Audiological Test Battery Research Articles

Objective Assessment of Hearing in Children: Update on Procedures and Protocols

Early identification and diagnosis of hearing loss in infants and young children is the first step toward appropriate and effective intervention and is critical for optimal communicative and psychosocial development. Limitations of behavioral assessment techniques in pediatric populations necessitate the use of an objective test battery to enable complete and accurate assessment of auditory function. Since the introduction of the cross-check principle 35 years ago, the pediatric diagnostic test battery has expanded to include, in addition to behavioral audiometry, acoustic immittance measures, otoacoustic emissions, and multiple auditory evoked responses (auditory brainstem response, auditory steady state response, and electrocochleography). We offer a concise description of a modern evidence-based audiological test battery that permits early and accurate diagnosis of auditory dysfunction.

A preliminary study of the effects of aircraft noise on families who reside in close proximity to an airport

AbstractBackground: The use of air transportation has grown in the last century, escalating the noise exposure of families residing in close proximity to airports. The audiological effects need to be assessed to determine the impact of this increase on children and young adults living near to airports in South Africa.Method: Hearing patterns for these individuals were compared to those residing 30 km away from the airport. Sixty people, between the ages of 12–30 years, were assessed. Participants completed a questionnaire and were subjected to a diagnostic audiological test battery and tested using diagnostic distortion product otoacoustic emissions (DPOAEs).Results: Participants residing in close proximity to the airport presented with a notch configuration in the high frequencies, as opposed to those who lived further away. DPOAEs indicated a change in hearing in the high frequencies between the test populations. The positive relationship between the pure tone results and the DPOAEs strengthens the clai...

DFNB1-associated deafness in Portuguese cochlear implant users: Prevalence and impact on oral outcome

Objectives Hearing loss is a condition that interferes with the development of the child at a cognitive and language level. Therefore, early diagnosis of deafness is important for (re)habilitation, namely through the use of cochlear implant (CI). The present study aimed at screening CI Portuguese individuals for the presence of mutations in the genes GJB2 and GJB6 (DFNB1 locus), and searching a possible correlation between the genotype and the oral habilitation outcome following implantation. Methods Our sample included 117 CI individuals implanted longer than 5 years. Sequencing of GJB2 entire coding region was first performed. The presence of deletions del( GJB6-D13S1830) and del( GJB6-D13S1854) was subsequently tested by multiplex PCR. To assess the oral outcome of these individuals, a global score is calculated through a formula that integrates the results of a battery of speech and audiological tests routinely used in ORL services. This global oral performance score was used to test whether individuals with DFNB1-associated deafness perform significantly better than individuals without DFNB1-associated deafness. Results In 35% of the cases, deafness was clearly associated to DFNB1. The most common mutated allele was c.35delG (85%). Other variants have also been found, namely p.Gly130Ala, p.Asn206Ser, p.Val37Ile, p.Glu47X, p.Arg184Trp, p.Trp24X and the two common GJB6 deletions, del( GJB6-D13S1854) and del( GJB6-D13S1830), the last one identified for the first time in our population. Regarding the oral outcome, after testing the homogeneity of the two groups it could be observed that, in mean, the individuals with DFNB1-associated deafness perform significantly better ( p = 0.012) than the individuals without DFNB1-associated deafness. Discussion and conclusion This first screening of DFNB1 genes in the Portuguese CI population provides clear evidence of the high proportion of DFNB1-associated deafness amongst the Portuguese implanted individuals. DFNB1 status is significantly associated to higher oral performance scores, with DFNB1 individuals performing, on average, 6% better than the individuals without DFNB1-associated deafness.

Hearing organ disorders in patients with systemic sclerosis

In systemic sclerosis (SSc), there may develop hearing and balance disorders as a result of the immune-mediated vasculitis and fibrosis in the inner ear. The objective of the study was evaluation of the hearing organ function in patients with SSc with relationship to duration of the disease and Raynaud phenomenon and also to type and severity of the disease. Twenty unselected, consecutive patients with SSc diagnosed in compliance with the international diagnostic criteria of the American Rheumatism Association (1982), were enrolled into the study. The control group consisted of 26 otologically healthy persons matched to the SSc group for age and sex. Case history was recorded for all patients from questionnaire data. Otolaryngological examination and battery of audiological tests (pure tone audiometry, speech audiometry, impedance audiometry and auditory brainstem response-ABR) were performed. In the anamnesis 60% of patients reported vertigo, 55% headaches, 50% tinnitus, 40% hyperacusis, 40% hearing loss and 30% ear fullness. It was found that patients with SSc had significantly poorer mean hearing thresholds than the control group for 0.5, 1, 6 and 8 kHz. In ABR there were no differences between SSc and control groups although an increase of latency averages in the group of limited patients with SSc compared with the diffuse patients with SSc was observed. In eight patients (40%) sensorineural hearing loss, mostly bilateral and symmetrical was found. Furthermore, no relation was seen between hearing level and duration, type and severity of the disease. Ear involvement is frequent in systemic sclerosis and should be taken into consideration during diagnostic and therapeutic procedures.

