Noise Hearing Research Articles

The Study on the Environmental Noise Exposure and Hearing Loss of Train Drivers in Taiwan

The Study on the Environmental Noise Exposure and Hearing Loss of Train Drivers in Taiwan

The Objective and Subjective Evaluation of Low-Frequency Expansion in Wide Dynamic Range Compression Hearing Instruments

The effects of low-frequency expansion on the objective and subjective evaluation of four channel in-the-ear hearing instruments was investigated. Three expansion settings were programmed in each device: expansion off, expansion restricted to channel one, and expansion restricted to channels one and two. Objective evaluations were conducted in quiet (Connected Speech Test) and in noise (Hearing in Noise Test) with speech levels fixed at 40 dB SPL. Subjectively, each participant rated expansion satisfaction in quiet and listening to low-level speech in a sound-treated room then indicated the expansion condition preferred overall. Listeners performed significantly better in quiet and in noise for the Off and Channel 1 conditions than the Channels 1 and 2 condition; however, performance was similar between the Off and Channel 1 conditions. Expansion effects on listener satisfaction ratings depended on the listening environment. Overall, listeners preferred expansion in Channel 1 to expansion in Channels 1 and 2; however, preference was not significantly different between the Channel 1 and Off conditions. Results indicate restricting expansion to 1000 Hz overcomes speech-recognition deficits observed with expansion active across a broader spectrum without significantly reducing subjective benefit or preference.

No evidence for enhanced noise induced hearing loss after prenatal stress or dexamethasone

It was recently implied that prenatal stress and fetal exposure to glucocorticoids may interfere with hearing ability and noise induced hearing loss in adulthood. In the present study pregnant Wistar rats were stressed during gestation by Chronic Mild Stress (CMS, a variable schedule of different stressors) or by dexamethasone (a synthetic glucocorticoid, i.e. a pharmacological stressor). At birth, but not at weaning, the dexamethasone offspring exhibited significantly decreased body weight compared to both control offspring and progeny from dams exposed to CMS during pregnancy. As adults, male offspring were exposed to 105 dB sound pressure level (SPL) wide band noise either continuously for eight hours or for two hours per day on three consecutive days. Oto-acoustic emissions and auditory brainstem responses were recorded before and after exposure to noise. Neither prenatal chronic stress nor prenatal dexamethasone exposure was associated with significantly enhanced noise induced hearing loss compared to controls, and these results were consistent in both subsets of animals. Our data do not support previous reports that prenatal exposure to mild stress nor to dexamethasone is detrimental to the hearing organ per se. However, hearing may be modulated by prenatal stressors under certain circumstances, of which the timing and degree are probably the most important.

Hidden Markov Models and Multiple Transfer Functions for Voice Subtraction in an Acoustic Dosimeter

The exposure of an individual to noise is a critical topic in relation to noise-induced hearing loss and noise annoyance. Unfortunately, this exposure is difficult to quantify, because the individual's voice affects the noise itself. A new dosimeter is presented, relying on an accelerometer and a microphone system. The accelerometer (placed behind the user's ear, in close contact with the skull) is moderately sensitive to environmental noise. It can be used as an estimate of the clean voice, which can then be removed from the overall acoustic signal. Eventually, the voice-free signal can be processed to measure the noise exposure in a straightforward manner. In order to obtain an estimate of the clean voice, the accelerometric signal may be mapped to a virtual microphone signal. We apply autoregressive exogenous (ARX) models to realize such a mapping. As the ARX is a time-invariant model, we use hidden Markov models to split the input sequence into segments on a phonetic-class basis. Specialized ARX models are then estimated for each one of the classes. Simulation results and a real-world binaural digital signal processing (DSP) implementation of the system validate the approach to a significant extent.

