Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “NOISE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed2006

Evaluation of occupational environment in two textile plants in Northern India with specific reference to noise.

Occupational Noise exposure has been linked with a range of negative health effects by various researchers. The resulting injury of occupational hearing loss is also a well recognized and global problem. To protect workers from hearing damage due to noise exposure and other related health effects, a vast store of knowledge has been accumulated till date about its nature, etiology and time course. There is still ignorance, amongst majority of people working in industries in developing and third world countries including India about ill effects of exposure to high values of noise. The study being reported here has been carried out in two textile plants located in Northern Indian state of Punjab. Equivalent sound pressure level L(eq) has been measured in various sections of these plants with the help of a Class-I type digital sound level meter. The noise spectrum has been evaluated with the help of 1/3 octave filter set. A cross sectional study involving 112 workers exposed to different levels of occupational noise has been conducted. The results of the study establish the fact that noise level in certain sections of the plants i.e Loom Shed, Spinning, Ring Frame, TFO Area is more than the acceptable limit of 90 dBA for 8 h exposure stipulated by OSHA. The noise level in other sections like carding, blow room, combing etc., although is less than 90 dB(A), but is quite higher than limits used for assessment of noise for community response. Octave band analysis of the noise shows the presence of high sound level in 4,000 Hz frequency range, which can be a major reason for causing occupational hearing loss. The results of the interview questionnaire which included a number of parameters reveal the following; (i) only 29% workers are aware about the effects of noise on health (ii) 28% workers are using ear protectors (iii) the satisfaction with the working environment is related to noise level, as workers exposed to comparatively less noise level report better satisfaction (iv) 70% of the workers reported that high noise level causes speech interference (v) 42% workers report the noise to be annoying. The study thus demonstrates the presence of gross occupational noise exposure in both the plants and the author believes that occupational noise exposure and the related effects in India is a widespread problem.

Humans↗
PubMedDate not supplied

[Assessment of occupational noise exposure: methodology, measurement error, evaluation criteria].

BACKGROUND: Occupational noise exposure can be monitored directly by personal sampling or indirectly, by area sampling. Personal sampling is performed using an integrating sound level meter, worn by the worker while performing his/her job. When area sampling is used, measurements need to be made in all locations where a typical worker stays while performing his/her tasks; the respective partial lengths of exposure need to be accurately monitored, and the time-weighted average sound level of the measured noise levels must be calculated. OBJECTIVES: Current regulations identify three different thresholds, corresponding to different types of action, but they do not propose any standard criteria to decide whether a threshold has been exceeded. Defining standard procedures to assess occupational noise exposure and identifying such thresholds is crucial. METHODS: Using empirical data collected in the field, the effects are illustrated of the number of sampling locations and of the partial lengths of exposure on area sampling measurements, and the effects of duration of noise exposure on both area and personal samplings. RESULTS: When dealing with area samplings, an accurate definition of both sampling locations and partial lengths of exposure is crucial. When arbitrary decisions are taken in selecting sampling locations and/or establishing partial lengths of exposure, spatial changes in noise level and operator' displacements while performing his/her tasks may affect results. Sampling for less than the duration of noise exposure is the major contributor to measurement error, particularly under conditions of unpredictable variation in noise level. In fact, as noise level in the non-monitored time fraction is unknown, measurement error cannot be determined. We estimate that, even under the most favorable circumstances, sampling should last not less than 40% of the duration of a given noise-generating occurrence, for repeated measurements to be dispersed within a range not wider than that generated by the instrumental error. Inter-daily variability is another important aspect in personal noise exposure evaluation. This is a general occurrence, whose effects cannot be controlled by simply considering weekly instead of daily exposures. Results of an investigation, covering about 60 different jobs within a primary aluminum plant, show an inter-daily variability in noise exposure greater than 5 dBA in about 75% of cases. CONCLUSIONS: Personal sampling, when correctly performed and covering the total duration of exposure, provides the most reliable result as it integrates noise over all locations where the worker actually stays while performing his/her tasks, and over the total length of time spent in each task. We propose extending personal sampling to the total duration of actual noise exposure as the standard procedure for monitoring daily personal noise exposure, and valid for the majority of work places. When the range of daily noise exposure includes one regulatory threshold, corresponding to a given type of action, we propose as a standard decision criterion to refer prudentially to the upper 95% confidence limit of the LEP,d arithmetic mean. Such criterion would allow to standardize procedures and decision methods, with the prospect of further improvements in the assessment of exposure to noise.