Wideband Reflectance in Normal Caucasian and Chinese School-Aged Children and in Children with Otitis Media with Effusion

Wideband reflectance (WBR) is a middle ear analysis technique that quantifies frequency-specific sound conduction over a wide range of frequencies. One shortcoming of WBR is that there is limited normative data, particularly for pediatric populations and children with middle ear pathology. The goals of this study were to establish normative WBR data for early school-aged children; to determine whether WBR differs significantly between Caucasian and Chinese children, male and female children, and children and adults (experiment 1); and to compare the normative pediatric WBR data with the WBR data obtained from children with abnormal middle ear conditions (experiment 2). WBR was measured from 78 children with normal middle ear status with an average age of 6.15 yrs and 64 children with abnormal middle ear status with an average age of 6.34 yrs. Control group subjects and subjects without previously diagnosed middle ear pathology were recruited from eight elementary schools in the Greater Vancouver Area. Subjects with known middle ear pathology were recruited through the British Columbia Children's Hospital Otolaryngology department. Middle ear effusion (MEE) was identified in one of the two ways. In the British Columbia Children's Hospital group, MEE was diagnosed by a pediatric otolaryngologist (OTL) using pneumatic otoscopy and video otomicroscopy. These cases (21 ears) were classified as OTL confirmed. Subjects who were assessed through screenings at their elementary schools and suspected to have MEE based on audiological test battery results including elevated air conduction thresholds, flat low- and high-frequency tympanograms, and absent transient-evoked otoacoustic emissions were classified as not OTL confirmed (21 ears). Data were statistically analyzed for effects of gender, ethnicity (Caucasian versus Chinese), age (child versus adult), and middle ear condition. WBR equipment used for this study was from Mimosa Acoustics (RMS-system, version 4.03). Data were averaged in one-third octave bands collected from 248 frequencies ranging from 211 to 6000 Hz. Control group subject data (experiment 1) revealed no effects of gender or ear, and their interactions with frequency were not significant. There was a significant interaction between ethnicity (Caucasian versus Chinese) and frequency. Chinese children had lower energy reflectance (ER) values over the mid-frequency range. ER was significantly different between pediatric data and previously collected adult data. Diseased group ER was significantly different among all four middle ear conditions (normal, mild negative middle ear pressure, severe negative middle ear pressure, and MEE) (experiment 2). The overall test performance of ER was objectively evaluated using receiver operating characteristic (ROC) curve analyses; it was compared across frequencies averaged in one-third octave bands. Statistical comparison of the area under ROC (AUROC) plots revealed that ER above 800 Hz (except for ER at 6300 Hz) had better test performance in distinguishing normal middle ear status from MEE compared with ER at 630 and 800 Hz. Although not statistically different from other frequencies between 800 and 5000 Hz, ER at 1250 Hz had the largest AUROC curve (sensitivity of 96% and specificity of 95%) and was selected for further analysis. Comparison of AUROC curves between WBR at 1250 Hz and static admittance at 226-Hz probe tone frequency revealed significantly better test performance for WBR in distinguishing between healthy ears and MEE. A preliminary set of normative ER data have been generated for a pediatric population between the ages of 5 and 7 yrs, which were significantly different from previously gathered normative adult ER data. In this study, pediatric normative data were warranted for testing children, but ethnic-specific norms were not required to detect middle ear pathology and changes in middle ear status. WBR shows promise as a clinical diagnostic tool for measuring the mechanoacoustic properties of the middle ear and the changes that result in the presence of negative middle ear pressure or MEE.

