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PubMed1982

Effect of intermittent (traffic) noise on man--temporary threshold shift, and change in urinary 17-OHCS and saliva cortisol levels.

Eight healthy male college students were selected and eight noise exposure conditions were planned. The noise exposure time of all the experiments was 14 h. Measurement of the TTS growth at 4 kHz was investigated during these 14 h. Saliva collected every 3 h was also examined for cortisol throughout the 24-h period. The exposure noises used in this experiment were pink noise and pure tone of 3 kHz. The time patterns of trapezoidal noise were as follows. The rise and decay times were 1 s respectively and the peak level was 1 s for the (A I type), being 500 ms and 1.5 s respectively for the (A II type). Three measurements were made: 1. TTS. Under intermittent noise exposure at 80 dB(A), exposure of 20% of the on fraction induced significant TTS growth, but exposure of 13% of the on fraction did not induce TTS growth. Under exposure at 75 dB(A), exposure of 66% of the on fraction did not induce TTS growth. Under pure tone exposure of 3 kHz at 75 dB(A), exposures of 20% and 30% of the on fraction did not induce TTS growth. There was a significant difference between the TTS induced by a steady state of of 73 dB (A) (Leq of Exp. 2) and that of Exp 2. 2. Urinary 17-OHCS Level. During the noise exposure period (14h), there was a statistically significant difference between the urinary 17-OHCS level of the control condition and that of Exp. 3. In addition, there was no statistically significant difference among the urinary 17-OHCS levels of post-noise exposure. 3. Saliva Cortisol. With intermittent "pink noise" of 75 or 80 dB(A) (Exp. 2, 3, and 4), however, temporary elevation of the saliva cortisol level occurred only at the initial stage of exposure, and lasted for only one hour. Moreover, with steady state noise exposure, evanescent elevation occurred at the lower level of 71 dB(A).

17-Hydroxycorticosteroids↗
PubMed1993

Noise level of dental handpieces and laboratory engines.

Impaired hearing in dental practitioners has been the subject of various investigations. Although individual age and susceptibility can play a significant role, the intensity of the noise, distance from the noise source, and total duration of the noise are the important factors in hearing. In this study the noise levels of different handpieces and laboratory engines were evaluated. Handpiece noise measurements were made while instruments were running free and during operation with various cutting tools. These measurements were performed with two kinds of noise-measuring equipment: (1) a precision sound level meter and (2) a noise recording and analyzing circuit. The results indicated that (1) there were significant differences among the noise levels of the various dental engines used, (2) the low-speed, angled-design handpiece has the lowest noise level, whereas the laboratory engine has the highest, (3) the noise level increases during cutting was compared with noncutting, and (4) there was no significant difference between the two methods of measurement.

Dental High-Speed Equipment↗
PubMed2006

Prestin gene expression in the rat cochlea following intense noise exposure.

Noise-induced permanent loss of cochlear amplification was observed previously with the majority of outer hair cells (OHCs) still surviving in the cochlea and even with a normal OHC receptor potential, indicated by CM (cochlear microphonics) recording [Chen, G.D., Fechter, L.D., 2003. The relationship between noise-induced hearing loss and hair cell loss in rats. Hear. Res. 177(1-2), 81-90; Chen, G.D., Liu, Y., 2005. Mechanisms of noise-induced hearing loss potentiation by hypoxia. Hear. Res. 200, 1-9]. This study focused on effects of an intense noise exposure (10-20 kHz at a level of 110 dB SPL for 4 h) on the OHC motor protein (prestin) and structural proteins in the OHC membrane skeleton. The noise exposure significantly disrupted CM and CAP (cochlear compound action potential). The injured CM recovered after 1-week resting period. The impaired CAP at frequencies lower than the noise band also recovered. However, the CAP recovery at frequencies of the noise band stopped at a linear line one week after the noise exposure, indicating a permanent loss of cochlear amplification. Gene expression of prestin, beta-spectrin, and beta-actin was significantly up-regulated after the noise exposure. The elevated gene expression peaked at the 3rd post-exposure day and returned to baseline 4 weeks after the noise exposure. The up-regulated gene expression may be in response to injury of the proteins, which may be responsible for the loss of cochlear amplification.

