Management of a sophisticated hearing conservation program.
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Ear Protective Devices↗
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Occupational hearing loss.
Hearing loss is a significant and unfortunately common occupational malady. Over the past several decades both the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) have initiated efforts to better understand and to limit the occurrence of occupational hearing loss, particularly as it relates to excessive noise exposure. This paper briefly addresses the pathophysiology of noise-induced hearing loss and then describes the occupational and non-occupational factors which influence a worker's risk of hearing loss. The primary foci of this discussion are the clinical evaluation, diagnosis, and management of occupational hearing loss. Issues of prevention, OSHA-mandated hearing conservation efforts and compensation are reviewed.
Ear Protective Devices↗
Comparison of NIOSH noise criteria and OSHA hearing conservation criteria.
BACKGROUND: This study was conducted to compare noise exposure measurements based on the recently revised noise exposure criteria recommended by the U.S. National Institute for Occupational Safety and Health (NIOSH) and the current U.S. Occupational Safety and Health Administration (OSHA) Hearing Conservation Amendment to the occupational noise standard. METHODS: Daily 8-hour time-weighted average (TWA) personal noise exposures were obtained for 61 workers using dosimeters set simultaneously to the NIOSH and OSHA Hearing Conservation Amendment (OSHA-HCA) criteria. A variety of work groups with the potential for noise exposure were evaluated as a part of this investigation. RESULTS: Noise dose based on the NIOSH criteria was higher than the corresponding OSHA-HCA noise dose with differences in noise exposures measured under the two criteria equal to 6.6 dBA. Should the new NIOSH recommendation on noise measurement be adopted as standard, the number of workers to be enrolled in a hearing loss prevention program was estimated to increase by 2. 7-fold from 23% to 75% of the study population. CONCLUSIONS: The results of this study indicate that if the NIOSH criteria are to be adopted as an OSHA standard, there is likely to be a substantial increase in the number of workers in hearing conservation programs.
Acoustics↗
Test of the health promotion model as a causal model of construction workers' use of hearing protection.
The health promotion model (HPM) was tested as a causal model of construction workers' use of hearing protection (N = 359). Theoretical and exploratory models fit well, with the theoretical model accounting for 36.3% of variance and the exploratory model accounting for 50.6% of variance in hearing protection use. Value of use (benefits of using hearing protection), barriers to use, and self-efficacy were significant predictors in both the theoretical and exploratory models, but perceived health status was a predictor only in the theoretical model. In the exploratory model, where modifying factors were allowed direct relationships with use of hearing protection, two modifying factors--noise exposure and interpersonal influences-modeling--were significant predictors. Results of this test of the HPM are consistent with the revised HPM (Pender, 1996). There were significant direct paths from modifying factors to behaviour. Use of hearing protection was best predicted by behavior-specific predictors, such as perceived barriers to use of hearing protection. Results support the use of the HPM to predict use of hearing protection.
Adult↗
Interventions to promote the wearing of hearing protection.
BACKGROUND: Noise induced hearing loss can only be prevented by eliminating or lowering noise exposure levels. Where the source of the noise can not be eliminated workers have to rely on hearing protective equipment. Several trials have been conducted to study the effectiveness of interventions to influence the wearing of hearing protection and to decrease noise exposure. We aimed to establish whether interventions to increase the wearing of hearing protection are effective. OBJECTIVES: To summarise the evidence for the effectiveness of interventions to enhance the wearing of hearing protection among workers exposed to noise in the workplace. SEARCH STRATEGY: We searched the Cochrane Ear, Nose and Throat Disorders Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2 2005), MEDLINE (1966 to June 2005), EMBASE (1980 to June 2005), NIOSHTIC, CISDOC, CINAHL, LILACS (1982 to June 2005) and Scientific Electronic Library Online. The date of the last search was June 2005. SELECTION CRITERIA: Studies were included if they had a randomised design, if they were among noise exposed (> 80 dB(A)) workers or pupils, if there was some kind of intervention to promote the wearing of hearing protection (compared to another intervention or no intervention), and if the outcome measured was the amount of use of hearing protection or a proxy measure thereof. DATA COLLECTION AND ANALYSIS: Two reviewers selected relevant trials, assessed methodological quality and extracted data. There were no cases where the pooling of data was appropriate. MAIN RESULTS: Two studies were found. One study was a two-phased randomised controlled trial. A computer-based intervention tailored to the risk of an individual worker lasting 30 minutes was not found to be more effective than a video providing general information among workers, around 80% of whom already used hearing protection. The second phase of the trial involved sending a reminder to the home address of participants at 30 days, 90 days or at both 30 and 90 days after the intervention, or no reminder. No significant differences in the mean use of hearing protection were found. A second randomised controlled trial evaluated the effect of a four year school based hearing loss prevention programme among pupils working at their parents farms (N=753) in a cluster randomised controlled trial. The intervention group was twice as likely to wear some kind of hearing protection as the control group that received only minimal intervention. All results are based on self reported use of hearing protection. AUTHORS' CONCLUSIONS: Limited evidence does not show whether tailored interventions are more or less effective than general interventions in workers, 80% of whom already use hearing protection. Long lasting school based interventions may increase the use of hearing protection substantially. These results are based on single studies only. Better interventions to enhance the use of hearing protection need to be developed and evaluated in order to increase the prevention of noise induced hearing loss among workers.
