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At least 433 records · Page 24Linked to original sources
PubMedDate not supplied

Hearing protector performance and standard deviation.

The attenuation performance of a hearing protector is used to estimate the protected exposure level of the user. The aim is to reduce the exposed level to an acceptable value. Users should expect the attenuation to fall within a reasonable range of values around a norm. However, an analysis of extensive test data indicates that there is a negative relationship between attenuation performance and the standard deviation. This result is deduced using a variation in the method of calculating a single number rating of attenuation that is more amenable to drawing statistical inferences. As performance is typically specified as a function of the mean attenuation minus one or two standard deviations from the mean to ensure that greater than 50% of the wearer population are well protected, the implication of increasing standard deviation with decreasing attenuation found in this study means that a significant number of users are, in fact, experiencing over-protection. These users may be disinclined to use their hearing protectors because of an increased feeling of acoustic isolation. This problem is exacerbated in areas with lower noise levels.

Australia↗
PubMedDate not supplied

Sound source identification with ANR earmuffs.

The effect of hearing protective earmuffs which incorporate active noise reduction (ANR) on sound source identification was studied. The purpose was determine whether ANR interfered with the encoding of cues normally used for directional hearing. Right/left, front/back and within quadrant confusions were assessed in quiet using a circular array of eight loudspeakers. Three stimuli, one-third octave bands centred at 0.5 kHz and 4 kHz and broadband noise, were presented. These enabled an assessment of the utilization of mainly interaural time-of-arrival and level differences, and binaural and spectral cues in combination, respectively. Two groups of normal hearing subjects aged 18-30 and 40-55 years, half male and half female, participated. Overall, age, gender, and ANR were not significant determinants of outcome. The probably of correctly discriminating among the eight speakers decreased significantly with the muffs worn, relative to unoccluded listening by 10%, 35% and 40% for the 0.5 kHz, 4 kHz and broadband stimuli, respectively. The pattern of errors indicated that the earmuffs interfered with the encoding of both binaural (interaural level differences) and spectral cues. With ANR small additional right/left confusions were observed for the low-frequency stimulus (time-of arrival cue) for speakers close to the midline axis. The results provide further evidence that earmuffs should not be used in situations where the perception of the direction of hazard is a concern. ANR technology does not appear to increase the handicap.

Adolescent↗
PubMedDate not supplied

European standardisation of hearing protectors.

European legislation based on the New Approach requires that technical requirements for products are given in harmonised European standards. The Directive 89/686/EEC on Personal Protective Equipment came into force in 1995. The existence of product and testing standards is a prerequisite for the effective implementation of the directive. There was a need to develop several standards in a very short time period and the basic standards for hearing protectors have already been revised once. It is important to continue the validation of the standardised testing methods and requirement levels. This requires good co-operation and research between test laboratories and research institutes, especially as it is necessary to ensure new products comply with these technical requirements.

Ear Protective Devices↗
PubMedDate not supplied

Effects of coldness on the protective performance of earmuffs.

The type test of hearing protectors (HPD) for certification purposes will be conducted in laboratory at room temperature. Optionally, the mechanical durability of HPDs will be tested in cold environment by a drop test. The purpose of this study was to find out the relevance of the drop test, the change of performance in HPD protection, and finally to estimate the possible change of protection efficiency against noise in cold environment. In total, 22 HPDs were selected to the measurements: 18 earmuffs, and 4 earmuffs attached to an industrial helmet. Attenuation of each earmuff cup was measured by applying insertion loss method for the test subjects in cold. The change of attenuation and temperature of cushion ring was followed up to nine minutes using 30-second intervals for sampling. Three HPDs were damaged in the test. The replaceable cushion was broken in two earmuffs and in one helmet-mounted HPD. The replaceable parts were replaced, and the HPD with attachment failure was removed from insertion loss measurement. In nine HPDs the relative change was less than 3 dB, and was at worst 10 dB. This change was typically at low frequencies, 125 Hz at the beginning when cooled HPDs were placed. In various HPDs the time to get the attenuation levelled varied from 1.5 minutes to 8 minutes. The recovery was dependent on the temperature of the cushion ring. In all cases the temperature of the full attenuation was achieved when the cushion ring reached 7 degrees C. This temporary decrease in attenuation will have a minor effect to the protection efficiency, when the HPD is used full time during the whole exposure duration. A typical group of forest workers will have their exposure interrupted. The chain saws have to refuel, and the chain needs to be sharpened about every 40 minutes. During 6 hour daily operational time there will be about 9-10 minute break, long enough to cool the cushion ring back to below zero at -10 degrees C, if the helmet mounted earmuffs are placed in stand-by position. In the worst case this will cause 1.6 dB increase in daily exposure level to noise.