Action Potentials↗
PubMed1999

Potentiation of octave-band noise induced auditory impairment by carbon monoxide.

In previous studies from our lab, broadband noise induced hearing loss has been found to be potentiated by simultaneous carbon monoxide (CO) exposure. In the present study, octave-band noise induced auditory impairment was studied with the presence of CO at levels of 1500, 1200, 700, 500 and 300 ppm and zero (noise alone). Four octave-band noises (1.2-2.4, 2.4-4.8, 4.8-9.6 and 9.6-19.2 kHz) were used. Experimental subjects (rats) were grouped for the exposure (8 h) to each noise, CO and their combinations. The compound action potential (CAP) and cochlear microphonics (CM) were recorded 4 weeks after the exposure. The noise induced elevation of the CAP threshold and the CM iso-amplitude curve were potentiated by the simultaneous CO exposure when the CO level reached 500 ppm or higher. CO exposure alone had no effect on CAP or CM. The CO potentiation can occur in any frequency region depending on the noise band. The combined exposure can also induce threshold shifts in some cases in which both the noise and the CO alone did not cause threshold shifts. The size of the potentiation shown by CAP and CM was similar, indicating a possible origin of the CO potentiation from the damage to the outer hair cells. Interestingly, the hearing loss induced by noise alone gradually recovered (partially), but the hearing loss caused by the combined exposure did not. The potentiation may be due to the reduction of the cell's ability to repair noise induced damage by CO.

Animals↗
PubMed2000

Threshold shifts and enhancement of cortical evoked responses after noise exposure in rats.

The effect of exposure to various types of noise (broadband, high-frequency or low-frequency) was studied in adult pigmented rats. Thresholds and amplitudes of middle latency responses (MLR) recorded from electrodes implanted on the surface of the auditory cortex were analyzed before and after noise exposure. Exposure to noise with intensities ranging from 105 to 120 dB for 1 h produced only temporary threshold shifts (TTS). Exposure to broadband noise produced TTS throughout the whole frequency range of the rat's hearing, mostly expressed at frequencies of maximal hearing sensitivity (16-32 kHz). Hearing loss produced by high- or low-frequency noise exposure was related to the spectral characteristics of the noise. The exposure to high-intensity noise may also result in amplitude enhancement of the MLR. This phenomenon was seen mainly after broadband noise exposure and occurred in response to both low-frequency and high-frequency test stimuli. High-frequency and low-frequency noise produced amplitude enhancement mainly at frequencies which corresponded to the maximum exposure energy. In contrast to the relatively similar values of TTS obtained in different rats under the same conditions of noise exposure, great inter-individual variability was found in the MLR amplitude enhancement. In all rats the dynamics of recovery functions for amplitude enhancement were different from those for MLR thresholds. The data indicate that whereas post-exposure TTS are related to peripheral changes, the post-exposure MLR amplitude enhancement is most probably connected with a change in the processing of auditory information in the central nervous system.

Acoustic Stimulation↗
PubMed1985

Sensitivity to noise in a community sample: II. Measurement of psychophysiological indices.

A sample of 77 women of high and low noise sensitivity in 1977, living in areas of high and low exposure to aircraft noise, were interviewed in the community in 1980. High, intermediate and low noise sensitive women were compared, using measures of blood pressure, heart rate, skin conductance, hearing threshold, uncomfortable loudness level and magnitude estimation of six tones. These physiological measures did not clearly distinguish different noise sensitivity groups, except that highly noise sensitive women had a consistently slower heart rate. Noise sensitivity was not related to auditory threshold. In the high aircraft noise area there were significantly more skin conductance responses than in the low aircraft noise area irrespective of noise sensitivity. This may be the result of chronic exposure to high aircraft noise.

Adolescent↗
PubMed1981

Psychiatric admissions and aircraft noise from London Airport: four-year, three-hospitals' study.