Humans↗
PubMed2006

Community noise annoyance assessment in an urban agglomeration.

In urban areas community noise is one of the important factors in producing deterioration of both well-being and the quality of life. The aim of the study was to compare two noise annoyance surveys and two noise annoyance scales in the period of 15 years in selected areas of Slovak capital Bratislava, to calculate risks of community noise annoyance and disturbance in the observed samples. Noise annoyance risks were calculated by bivariate and stratified analysis in the form of odds ratio and Mantel-Haenszel weighted odds ratio from 2x2 and 2xn tables. The use of validated five-grade scale of noise annoyance assessment gives higher possibilities for more detailed analysis, allows to calculate the indicator--percentage of highly annoyed subjects (% HA), the rate of highly annoyed individuals. The percentage of highly annoyed subjects was 18% in the year 2004, which is comparable with recently published studies. The percentage of respondents that were not at all annoyed by road traffic noise has been decreased during the 15 year period by 10% (42% vs 32%). The increase of subjective community noise annoyance risks has been observed after 15 years as well. The sample from the year 2004 has been more annoyed by road traffic noise, neighbourhood noise, noise from entertainment facilities, noise from industry and railway noise. The highest risk increase has been observed in the entertainment facilities noise annoyance (OR(MH) =1.51; 95% CI = 0.90-2.52 vs OR(MH) = 4.47; 95% CI = 2.75-7.33). Using of standard five-grade noise annoyance questionnaire gives higher possibilities for data analysis in the studies investigating the influence of environmental noise annoyance on selected population groups (Tab. 3, Ref. 7).

Adult↗
PubMed1985

[Speech discrimination in environment-specific noise].

Taking into account the changes in language discrimination due to specific environmental noise of varying quality, we determined the influence of cocktail party noise, traffic noise and factory noise by means of free field adjusted headphones, thus analysing the discrimination of monosyllables for different types and degrees of noise in normal and pathological hearing. The results confirm that language discrimination without specially considering noise interference does not satisfactorily describe actual communication conditions in the everyday life of those with disturbed hearing. Even noise interference using a speech-related spectral distribution or white noise cannot sufficiently simulate the actual interference quality in everyday life. Cocktail party noises proved useful to register frequent selection interference in language-similar surroundings. For specific interference influence, additional street noise or factory noise may be used. With regard to standardisation of noise interference, comparative examination of language-simulating noise available as test noise on every normal language cassette should be performed. The present study underlines, to say the least, that for comprehension of language discrimination disturbances in the presence of noise interference, a broad-spectrum range of possible noise should be available for a comprehensive coverage of the manifold communications situations that can arise.

Auditory Threshold↗
PubMed1987

Non-auditory effects of noise in industry. VI. A final field study in industry.

Non-auditory effects of noise were studied among 539 male workers from seven industries. The LAeq, assessed by personal noise dosimetry, has been used to study acute effects. Various indices of total noise exposure, involving level and duration, were developed for long-term effect studies. In the analysis close attention was paid to prevent confounding, e.g. by other adverse working conditions. As expected, hearing loss increased with total noise exposure. Tinnitus was related particularly to hearing loss. Dizziness and hoarseness, however, were not related with noise exposure in this study. Also no correlation could be demonstrated between blood pressure and total noise exposure after correction for age, relative weight and various confounding variables. Use of hearing protection, selection processes and incomplete analysis of interactions between independent variables are suggested for possible explanation. About two-thirds of the workers reported noise annoyance. Various aspects were mentioned, such as irritation, surprise and impairment of communication and perception. Mentally stressful tasks appeared to be the most noise-sensitive. Particularly annoying noise sources, mental work load and time pressure had a relatively large impact on noise annoyance in comparison with the influence of noise level (LAeq) itself. Stress responses were not simply related to the noise exposure level, although consistent positive relations could be demonstrated between symptoms of stress and noise annoyance. Various findings led to the conclusion that noise exposure together with stressful mental activities may lead to disturbed concentration, irritation and annoyance. Experienced stress in turn may render workers more susceptible to noise. To overcome some limitations of this study, cohort studies and studies designed to assess interaction-effects are recommended.

