[Reply to the paper by D. Kirchhoff et al., "The Effect of Instructional Work on the Use of Individual Hearing Protective Devices by Noise-Exposed Workers"].
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The published literature describing three real-ear-attenuation-at-threshold (REAT), nine above-threshold, and four objective methods of measuring hearing protector attenuation is reviewed and analyzed with regard to the accuracy, practicality, and applicability of the various techniques. The analysis indicates that the REAT method is one of the most accurate available techniques since it assesses all of the sound paths to the occluded ear and, depending upon the experimenter's intention, can reflect actual in-use attenuation as well. An artifact in the REAT paradigm is that masking in the occluded ear due to physiological noise can spuriously increase low-frequency (less than or equal to 500 Hz) attenuation, although the error never exceeds approximately 5 dB, regardless of the device, except below 125 Hz. Since the preponderance of available data indicates that attenuation is independent of sound level for intentionally linear protectors, the use of above-threshold procedures to evaluate attenuation is not a necessity. An exception exists in the case of impulsive noises, for which the existing data are not unequivocal with regard to hearing protector response characteristics. Two of the objective methods (acoustical test fixture and microphone in real ear) are considerable time savers. All objective procedures are lacking in their ability to accurately determine the importance of the flanking bone-conduction paths, although some authors have incorporated this feature as a post-measurement correction. The microphone in real-ear approach is suggested to be one of the most promising for future standardization efforts and research purposes, and the acoustical test fixture technique is recommended (with certain reservations) for quality control and buyer acceptance testing.
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Patients, parents, and physicians are all concerned about the risks of swimming unprotected with middle ear ventilation tubes. The risks have not previously been carefully quantified or correlated with the degree of swimming activity. In this study, 53 children with tympanometrically proven patent long-shafted tubes were allowed to swim unprotected. They suffered six middle ear infections that were clearly caused by swimming. Five of these infections occurred in divers. The rate of infections for divers was approximately one per 100 days of swimming activity. The rate for non-divers was approximately one per 600 days. Unprotected swimming was well accepted by almost all parents and patients. The need for earplugs for all children who swim with long-shafted ventilation tubes is questioned.
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OBJECTIVES: This study tested the hypotheses that, in high noise levels [> or = 85 dB(A)], hearing protection devices are used largely by workers sensitive to noise, as reflected by reports of noise annoyance, and that the usage would reduce distress symptoms. METHODS: Data collected from 1587 healthy male blue-collar workers included noise exposure level, noise annoyance, use of hearing protection devices, distress symptoms (somatic complaints and poststress irritability), and possible confounding by age, education and ethnic origin. RESULTS: Multiple logistic regression results indicated that the use of hearing protection devices was related to noise exposure level [odds ratio (OR) 2.94, 95% confidence interval (95% CI) 2.58--3.30], but more so to high noise annoyance (OR 3.03, 95% CI 2.77--3.29), even after control for age, education, and ethnic origin. No interaction was found between noise level and noise annoyance. These findings highlight the contribution of noise annoyance to the use of hearing protection devices. Of the 42.6% of workers using hearing protection devices in the presence of high ambient noise, 60% were highly annoyed. Noise-annoyed workers also tended to wear hearing protection devices even in low noise levels. The use of hearing protection devices was associated with lower distress symptoms among the low and moderately annoyed workers, but among the highly annoyed workers the reverse was true. CONCLUSIONS: Thus, for the highly annoyed workers, the use of hearing protection devices was perhaps an additional source of stress. One immediate implication of this study is that future intervention procedures should focus on unannoyed workers who tend to use hearing protection devices less.
Surface swimming in fresh or ocean water is not contraindicated in children with otitis media or in children with tympanostomy tubes. Diving should be prohibited in children with acute or chronic otitis media or in children with tympanostomy tubes. Hot tub water, bath water, chlorinated water, or water from stagnant ponds may pose a risk for either otitis media or otitis externa.
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This paper investigates two main features of the human head which influence the measured attenuation of circumaural and intraaural hearing protection devices (HPDs): the external ear and the different pathways of bone conduction. A theoretical model for the external ear shows that its influence on the insertion loss of HPDs, on the sensitivity level of headphones or earphones, and on the insertion gain of hearing aids, all can be described by one equation. While it is not necessary to simulate the eardrum impedance in order to measure the insertion loss of earmuffs and the sensitivity level of headphones with acoustical test fixtures (ATFs), the required accuracy of an ear simulator is more stringent when the same measurements are performed on intraaural devices. For the evaluation of HPDs, bone conduction plays an important role. We have developed a model to estimate HPD-dependent bone conduction effects. The model includes two bone conduction sources: one in the external ear and one in the middle ear. The model explains, for example, the occlusion effect of HPDs and the masking error at low frequencies due to physiological noise that arises when real-ear attenuation at threshold (REAT) measurements are made. Consequently, objectively measured insertion loss can now be used to predict REAT with improved accuracy. ATF and REAT data are compared using nine earmuffs and nine earplugs. In the majority of cases, the two sets of data agree well. Discrepancies are discussed.
Based on the objective assessment of the threshold of the stirrup reflex, the author evaluated the inhibitory action of seven types of protective anti-noise devices. The results are summarized in a table.
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