Prevalence of Dead Regions in Subjects with Sensorineural Hearing Loss

To estimate the prevalence of dead regions in adult subjects with sensorineural hearing impairment as a function of audiometric threshold and frequency and to assess the extent to which the presence/absence of a dead region can be predicted from the audiogram, gender, or age. Data were obtained from a random sample of adults attending an audiology clinic in Mysore, India. Audiometric air and bone conduction thresholds and tympanometry were used to identify 317 subjects (592 ears) with sensorineural hearing loss. Their ages ranged from 17 to 95 yr (mean = 57 yr). The threshold-equalizing noise hearing level (TEN (HL)) test, administered using the TEN(HL)-test CD and an audiometer, was used to determine the presence or absence of dead regions in these subjects for test frequencies ranging from 0.5 to 4 kHz. Nine subjects had to be excluded as the absolute thresholds were too high for the TEN(HL) test to be administered. Of the remaining 308 subjects (556 ears), 209 (68%) were male and 99 (32%) were female. The hearing losses ranged from mild to severe. Results are presented only for frequencies and ears for which the TEN level could be made high enough to produce at least 10 dB of masking. Classifying by subject, 177 (57.4%) were found to have a dead region in one or both ears for at least one frequency. Fifty-four women (54.5%) and 123 men (58.8%) had dead regions in one or both ears. Classifying by ear, 256 (46%) were diagnosed as having a dead region at one frequency or more: 233 ears (41.9%) had only a high-frequency dead region, 13 ears (2.3%) had only a low-frequency dead region, and 10 ears (1.8%) had a dead region at both low and high frequencies, with a surviving middle-frequency region. It was not possible to achieve both high sensitivity and high specificity when attempting to predict the presence/absence of a dead region from the audiogram. However, for each test frequency, 59% or more of ears had a dead region when the absolute threshold was above 70 dB HL. A very steep slope of the audiogram is suggestive of a high-frequency dead region but does not provide a reliable diagnostic method. Chi-square tests indicated that the prevalence of dead regions did not vary significantly with age or gender. The results indicate a relatively high prevalence of dead regions in adults with sensorineural hearing impairment, especially for frequencies at which the hearing loss exceeds 70 dB HL.

A Psychoacoustical Model for Specifying the Level and Spectrum of Acoustic Warning Signals in the Workplace

A psychoacoustic model is presented to facilitate the installation of acoustic warning devices in noisy settings, reflecting a major upgrade of a former tool, Detectsound. The model can be used to estimate the optimal level and spectrum of acoustic warning signals based on the noise field in the workplace, the hearing status of workers, and the attenuation provided by hearing protectors. The new version can be applied to a wider range of situations. Analyses can now be conducted to meet the functional requirements for a specific worker or to suit the needs for a group of co-workers sharing a work area. Computation of optimal warning signals can also be made from estimated hearing parameters based on the worker age, gender, and level and duration of noise exposure. The results of a laboratory validation study showed that the mean error in estimating detection thresholds for normal hearing individuals is typically within ±1 dB with a standard deviation of less than 2.5 dB in white noise or continuous noise fields. The model tends to yield slightly overestimated warning signal detection thresholds in fluctuating noises. Proper application of the tool also requires consideration of the variability in estimating noise levels, hearing status, and hearing protector attenuation under field conditions to ensure that acoustic warning signals are sufficiently loud and well adjusted in practice.

Hearing impairment among mill workers in small scale enterprises in southwest Nigeria

This cross-sectional study was conducted among mill workers in a large market in Ibadan, southwest Nigeria. These workers are engaged in small scale businesses with little or no regulation of work exposures. Questionnaires administered to mill workers sought information on personal characteristics, length of time engaged in the job, type of milling done and symptoms of hearing impairment. Noise exposure and hearing impairment were assessed among 85 mill workers. Audiometry was done on mill workers and 45 controls with no known exposure to noise and no history of aural disease. Noise levels at work stations ranged from 88-90dB for small mills and 101-105 for larger mills. None of the workers used hearing protection. Analysis based on total number of ears showed that 56% of the workers had hearing impairment ranging from mild (49%) moderate (6.4%) to severe (0.6%) whilst 33% of the controls had hearing impairment which was mild (26%), moderate (7%) and no severe losses, P = 0.001. There was no association between age and hearing impairment but prevalence of hearing impairment was highest among those who had been engaged in the trade for more than 20 years. There is a need for regulation of small scale enterprises to protect the health of workers. Health education and provision of low cost ear plugs will reduce the occurrence and severity of hearing impairment among these low income workers.

Amplification in the Rehabilitation of Unilateral Deafness: Speech in Noise and Directional Hearing Effects with Bone-Anchored Hearing and Contralateral Routing of Signal Amplification

Amplification in the Rehabilitation of Unilateral Deafness: Speech in Noise and Directional Hearing Effects with Bone-Anchored Hearing and Contralateral Routing of Signal Amplification

Recent advances in hearing and sound communication by fishes

Acoustic displays have been observed in representatives of 30 or more families of bony fishes. Thanks to Art Myrberg’s groundbreaking work, we have insights into the multitude of functions of acoustic signalling in fishes including mate choice, individual and species recognition, reduction of territory intrusions, and interception. Recent studies, many of which have arisen from Art’s work, focus on ontogenetic and seasonal changes, female vocalizations, and effects of ambient and anthropogenic noise in hearing and sound communication. In croaking gouramis (labyrinth fishes), for example, ontogenetic development of acoustic communication depends on changes in sound parameters, increases in sound levels, and auditory sensitivities. The importance of seasonal changes in hearing was recently uncovered in toadfish and cyprinids. Generally male fish display acoustically to attract females, but the opposite may occur. Only female croaking gouramis vocalize during mating. Ecoacoustical investigations reveal that hearing specialists (cyprinids) are well adapted to the low ambient noise levels of standing freshwaters. They are heavily masked in flowing waters, unlike generalists, which are merely affected by ambient noise. Gaussian and ship noise diminishes a fish’s ability to detect sounds and resolve temporal patterns, indicating that human‐made noise affects acoustic orientation and communication in fishes. [Work supported by FWF.]

