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Results for “Ear Protective Devices”

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At least 343 records · Page 19Linked to original sources
PubMed1992

Hearing protection against high-level shooting impulses in relation to hearing damage risk criteria.

The earmuff attenuation of acoustic impulses produced by large-caliber weapons was measured with a high-speed microcomputer controlled unit. The estimated accuracy was +/- 1 dB in peak sound-pressure level measurements. The peak levels outside earmuffs were 184 dB for the heavy bazooka and 172 dB for the hand-held bazooka (re: 20 microPa). Heavy bazooka impulse peak levels were attenuated from 7 to 19 dB by the earmuffs depending on the mass and volume of the measured three types of earmuffs. Hand-held bazooka impulse peak levels were attenuated by the earmuffs from 9 to 15 dB. The risk limits for hearing loss from a single impulse were exceeded in spite of the use of earmuffs when the criteria of CHABA (USA) or Pfander (Germany) were applied. The unexpectedly low attenuation was due to the low-frequency waveform of the high-level impulses. The earmuffs were found to prolong the impulse duration, which may reduce the benefit otherwise achieved by attenuation of the peak levels.

Acoustics↗
PubMed1998

A theoretical formulation of active control eardefenders.

This paper is concerned with the analysis and design of a feedback control active eardefender. By using classical control theory, the authors investigated the system stability and robustness of stability, the noise reduction level and its parameter sensitivity, and the working frequency range of the active eardefender. A general method for designing a stable feedback control eardefender is developed. In this theory, a special type of second-order compensator is used to improve the robustness of stability, the noise reduction level and its robustness, and the working area of the active eardefender, particularly at the low-frequency range of interest.

Ear Protective Devices↗
PubMed1994

Hearing loss in Grand Prix motorcyclists: occupational hazard or sports injury?

The prevalence of noise-induced hearing loss (NIHL) in current motorcycle grand prix racers was investigated. A total of 44 riders was randomly recruited and underwent interview, otological examination and pure tone audiometry. The median age was 28 (range 18-37) years and median racing experience was 10 (range 2-21) years. Twenty riders (45%) had hearing losses greater than expected for age matched controls. Not surprisingly this hearing deficit tended to increase with racing experience (r = 0.5, t = 2.51, 19 d.f., P < 0.05). Only 17 riders (39%) were regular users of earplugs and only nine had used them for most of their racing careers. There is a need to raise awareness to this problem and increase the use of earplugs to avoid NIHL in grand prix motorcyclists.

Acoustic Impedance Tests↗
PubMed1995

Noise induced hearing loss in military helicopter aircrew--a review of the evidence.

Noise Induced Hearing Loss (NIHL) has been recognised for some time. In the military environment one group of personnel at risk are Army helicopter aircrew who are exposed to continuous noise levels of up to 100 dB(A) in flight. The evidence for the damaging effect of this occupational noise is reviewed and some of the difficulties in drawing conclusions are highlighted. The current protection offered for the Mk 4 helmet is discussed and the incorporation of Active Noise Reduction (ANR) is suggested as a likely way of ensuring that the in-flight noise exposure in Army aircrew is kept as low as possible.

Adult↗
PubMed2006

Noise exposure and hearing loss prevention programmes after 20 years of regulations in the United States.

OBJECTIVES: To evaluate noise exposures and hearing loss prevention efforts in industries with relatively high rates of workers' compensation claims for hearing loss. METHODS: Washington State workers' compensation records were used to identify up to 10 companies in each of eight industries. Each company (n = 76) was evaluated by a management interview, employee personal noise dosimetry (n = 983), and employee interviews (n = 1557). RESULTS: Full-shift average exposures were > or =85 dBA for 50% of monitored employees, using Occupational Safety and Health Administration (OSHA) parameters with a 5 dB exchange rate (L(ave)), but 74% were > or =85 dBA using a 3 dB exchange rate (L(eq)). Only 14% had L(ave) > or =90 dBA, but 42% had L(eq) > or =90 dBA. Most companies conducted noise measurements, but most kept no records, and consideration of noise controls was low in all industries. Hearing loss prevention programmes were commonly incomplete. Management interview scores (higher score = more complete programme) showed significant associations with percentage of employees having L(ave) > or =85 dBA and presence of a union (multiple linear regression; R2 = 0.24). Overall, 62% of interviewed employees reported always using hearing protection when exposed. Protector use showed significant associations with percentage of employees specifically required to use protection, management score, and average employee time spent > or =95 dBA (R2 = 0.65). CONCLUSIONS: The findings raise serious concerns about the adequacy of prevention, regulation, and enforcement strategies in the United States. The percentage of workers with excessive exposure was 1.5-3 times higher using a 3 dB exchange rate instead of the OSHA specified 5 dB exchange rate. Most companies gave limited or no attention to noise controls and relied primarily on hearing protection to prevent hearing loss; yet 38% of employees did not use protectors routinely. Protector use was highest when hearing loss prevention programmes were most complete, indicating that under-use of protection was, in some substantial part, attributable to incomplete or inadequate company efforts.

Adult↗
PubMed1979

Dependence of acoustic attenuation of hearing protectors on incident sound level.