Hearing and quality of life in a south European BAHA population

Conclusion: The overall results show a high ratio of satisfaction in the sample population, which is in accordance with a successful BAHA counselling and rehabilitation of their hearing impairment. Objectives: The acceptance of a bone anchored hearing aid (BAHA) device by a south European population, which could be expected to have some reticence for wearing this device, has been investigated. Methods: The outcome of BAHA implantation was assessed in 24 patients with bilateral and unilateral hearing loss by administration of several questionnaires, such as the Handicap Hearing Inventory (HHI), Client Oriented Scale of Improvement (COSI), Open and General Glasgow Benefit Inventory and Entific Medical System QoL, along with a complete audiological test battery. Results: Speech reception threshold (SRT) in bilateral cases improved both in quiet and in noise. In unilateral cases, word perception and accuracy of sound localization improved when sound was presented from the back. COSI scores, at both the intermediate and the final evaluations, showed a fair adaptation level of the patients and their satisfaction for prefixed targets.

Auditory testing profiles of Pelizaeus-Merzbacher disease.

To characterize the auditory manifestations of patients diagnosed with Pelizaeus-Merzbacher Disease (PMD), a rare X-linked disorder of myelin classically characterized by nystagmus, spastic quadriparesis, ataxia, and cognitive delay in early childhood or progressive disease in adulthood. A prospective case study of 5 pediatric and 3 adult patients diagnosed with PMD who demonstrate varying degrees of abnormal auditory function. These patients underwent comprehensive audiological evaluations (audiometry, tympanometry, otoacoustic emissions), auditory processing tests (Dichotic Listening, Frequency Pattern Test, Duration Pattern Test), and electrophysiological measures (Auditory Brainstem Response). Abnormal electrophysiological findings with normal cochlear function were found in all test subjects. Further testing completed on adult subjects revealed further central auditory dysfunction via auditory processing tests. All the adult test subjects had abnormal results on auditory processing tests including significant left ear deficits on dichotic digits and poor duration pattern test scores. Auditory processing test results indicated strong right ear advantages for all adult PMD test subjects in Dichotic Digit testing. The degree of audiological central dysfunction findings was more severe in subjects with greater symptoms of the disease. Our findings indicate the need for a full audiological test battery on all patients with Pelizaeus-Merzbacher disease and other severe neurological disorders.

Dynamics of Hearing Status in Closed Head Injury

Hearing impairment can be one of the more subtle deficits seen after closed head injury (CHI), and it may not be diagnosed until late in the recovery phase if at all. Most studies have assessed patients immediately after CHI. Repeated assessments at regular intervals were not performed in the majority of studies done to assess whether any initial hearing loss regressed or progressed. Follow-up at later stages will shed more light on the audiological consequences of CHI. The aim of this study was to analyze the long-term audiological consequences of CHI. A total of 290 subjects with CHI were chosen and followed-up at 3, 6, and 12 months. The audiological test battery comprised pure tone audiometry (PTA), speech audiometry, tympanometry, auditory brainstem response (ABR), and middle latency response (MLR), and was administered to all subjects. The data from 96 subjects who completed all three follow-ups were analyzed for tympanometry, ABR, and MLR. However, for PTA and speech audiometry, data from only 76 subjects were analyzed, as unconscious and disoriented subjects could not undergo these tests at initial testing. The results revealed that hearing status after CHI varies, and that at follow-up significant changes in hearing were seen. Hearing of low frequencies improved, due primarily to improvements in middle ear function. Significant changes in ABR latencies and MLR amplitudes were also observed. This reflects the unequal rates of recovery observed in the different parts of the central auditory nervous system.

Audiological Deficits After Closed Head Injury

Damage to the peripheral auditory structures has long been recognized as a common component of head injury. It is estimated that a majority of patients with skull trauma have resultant hearing impairment. Damage to the peripheral and/or central auditory pathways can occur as a primary or secondary injury. Considering the high incidence of hearing loss, it was considered worthwhile to conduct an in-depth investigation by administering a comprehensive audiological test battery on head-injured patients. The sample population consisted of 290 subjects with closed head injury (study group) and 50 subjects with otologically normal subjects (control group). The subjects in the study group were further divided into mild (n = 150), moderate (n = 100), and severe (n = 40) category on the basis of Glasgow Coma Scale score. The audiological assessment consisted of pure tone audiometry, speech audiometry, tympanometry, acoustic reflex testing, auditory brain stem response audiometry, and middle latency response audiometry. It is concluded that there is higher prevalence of hearing impairment in the study group compared with control group. Majority of the patients who incur hearing loss after closed head injury have mild degree of hearing impairment. A significant difference between the study and control group observed on majority of the auditory brain stem response and middle latency response parameters studied.