Ear Protective Devices↗
Sound-level measurements and calculations of safe noise dosage during EPI at 3 T.
This paper describes systematic methods for measuring and controlling sound levels within a magnetic resonance scanner. The methods are illustrated by application to the acoustic noise generated by a 3 T scanner during echoplanar imaging (EPI). Across five measurement sessions, sound pressure levels at the center of the head gradient coil ranged from 122 to 131 dB SPL [123 to 132 dB(A)]. For protection against damaging noise exposure, UK and US industrial guidelines stipulate that the maximum permitted daily noise dosage is equivalent to 90 dB(A) for 8 hours, where noise dosage is a function of the level of an acoustic signal and the length of exposure to it. Without hearing protection, this equivalent level would be exceeded by less than 5 seconds of exposure to the measured levels of scanner acoustic noise. These findings highlight the importance of noise reduction and hearing protection for those exposed to the acoustic noise generated during EPI.
Auditory Threshold↗
Auditory noise associated with MR procedures: a review.
This review article discusses the various types of acoustic noise produced during the operation of MR systems, describes the characteristics of the acoustic noise, and presents information regarding noise control techniques. In addition, the problems related to acoustic noise for patients and healthcare workers are discussed.
Auditory Threshold↗
Investigation of acoustic noise on 15 MRI scanners from 0.2 T to 3 T.
Acoustic noise levels for fast MRI pulse sequences were surveyed on 14 systems with field strengths ranging from 0.2 T to 3 T. A microphone insensitive to the magnetic environment was placed close to the magnet isocenter and connected via an extension cable to a sound level meter outside the scan room. Measured noise levels varied from 82.5 +/- 0.1 dB(A) for a 0.23 T system to 118.4 +/- 1.3 dB(A) for a 3 T system. Further measurements on four of the closed-bore systems surveyed showed that: 1) pulse sequence parameters (particularly FOV and TR) were more influential in determining noise level than field strength, 2) the noise level was found to vary along the z-direction with a maximum near the bore entrance, and 3) in one of two systems tested there was a significant increase in noise with a volunteer present instead of a test object. The results underline the importance of hearing protection for patients and for staff spending extended periods in the scan room.
Ear Protective Devices↗
An investigation of noise levels in Alberta sawmills.
BACKGROUND: Noise exposure in the sawmill industry is an area of concern. This study documents the level of noise exposure in nine sawmills in the province of Alberta, Canada. METHODS: Personal noise monitoring data were collected in nine Alberta sawmills, in winter and in summer (n = 213). Exposures were considered in light of an estimated "real world" noise reduction rating (NRR) calculation assuming use of conventional hearing protection. Limited comparisons were made with spot area monitoring data. RESULTS: Only 10% of the personal monitoring measurements were below the Alberta 8-hr exposure limit of 85 dBA. Twenty-seven percent of the personal monitoring measurements were 95 dBA or higher. Worker enclosures played a large role in reducing noise exposure. There were no significant differences between seasons in noise category distributions (P = 0.61). The planermen and planer infeed operators had the highest percentage of personal monitoring measurements 95 dBA or higher (62% and 82%, respectively). CONCLUSIONS: Based on a conservative formula, a risk of excess noise exposure could exist even when wearing required hearing protection due to very high noise levels found in planing operations in sawmills.
