Masking Level Difference Test Research Articles

Examining the utility of near infrared light as pre-exposure therapy to mitigate temporary noise-induced hearing loss in humans.

This study sought to determine the effect of Occupational Safety and Health Administration (OSHA) compliant noise on auditory health and assess whether pre-noise near infrared (NIR) light therapy can mitigate the effects of noise exposure. Over four visits, participants (n = 30, NCT#: 03834714) with normal hearing completed baseline hearing health assessments followed by exposure to open ear, continuous pink noise at 94 dBA for 15 min. Immediately thereafter, post-noise hearing tests at 3000, 4000, and 6000 Hz and distortion product otoacoustic emissions (DPOAEs) were conducted along with the Modified Rhyme Test (MRT), Masking Level Difference Test (MLD), and Fixed Level Frequency Tests (FLFT) [collectively referred to as the Central and Peripheral Auditory Test Battery (CPATB)] to acquire baseline noise sensitivity profiles. Participants were then randomized to either Active or Sham NIR light therapy for 30 min binaurally to conclude Visit 1. Visit 2 (≥24 and ≤ 48 h from Visit 1) began with an additional 30-min session of Active NIR light therapy or Sham followed by repeat CPATB testing and noise exposure. Post-noise testing was again conducted immediately after noise exposure to assess the effect of NIR light therapy. The remaining visits were conducted following ≥2 weeks of noise rest in a cross-over design (i.e., those who had received Active NIR light therapy in Visits 1 and 2 received Sham therapy in Visits 3 and 4). Recovery hearing tests and DPOAEs were completed at the end of each visit. Participants experienced temporary threshold shifts (TTS) immediately following noise exposure, with a mean shift of 6.79 dB HL (±6.25), 10.61 dB HL (±6.89), and 7.30 dB HL (±7.25) at 3000, 4000, and 6000 Hz, respectively, though all thresholds returned to baseline at 3000, 4000, and 6000 Hz within 75 min of noise exposure. Paradoxically, Active NIR light therapy threshold shifts were statistically higher than Sham therapy at 3000 Hz (p = 0.04), but no other differences were observed at the other frequencies tested. An age sub-analysis demonstrated that TTS among younger adults were generally larger in the Sham therapy group versus Active therapy, though this was not statistically different. There were no differences in CPATB test results across Active or Sham groups. Finally, we observed no changes in auditory function or central processing following noise exposure, suggestive of healthy and resilient inner ears. In this study, locally administered NIR prior to noise exposure did not induce a significant protective effect in mitigating noise-induced TTS. Further exploration is needed to implement effective dosage and administration for this promising otoprotective therapy.

Development of a Binaural Masking Level Differences Test Application Using Tonal and Speech Stimuli in Persian and Assessing its Test-Retest Reliability in Normal-Hearing Young People

Background and Aim: The masking level difference (MLD) test is a behavioral test that assesses binaural interactions and central auditory processing. This study aims to design a binaural MLD (BMLD) test application using tonal and Speech Stimuli in Persian.
 Methods: In the first stage, the BMLD test application was designed in MATLAB software. Then, the spondaic words were recorded and added to the sound processing panel of the application. In the next stage, the MLD of tonal and speech stimuli was measured on 20 subjects aged 18–25 years. To examine the test-retest reliability of the application, all steps were repeated after one week.
 Results: The MLD values for tonal and speech stimuli under the SoNo-SπNo condition were significantly different from those under the SoNo-SoNπ condition (p<0.05). These values for tonal and speech stimuli were 10.50 and 6.12 dB under the SoNo- SπNo condition, and 6.85 and 4.43 under the SoNo- SoNπ condition. There was no significant difference in the MLD values between males and females. The intraclass correlation coefficient value for different phase conditions was more than 0.8, indicating the high reliability of the BMLD test application for tonal and speech stimuli in Persian (p<0.05).
 Conclusion: The designed BMLD test application using tonal and speech stimuli in Persian has similar results compared to the conventional methods of MLD test for other languages, therefore, this application can be used in audiology clinics in Iran to perform the MLD test.
 Keywords: Release from masking; masking; binaural hearing; software

A Study on the Reference Values and Cutoff Criteria of Masking Level Difference for Children Aged 7-12 Years.

