS∼21.5 dB at 4 kHz after NBN and ∼11.5 dB at 6 kHz after music exposure. All participants recovered their hearing, except for one participant in one study. In the 13 non-hearing loss studies, no hearing testing was performed after exposure, but loud noise was associated with temporary stress, bradygastria, and cardiovascular changes. Noise-induced subjective stress may be higher for participants with tinnitus. Loud noise (100 dBA, 10') increased diastolic and mean blood pressure only in participants with hypertension. Experimental exposure paradigms can produce temporary changes to hearing without measurable long-term health consequences. Methodological and ethical aspects identified in this review should be considered for the development of future paradigms.

Transient Evoked and Distortion-Product Otoacoustic Emissions in Normal Ear of Patients with Sudden Unilateral Sensory Neural Hearing Loss

Transient Evoked and Distortion-Product Otoacoustic Emissions in Normal Ear of Patients with Sudden Unilateral Sensory Neural Hearing Loss

Non-invasive intracranial pressure monitoring for high-grade gliomas patients treated with radiotherapy: results of the GMaPIC trial.

Patients with high-grade gliomas are at risk of developing increased intracranial hypertension (ICHT) in relation to the increase in volume of their tumor. ICP change cannot be measured by invasive method but can be estimated by using routine clinical signs, in combination with a standard imaging method, magnetic resonance imaging (MRI). A non-invasive monitoring of ICP could be of interest in high-grade glioma, in particular after radiotherapy treatment with as major side effect a cerebral oedema. This prospective clinical study aimed to compare the ICP changes (estimated by a non-invasive method based upon distortion product otoacoustic emissions (DPOAE) monitoring) with volume changes observed on MRI in patients with high-grade gliomas treated with radiotherapy. DPOAE measurements were performed one month after the end of radiotherapy and then every 3 months for one year. At each visit, the patient also underwent MRI as well as an evaluation of clinical signs. The variation in the estimate of intracranial pressure readout measured at each follow-up visit (in absolute value with respect to the baseline measurements) was significantly associated with the variation of T2/FLAIR volume (n=125; p<0.001) with a cut off value of change ICP readout of 40.2 degrees (e.i. an estimated change of 16 mm Hg). The GMaPIC trial confirm the hypothesis that the ICP change estimated by DPOAEs measurement using a non-invasive medical device is correlated with the change of the tumor or edema in high grade glioma after radiotherapy. The device could thus become an easy-to-use and non-invasive intracranial pressure monitoring tool for these patients. Clinicaltrials.gov, identifier (NCT02520492).

A genome-wide association study reveals a polygenic architecture of speech-in-noise deficits in individuals with self-reported normal hearing

Speech-in-noise (SIN) perception is a primary complaint of individuals with audiometric hearing loss. SIN performance varies drastically, even among individuals with normal hearing. The present genome-wide association study (GWAS) investigated the genetic basis of SIN deficits in individuals with self-reported normal hearing in quiet situations. GWAS was performed on 279,911 individuals from the UB Biobank cohort, with 58,847 reporting SIN deficits despite reporting normal hearing in quiet. GWAS identified 996 single nucleotide polymorphisms (SNPs), achieving significance (p < 5*10−8) across four genomic loci. 720 SNPs across 21 loci achieved suggestive significance (p < 10−6). GWAS signals were enriched in brain tissues, such as the anterior cingulate cortex, dorsolateral prefrontal cortex, entorhinal cortex, frontal cortex, hippocampus, and inferior temporal cortex. Cochlear cell types revealed no significant association with SIN deficits. SIN deficits were associated with various health traits, including neuropsychiatric, sensory, cognitive, metabolic, cardiovascular, and inflammatory conditions. A replication analysis was conducted on 242 healthy young adults. Self-reported speech perception, hearing thresholds (0.25–16 kHz), and distortion product otoacoustic emissions (1–16 kHz) were utilized for the replication analysis. 73 SNPs were replicated with a self-reported speech perception measure. 211 SNPs were replicated with at least one and 66 with at least two audiological measures. 12 SNPs near or within MAPT, GRM3, and HLA-DQA1 were replicated for all audiological measures. The present study highlighted a polygenic architecture underlying SIN deficits in individuals with self-reported normal hearing.

Predictors of Speech-in-Noise Understanding in a Population of Occupationally Noise-Exposed Individuals.