Adult↗
PubMed1992

Active noise control: a review of the field.

Active noise control (ANC) is the application of the principle of the superposition of waves to noise attenuation problems. Much progress has been made toward applying ANC to narrow-band, low-frequency noise in confined spaces. During this same period, the application of ANC to broad-band noise or noise in three-dimensional spaces has seen little progress because of the recent quantification of serious physical limitations, most importantly, noncausality, stability, spatial mismatch, and the infinite gain controller requirement. ANC employs superposition to induce destructive interference to affect the attenuation of noise. ANC was believed to utilize the mechanism of phase cancellation to achieve the desired attenuation. However, current literature points to other mechanisms that may be operating in ANC. Categories of ANC are one-dimensional field and duct noise, enclosed spaces and interior noise, noise in three-dimensional spaces, and personal hearing protection. Development of active noise control stems from potential advantages in cost, size, and effectiveness. There are two approaches to ANC. In the first, the original sound is processed and injected back into the sound field in antiphase. The second approach is to synthesize a cancelling waveform. ANC of turbulent flow in pipes and ducts is the largest area in the field. Much work into the actual mechanism involved and the causal versus noncausal aspects of system controllers has been done. Fan and propeller noise can be divided into two categories: noise generated directly as the blade passing tones and noise generated as a result of blade tip turbulence inducing vibration in structures. Three-dimensional spaces present a noise environment where physical limitations are magnified and the infinite gain controller requirement is confronted. Personal hearing protection has been shown to be best suited to the control of periodic, low-frequency noise.

Ear Protective Devices↗
PubMedDate not supplied

[Noise exposure in neonatal intensive care units].

This study evaluates the exposure of newborn babies in neonatal intensive care units (NICU) to noise which can cause hearing lesions directly (acoustic trauma) as well as indirectly (hypoxia). Moreover, noise can have an aggravating effect when combined with other potentially harmful factors in the NICU, such as ototoxic medication or stress due to other external stimuli, such as excessively bright light, lack of a day/night rhythm or pain. Sound pressure levels were measured in the NICU and inside the cribs in various experimental conditions, classified under 3 different types of sound events: constant background noise, variations in background noise and impulsive events. The main sources of noise detected were crib noise generated by ventilation and temperature control systems, ambient noise in the room, noise caused by the staff in the NICU, noise generated by crib alarm systems and NICU apparatus and noise caused by activity on the crib cover or on its plexiglas top. Findings revealed that the influence of ambient noise is fairly irrelevant. Background noise and its variations concerned with activities in the department never exceeded the limits considered potentially harmful to adults (DRC), whereas the impulsive noise generated by staff on the cribs or on the plexiglas tops was considerable and potentially harmful. These findings demonstrate that it is feasible and relatively easy to control noise in the NICU and significantly reduce the impulsive noise component by training staff to be more careful and avoid any unnecessary jolting and rough handling on and near the cribs.

Environmental Exposure↗
PubMed2005

[Noise induced annoyance and morbidity. Results from the pan European LARES-survey].