The Masking Level Difference (MLD) test is one of the main instruments for investigating binaural interaction. Studies with children aged 7–12 years still disagree about the influence of age on test performance and present discordant reference values. This study aimed to verify the effect of age on the performance of children aged 7–12 years in the MLD test and to establish reference values and cutoff criteria for this age group. Fifty-nine children with normal hearing were organized in three groups according to their age: 7–8 (n = 20), 9–10 (n = 20), and 11–12 (n = 19) years. The participants completed the MLD test by Auditec®. The Kruskal–Wallis statistical test was used to compare groups. Reference values were obtained by calculating mean, standard deviation, median, mode, and percentiles, while the cutoff criterion was obtained by subtracting two standard deviations from the mean. No statistically significant differences were observed between the groups regarding the MLD test measures. The mean MLD was 10.51 ± 1.84 dB and the cutoff point was set at 7 dB. Thus, reference values for the MLD test were established for children aged 7–12 years, who presented no effect of age on test performance.

ZDOLNOŚCI SŁUCHOWE U OSÓB Z FORMALNYM WYKSZTAŁCENIEM MUZYCZNYM I BEZ TAKIEGO WYKSZTAŁCENIA

IntroductionAuditory perception can be enhanced by musical training and practice. Considering the multiple brain areas involved in musical learning, good auditory perceptual skills can contribute to phonological awareness, speech recognition in the presence of noise, reading, syllable recognition, and other language skills.Material and methodsThere were 30 adults between 18 and 27 years old who participated. They were divided into two groups: 15 individuals without formal musical training (Non-Musicians) and 15 individuals with 5 years or more of formal musical training (Musicians), paired by gender and age. Procedures used for assessing their hearing skills were the Duration Pattern test, Staggered Spondaic Word test, Masking Level Difference test, and Dichotic Consonant–Vowel test.ResultsIn all tests, the Musicians group showed a higher average score than the Non-Musicians. In the MLD test, the average level difference was 3 dB higher for the Musicians than for the Non-Musicians (p = 0.001). There were also statistically significant mean differences between the groups for the DP test, SSW test in the right ear, and DCV test (number of errors).ConclusionsIndividuals with formal musical training show better auditory attention abilities, which are important for developing good listening skills, resulting in good communication and linguistic performance compared to individuals without prior musical training.

Masking level difference among brazilian military personnel: a comparison between pilots and non-pilots

Objectives The aims of this study were to investigate auditory habits and binaural interaction among pilot and non-pilot military personnel from the Brazilian Air Force. Design A cross-sectional study using (1) an auditory habits questionnaire to outline the groups auditory profile and (2) the masking level difference test (MLD, Auditec, Saint Louis®) to evaluate and compare the groups. Study Sample Forty military male personnel aged between 30–40 years old, all with normal hearing, comprising 20 pilots in the study group (SG), and 20 non-pilots, not exposed to noise, in the control group (CG). Results There was no significant difference between groups regarding auditory habits. In the MLD test, a significantly better performance under the homophasic condition (S0N0) was found in the SG. Under the antiphasic condition (SπN0) there were no differences between groups. This combination resulted in a significantly lower MLD in the SG compared to the CG. Conclusions Repeated exposure to conditions where active pilots have to learn to recognise speech in noisy backgrounds may lead to a better performance in the MLD’s homophasic condition (S0N0).