Sensorineural hearing loss in high school teenagers in Mexico City and its relationship with recreational noise

The aim of this study was to measure the frequency of hearing loss in a sample of typical public high-school students exposed to recreational noise, and determine associated risk factors. The sample was made up of 214 teenagers from a high-school in Mexico City; subjects were selected randomly per strata. We applied a questionnaire to identify risk factors for hearing loss and performed a battery of audiologic tests consisting of otoscopy, tympanometry, and pure-tone audiometry. The mean age of the sample was 16 +/- 1.07 years; 73% were male and 27%, female. Hearing loss was found in 21% of students. The main hearing loss-related risk factor was exposure to recreational noise: frequent attendance at discotheques and pop-music concerts; use of personal stereos; and noise exposure in school workshops. The high frequency of hearing loss in high school students from one Mexico City school (nearly one fifth of the sample) was found to be related to noise exposure mainly during recreational activities.

Peripheral and Central Auditory Dysfunction Induced by Occupational Exposure to Organic Solvents

To examine the effects of solvent exposure on hearing function, through an audiological test battery, in a population not occupationally exposed to high levels of noise. One hundred ten workers from a coating factory were studied. Jobs at the factory were divided into three different levels of solvent exposure. Hearing status was assessed with a test battery including pure-tone hearing thresholds (0.5-8 kHz), high-frequency hearing thresholds (12 and 16 kHz), and dichotic listening measured through dichotic digits test. Multiple linear regression models were created to explore possible association between solvent exposure and each of the hearing outcomes. Significant associations between solvent exposure and the three hearing outcomes were found. Covariates such as age, gender, race, and ethnicity were also significantly associated with the studied hearing outcomes. Occupational exposure to solvents may induce both peripheral and central auditory dysfunction. The dichotic digits test seems as a sensible tool to detect central auditory dysfunction associated with solvent exposure. Hearing loss prevention programs may use this tool to monitor hearing in solvent-exposed workers.

Analysis of auditory measures in normal hearing young male adult cigarette smokers using multiple variable selection methods with predictive validation assessments.

Studies have shown that cigarette smoking is a risk factor for hearing loss; however, no information is available on auditory preclinical indicators in young chronic cigarette smokers. Cigarette smoking involves exposure to many harmful chemicals including carbon monoxide (CO). In this study, the CO level in 16 young normal hearing male chronic smokers was measured with a CO monitor, and was used as the outcome measure. Subjects were administered a battery of audiological tests that included behavioral and electrophysiologic measures. The goal was to investigate which auditory test measures can be used as potential predictors of the outcome measure. Using ordinary least squares estimation procedures with best-subsets selection and bootstrapped stepwise variable selection procedures, an optimal predictive multiple linear regression model was selected. Results of this approach indicated that auditory brainstem response peak V amplitudes and distortion product otoacoustic emissions had the highest predictive value and accounted for most of the variability.

Auditory steady-state responses to bone conduction stimuli in children with hearing loss

The auditory steady-state response (ASSR) to air-conduction (AC) stimuli has been widely incorporated into audiological test-batteries for the pediatric population. The current understanding of ASSR to bone conduction (BC) stimuli, however, is more limited, especially in the case of infants and children. There are few reports on ASSR thresholds to BC stimuli in infants and young children, and none for infants or children with hearing loss. The objective of this study was to investigate BC ASSR thresholds in young children with normal hearing and various types and degrees of hearing loss. AC and BC ASSR thresholds are reported for 48 young children (mean age+/-SD=2.8+/-1.9 years; age range=0.25-11.5 years; 23 female). Hearing status was classified by assessing all children with a comprehensive test battery including tympanometry, diagnostic distortion-product otoacoustic emissions, click-evoked AC auditory brainstem response, AC and BC ASSR thresholds, and an otologic examination. The subjects were assigned to the categories normal hearing, conductive loss, and sensorineural loss (mild-to-moderate or severe-to-profound), for group analysis. AC and BC ASSR stimuli (carrier frequencies: 0.25-4 kHz; 67-95 Hz modulation rates; 100% amplitude and 10% frequency modulated) were presented using the GSI Audera system. Minimum levels at which spurious BC ASSR occur were established in the group of children with severe-to-profound sensorineural hearing loss (25, 40, 60, 60 and 60 dB for 0.25, 0.5, 1, 2, and 4 kHz, respectively). Children with normal hearing presented mean (1 SD) BC ASSR thresholds of 19 (9), 18 (7), 16 (11), 24 (7), and 26 (8) dB HL at 0.25, 0.5, 1, 2, and 4 kHz, respectively. Significantly lower thresholds (p<0.0001) were obtained for 0.25, 0.5 and 1 kHz than for 2 and 4 kHz. At 0.25 kHz, 39% of thresholds were at the minimum level of spurious response occurrence. More than half (54%) of the BC thresholds in the group with mild-to-moderate sensorineural hearing loss were recorded at or above the minimum levels at which spurious response occurred. In children with conductive hearing loss, the average BC ASSR thresholds corresponded closely to those in the normal hearing group except at 1 kHz and revealed an air-bone gap. Spurious bone conduction ASSR responses limit the intensity range for which the technique may be employed in infants and children, especially at lower frequencies. Consequently, the 0.25 kHz stimulus is not recommended for clinical use. In infants and young children, sensorineural hearing loss of a moderate or greater degree in the high frequencies (1-4 kHz), and of a mild or greater degree in the low frequencies (0.5 kHz), cannot be quantified using BC ASSR. This is due to the presence of the stimulus artifact. In cases of conductive hearing loss, BC ASSR can effectively quantify sensory hearing between 0.5 and 4 kHz, but interpretations must be made cautiously within the limitations of stimulus artifact occurrence across frequencies.