Nine thousand persons admitted to three large psychiatric hospitals, over a period of four years, were classified according to the aircraft noise exposure of their home address, using the Noise and Number Index. The analysis searched first for simple associations between exposure and admission rates, then for complex interactions with socio-economic characteristics of the area of residence. There was no common pattern of admissions across the three hospitals: in one case the rates decreased with aircraft noise; in the other two the rates increased with noise exposure. However, since in all cases the trends could be attributed to non-noise factors characteristic of the population, it was concluded that the effects of noise, if any, could only be small, weakly influencing other causal variables but not overriding them. Further analyses showed that positive associations between noise and admissions occurred in some groups and in some districts. People 45 years old and over exhibited higher admission rates than expected in the highest noise zone in one hospital. The districts where a positive trend between noise and admissions was evident were those with a higher proportion of one-person households, a higher proportion of immigrants, or a higher proportion of professionals and managers; however, these results were only found in one hospital with counterexamples in others. No strong, significant noise effect could be found. Limitations of the hospital records and specific difficulties in setting up the data for these studies are discussed.

Adult↗
PubMed2006

Hearing loss induced by occupational and impulse noise: results on threshold shifts by frequencies, age and gender from the Nord-Trøndelag Hearing Loss Study.

The aim of the study was to compare the frequency-specific effects of noise on hearing acuity across the range 250-8000 Hz and the extent to which the patterns of frequency-specific threshold shifts differ between occupational noise and impulse noise. Pure-tone audiometry was administered to an adult general population sample with 51 975 subjects who also provided questionnaire information about noise exposure and other risk factors. Threshold shifts induced by life-long occupational noise and impulse noise (mostly shooting) were estimated separately in six age and sex groups for eight frequencies. Reported noise exposure, as well as observed threshold shifts, were moderate among women. Threshold shifts averaged over both ears among subjects in the higher 2% of exposure to occupational noise, reached 13 dB (3000 Hz, age 65 years + ) among men and were generally largest at 3000-4000 Hz. The shifts induced by impulse noise reached approximately 8 dB among men 45-64 years and men 65 years+. The effects of impulse noise were strongest at 3000-8000 Hz and varied little within this frequency range.

Adult↗
PubMed2004

Dog noise as a risk factor for hearing loss among police dog handlers.

AIM: To determine the sources of noise exposure among police dog handlers and to examine whether these levels might lead to noise-induced hearing loss. METHODS: We conducted a cross-sectional study at four Royal Air Force bases using a noise survey, a postal questionnaire and medical record review. The noise survey was conducted following task analysis. We surveyed police dog handlers and a comparison group of police who had never been dog handlers, using a postal questionnaire on noise exposures and confounders. Audiometric and otological data were extracted from medical records. RESULTS: The noise survey revealed significant exposures due to dogs, travelling in vans and aircraft noise during foot patrol. The overall response rate to the questionnaire was 56% (29 police dog handlers, 24 police officers). Five subjects (9.4%) had age-corrected hearing loss exceeding 10 dB, averaged over the 4 and 6 kHz frequencies, affecting the left ear only, but there were no differences between dog handlers and controls. CONCLUSION: Although the measured noise exposures of police dog handlers did not exceed current legal limits, the noise levels at times are such that the proposed Physical Agents (Noise) Directive has implications for employers who use dogs for security purposes.

Adult↗
PubMed2003

Evaluation of the risk of noise-induced hearing loss among unscreened male industrial workers.

Variability in background risk and distribution of various risk factors for hearing loss may explain some of the diversity in excess risk of noise-induced hearing loss (NIHL). This paper examines the impact of various risk factors on excess risk estimates of NIHL using data from the 1968-1972 NIOSH Occupational Noise and Hearing Survey (ONHS). Previous analyses of a subset of these data focused on 1172 highly "screened" workers. In the current analysis, an additional 894 white males (609 noise-exposed and 285 controls), who were excluded for various reasons (i.e., nonoccupational noise exposure, otologic or medical conditions affecting hearing, prior occupational noise exposure) have been added 2066) to assess excess risk of noise-induced material impairment in an unscreened population. Data are analyzed by age, duration of exposure, and sound level (8-h TWA) for four different definitions of noise-induced hearing impairment, defined as the binaural pure-tone average (PTA) hearing threshold level greater than 25 dB for the following frequencies: (a) 1-4 kHz (PTA1234), (b) 1-3 kHz (PTA123), (c) 0.5, 1, and 2 kHz (PTA512), and (d) 3, 4, and 6 kHz (PTA346). Results indicate that populations with higher background risks of hearing loss may show lower excess risks attributable to noise relative to highly screened populations. Estimates of lifetime excess risk of hearing impairment were found to be significantly different between screened and unscreened population for noise levels greater than 90 dBA. Predicted age-related risk of material hearing impairment in the ONHS unscreened population was similar to that predicted from Annex B and C of ANSI S3.44 for ages less than 60 years. Results underscore the importance of understanding differential risk patterns for hearing loss and the use of appropriate reference (control) populations when evaluating risk of noise-induced hearing impairment among contemporary industrial populations.