Masking Level Difference: Performance of School Children Aged 7–12 Years

Background and ObjectivesIn masking level difference (MLD), the masked detection threshold for a signal is determined as a function of the relative interaural differences between the signal and the masker. Study 1 analyzed the results of school-aged children with good school performance in the MLD test, and study 2 compared their results with those of a group of children with poor academic performance.Subjects and MethodsStudy 1 was conducted with 47 school-aged children with good academic performance (GI) and study 2 was carried out with 32 school-aged children with poor academic performance (GII). The inclusion criteria adopted for both studies were hearing thresholds within normal limits in basic audiological evaluation. Study 1 also considered normal performance in the central auditory processing test battery and absence of auditory complaints and/or of attention, language or speech issues. The MLD test was administered with a pure pulsatile tone of 500 Hz, in a binaural mode and intensity of 50 dBSL, using a CD player and audiometer.ResultsIn study 1, no significant correlation was observed, considering the influence of the variables age and sex in relation to the results obtained in homophase (SoNo), antiphase (SπNo) and MLD threshold conditions. The final mean MLD threshold was 13.66 dB. In study 2, the variables did not influence the test performance either. There was a significant difference between test results in SπNo conditions of the two groups, while no differences were found both in SoNo conditions and the final result of MLD.ConclusionsIn study 1, the cut-off criterion of school-aged children in the MLD test was 9.3 dB. The variables (sex and age) did not interfere with the MLD results. In study 2, school performance did not differ in the MLD results. GII group showed inferior results than GI group, only in SπNo condition.

Age-related altering temporal processing and binaural interaction functions in normal hearing individuals: Observational and cross-sectional study

ObjectiveThis study aimed to investigate the temporal processing and binaural interaction functions of central auditory processing tests according to the anatomical localizations of young and elderly individuals. It also sought to evaluate the relationships between the same individuals’ central auditory processing tests. MethodsThis observational and cross-sectional study included individuals with normal hearing between 18 and 30 and 60–75 years of age, who were referred to as the young group and the elderly group, respectively. The evaluation of the central auditory processing tests was completed using the frequency pattern test, duration pattern test, masking level difference test, and random gap detection test. Furthermore, speech discrimination and speech in noise scores were analyzed for both groups. ResultsStatistically significant differences were identified between the groups’ scores for the speech in noise test, masking level difference test, random gap detection test, frequency pattern test, and duration pattern test (p < 0.05). A statistically significant relationship was observed between the age and the results of the central auditory processing tests (p < 0.05). ConclusionWhen compared to younger individuals, elderly individuals presented with declined temporal sequences, temporal resolutions, and binaural interaction skills.

Masking Level Difference and Electrophysiological Evaluation in Adults with Normal Hearing.

Introduction The auditory structures of the brainstem are involved in binaural interaction, which contributes to sound location and auditory figure-background perception. Objective To investigate the performance of young adults in the masking level difference (MLD) test, brainstem auditory-evoked potentials (BAEPs) with click stimulus, and frequency-following response (FFR), as well as to verify the correlation between the findings, considering the topographic origin of the components of these procedures. Methods A total of 20 female subjects between 18 and 30 years of age, with normal hearing and no complaints concerning central auditory processing underwent a basic audiological evaluation, as well as the MLD test, BAEP and FFR. Results The mean result on the MLD test was of 10.70 dB. There was a statistically significant difference in the absolute latencies of waves I, III and V in the BAEPs of the ears. A change in the FFR characterized by the absence of the C, E and F waves was noticed. There was a statistically significant difference in the positive correlation of wave V in the BAEPs with the MLD. There was a statistically significant difference in the positive correlation of the mean MLD and the V, A and F components of the FFR. Conclusion The mean MLD was adequate. In the BAEPs, we observed that the click stimulus transmission occurred faster in the right ear. The FFR showed absence of some components. The mean MLD correlated positively with the BAEPs and FFR.