Applicability of impulse noise hearing damage risk criteria (DRCs) to hearing protectors

Hearing damage risk criteria, DRC, concerning exposure to impulse noise, developed by CHABA [Ward CHABA Report (1968)], Pfander [J. Acoust. Soc. Am. 67, 628–633 (1980)], Smoorenburg [New Perspectives on Noise] (Raven, New York, 1982), pp. 471–490], and Dancer [Acust. Acta Acust. 3, 539–547 (1995)], have been destined for impulses encountered in open space, in free-field conditions. To adapt these criteria for conditions in which hearing protective devices (HPDs) are used, a standard procedure was proposed in the literature (e.g., by Pfander) that consists in subtracting the attenuation of the HPD, typically 25 dB, from the impulse’s peak SPL. Such a simple method does not take into account the change of the signal waveform under the HPD, usually resulting in increased A, C, or D duration. In this study, the subtraction method was verified by a comparison of impulse noise DRC with the parameters of acoustic impulses measured under the earmuff: peak SPL, rise time, and A, C, and D duration. Results show that the subtraction method underestimates the possible hearing damage risk posed by exposure to impulse noise when a hearing protector is used. [Work supported by the Polish Ministry of Science and Education, Grants T07B00428 and SP03.1].

Terapia de reentrenamiento (TRT) en el acúfeno de la enfermedad de Ménière

To evaluate the response of tinnitus in Meniere's disease patients (MD) using the Tinnitus Retraining Therapy (TRT). This management includes a wide cognitive medical counselling and natural or prosthetic sound therapies (hearing aid or noise generator). Descriptive prospective study (EBM level 3). Twenty-five patients diagnosed as definitive MD (AAO-HNS 95 criteria) were enrolled in our tinnitus protocol. Tinnitus changes were reported according to patient's self-evaluation, a visual analogue scale on tinnitus intensity (EVA) and the Tinnitus Handicap Inventory (THI). Seventy-three percent of the patients improved their tinnitus after 6 months of treatment (p < 0.05). THI scores were reduced from the initial 47% to 24% (p < 0.05) and EVA from 6.6 to 5.2 (p < 0.05). After 12 months, the response was slightly worse: 68% improved according to their self-evaluation (p < 0.05), THI score reached 20% (p < 0.05) but EVA did not improve significantly (6.4). Patients that refused prosthesis adaptation (hearing aid or noise generator) did not improved and the THI score (48%) and EVA score (6.6) did not change. TRT has proved to be an effective method for tinnitus treatment in MD that improves patient's self-evaluation, tinnitus loudness and handicap scores. Individualized medical counselling and an exhaustive prosthesis adaptation are crucial to guarantee satisfactory results.

Noise and Chemical Induced Hearing Loss

Farm youth face multiple risks for injury and illness in agriculture. Reviewed here is evidence from current literature illustrating the noise and chemical exposure hearing risks that farm youth potentially face. Sources of noise (e.g., machinery) and potentially toxic chemical exposures (e.g., solvents and pesticides) common in the farm environment are reviewed, illustrating the need for heightened research attention to a problem that may affect up to 2 million children in the United States alone and that requires both public and occupational health solutions. As existing studies have not sufficiently explored potential ototoxic effects of these exposures on children and adolescents, recommendations are outlined for research characterizing both chemical and noise exposures to farm youth and their combined effects on hearing.

William W. Lang’s contributions to the development of the International Institute of Noise Control Engineering

Bill Lang has been a member of the Board of I‐INCE since its first meeting in 1975 in Sendai, Japan. From 1988 to 1999 he served as the President, and to this day remains a very active member of the Board. The INTER‐NOISE congress series has been the core activity of I‐INCE, and in every case Bill has contributed very actively to secure an excellent congress. He has also taken a number of initiatives both to improve the organization itself and to develop new activities, especially the Technical Study Groups that have prepared consensus reports on important issues such as noise barrier effectiveness and industrial noise hearing conservation policy. At present, he is very active in attempting to develop a global noise control policy.

Limit cycles, noise, and chaos in hearing.