Adult↗
PubMed1991

Hearing loss in the chinchilla from impact and continuous noise exposure.

The relative hazard posed to the peripheral auditory system by impact/impulse and continuous noise of the same power spectrum was determined. Impact noise was generated by striking a nail with a hammer and was digitally recorded. The acoustical power spectrum of the impact was determined and pink noise was filtered to produce a continuous noise stimulus with the same acoustic power spectrum. Pre-exposure auditory evoked response (AER) thresholds were obtained at 1, 2, 4, and 8 kHz on 16 adult chinchillas. The pool of animals was divided into two equal groups based upon pre-exposure AER thresholds. One group was exposed to impact noise and the other group to the filtered pink noise. Exposures were 4 h/day for 5 days. Thirty days following the exposure, auditory evoked response thresholds were remeasured. Changes in auditory sensitivity were determined by subtracting the pre-exposure thresholds from the post-exposure thresholds. Hearing threshold shifts of the impact noise group were significantly greater (p less than 0.0001) than the hearing threshold shifts of the continuous noise group. These data indicate a need to more closely examine the parameters and effects of impact noise. There may be a need to develop expanded damage-risk criteria for occupational exposure to impulse/impact noise.

Animals↗
PubMed2005

Farm noise emissions during common agricultural activities.

Noise injury in agriculture is a significant yet often unrecognized problem. Many farmers, farm workers, and family members are exposed to noise levels above recommended levels and have greater hearing loss than their non-farming contemporaries. The aim of this study was to gather up-to-date information on farm noise levels and to enhance the quality of information available to assist farmers in reducing noise exposure and meeting Occupational Health and Safety (OHS) regulations regarding noise management. Farm visits were conducted on 48 agricultural establishments that produce a range of commodities. Noise levels were measured at the ears of operators and bystanders involved in typical activities on farms. The average and peak noise levels were measured for 56 types of machinery or sites of farming activity, totaling 298 separate items and activities. Common noise hazards identified included firearms, tractors without cabs, workshop tools, small motors (e.g., chainsaws, augers, pumps), manual handling of pigs, shearing sheds, older cabbed tractors, and heavy machinery such as harvesters, bulldozers, and cotton module presses. We found that use of firearms without hearing protection presents a pressing hearing health priority. However, farming activities involving machinery used for prolonged periods also present significant risks to farmers' hearing health. Noise management strategies on the farm are essential in order to prevent noise injury among farmers.

Agricultural Workers' Diseases↗
PubMed2001

Occupational noise exposure and hearing loss of workers in two plants in eastern Saudi Arabia.

OBJECTIVE: To determine the prevalence of hearing loss associated with occupational noise exposure and other risk factors. DESIGN: A cross-sectional study involving 269 exposed and 99 non-exposed subjects (non-industrial noise exposed subjects) randomly selected. Current noise exposure was estimated using both sound level meter and noise-dosimeter. Past noise exposure was estimated by interview questionnaire. Otoscopic examination and conventional frequency (0.25-8 kHz) audiometry were used to assess the hearing loss in each subject. RESULTS: 75% (202 subjects) from the exposed group were exposed to a daily Leq above the permissible level of 85 dB(A) and most (61%) of these did not and had never used any form of hearing protection. Hearing loss was found to be bilateral and symmetrical in both groups. Bivariate analysis showed a significant hearing loss in the exposed vs non-exposed subjects with a characteristic dip at 4 kHz. Thirty eight percent of exposed subjects had hearing impairment, which was an 8-fold higher rate than that found for non-exposed subjects. Multivariate analysis indicated exposure to noise was the primary, and age the secondary predictor of hearing loss. Odds of hearing impairment were lower for a small sub-group of exposed workers using hearing protection (N=19) in which logistic regression analysis showed the probability of workers adopting hearing protective devices increased with noise exposure, education, and awareness of noise control. Hearing loss was also greater amongst those who used headphones to listen to recorded cassettes. CONCLUSION: Gross occupational exposure to noise has been demonstrated to cause hearing loss and the authors believe that occupational hearing loss in Saudi Arabia is a widespread problem. Strategies of noise assessment and control are introduced which may help improve the work environment.