Cold Temperature↗
PubMedDate not supplied

The influence of aging on the noise attenuation of ear-muffs.

Ear-muffs are commonly used as personal protectors against the effect of noise. The methods of calculation the A-weighted sound pressure level under the cups of ear-muffs are based on the results of laboratory measurements of noise attenuation, which are carried out in the certification process of the product on brand new samples. Hearing protectors are usually stored for certain periods of time. Next, workers use them in different ambient outdoor conditions as long as there are no signs of their physical damage. The question is. What is the influence of ambient outdoor conditions, usage and storage time of ear-muffs on their attenuation? To answer this question, a three-year study has been undertaken. Four types of ear-muffs, most popular in the Polish work environment, made in Europe, meeting the certification requirements and granted a certification mark, were used in this study. Sixty samples of ear-muffs were worn by workers at noisy workplaces, 40 samples were stored and another 40 were exposed to ambient outdoor conditions. The workers were asked to evaluate subjectively the noise attenuation of the ear-muffs. After one, two and three years time of usage and storage, the sound attenuation of ear-muffs was measured. After the two years the headband force and the cushion pressure of tested samples were measured. The results of sound attenuation measurements were used to calculate the attenuation against high- (H), medium- (M) and low- (L) frequency noise and single number rating (SNR) of the tested earmuffs. The results of the study showed that the attenuation of ear-muffs can be significantly reduced as a function of usage, storage, and exposure to ambient outdoor conditions. The observed decrease of the ear-muffs attenuation corresponded to decrease of the cushion contact area but did not correspond to the subjective workers' assessment.

Climate↗
PubMedDate not supplied

Risk by use of hearing protectors--expert programme supports SMEs in appropriate selection and use.

Comprehensive protection by use of PPE against the hazards at work requires more than proper selection based on the protection level needed: The PPE user directive (Council Directive 89/656/EEC, Official Journal of the European Communities L 393, 30/12/1989 p.0018 - 0028) requires an assessment of personal protective equipment itself, which has to consider the risks which may be introduced by use of PPE or use of combinations of PPE. As an example risks which may be introduced by use of hearing protectors are described. Assistance in the assessment required by PPE user directive (Council Directive 89/656/EEC, Official Journal of the European Communities L 393, 30/12/1989 p. 0018 - 0028) and in selection and use of hearing protectors with regard to this assessment is presented.

Decision Making↗
PubMedDate not supplied

Protection efficiency of hearing protectors against military noise from handheld weapons and vehicles.

Noise attenuation against military noises has been measured in several cases under practical field conditions. Commercial and military versions of earmuff noise attenuation were measured against rifle noise. All the tested earmuffs attenuated the C-weighted peak level to less than 135 dB, which is less than the proposed recommendation value. Combat and shooting exercises create a risk of hearing damage, reaching a peak level of 180 dB. Measurements were done during attack exercises with blank and normal cartridges and during a defence exercise with normal cartridges. The noise exposure levels were relatively moderate (outside the ear 95-97 dB, in ear canal 82-85 dB) for military exercises. Peak levels of 110-120 dB for military trainers were measured in the ear canal during the conscript use of small-bore weapons. Combat vehicles and tanks are noisy, and for noise control during their use headgear with communication properties is worn. Noise inside such headgear was found to reach up to 120 dB, and the noise doses varied between 90 and 105 dB. Noise was also measured for aviation pilots in Finnish jet fighters. The cockpit values averaged 96 dB - 100 dB over the flight, whereas noise in the ear canal averaged 88 dB - 95 dB. The analyses indicated that radio noise is 4-10 dB higher inside the helmet than the background noise is, when measured as equivalent noise. The technicians on the ground were exposed to noise levels varying from 93 to 97 dB over the day. In practice, hearing protectors attenuate noise by 10-30 dB, depending on the frequency content of the noise sources. However, the difference when measured outside and inside hearing protectors varies by 5-10 dB because communication increases the noise level at the entrance of ear the canal. Currently the best protection for soldiers seems to be active noise cancellation ear muffs that are equipped for communication purposes and worn during the entire military exercise.

Ear Protective Devices↗
PubMed2003

Noise induced hearing loss among industrial workers in Dar es Salaam.