Based on insight obtained from a newly developed cochlea model, we argue that noise-driven limit cycles are the basic ingredient in the mammalian cochlea hearing process. For insect audition, we provide evidence in favor of the persistence of this principle. We emphasize the role of bifurcations for the emergence of broad-range sound perception, both in the frequency and amplitude domain, and indicate that this crucially depends on the correct coupling between limit cycles. We review the limit-cycle coupling universality, and outline how it can be used to encode information. Cortical noise is the microscopic basis for this encoding, whereas chaos emerges as the macroscopic expression of computation being done in the network. Large neuron firing variability is one possible consequence of the proposed mechanism that may apply to both vertebrate and insect hearing.

The effect of middle ear stiffness changes on noise hearing thresholds in presence of a high level background pure tone

In this study the interaction of two different sounds, loud low frequency pure tone and noise in threshold level was evaluated during air pressure changes in order to determine the effects of middle ear stiffness changes on noise threshold, with presence of a high level background pure tone. Forty-two normal hearing subjects after otoscopy, audiometry, and tympanometry participated in this experiment. During the presence of a background pure tone (220 Hz, 90 dB), the thresholds of wide band, low pass filtered, and high pass filtered noises were measured (in dB SPL) in three ear canal air pressure conditions (0, +300, −300 dapa) through a probe set. The pump manometer system of an AZ7 impedance audiometer was used to change the air pressure in an external auditory canal. The means of noise thresholds were significantly greater in 0 dapa than +300 and −300 dapa. But there was no significant difference between noise thresholds in +300 and −300 dapa. By increasing the middle ear stiffness, the transmission of background loud tone will decrease and ear overload is omitted, then the noise hearing thresholds will be better.

Examination of the validity of auditory traits and tests.

In an unaided context, and in spite of obvious conceptual differences, direction and distance hearing, soft sounds hearing, and speech understanding in noise hearing are so strongly interrelated that accurate measures of a listener's particular abilities on one of these traits would be difficult to obtain, given prior knowledge of performance on at least one of the others. The tests that are commonly used to estimate a listener's hearing performance do not provide sufficiently accurate and unbiased information. Most auditory tests are heavily influenced by method-related factors that are not impacted by the trait expected to be measured by the test. Method-related variance in test scores is not related to the trait of interest, but might still provide useful information about the person being tested. If a tester must use a set of tests with small amounts of trait variance, he/she can obtain better estimates of a person's performance on the trait by: including tests that use very different measurement methods (e.g., psychophysical, self-report, and significant-other report) converting the scores from these tests into the same metric (e.g., standardized scores) and combining the scores into an overall score. Although this is informally done in most clinical situations, formal procedures and norms should be developed. In clinical trials, outcome measures with large amounts of method variance are less likely to identify treatment options that are indeed beneficial. Method variance is systematic (i.e., an individual's bias associated with a measurement method can be expected to be stable over time and consistently different from people with other method biases. Because of this, the method variance component of a person's test score cannot be expected to average out over repeated samples, nor can it be expected to be changed by a treatment designed to change performance on a trait. Observable differences between treatments are reduced by method variance in outcome measures. Acknowledgments The author thanks Robyn Cox and Will Shadish for their consultation and assistance with this project, and Ruth Bentler, Martyn Hyde, and an anonymous reviewer for their helpful comments on an earlier version of this manuscript. Chris Bentler and Jason Ruyle also deserve recognition for their help entering the simulation study data.

Call for help.

Call for help.

An assessment of tinnitus retraining therapy

Based on the neurophysiological model of tinnitus developed by Jastreboff and Hazell [39] there have been some important developments in understanding and therapy of tinnitus over the last decade. The clinical applications of this model are known as "tinnitus retraining therapy", which has the objective of reducing both the distress associated with tinnitus and the tinnitus perception itself. As a form of systematic, repeated and skilled counselling over a long period of up to 2 years supported by sound therapy (hearing aid or noise generator) the evidence for their high degree of effectiveness is overwhelming. On the basis of a "German concept" of tinnitus retraining therapy developed and proposed by the ADANO (Arbeitsgemeinschaft deutschsprachiger Audiologen und Neurootologen) the current status of this treatment will be briefly reviewed including some actual studies of Goebel et al. [14] that confirm the world wide critical comments on the recent developments in the management of tinnitus especially with regard to tinnitus retraining therapy [79].

Use of Hearing Protection and Perceptions of Noise Exposure and Hearing Loss Among Construction Workers

Use of Hearing Protection and Perceptions of Noise Exposure and Hearing Loss Among Construction Workers

Listening to Prozac and hearing noise: Commentary on Kirsch and Sapirstein's "Listening to Prozac but hearing placebo".

Listening to Prozac and hearing noise: Commentary on Kirsch and Sapirstein's "Listening to Prozac but hearing placebo".