Adult↗
PubMed2000

[Application of extended high frequency audiometry in the early diagnosis of noise--induced hearing loss].

OBJECTIVE: To assess the application of 10-20 kHz audiometry in early diagnosis of noise-induced hearing loss and to explore the relationship between hearing loss and subjects' age, the exposure time as well as the noise level. METHODS: One thousand workers with noise exposure history were examined by pure tone audiometry(0.5-20 kHz). One hundred and twenty normal subjects served as the control group. RESULTS: The noise levels at working sites ranged from 95 to 115dB(A). Compared with the control group, noise-exposed subjects showed minor changes in the thresholds from 0.5 to 6 KHz, whereas the thresholds were elevated in the high frequency range of 10-16 kHz (P < 0.001). The incidence of ears without any response to the maximum output at the frequency range of 14 to 20 kHz was much higher (P < 0.01) than that of the control group. In the animals exposed to noise, the thresholds of 10-18 kHz increased with the aging and with increase of working time (6-10 years), but there were no significant differences among subjects exposed to the noises at different levels(P > 0.05). CONCLUSION: In noise-exposed ears, the occurrence of threshold changes in the high frequency range (10 to 20 kHz) is earlier than that in the low frequency range (0.5 to 6 kHz). Aging and working time also affect the 10-20 kHz hearing thresholds. The lack of responses to maximum output and the changes in thresholds in the high frequency range (10-20 kHz) can be used as indices for the diagnosis of early noise-induced hearing loss and for the assessment of the susceptibility of the subject to noise damage.

Adolescent↗
PubMed1991

[Effect of noise, exertion and thermal load on temporary auditory threshold shift (TTS) and on fatigue].

Temporary threshold shifts were determined in 14 voluntary subjects who were exposed during one hour to noise levels 70, 85 and 100 dB(A) accompanied by physical exercise (30% VO2max), thermal load (TE = 32.0 +/- 0.8 degrees C), and after combined exposure to these three factors. Before and after each exposure, temporary were measured threshold shifts (TTS2) at frequencies 3, 4 and 6 kHz. The psychophysical fatigue was determined using flicker and blinking tests. The results showed that exposure to noise, noise and thermal load, noise and exercise, and combined noise-exercise -thermal load exposure induced statistically significant increases of TTS values, especially at 85 and 100 dB(A) noise levels. Noise and thermal load, noise and exercise, and the combination of the three did not cause psychophysical fatigue, probably on account of the short duration of exposure. The results of this work show that estimation of exposure to noise, performed by measuring noise levels at workplaces and comparing them with the current standards without considering the effects of exercise and/or thermal load is not sufficient to evaluate occupational exposure and the risk of permanent hearing loss.

Adult↗
PubMed2002

The effect of noise exposure in the presence of canal fenestration on the amplitude of short-latency vestibular evoked potentials.

BACKGROUND: Exposure to high-intensity noise causes little, if any, reduction in vestibular function in normal animals as shown by short-latency vestibular evoked potentials (VsEPs). OBJECTIVE: To investigate the effect of noise exposure on VsEPs following fenestration of the horizontal semicircular canal. DESIGN AND METHODS: Psammomys obesus (fat sand rat) underwent labyrinthectomy in 1 ear, while the lateral semicircular canal in the other ear was fenestrated. Control VsEPs to linear acceleration (approximately 3g; rise time, approximately 1-2 milliseconds) were recorded immediately after the operation. The experimental group animals were then subjected to loud white noise (113-dB sound pressure level) for 1 hour. Immediately after the noise exposure in the experimental group animals, VsEPs were once more recorded. RESULTS: The VsEPs in the experimental group animals were significantly reduced immediately following the noise exposure, while there was no change in the recordings from the control group animals (fenestrated but not noise exposed; noise exposed but not fenestrated), even though the noise exposure induced a mean 47-dB threshold elevation of the auditory brainstem response. CONCLUSIONS: The presence of the fenestration caused the vestibular end organs to become vulnerable to noise exposure. The fenestration may create a pathway enabling pressure release through the vestibular end organs during noise exposure, thus increasing the possibility of damage to the vestibular end organs. This did not occur in the intact, nonfenestrated animals.