Charactering the individual ear by the "Auditory Profile"

This paper describes a new approach to auditory diagnostics, which is one of the central themes of the EU-project HEARCOM. For this purpose we defined a so-called Profile that can be assessed for each individual listener using a standardized battery of audiological tests that - in addition to the pure-tone audiogram - focus on loudness perception, frequency resolution, temporal acuity, speech perception, binaural functioning, listening effort, subjective hearing abilities, and cognition. For the sake of testing time only summary tests are included from each of these areas, but the broad approach of characterizing auditory communication problems by means of standardized test is expected to have an added value above traditional testing in understanding the reasons for poor speech reception. The Auditory profile may also be relevant in the field of auditory rehabilitation and for design of acoustical environments. The results of an international 5-center study (in 4 countries and in 4 languages) will be presented and the relevance of a broad but well-standardized approach will be discussed.

Noise induced hearing loss and other hearing complaints among musicians of symphony orchestras

An investigation of the hearing status of musicians of professional symphony orchestras. Main questions are: (1) Should musicians be treated as a special group with regard to hearing, noise, and noise related hearing problems (2) Do patterns of hearing damage differ for different instrument types (3) Do OAE have an added value in the diagnosis of noise induced hearing loss (NIHL) in musicians. 241 professional musicians, aged between 23-64 participated. A brief medical history and the subjective judgment of their hearing and hearing problems were assessed. Musicians were subjected to an extensive audiological test battery, which contained testing of audiometric thresholds, loudness perception, diplacusis, tinnitus, speech perception in noise, and otoacoustic emissions. Most musicians could be categorized as normal hearing, but their audiograms show notches at 6 kHz, a frequency that is associated with NIHL. Musicians often complained about tinnitus and hyperacusis, while diplacusis was generally not reported as a problem. Tinnitus was most often localized utmost left and this could not be related to the instrument. It was usually perceived in high frequency areas, associated with NIHL. In general, musicians scored very well on the speech-in-noise test. The results of the loudness perception test were within normal limits. Otoacoustic emissions were more intense with better pure-tone thresholds, but due to large individual differences it can still not be used as an objective test for early detection of NIHL. Musicians show more noise induced hearing loss than could be expected on the basis of age and gender. Other indicators, such as complaints and prevalence of tinnitus, complaints about hyperacusis and prevalence of diplacusis suggest that musicians' ears are at risk. Continuing education about the risks of intensive sound exposure to musicians, with the emphasis on the possible development of tinnitus and hyperacusis and the need for good hearing protection is warranted.

Audiological findings in individuals exposed to organic solvents: Case studies

Millions of people around the world are exposed to industrial organic solvents such as toluene and xylene in the manufacturing sectors. Solvents are neurotoxic substances that are detrimental to the functioning of the nervous system, including the central auditory nervous system (CANS). This study investigated hearing and auditory processing in seven individuals with a history of exposure to industrial solvents. A battery of audiological tests was administered to all subjects: pure tone, speech, and impedance audiometry, otoacoustic emissions tests, auditory brainstem responses, middle latency responses, as well as the SCAN-A and R-SPIN tests with low predictability sentence lists. All individuals in this study exhibited findings consistent with retrocochlear and/or central abnormality. Two of the seven subjects in this study had normal pure tone thresholds at all frequencies bilaterally, yet showed abnormal retrocochlear/central results on one or more tests. The auditory test battery approach used in this study appears to be valuable in evaluating the pathological conditions of the CANS in solvent-exposed individuals.