Alberta↗
Predictors of hearing loss in New York farmers.
BACKGROUND: Data from the telephone interview portion of the New York Farm Family Health and Hazard Surveillance were used to study self-reported hearing loss in New York farmers. METHODS: One thousand six hundred and twenty-two persons completed the hearing loss and noise exposure interview. Hearing loss was defined as at least some trouble hearing in one or both ears. Predictors of hearing loss were determined using logistic regression. RESULTS: Twenty-two percent of participants reported hearing loss. From the logistic regression, significant confounders are age (P = 0.0001), gender (P = 0.0001), being from a livestock farm (P = 0.012), and loss of consciousness due to head trauma (P = 0.04). Significant noise exposures are more hours of lifetime exposure to noisy farm equipment (P = 0.001) and having had a noisy non-farm job (with some hearing protection P = 0.002, without any hearing protection P = 0.0001). CONCLUSIONS: Farm noise exposure is a serious risk to the hearing of this population. Although use of hearing protection should be encouraged, replacing and modifying farm equipment to decrease noise at the source should be the first priority.
Adult↗
New growth of axons in the cochlear nucleus of adult chinchillas after acoustic trauma.
This study determined the effect of acoustic overstimulation of the adult cochlea on axons in the cochlear nucleus. Chinchillas were exposed to an octave-band noise centered at 4 kHz at 108 dB sound pressure level for 1.75 h. One chinchilla was never exposed to the noise, and several others had one ear protected by an ear plug or prior removal of the malleus and incus. Exposure of unprotected ears caused loss of inner and outer hair cells and myelinated nerve fibers, mostly in the basal half of the cochlea. Cochlear nerve fiber degeneration, ipsilateral to the exposed ears, was traced to regions of the cochlear nucleus representing the damaged parts of the cochlea. In silver impregnations of a deafferented zone in the posteroventral cochlear nucleus, the concentration of axons decreased by 43% after 1 month and by 54% after 2 months. However, by 8 months, the concentration of thinner axons, with diameters of less than 0.46 microm, increased by 46-90% over that at 2 months. The concentration of axons with larger diameters did not change. Between 2 and 8 months small axonal endings appeared next to neuronal cell bodies. This later increase of thinner axons and endings is consistent with a reactive growth of new axons of relatively small diameter. The emergence of small perisomatic boutons suggests that the new axons formed synaptic endings, which might contribute to an abnormal reorganization of the central auditory system and to the pathological changes that accompany acoustic overstimulation.
Animals↗
Noise in small industry.
Exposure to noise, the availability and the use of ear protectors, and the adequacy of the medical surveillance of noise-exposed workers were surveyed in the small industry of Finland in order to provide information for the development of occupational health care. One hundred workplaces were chosen by random sampling to represent the small industry (personnel 5-49) in the province of Uusimaa. About a third (32%) of the workers (n = 1181) were exposed to a noise level of at least 85 dB (leq) when at work. However, the prevalence of noise exposure varied greatly, from 3 to 82% according to the type of industry. One in five workers exposed to noise was under periodic medical surveillance (audiogram). Ear protectors were available to about a half of the workers. Fewer than half of the workers with ear protectors at their disposal actually used them. Preventive measures are discussed with respect to noise-induced hearing loss among the personnel working in small industry.
Ear Protective Devices↗
A tentative proposal for classification of audiograms in noise-induced deafness: relationship between audiogram and subjective complaints in noise-exposed workers.
Audiograms obtained from workers exposed to occupational noise were classified into six stages, namely, "normal" and stages I-V of noise-induced deafness, using the audiometric chart and the classification table designed by the authors. Close correlations were observed between the severity of the stage and the degree of hearing in daily life, which support our classification method. On the other hand, the prevalence rate of tinnitus also showed a linear increase in proportion to the severity of the stage, although the mechanism of tinnitus in noise-induced deafness has not yet been elucidated. From the viewpoint of protecting workers from hearing damage due to noise exposure, further investigation is required to make the best use of our classification method in noisy workplaces.