Analysis of Variance↗
PubMed2000

Protective effects of phenyl-N-tert-butylnitrone on the potentiation of noise-induced hearing loss by carbon monoxide.

Free radical injury has been implicated in cochlear damage resulting from exposure to high-intensity noise and due to carbon monoxide (CO) hypoxia. Although exposure to noise plus CO is common in occupational settings and noise-induced hearing loss (NIHL) is enhanced in the presence of CO, potential mechanisms resulting in auditory impairment have not been studied. This study evaluates protective effects of the free radical scavenger phenyl-N-tert-butylnitrone (PBN) against potentiation of NIHL by CO. Three PBN administration protocols have been evaluated in subjects exposed to noise plus CO or noise alone. Long Evans hooded rats were exposed to octave band noise at 100 dB(Lin), center frequency (cf) = 13.6 kHz for a duration of 2 h. The level of CO used was 1200 ppm. Endpoints used to detect permanent auditory impairment were compound action potential (CAP) threshold and 1 microV root mean square (RMS) cochlear microphonic (CM). Testing was done 4 weeks following exposure. PBN administration prior to and following simultaneous exposure provided significant protection against auditory impairment in subjects receiving noise plus CO. Partial protection was observed in the protocols where PBN was injected following noise plus CO exposure. PBN administration appeared to reduce auditory impairment in animals exposed to noise alone, but the difference was not found to be statistically significant. Protective effects of PBN following simultaneous exposure to noise plus CO suggest that free radicals may be generated during combined exposure.

Animals↗
PubMed1987

Sampling, log binning, fitting, and plotting durations of open and shut intervals from single channels and the effects of noise.

(1) Analysis of the durations of open and shut intervals measured from single channels currents provides a means to investigate the mechanisms of channel gating. Durations of open and shut intervals are conveniently measured from single channel data by using a threshold level to indicate transitions between open and shut states. This paper presents a detailed characterization of sampling, binning, and noise errors associated with 50% threshold analysis, provides criteria to reduce these errors, methods to correct for them, and presents an efficient means of data handling for binning and plotting interval durations. (2) Measuring interval durations by sampling at a fixed rate introduces two types of errors, (a) the number of intervals of a given measured duration are increased (promoted) over that expected in the absence of sampling, producing a sampling promotion error, (b) sampling decreases the total fraction of true intervals that are detected, producing a sampling detection error. Sampling errors can be reduced to negligible levels if the actual or effective (after interpolation) sampling period is less than 10-20% of both the dead time and fastest time constant in the distribution of intervals. Dead time is given by the duration of a true interval that has a filtered amplitude equal to 50% of the true amplitude. (3) Methods are presented to correct for sampling promotion error during least squares and maximum likelihood fitting. Sampling detection error is more difficult to correct, but an empirical description of the sampling detection error can be used to calculate the effective fraction of detected events with sampling. (4) Noise in the single channel current record can produce two types of error. (a) If noise peaks in the absence of channel activity exceed the threshold for detection, then false channel events of brief duration are produced. Sufficient filtering will prevent this type of error. (b) Noise can also increase the total fraction of true intervals that are detected, producing a noise detection error. Increased filtering over that required to prevent false events is not necessarily the best method for reducing noise detection error, as increased filtering can prevent detection of the faster exponential components. (5) Noise detection error can be reduced in two ways: (a) an empirical description of the noise detection error can be used to calculate the effective fraction of detected events in the presence of noise. (b) The sampling period can be selected so that the sampling detection error cancels the noise detection error.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