Electric acoustic stimulation of the auditory system: results of a multi-centre investigation

Conclusion. A high rate of hearing preservation during cochlear implantation for electric acoustic stimulation (EAS) is possible, even when surgery is conducted by a number of different surgeons. Objectives. This study aimed to determine the degree of hearing preservation using surgery for EAS in a European multi-centre clinical investigation. It also aimed to demonstrate the effect of EAS in individuals with residual low frequency hearing, both on speech perception and on subjective quality of life measures. Patients and methods. Eighteen patients with profound high frequency hearing loss were recruited in five participating European centres. Subjects were assessed based on an audiologic test battery, as well as on a subjective hearing aid benefit questionnaire. Each subject underwent attempted hearing preservation cochlear implantation using the MED-EL C40+ device with a Medium electrode. Residual ipsilateral hearing and speech discrimination abilities were assessed at defined intervals up to 12 months after the combined electric-acoustic mode was introduced. Results. Results showed that some degree of hearing preservation was possible in 15718 patients. All subjects showed statistically significant benefit on all three speech perception tests over time. These significant benefits were also reflected in the subjective benefit outcomes.

Etiology of vertigo in children

To detect the most common causes of vertigo in children. Fifty-four children (20 boys and 34 girls) aged 3-16 years, who presented with vertigo attacks during a 3-year period, were studied. A detailed medical history for vestibular symptoms and migraine was obtained from our patients or their parents. All patients underwent otolaryngologic, ophthalmologic and neurologic clinical evaluation. A detailed laboratory examination, including serologic tests for viral infections, was also obtained. Additionally, a complete audiological and neurotologic evaluation was performed. Computed tomography (CT) scans and magnetic resonance imaging (MRI) were obtained in selected cases. Viral infections, benign paroxysmal vertigo of childhood and migraine were the most common causes of vertigo accounting for approximately 65% of our patients. Otitis media, head trauma, benign paroxysmal positional vertigo, Meniere's disease and brain tumor were less common causes of vertigo. A peripheral type of vertigo was found in most cases. Diagnostic approach in vertigo in children should include a detailed history and clinical examination in conjunction with a test battery of audiological and neurotologic tests. When a central cause of vertigo is suspected an MRI or CT scan should be ordered.

The Status of Diagnostic Testing following Referral from Universal Newborn Hearing Screening

The Joint Committee on Infant Hearing 2000 position statement includes guidelines for the development of Early Hearing Detection and Intervention programs. These guidelines provide specific recommendations for the audiologic test battery for infants who fail a newborn infant hearing screening. The recommended test battery includes electrophysiologic measures such as the ABR, frequency specific electrophysiologic tests, bone-conducted ABR, OAEs, tympanometry using high frequency probe stimuli, and acoustic reflexes. In the Commonwealth of Kentucky, 42 centers are listed as providing follow-up diagnostic testing services for infants failing the newborn hearing screening. The purpose of this investigation was to determine how many of these centers were abiding by the Joint Committee guidelines. Results show that only three of 42 centers listed are providing services that meet the guidelines. Less than 50% of infants identified with hearing loss are referred for genetic evaluations by the audiologist. Only 19 of the 42 sites listed provide amplification services for infants identified with hearing loss.

Audiological findings in workers exposed to styrene alone or in concert with noise

Audiological testing, interviews and exposure measurements were used to collect data on the health effects of styrene exposures in 313 workers from fiberglass and metal-product manufacturing plants and a mail terminal. The audiological test battery included pure-tone audiometry, distortion product otoacoustic emissions (DPOAE), psychoacoustic modulation transfer function, interrupted speech, speech recognition in noise and cortical response audiometry (CRA). Workers exposed to noise and styrene had significantly poorer pure-tone thresholds in the high-frequency range (3 to 8 kHz) than the controls, noise-exposed workers and those listed in a Swedish age-specific database. Even though abnormalities were noted on DPOAE and CRA testing, the interrupted speech and speech recognition in noise tests were the more sensitive tests for styrene effects. Further research is needed on the underlying mechanisms to understand the effects of styrene and on audiological test batteries to detect changes in populations exposed to solvents.