Audiometry↗
Efficiency of ear protectors in laboratory and real life tests.
The effectiveness of ten different ear-protectors (6 types of earmuffs and 4 types of earplugs) has been tested under laboratory conditions and in the real occupational environment. Three methods were used: (1) physical, utilizing a dummy head; (2) subjective, real-ear, executed on trained human subjects; (3) subjective, measuring TTS2 resulting from occupational, one-workday exposure. It could be shown that the ear protection efficiency ascertained on the basis of TTS2 measurements on workers exposed to noise in their occupational environment is, in nearly all cases, smaller than the efficiency expected, taking into account the sound damping of the same protectors, tested under laboratory conditions, using the physical or real-ear method. Measurements of TTS2 were found to give the best data needed to define the protectors' efficiency, since they include, simultaneously, the impact of various environmental factors, the subjective reactiveness, the nature of the professional task and the acoustical features of the protector used. Therefore this method enables the estimation of the real protection given to workers with a risk of noise-induced hearing loss.
Adult↗
Sleep disturbance due to transportation noise: ear plugs vs oral drugs.
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Adolescent↗
Industrial wideband noise reduction for hearing aids using a headset with adaptive-feedback active noise cancellation.
High-intensity noises are a health hazard for industrial workers, and hearing protection is necessary to prevent hearing loss. Passive methods, such as ear muffs, are ineffective against low-frequency noise. Moreover, many hearing-impaired workers must wear hearing aids to enable communication at their workplace, and such aids can amplify ambient noise. To overcome this problem, the present study developed a headset equipped with a digital signal processing system to implement adaptive-feedback active noise cancellation (AFANC) to reduce low-frequency noise. The proposed AFANC headset was effective against wideband industrial noise, with a maximum noise spectrum power reduction of 30 dB. Furthermore, when used with a hearing aid, it improved the speech signal-to-noise ratio by up to 14 dB. These results suggest that a headset with AFANC would be useful for hearing protection in workplaces with high levels of low-frequency industrial noise, especially for hearing-impaired workers.
Ear Protective Devices↗
[Effect of information about hearing damage caused by loud music. For adolescents the music in discoteques is too loud despite loudness limits].
BACKGROUND: Information campaigns are regarded useful to prevent adolescents from hearing-damage due to loud music. This study examined whether adolescents who are informed on the risk of a hearing-damage, exhibit preventive behavior when attending discotheques. METHOD: 253 pupils (age 14 to 19 years) were interviewed about their disco attending habits and about their information on the risk associated with listening to loud music. RESULTS: About 85% of the sample were informed about the risk. Informed and uninformed pupils did not significantly differ in the frequency of disco attendance nor in the frequency of using ear-plugs. However, significantly more informed pupils experienced disco music as too loud (p < 0.05). CONCLUSIONS: Information influences the subjective appraisal of loudness perception, but has little effect on preventive behavior. Instead, experimental forms of educational campaigns may be more effective. Additional provisions (lowering sound levels in discotheques) are necessary.
Adolescent↗
Occupational noise exposure and sensorineural hearing loss among workers of a steel rolling mill.
Hearing loss is one of the most common chronic health conditions and has important implications for the patient's quality of life. However, hearing loss is substantially underestimated and under treated. The purpose of this study was to determine the prevalence of sensorineural hearing loss among the workers in a steel rolling mill in Nigeria. Each of the 150 randomly selected subjects had a structured questionnaire administered to them, followed by a full otological examination. Of these, 116 had tympanometry and pure-tone audiometry. Also a noise mapping of their respective work units was done. The workers were exposed to noise levels varying from 49 to 93 dBA. About 28.2% of the 103 who had their audiogram analysed had mild to moderate sensorineural hearing loss in their better ear and 56.8% of them had mild to moderate sensorineural hearing loss in their worse ear. The pure-tone average and the average hearing thresholds at 4 kHz for the groups significantly increased with an increasing noise exposure level. The prevalence of sensorineural hearing loss among the study population is high; and noise exposure is at least contributory. Pre-employment and regular audiometry while on the job is highly recommended.
Adult↗