Traffic noise (road, train and flight noise, and the noise of parking cars), is the dominant source of annoyance in the living environment of many European countries. This is followed by neighbourhood noise (neighbouring apartments, staircases and noise within the apartment). The subjective experience of noise stress can, through central nervous processes, lead to an inadequate neuro-endocrine reaction and finally to regulation diseases. Within the context of the LARES-survey, noise annoyance within the everyday living environment was collected and evaluated in connection with medically diagnosed illnesses. Adults who indicated chronically strong annoyance due to neighbourhood noise were found to have an increased health risk in the cardiovascular system, the movement apparatus as well as depression and migraine. For adults with chronically strong annoyance caused by traffic noise, the risks to the respiratory system also increased. In older people, both neighbourhood and traffic noise indicated, in general, a lower risk of noise annoyance induced illness than in adults. It can be assumed that the effects of noise induced annoyance in older people is concealed by the physical consequences of age (with a strong increase in illnesses). With children, the effects of noise induced annoyance from traffic as well as neighbourhood noise is evident in the respiratory system. The increased illness risks in the respiratory system in children do not seem to be caused primarily by air pollutants but rather, as with case of neighbourhood noise, though emotional stress.

Adolescent↗
PubMed2001

Ways to promote a noise control programme.

The purpose of this study was to find out the proper ways to promote and to start a noise control programme in small and medium size industries. The situation of the noise control programme was inspected in four industrial enterprises. The noise exposure and the noise sources were studied and recommendations for noise reduction were given. The information concerning the noise control programme and noise levels was given to the personnel. How the noise control programme was started in the companies and which were the best ways to promote the programme were examined after 1 year. Noise reduction work was carried out in companies during the past year and new ideas were awaiting investment. The systematic noise control programme was not written on paper or connected to a risk management programme. The lack of proper models of a programme, lack of time and knowledge of easy means to reduce the noise were reasons for missing noise control programmes. The best ways to push up the noise control programme were to give information and examples of the programme. The EU-directive concerning machines and its noise information was a help in the noise reduction work connected with new investments.

Health Promotion↗
PubMed1984

Effects of continuous noise backgrounds on rate response of auditory nerve fibers in cat.

This study describes the effects of broadband background noise on the average discharge rate to best-frequency (BF) tones of auditory nerve fibers in the cat. The effects of exposure to long-term continuous noise are compared to the effects of noise gated on and off simultaneously with test tones. Addition of background noise causes a shift of the dynamic portion of tone-evoked rate versus level functions to higher tone intensities. The shift occurs at a mean rate of 0.61 dB of shift for each 1-dB increment in noise level. The rate of shift is independent of best frequency and spontaneous discharge rate. The noise level at which the shift begins is frequency dependent and is consistent with the frequency-dependent bandwidths of auditory nerve fiber tuning curves. The adjustment of the dynamic range shows many similarities to two-tone suppression. Therefore, it is most likely that it is caused by suppression of the response to the BF test tone by energy present in the noise at surrounding frequencies. At high noise levels, the ability of auditory nerve fibers to respond to test tones is limited by the rate response to the noise. As noise level increases, the discharge rate it evokes approaches a fiber's saturation rate and ultimately eliminates the fiber's ability to respond to test tones. Low spontaneous rate fibers, which have been shown to have higher thresholds and wider dynamic range (17,29), are significantly more resistant to saturation by high noise levels. Exposure to broadband noise prior to onset of test tones produces an overall decrement in response rate. This phenomenon is similar to the effects of short-term adaptation (32) and seems to develop independently of the shift of dynamic range. At high noise levels, previous exposure to the noise produces a small dynamic range shift. This effect is similar to that produced by suppression but is smaller. The effect is occluded in continuous noise backgrounds by the adjustment of sensitivity produced by suppression.

Animals↗
PubMed1999

Desynchronizing responses to correlated noise: A mechanism for binaural masking level differences at the inferior colliculus.