OBJECTIVES: To determine whether sound in the study areas was of sufficient intensity to cause hearing loss and if so whether those exposed have been affected and to determine whether workers/employees in the study areas were aware that sound can cause hearing loss and if so whether they knew that this can be prevented by ear protection. DESIGN: Cross-sectional study. SETTING: Industrial area A and B randomly selected from among industries in Dar es Salaam. SUBJECTS: One hundred and fifty workers from area A and fifty two employees from area B. RESULTS: In both study areas the noise levels were above the safe limit of 85dB(A). In area A 28 workers and in area B eight employees had noise induced hearing loss. In area A 81.1% of the workers and in area B 85% of the employees knew that noise causes hearing loss. All workers/employees from both study areas knew that noise induced hearing loss could be prevented by some form of ear protection. CONCLUSION: Workers/Employees exposed to noise above 85dB(A) will eventually develop hearing loss. Workers/employees are aware of this hazard. There is therefore a need to educate those exposed on how best to protect their ears from the hazard and provide them with protective gear.

Adult↗
PubMed1994

Prolonged exposure to gunfire noise among professional soldiers.

OBJECTIVES: The aim of the study was a retrospective assessment of the exposure of professional soldiers to impulse noise from gunfire. METHODS: A questionnaire on noise exposure and use of hearing protectors was administered to a stratified random sample of 699 army officers (mean age 39.8 years) with an average of 18 years of exposure to shooting noise. For a comparison of the number of shots from different weapons, the peak sound pressure levels of shots were adjusted in relation to one pistol shot according to the equal energy principle. Total exposure time was estimated with the equal energy principle, the number of shots from different weapons, the energy levels of different shots, the effectiveness of hearing protection, and the distance from the noise source being taken into account. RESULTS: Rifles, shotguns, and pistols were the predominant exposure sources. Impulse noise exposure averaged 164,183 shots from different weapons. After adjustment to the energy level of one pistol shot, the average was 78,000 personally fired shots. The total shooting noise exposure averaged 218,000 adjusted shots. Translated into exposure to steady noise of 85 dB(A) for 40 h a week, the exposure to noise from personally fired shots equaled an exposure time of 22.0 years and the total exposure averaged 61.0 years. The heaviest exposure occurred during the first 10-15 years of the men's careers. CONCLUSIONS: Exposure to gunfire noise among professional soldiers is high enough to cause severe hearing deterioration already at early career stages if effective hearing protectors are not worn at all times on shooting occasions.

Adult↗
PubMed1988

Impulse noise and hand-arm vibration in relation to sensory neural hearing loss.

The present study was carried out to determine whether impulse noise and simultaneous exposure to noise and vibration can aggravate sensory neural hearing loss (SNHL) among forest (N = 199) and shipyard (N = 171) workers. The average level of exposure to noise outside the used earmuffs and the average exposure over time were nearly equal for the two groups. The impulsiveness of the noise and the average exposure level inside the earmuffs were measured with a miniature microphone. The hearing threshold of the workers was measured at 4 kHz and then estimated according to Robinson's model to compare the observed and expected hearing loss. The impulsiveness of the noise was greater both outside and inside the earmuffs in shipyard work than in forest work. The average SNHL was higher than predicted for the shipyard workers and about the same as predicted for the forest workers. The total exposure level inside the earmuffs was influenced by the total wearing time. The low frequencies of the chain-saw noise were not attenuated sufficiently by the earmuffs to protect the workers' hearing. The present study suggests that exposure to impulse noise increases the risk of SNHL, but that simultaneous exposure to hand-arm vibration and noise does not.

Ear Protective Devices↗
PubMed1988

Heart-rate and blood-pressure response in medium-artillery gun crews.

A pilot study of the effect of firing the L118/119 British light gun on the heart rate and blood pressure of crewmen who were wearing EAR ear-plugs was carried out. The firing took place on two successive days, with a higher (louder) charge being used on the second day. Each day 40 rounds were fired from each of two guns which were placed 7 m apart. The results suggest that an increase in heart rate of 10%-30% occurs which is attributable to the noise and which does not habituate to successive firings, and that an acute rise in blood pressure may have been associated with the firing of the higher-powered charge. It is considered that these preliminary observations warrant further, controlled experimentation with a larger number of subjects and improved methods of monitoring blood pressure levels.

Adolescent↗
PubMed2004

Hearing health risk in a population of aircraft carrier flight deck personnel.