Central auditory processing: behavioral and electrophysiological assessment of children and adolescents diagnosed with stroke

IntroductionCentral auditory processing refers to the efficiency and effectiveness with which the central nervous system uses auditory information: it may be altered in neurological disorders and brain injuries, such as strokes. However, despite evidence of probable alterations in the pediatric population, functional abilities and post-stroke limitations are still not well documented in the literature. ObjectiveTo analyze the findings of the electrophysiological and behavioral evaluations of central auditory processing of children and adolescents diagnosed with stroke from a reference outpatient clinic, as well as to investigate possible associations with the variables: type and location of the stroke and age group. MethodsThe present study is characterized as comparative cross-sectional. The sample, for convenience, included individuals aged 7–18 years divided into two groups: study group, composed of individuals with a diagnosis of stroke, and control group, composed of individuals with typical development. The evaluation consisted of the following procedures: anamnesis, basic audiological evaluation, behavioral evaluation of the auditory processing disorder (dichotic digit test, dichotic consonant-vowel, synthetic sentence identification/pediatric speech intelligibility, gaps in noise, pitch pattern sequence, masking level difference), and electrophysiological evaluation (P300 and mismatch negativity). ResultsNineteen children and adolescents were included in the study group. The control group was composed of 19 children and adolescents with typical development. In the comparison between the groups, a worse performance is observed for the study group in all the evaluated tests, behavioral and electrophysiological. In the behavioral evaluation of central auditory processing, there was a statistical difference for all tests, except for masking level difference and dichotic digit test, binaural separation step on the left. In the electrophysiological evaluation, there was a statistical difference in the latency of mismatch negativity and P300. No associations were found between the behavioral and electrophysiological findings and the location of the stroke and age group variables. ConclusionChildren and adolescents diagnosed with stroke present a worse performance in the electrophysiological and behavioral evaluations of central auditory processing when compared to a control group.

Comparing musicians and non-musicians in signal-in-noise perception

Objectives: The objective is to compare musicians and non-musicians in signal-in-noise perception.Design: Participants underwent the following tests: (1) High-frequency (HF) audiometry, (2) QuickSIN (a test for speech perception in noise), and (3) Binaural Masking Level Difference (BMLD) test (a test that examines the hearing threshold of a low-frequency tone from noise masking when the phase of the signal or noise in one ear is reversed with respect to the phase of the signal or noise in the other ear, i.e. the difference in the threshold for detection of the tone in noise under the SπNo and SoNo conditions).Study sample: Thirty-four healthy young normal-hearing listeners including 17 musicians (M) and 17 non-musicians (NM).Results: There were no study group difference in HF audiometry and QuickSIN. The M group had a significantly better performance under the SoNo but not under the SπNo condition. As a result, the BMLD value (SoNo–SπNo) was significantly smaller in the M group than in the NM group.Conclusions: There is a musicians’ advantage in binaural tone-in-noise detection in the BMLD task under the SoNo condition, suggesting that long-term music training positively shapes the auditory system.

Masking Level Difference in schoolchildren: environmental analysis.

To investigate the auditory ability of selective attention in the school population and to identify reference values to the age group from seven to ten years old through the Masking Level Difference Test, and to identify if the parents' schooling, as well as the family income can influence the test results. Thirty-one schoolchildren who match the eligibility criteria attended the study, being 20 female and 11 male. An anamnesis was conducted to question the familiar income and the schooling of the children´s parents; we also performed visual inspection of the External Acoustic Meatus, Pure Tone Audiometry, Speech Audiometry, Acoustic Immittance Measures, Dichotic Digits Test and Masking Level Difference test. The mean age of the individuals was 8.67 years. There were no observed differences between genders and between the evaluated ages in the MLD performance. There was no relation between the parents' schooling and the average monthly income with the performance of the children in MLD Test. The MLD mean was 7.65 dB and standard deviation of 2.51 dB. The Masking Level Difference in schoolchildren from seven to ten years old is 7.65 dB and is independent of the gender, parents' schooling and the average monthly income of the schoolchild.