We examined the adequacy of decorrelation of the responses to dichotic noise as an explanation for the binaural masking level difference (BMLD). The responses of 48 low-frequency neurons in the inferior colliculus of anesthetized guinea pigs were recorded to binaurally presented noise with various degrees of interaural correlation and to interaurally correlated noise in the presence of 500-Hz tones in either zero or pi interaural phase. In response to fully correlated noise, neurons' responses were modulated with interaural delay, showing quasiperiodic noise delay functions (NDFs) with a central peak and side peaks, separated by intervals roughly equivalent to the period of the neuron's best frequency. For noise with zero interaural correlation (independent noises presented to each ear), neurons were insensitive to the interaural delay. Their NDFs were unmodulated, with the majority showing a level of activity approximately equal to the mean of the peaks and troughs of the NDF obtained with fully correlated noise. Partial decorrelation of the noise resulted in NDFs that were, in general, intermediate between the fully correlated and fully decorrelated noise. Presenting 500-Hz tones simultaneously with fully correlated noise also had the effect of demodulating the NDFs. In the case of tones with zero interaural phase, this demodulation appeared to be a saturation process, raising the discharge at all noise delays to that at the largest peak in the NDF. In the majority of neurons, presenting the tones in pi phase had a similar effect on the NDFs to decorrelating the noise; the response was demodulated toward the mean of the peaks and troughs of the NDF. Thus the effect of added tones on the responses of delay-sensitive inferior colliculus neurons to noise could be accounted for by a desynchronizing effect. This result is entirely consistent with cross-correlation models of the BMLD. However, in some neurons, the effects of an added tone on the NDF appeared more extreme than the effect of decorrelating the noise, suggesting the possibility of additional inhibitory influences.

Acoustic Stimulation↗
PubMedDate not supplied

Qualitative responses of children to environmental noise.

Results from recent quantitative research consistently demonstrate that children are a high risk group, vulnerable to the adverse effects of noise exposure, especially effects on cognitive performance, motivation and annoyance. The aims of the two qualitative studies reported in this paper are to explore children's a) perception of noise exposure; b) perceived risk of and attitudes towards noise pollution; c) coping strategies; and d) the annoyance response. The Millennium Conference Study involved focus group interviews with an international sample (n=36) unselected by exposure. The West London Schools Study involved individual interviews, conducted with a purposively selected sample (n=18) exposed to aircraft noise. The children in the focus groups reported being most affected by neighbours' noise and road traffic noise, whereas children exposed to aircraft noise were most affected by aircraft noise. As expected, the impact of noise pollution on everyday activities (e.g. schoolwork, homework and playing) was larger for the children exposed to high levels of aircraft noise compared with the low noise exposed children and focus group samples. The range of coping strategies that children employed to combat noise exposure in their lives was dependent upon the amount of control they had over the noise source. The emotional response of children describing the annoyance reaction to noise was consistent with adult reactions and it would seem that child noise annoyance is the same construct. Future research should employ qualitative methods to supplement quantitative investigations.

Adolescent↗
PubMedDate not supplied

A descriptive cross-sectional study of annoyance from low frequency noise installations in an urban environment.

In order to improve the living conditions for respondents highly exposed to traffic noise, it has been recommended that one side of the building should face a "quiet side". Quiet may, however, be spoilt by noise from installations such as ventilation and air-conditioning systems. The noises generated by installations of this kind often have a dominant portion of low frequencies (20-200 Hz) and may be a source of great annoyance and sleep disturbance. This paper describes the cross-sectional part of an intended intervention study among residents exposed to traffic noise on one side of the building and to low frequency noise from installations on the other side of the building. A questionnaire masked as a general living environment study was delivered to a randomly selected person in each household. In total 41 respondents answered the questionnaire (71% response rate). Noise from installations was measured indoors in a bedroom facing the courtyard in a selection of apartments and outdoors in the yard. 24h traffic noise outdoor and indoor levels were calculated. The noise levels from installations were slightly above or at the Swedish recommendations for low frequency noise indoors with the window closed and exceeded the recommendations by about 10 dB SPL when the window was slightly opened. The proportion of persons who reported that they were very or extremely annoyed indoors from noise from installations was more than twice as high as for traffic noise. Installation noise also affected respondents' willingness to have their windows open and to sleep with an open window. The high disturbance of installation noises found in this study indicates the importance of also regulating the noise exposure on the "quiet side" of buildings. Further studies will give a better base for the extent of annoyance and acceptable levels of installation noises.