Understanding speech in noise is particularly difficult for individuals occupationally exposed to noise due to a mix of noise-induced auditory lesions and the energetic masking of speech signals. For years, the monitoring of conventional audiometric thresholds has been the usual method to check and preserve auditory function. Recently, suprathreshold deficits, notably, difficulties in understanding speech in noise, has pointed out the need for new monitoring tools. The present study aims to identify the most important variables that predict speech in noise understanding in order to suggest a new method of hearing status monitoring. Physiological (distortion products of otoacoustic emissions, electrocochleography) and behavioral (amplitude and frequency modulation detection thresholds, conventional and extended high-frequency audiometric thresholds) variables were collected in a population of individuals presenting a relatively homogeneous occupational noise exposure. Those variables were used as predictors in a statistical model (random forest) to predict the scores of three different speech-in-noise tests and a self-report of speech-in-noise ability. The extended high-frequency threshold appears to be the best predictor and therefore an interesting candidate for a new way of monitoring noise-exposed professionals.

Reliable Long-Term Serial Evaluation of Cochlear Function Using Pulsed Distortion-Product Otoacoustic Emissions: Analyzing Levels and Pressure Time Courses.

To date, there is no international standard on how to use distortion-product otoacoustic emissions (DPOAEs) in serial measurements to accurately detect changes in the function of the cochlear amplifier due, for example, to ototoxic therapies, occupational noise, or the development of regenerative therapies. The use of clinically established standard DPOAE protocols for serial monitoring programs appears to be hampered by multiple factors, including probe placement and calibration effects, signal-processing complexities associated with multiple sites of emission generation as well as suboptimal selection of stimulus parameters. Pulsed DPOAEs were measured seven times within 3 months for f2 = 1 to 14 kHz and L2 = 25 to 80 dB SPL in 20 ears of 10 healthy participants with normal hearing (mean age = 32.1 ± 9.7 years). L1 values were computed from individual optimal-path parameters derived from the corresponding individual DPOAE level map in the first test session. Three different DPOAE metrics for evaluating the functional state of the cochlear amplifier were investigated with respect to their test-retest reliability: (1) the interference-free, nonlinear-distortion component level (LOD), (2) the time course of the DPOAE-envelope levels, LDP(t), and (3) the squared, zero-lag correlation coefficient () between the time courses of the DPOAE-envelope pressures, pDP(t), measured in two sessions. The latter two metrics include the two main DPOAE components and their state of interference. Collated over all sessions and frequencies, the median absolute difference for LOD was 1.93 dB and for LDP(t) was 2.52 dB; the median of was 0.988. For the low (f2 = 1 to 3 kHz), mid (f2 = 4 to 9 kHz), and high (f2 = 10 to 14 kHz) frequency ranges, the test-retest reliability of LOD increased with increasing signal to noise ratio (SNR). On the basis of the knowledge gained from this study on the test-retest reliability of pulsed DPOAE signals and the current literature, we propose a DPOAE protocol for future serial monitoring applications that takes into account the following factors: (1) separation of DPOAE components, (2) use of individually optimal stimulus parameters, (3) SNR of at least 15 dB, (4) accurate pressure calibration, (5) consideration of frequency- and level-dependent test-retest reliabilities and corresponding reference ranges, and (6) stimulus levels L2 that are as low as possible with sufficient SNR to capture the nonlinear functional state of the cochlear amplifier operating at its highest gain.

Pulsed DPOAEs in serial measurements : Combined analysis paradigm of simultaneously occurring changes in hearing thresholds and DPOAEs. German version

To date, there is no consensus on how to standardize the assessment of ototoxicity in serial measurements. For the diagnosis of damage to the cochlear amplifier, measurement methods are required that have the highest possible test-retest reliability and validity for detecting persistent damage. Estimated distortion-product thresholds (LEDPT) based on short-pulse distortion-product otoacoustic emission (DPOAE) level maps use individually optimal DPOAE stimulus levels and allow reliable quantitative estimation of cochlea-related hearing loss. Hearing thresholds were estimated objectively using LEDPT and subjectively using modified Békésy tracking audiometry (LTA). Recordings were performed seven times within threemonths at 14frequencies (f2 = 1-14 kHz) in 20ears (PTA4 (0.5-4 kHz) < 20 dB HL). Reconstruction of the DPOAE growth behavior as afunction of the stimulus levels L1, L2 was performed on the basis of 21DPOAE amplitudes. Anumerical fit of anonlinear mathematical function to the three-dimensional DPOAE growth function yielded LEDPT for each stimulus frequency. For the combined analysis, probability distributions of hearing thresholds (LTA, LEDPT), DPOAE levels (LDP), and combinations thereof were determined. LTA and LEDPT each exhibited atest-retest reliability with amedian of absolute differences (AD) of 3.2 dB and 3.3 dB, respectively. Combining LEDPT, LDP, and LTA into asingle parameter yielded asignificantly smaller median AD of 2.0 dB. It is expected that an analysis paradigm based on acombination of LEDPT, suprathreshold LDP, and fine-structure-reduced LTA would achieve higher test performance (sensitivity and specificity), allowing reliable detection of pathological or regenerative changes in the outer hair cells.