Implementation and evaluation of a Danish test battery for auditory processing disorder in children

Objective: This study presents a Danish test battery for auditory processing disorder (APD). The tests were evaluated as to normative cut-off values (pass-fail criteria) and their test–retest reliability. Design: The battery consists of four behavioural tests: the filtered words (FW) test, the dichotic digits (DD) test, the gap detection (GD) test and the binaural masking level difference (BMLD) test. The tests were evaluated through listening experiments on children with no known history of auditory problems. Study sample: The normative cut-off values were obtained from 158 children (75 boys and 83 girls, aged 6–16 years), whereas the test–retest reliability was obtained from 20 children (10 boys and 10 girls, aged 6–11 years). Results: For each of the four tests one to four different cut-off values were determined depending on whether the scores from the two ears and the different age groups could be pooled. For each of the four tests the test–retest reliability was found to be satisfactory. The test–retest reliability was highest for the FW and the DD test. Conclusions: A Danish APD test battery is now available for clinical use with normative data.

Performance of children with mild or moderate sensory hearing loss on central auditory tests

Hearing is fundamental to the development of successful language skills. Deficits in hearing acuity and auditory processing (AP) can profoundly obstruct effective communication. Our study aimed to evaluate the performance of children with mild and moderate sensory hearing loss (HL) on central AP tests. The study included 50 children: 10 children with normal hearing who were used as controls; 20 children with mild sensory HL; and 20 children with moderate sensory HL. Both male and female children were equally represented. All children underwent otoscopic examination, pure tone audiometry, tympanometry, and acoustic reflex measurements. Questionnaires on central AP disorders, dyslexia, and attention deficit hyperactivity disorder were answered by the parents. Screening tests for AP abilities [pitch pattern sequence test, speech perception in noise (SPIN) right SPIN, left SPIN, dichotic digit test] were conducted. All children were then examined with the full versions of the previous tests in addition to auditory fusion test − revised, masking level difference test, binaural fusion test, competing sentence test, and low pass-filtered test. Arabic-version dyslexia assessment was carried out for those who failed the tests. The study revealed that children with mild and moderate HL who failed the screening tests also failed the full version tests, and when tested by the Arabic-version dyslexia assessment test, dyslexia was found as a comorbid condition.

Short-term visual deprivation can enhance spatial release from masking

This research aims to study the effect of short-term visual deprivation on spatial release from masking, a major component of the cocktail party effect that allows people to detect an auditory target in noise. The Masking Level Difference (MLD) test was administered on healthy individuals over three sessions: before (I) and after 90min of visual deprivation (II), and after 90min of re-exposure to light (III). A non-deprived control group performed the same tests, but remained sighted between sessions I and II. The non-deprived control group displayed constant results across sessions. However, performance in the MLD test was improved following short-term visual deprivation and performance returned to pre-deprivation values after light re-exposure. This study finds that short-term visual deprivation transiently enhances the spatial release from masking. These data suggest the significant potential for enhancing a process involved in the cocktail party effect in normally developing individuals and adds to an emerging literature on the potential to enhance auditory ability after only a brief period of visual deprivation.

Effect of musical training on masking paradigm

Background: Musicians outperform nonmusicians on brainstem and cortical level processing. However, there are limited literature comparing musicians and nonmusicians on the overall release of masking abilities and correlation across otoacoustic emissions (OAEs), masking level difference (MLD) and quick speech-in-noise (Quick-SIN). Aim: To investigate the physiological differences between musicians and nonmusicians by evaluating the effect of musical training on contralateral suppression (CAS) of OAE, MLD, and Quick-SIN. Materials and Methods: Distortion product OAEs (DPOAEs) recording with and without noise, MLD test using continuous (CMLD) and pulsating pure tones (PMLD) and Quick-SIN in Kannada were carried out on 15 musicians and 15 nonmusicians. Results: Musicians outperformed nonmusicians on Quick-SIN and CAS of OAEs. However, no significant difference was observed between two groups on CMLD and PMLD. There was a significant difference observed in CMLD, PMLD as well as suppression amplitude across frequencies tested in both groups. A significant difference between PMLD and CMLD was observed only for musicians at 2 kHz. In both groups, there was a significant level of correlation for CAS of DPOAE and Quick-SIN with CMLD and with PMLD between the parameters tested. Conclusion: The results of our finding suggest that CAS of DPOAE and Quick-SIN are sensitive tools to quantify the effect of musical training, compared to MLD. Musical training helps to strengthen afferent and efferent pathways, and hence it aids in speech perception abilities in noise. Hence, for the intervention of individuals with difficulties in speech perception in noise, musical training can be a choice to be considered. As well for appropriate diagnosis and interpretation, one needs to consider the musical experience of individual tested.