Adult↗
PubMed1984

[Changes of neurotransmitter, lipid peroxide and their metabolic related enzyme activities in the brain of rats exposed to noise and vitamin E].

Effects of noise on locomotor activities were analysed in rat. In addition, changes in lipid peroxide (LPX), their metabolic related enzyme activities, and neurotransmitter in the rat brain due to noise exposure and the effects of vitamin E on the rats were studied. The results obtained were as follows: After white noise exposure of 95 dB (A), the locomotor activities of rat increased. But 3 weeks after noise exposure, the activities began to decrease. LPX and glutathione peroxidase (GSH-Px) activities in hypothalamus and cortex increased at the 14th day after noise exposure or at the 21st day after noise exposure. Superoxide dismutase (SOD) activities increased in hippocampus at the 4th day after noise exposure, and decreased in midbrain and thalamus at the 14th day and the 21th day after noise exposure. Norepinephrine (NE) increased in hypothalamus at the 1st day, the 2nd day and the 7th day after noise exposure, and increased in striatum at the 7th day after noise exposure, in cortex at the 4th day and the 7th day after exposure. At the 14th day after noise exposure, NE decreased in cerebellum, in medulla and pons, in midbrain and thalamus, and in cortex. In cortex NE also decreased at the 21st day after noise exposure. Serotonin increased in hypothalamus and in midbrain and thalamus at the 1st and 4th day after noise exposure, and increased in striatum at the 7th day after noise exposure. Decrease in serotonin was observed in cerebellum at the 14th day after noise exposure. Vitamin E decreased LPX in rat brain and the liver.

Animals↗
PubMed1996

Perception of internally generated noise in hearing amplification.

Noise generated within hearing aid amplifiers is distracting and, if the level is high enough, may interfere with speech communication. For hearing aid specification and fitting, it is useful to know the acoustic levels at which internal amplifier noise becomes audible and at which it becomes objectionable. This paper reports, for eight subjects with moderate hearing losses, the perceived levels at which internal noise became both audible and objectionable, using a test amplifier with no acoustic input. For comparison purposes, five normal-hearing subjects were also tested. Two noise sources were tested. The first was a broadband noise that was shaped only by the receiver, used to simulate output stage noise. The second was a broadband noise shaped by the target National Acoustics Laboratory-Revised (NAL-R) frequency response for each subject's hearing loss, used to simulate input stage noise. For both types of noise, the overall levels and spectra of the noise are reported for each subject. The relationship between 1/3-octave measurements of the noise and the audiometric configuration of the subjects is explored. The internal level at which the noise was perceived to be audible could be related to 1/3-octave measurements of the noise through the audiometric configuration of each subject's hearing loss. The results for the frequency-shaped input-generated noise and for the output-generated noise were similar.

Aged↗
PubMed1987

Effect of electrical stimulation of the crossed olivocochlear bundle on auditory nerve response to tones in noise.

The discharge rates of single auditory-nerve fibers responding to best-frequency (BF) tones of varying level presented simultaneously with fixed level broadband noise were recorded with and without electrical stimulation of the crossed olivocochlear bundle (COCB). In the absence of COCB stimulation, monotonic increases in noise level produce monotonic increases in the low-level noise-driven response rate of auditory nerve fibers. As a result of adaptation, these increases in noise-driven response rate produce monotonic decreases in saturation discharge rate. At high noise levels, these compressive effects may eliminate the differential rate response of auditory nerve fibers to BF tones. COCB stimulation can restore this differential rate response by producing large decreases in noise-driven response rate and large increases in saturation discharge rate. In backgrounds of quiet, COCB stimulation is known to shift the dynamic range of single auditory nerve fiber BF tone responses to higher stimulus levels. In the presence of background noise, COCB stimulation produces upward shift of dynamic range, which decreases with increasing noise level. At high noise levels, COCB-induced decompression of rate-level functions may occur with little or no dynamic range shift. This enables auditory nerve fibers to signal changes in tone level with changes in discharge rate at lower signal-to-noise ratios than would be possible otherwise. Broadband noise also produces upward shift of the dynamic range of single auditory nerve fiber BF tone response. Noise-induced dynamic range shift of BF tone response was measured as a function of noise level with and without COCB stimulation. COCB stimulation elevates the threshold of noise-induced dynamic range shift. This shift is thought to result from two-tone rate suppression. Increases in the threshold of noise-induced shift due to COCB stimulation therefore suggests an interaction between the mechanism of two-tone rate suppression and the mechanism by which COCB stimulation produces dynamic range shift. These interactions were further investigated by recording auditory nerve fiber rate responses to fixed-level BF excitor tones presented simultaneously with fixed-frequency variable level suppressor tones. Rate responses were recorded with and without COCB stimulation. Experimental results were quantified using a phenomenological model of two-tone rate suppression presented by Sachs and Abbas.