This study evaluated the risk to hearing health associated with duty on the flight deck of a Nimitz class aircraft carrier. Descriptive data includes time-weighted average noise exposure and an evaluation of temporary threshold shift for a group of nonaviator flight deck personnel (FD), and a comparison of accrued permanent threshold shift among three shipboard occupational groups that had been matched for years of military service. The study participants included 76 FD personnel in a high-exposure group, 77 engineers in a moderate-exposure group, and 52 administrative personnel who were considered to have low occupational noise exposure. The study found a mean FD time weighted average of 109 dBA over workdays averaging 11.5 hours. Only 2 (4%) of 52 administrative personnel had any appreciable hearing loss (defined as worse than 20 dB at any frequency 1,000 through 4,000 Hz), whereas FD and engineers demonstrated 17% and 27% hearing impairment, respectively.

Adult↗
PubMed2006

Auditory perception with ear and cold weather face protection worn in combination.

The effects on hearing thresholds, sound attenuation, and consonant discrimination of wearing a balaclava under hearing-protecting earmuffs were studied. This combination is commonly worn during cold weather military operations. One group of 20 normal-hearing adults (10 male and 10 female subjects) was tested. Within-subject measurements were made of diffuse-field hearing thresholds from 0.25 kHz to 8 kHz and consonant discrimination in quiet with the ears unoccluded and protected with the earmuffs alone and with the balaclava worn full face or rolled. Attenuation was derived from the protected and unoccluded thresholds at each frequency. When the balaclava was worn full face, attenuation decreased by 16 to 18 dB, relative to the muff alone, below 6.3 kHz. With the balaclava worn as a cap, there was an inverted U-shaped decrement in attenuation of 18 to 27 dB from 0.25 Hz to 4 kHz. Consonant discrimination decreased by 7% with the muffs alone. These findings underscore the importance of assessing protective equipment under the conditions in which it will be worn.

Adolescent↗
PubMedDate not supplied

Reducing the effects of noise in hospital.

This article identifies noise as a factor in disturbing patients' sleep in hospital and discusses the usefulness of earplugs as a method of reducing perceptions of noise and enhancing sleep. A pilot study, comparing the quality and quantity of sleep in patients who used earplugs, with those who did not, showed them to be an acceptable and effective method of facilitating sleep.

Clinical Nursing Research↗
PubMed2002

Noise attenuation characteristics of a foam type earplug measured using a dummy head.

The attenuation characteristics of the earplug using a dummy head (KEMAR; Knowles Electronics Manikin for Acoustic Research) were measured, when it was exposed to pure tones or broadband noises at three different sound pressure levels (SPLs) of 70, 80 and 90 dB SPL in the 'wide frequency range from 250 to 20 k Hz. We ascertained the satisfactory capacity of noise attenuation except for from 10 k to 14 k Hz. The noise attenuation level increased with frequency until 2 k Hz, became almost constant until 8 k Hz, then decreased at around 10 k to 14 k Hz, and recovered in the range from 16 k to 20 k Hz. The frequency characteristics were identical among three different sound pressure levels and almost identical between pure tones and broadband noises. The change of frequency characteristics affected by the depth of the earplug that was inserted into the artificial ear canal of the KEMAR was also investigated. Measured sound pressure level by the builetin microphone in the KEMAR revealed a region in which the measured sound pressure levels were relatively higher around 10 k Hz. The frequency of the region moved higher when the earplug was inserted more deeply. Therefore it was considered that this phenomenon was related to the resonance frequency of the cylinder-like cavity made between the end section of the earplug and the diaphragm of the built-in microphone.

Audiometry, Pure-Tone↗
PubMed2003

[Development of a computerized sound attenuation measurement system of hearing protectors based on Japanese Industrial Standard(JIS)].

Sound attenuation measurement of hearing protectors is done in accordance with JIS T 8161 in Japan. In the JIS T 8161 it is stated that more than three non-coherent sets which include a noise generator, one-third octave band-pass filter, amplifier, calibrated attenuator and signal interrupter are required. To realize this measurement system, various expenses and a large space are required. In our study, four channel test signals were generated by our programs, and fed to a digital/analog converter. Consequently, the hardware of a noise generator and one-third octave band-pass filter could be reduced. Moreover, a program, which automatically controlled sound pressure level by digitally controlled attenuators, was developed with the result that the sound attenuation measurement could be performed by operating the mouse. Furthermore, sound attenuation of the earplug was measured in accordance with JIS T 8161 to evaluate our system. The result showed that practical sound attenuation values were obtained by easy operation. It was considered that this system was effective in hardware reduction, and useful for sound attenuation measurement of hearing protectors.

Adolescent↗
PubMed1999

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Ear Protective Devices↗