The relationship between incident sound level and acoustic attenuation for four types of earplug and four types of earmuff have been investigated using freshly prepared and instrumented cadaver ears. Pure tones and 1/3-octave bands of random noise in the frequency range 125-8000 Hz were employed as steady-state stimuli with sound pressure levels between 75 and 125 dB. Impulses with peak sound levels in the range 135-175 dB(P) were also presented. For the steady-state signals employed, the eight hearing protectors have been shown to have constant attenuation characteristics over the range of incident sound levels investigated. This was also the case for the six conventional protectors (with intentionally linear characteristics) for the impulse stimuli. The two intentionally amplitude-sensitive protectors provided attenuation which increased with incident sound level for impulse noises. Comparison of the protector attenuation-frequency characteristics determined for steady-state sounds shows good agreement with those obtained from subjective (threshold shift) national standard measurement procedures. It may be concluded, therefore, that the six conventional hearing protectors studied here have attenuation characteristics that are equal for incident sound levels at about 40 and 75 dB, and that they are constant for levels between 75 and 175 dB. Consequently, the results of national standard threshold-shift procedures, although measured at low sound levels, may be applied with confidence to occupations where hazardous high-level noises are present.

Acoustic Stimulation↗
PubMed2002

Interventional MR imaging at 1.5 T: quantification of sound exposure.

Sound pressure levels (SPLs) during interventional magnetic resonance (MR) imaging may create an occupational hazard for the interventional radiologist (ie, the potential risk of hearing impairment). Therefore, A-weighted and linear continuous-equivalent SPLs were measured at the entrance of a 1.5-T MR imager during cardiovascular and real-time pulse sequences. The SPLs ranged from 81.5 to 99.3 dB (A-weighted scale), and frequencies were from 1 to 3 kHz. SPLs for the interventional radiologist exceeded a safe SPL of 80 dB (A-weighted scale) for all sequences; therefore, hearing protection is recommended.

Ear Protective Devices↗
PubMed2004

Verbal communication in MR environments: effect of MR system acoustic noise on speech understanding.

PURPOSE: To assess the masking effect of magnetic resonance (MR)-related acoustic noise and the effect of passive hearing protection on speech understanding. MATERIALS AND METHODS: Acoustic recordings were made at 1.5 T at patient and operator (interventionalist in the MR suite) locations for relevant pulse sequences. In an audiologic laboratory, speech-to-noise ratios (STNRs) were determined, defined as the difference between the absolute sound pressure levels of MR noise and speech. The recorded noise of the MR sequences was played simultaneously with the recorded sentences at various intensities, and 15 healthy volunteers (seven women, eight men; median age, 27 years) repeated these sentences as accurately as possible. The STNR that corresponded with a 50% correct repetition was used as the measure for speech intelligibility. In addition, the effect of passive hearing protection on speech intelligibility was tested by using an earplug model. RESULTS: Overall, speech understanding was reduced more at operator than at patient location. Most problematic were fast gradient-recalled-echo train and spiral k-space sequences. As the absolute sound pressure level of these sequences was approximately 100 dB at patient location, the vocal effort needed to attain 50% intelligibility was shouting (>77 dB). At operator location, less effort was required because of the lower sound pressure levels of the MR noise. Fast spoiled gradient-recalled-echo and echo-planar imaging sequences showed relatively favorable results with raised voice at operator location and loud speaking at patient location. The use of hearing protection slightly improved STNR. CONCLUSION: At 1.5 T, the level of MR noise requires that large vocal effort is used, at the operator and especially at the patient location. Depending on the specific MR sequence used, loud speaking or shouting is needed to achieve adequate bidirectional communication with the patient. The wearing of earplugs improves speech intelligibility.

Acoustics↗
PubMed1988

Potential hearing loss resulting from MR imaging.

To determine if the loud noise generated by magnetic resonance (MR) imaging equipment is capable of inducing hearing loss, the hearing of 24 patients was tested before and after MR imaging. Fourteen patients were imaged without ear protection, and six (43%) suffered a temporary, mild loss of hearing (less than or equal to 15 dB at at least one frequency). Ten patients were imaged with ear protection, and only one experienced any hearing loss. Therefore, the noise generated by MR imagers may cause temporary hearing loss, and earplugs can prevent this loss. All threshold changes had returned to within 10 dB of baseline by 15 minutes after completion of the second audiometric test.

Adult↗
PubMed1996

Contact dermatitis of the ear due to a rubber earplug.

We report a case of contact dermatitis of the ear canal due to rubber earplugs. A 31-year-old Japanese woman had a 2-year history of eczema confined to her ears. Applications of various topical steroids had shown no beneficial effect upon her lesions. Considering contact dermatitis as a possible diagnosis we performed patch tests. Positive eczematous patch test results were obtained with mercaptobenzothiazole, tetramethylthiuram disulfide and her rubber earplugs, which she had used whenever she took a bath. The eruption cleared after the patient stopped using the rubber earplugs.

Adult↗
PubMedDate not supplied

Objective evaluation of earplugs for the control of water-borne infection.

Eighty-two cotton, foam, and solid core stock and custom earplug were evaluated objectively for water absorption and water penetration characteristics in order to determine their efficacy for control of water-borne infection in ears having open middle ear cavities. Cotton plugs, even when saturated with petroleum jelly, had poor consistency in resisting even minimal water pressure. Polymeric foam plugs, especially when saturated with petroleum jelly, appeared to inhibit water flow in conditions approximating actual ear protection use. No plugs evaluated, including custom elastomeric solid core plugs, inhibited water penetration in conditions approximating shallow surface dives. A clinical protocol for evaluation of potential earplugs for patient use is proposed on the basis of this study.

Ear Protective Devices↗
PubMed1995

A comparison of multiple indicators--observations, supervisor report, and self-report as measures of workers' hearing protection use.

The purpose of this study was to compare multiple indicators of behavior and identify the most viable measure of blue-collar workers' use of hearing protection. Three measures of use were employed: observations, supervisor report, and self-report. Supervisor report was highly discrepant from both self-report and observed use; self-report and observations were highly correlated, and discrepancies between the two were slight. These results suggest that, for this type of measurement, self-report is an appropriate measure and may be the best choice when time and monetary resources restrict measurement to one indicator.

Administrative Personnel↗