Acoustic Stimulation↗
PubMed2000

Acute and chronic endocrine effects of noise: Review of the research conducted at the Institute for Water, Soil and Air Hygiene.

This is a review of the research into endocrine effects of noise since the early 1980s at the Institute for Water, Soil and Air Hygiene. According to our knowledge, no other group has studied systematically the endocrine effects of acute and chronic noise exposure. Mechanisms of acute noise-induced stress reactions as well as long-term increase of stress hormones in animal and persons under chronic noise exposure were studied. Our theoretical background was Henry's psychophysiological stress model with the two reaction alternatives : (i) The fight-flight reaction, characterised by an increase in adrenalin and noradrenaline (ii) The defeat reaction with increased cortisol. Extremely intense acute noise exposure near the threshold of pain caused an increased release of cortisol from the suprarenal cortex but acute noise exposure with levels between 90 and 100 dB(A) caused an increase of catecholamines. Non-habituated noise increased primarily the release of adrenalin from the suprarenal medulla, whereas habituated noise caused a chronic increase of noradrenaline from the sympathetic synapses under longterm noise exposure at work. Environmental noise exposure (Leq >/= 60 dB(A)) caused catecholamine increase if activities such as conversation, concentration, recreation etc were disturbed through noise. In sleeping persons, traffic noise with only Leq >/= 30 dB (A) and Lmax >/= 55 dB(A) caused significant acute increase of cortisol, which developed into chronic increase if the noise exposure was repeated consistently. Parallel to cortisol, chronic noradrenaline increase was also observed. Based upon the empirical results, a noise stress model was developed which is a first step forward in the theoretical understanding of endocrine noise effects.

Journal Article↗
PubMed2003

Cochlear damage caused by continuous and intermittent noise exposure.

We compared the extent of permanent threshold shifts (PTS) and cochlear hair cell damage caused by continuous noise exposure with those caused by intermittent noise exposure. Twenty male pigmented guinea pigs that had been exposed to a one-octave band of noise at 4 kHz for 5 h were placed in four groups: exposure to 115 dB SPL continuous noise (group 1, n=5), 115 dB SPL intermittent noise (group 2, n=5), 125 dB SPL continuous noise (group 3, n=5), and 125 dB SPL intermittent noise (group 4, n=5). PTS at 2, 4, 8, and 16 kHz were assessed by means of auditory brainstem responses measured before noise exposure and 10 days after. The guinea pigs were killed 15 days after noise exposure, and the number of hair cells missing counted in surface preparations of the organs of Corti stained with rhodamine phalloidin. Groups 1 and 3 had significantly greater PTS (P<0.05) at all frequencies than intermittent groups 2 and 4. Group 3 had the greatest PTS at all the frequencies. Intermittent 125 dB noise total energy was greater than that of continuous 115 dB noise, but the latter elicited more PTS than the former. The extent of hair cell damage was comparable to the physiological findings. This indicates that continuous noise causes greater damage to the cochlea than intermittent noise of the same intensity and that, at the intensities tested, damage to the cochlea is not proportional to the total noise energy.

Acoustic Stimulation↗