Relação entre os achados do teste masking level difference e do reflexo acústico em crianças com transtorno fonológico

Resumo: OBJETIVO: investigar os achados do teste Masking Level Difference com os resultados do reflexo acústico e a composição do sistema fonológico de crianças com transtorno fonológico, com o propósito de verificar se há associações que possam auxiliar a compreensão do processo de aquisição de linguagem atípica. MÉTODOS: estudo quantitativo, observacional e descritivo, desenvolvido por meio de levantamento secundário de um banco de dados, constituído de avaliações fonoaudiológicas de 110 crianças com transtorno fonológico, com idades entre 5 e 10 anos. Para a composição do corpus deste estudo o requisito utilizado foi a realização da timpanometria, com curva timpanométrica do tipo A (Jerger) e possuir avaliação do Masking Level Difference. RESULTADOS: dos dados de 110 crianças, 57 se enquadraram nestes requisitos, compondo a população deste estudo, sendo 42 do sexo masculino e 15 do sexo feminino. Destas 57 crianças, 23 (40,3%) apresentam resultado do Masking Level Difference normal e 34 (59,7%) apresentam resultado alterado. Não foi encontrada diferença estatística na relação entre o Masking Level Difference com as variáveis idade, sexo, grau de inteligibilidade de fala e o resultado do reflexo acústico contralateral e ipsilateral. Na relação entre a aquisição fonológica dos fonemas em onsetinicial e medial, foi encontrada significância estatística entre a não aquisição dos fonemas /s/ e /ʀ/ em onset inicial e /s/ e /z/ em onset medial com o resultado do teste alterado. CONCLUSÃO: outras habilidades do processamento auditivo, além da interação binaural, devem ser estudadas a fim de identificar a relação deste com o transtorno fonológico.

How to Quantify Binaural Hearing in Patients with Unilateral Hearing Using Hearing Implants

Application of bilateral hearing devices in bilateral hearing loss and unilateral application in unilateral hearing loss (second ear with normal hearing) does not a priori lead to binaural hearing. An overview is presented on several measures of binaural benefits that have been used in patients with unilateral or bilateral deafness using one or two cochlear implants, respectively, and in patients with unilateral or bilateral conductive/mixed hearing loss using one or two percutaneous bone conduction implants (BCDs), respectively. Overall, according to this overview, the most significant and sensitive measure is the benefit in directional hearing. Measures using speech (viz. binaural summation, binaural squelch or use of the head shadow effect) showed minor benefits, except for patients with bilateral conductive/mixed hearing loss using two BCDs. Although less feasible in daily practise, the binaural masking level difference test seems to be a promising option in the assessment of binaural function.

The study of central auditory processing in stuttering children

Abstract There are evidences that indicate a relationship between auditory processing disorders and stuttering. The aim of the study was to evaluate central auditory processing in stuttering children and to compare the findings with those of normal fluent children. Twenty stuttering school-age children of both sexes were included in the study. A control group included 20 age-matched and sex-matched nonstuttering children. Full informed consent from all participants was taken before initiating the study. All participants were subjected to the following central auditory processing tests: pitch pattern sequence test (PPST), dichotic digit test (DDT), speech in noise test (children version) (SPIN), auditory fusion test revised (AFT-R), and binaural masking level difference (MLD) test. All patients were subjected to stuttering severity instrument III to assess their stuttering and its severity. The stuttering group scored significantly poorer in the PPST, DDT, and SPIN, whereas they scored similar to the control group in MLD and AFT-R. There was no correlation between the severity of stuttering and the performance on the central auditory processing tests. Stuttering children have an intact brain stem integrity shown by the normal MLD and an intact right hemisphere as signified by the normal right and left ear difference in the DDT and by the improvement in the PPST on humming. Left hemisphere deficit appears in more complicated tasks such as PPST, DDT, and SPIN, but not in simple tasks such as AFT-R. We can conclude that the deficit is within the left cerebral hemisphere. The effect of the usage of central auditory processing disorder rehabilitation programs on those children should further be assessed.

Xylene-Induced Auditory Dysfunction in Humans

Animal data indicate that xylene induces cochlear dysfunction, characterized by the loss of outer hair cells. There is little evidence regarding xylene-induced ototoxicity in humans. The aim of the study was to investigate the possible adverse effects of xylene on the peripheral and central auditory system in humans. A total of 30 medical laboratory workers who had been exposed to a mixture of xylene isomers, together with 30 nonexposed control participants matched for gender, age, and educational level were selected. Participants of both groups were not exposed to noise levels above 85 dBA time-weighted average. All participants were evaluated with a comprehensive audiological test battery, which included measures of peripheral and central auditory function. Peripheral auditory measures included pure-tone audiometry and distortion product otoacoustic emissions. Behavioral measures of central auditory function included a pitch pattern sequence test, an adaptive test of temporal resolution, a dichotic digit test, and a masking level difference test. The auditory brainstem response was used to objectively evaluate the function of the auditory pathways at the brainstem level. Speech perception in quiet and in noise was evaluated using the Hearing In Noise Test (HINT). The xylene-exposed participants were extensively evaluated with regard to their exposure to both noise and xylene. Noise dosimetry was conducted over an 8-hr work shift to obtain noise-exposure levels for each xylene-exposed worker. Airborne xylene concentrations were obtained at 11 different workstations throughout the medical laboratories, and methyl hippuric acid levels per gram of creatinine in urine were obtained for each xylene-exposed subject. Finally, a detailed interview exploring current and past solvent and noise exposure was conducted. The xylene-exposed participants showed significantly worse pure-tone thresholds in comparison with the nonexposed participants. The xylene-exposed participants demonstrated significantly worse results than the control group participants for the pitch pattern sequence test, dichotic digit test, HINT, and the auditory brainstem response (absolute and interpeak latencies). No significant differences between the xylene-exposed and nonexposed participants were observed for distortion product otoacoustic emissions, adaptive test of temporal resolution, or the masking level difference test. A significant correlation between the concentrations of methyl hippuric acid in urine and pure-tone thresholds (2 to 8 kHz) was found in xylene-exposed workers. Also, participants with high cumulative dose of xylene exposure presented with poorer test results than participants with low cumulative dose of xylene exposure. The results of the present research suggest that xylene is associated with adverse central auditory effects and poorer sound detection abilities in humans. A major limitation of the study is that the results found among xylene-exposed participants cannot be proved to be permanent, and thus further research should be conducted to clarify this limitation. Workers exposed to this chemical should be routinely evaluated with a comprehensive audiological test battery, to detect early signs of auditory dysfunction.

Preliminary Identification of Central Auditory Processing Screening Tests for Individuals with Multiple Sclerosis

Research suggests that individuals with multiple sclerosis (MS) may be susceptible to deficits in central auditory processing (CAP). Audiologists need to be able to select appropriate tests to screen for such deficits in this patient population. The purpose of this report is to identify promising CAP tests for screening patients with MS. A comprehensive behavioral CAP test battery was administered to 26 subjects with MS and 27 subjects without MS. Out of six potential tests, selected based on the CAP deficits reported in the scientific literature, results suggest that the Staggered Spondaic Word test and the SCAN-A, followed by the Masking Level Difference test, are the most promising screening tests in this patient population. The Frequency Patterns Test, the Dichotic Digits Test, and the Gaps-in-Noise Test, on the other hand, were less promising. It should be noted, however, that this is a preliminary analysis, and that no clinical recommendations can be made until the reference standards are established in a much larger sample population.