Industrial Noise Exposure Research Articles

Analysis of Occupational Safety and Health Administration (OSHA) noise standard violations over 50 years: 1972 to 2019

Noise exposure has long been an occupational health concern and has been an important area of focus of the Occupational Safety and Health Administration (OSHA) since its founding. Nevertheless, it remains unclear what effects OSHA's noise standards have had on employer efforts to reduce risks. Consequently, a review of OSHA noise standard violations was performed to clarify the violation trends between 1972 and 2019. Using the OSHA Information System, researchers identified 119 305 violations involving four noise standards between 1972 and 2019: 29 CFR 1910.95, occupational noise exposure in general industry; 1926.52, occupational noise exposure in construction; 1926.101, hearing protection in construction, and 1904.10, recording criteria for cases involving occupational hearing loss. Violation frequencies of noise standard subparagraphs and relationships to factors such as industry differences were analyzed using descriptive statistics and t tests. The most commonly violated noise standard was 1910.95 in manufacturing. Such violations rose between 1972 and 1985 and then declined steadily. Whether in general industry or construction, four noise standards were most-frequently cited: lack of feasible administrative or engineering controls (1910.95[b]and 1926.52[d]) and inadequate hearing conservation program (1910.95[c]and 1926.52[b]). These violations were more highly penalized (mean = $1036.50) than other subparagraph violations (mean = $915.80). Programmed and unprogrammed inspections generated similar violation quantities except between 1980 and 1985, when programmed inspections exhibited a sharp spike in violations. The study identified trends in OSHA noise standard violations and possible explanations for those trends. The study findings can support development of more practical noise-exposure protection policy.

Hygienic Assessment of the Occupational Risk of Noise Effects on the Organ of Hearing in Furniture Makers

Introduction: Industrial noise is one of the leading occupational risk factors in most industries. At the same time, noise has both a specific and non-specific effect on the human body: it is a stressor that disturbs psychological comfort of a person and negatively affects his autonomic nervous system, visual and vestibular apparatus. Occupational hearing loss is, in its turn, one of the most prevalent and socially significant types of occupational pathology, also common for woodworking enterprises. Objectives: Our purpose was to assess health risks of industrial noise exposures in furniture manufacturing workers. Material and methods: We conducted a sanitary and hygienic survey of 172 workplaces of the “Maria” furniture factory, 46 of which were characterized as exceeding the equivalent sound level. We made a comparative assessment of jobs by the level of furniture makers’ exposures to physical factors. The occupational risk assessment of all workplaces was carried out in accordance with the “Guidelines for Occupational Health Risk Assessment. Organizational and Methodological Aspects, Principles and Criteria R 2.2.1766–03” (2003). Results. We established that the noisiest working conditions were at the sites of woodworking machines, especially near the working engine of the aspiration system, and we classified them as workplaces of the 3rd degree of hazard class 3, which indicates a high (intolerable) risk requiring urgent risk abatement measures. Conclusions: The results of analyzing health effects of noise exposures in the furniture makers proved that 46 out of 172 surveyed workplaces posed risks to workers’ health and could be attributed to category 1A of the proven occupational risk according to R 2.2.1766–03.

Research and increase of efficiency of noise load monitoring and minimization of occupational risks in conditions of industrial noise exposure

The technical means development modern level allows to implement large-scale and continuous approaches to the detection of noise levels affecting the worker.However, IT-technologies of collecting data on working area and residential area noise characteristics, on which basis it is possible to carry out risks prognostic assessments of noise exposure to humans without limitation to the working conditions, industrial control and environmental monitoring special assessment results, are underdeveloped.The research purpose is to assess the collecting data possibility on the noise levels distribution within the working area, residential area and the high levels occupational risk areas determining possibility by the industrial noise factor by means of smart phones. A method was developed for collecting data on the noise levels distribution within the working area, residential area, on which basis a software product for recording and processing data on the noisenature was developed. The industrial noise levelsspatial distribution constructing possibility on the construction site in real time as a result of using a special software product was shown. The metadata continuous collection on the noise nature makes it possible to clarify the occupational risks levels associated with noise exposure and to select measures to manage these risks.

The effects of industrial noise exposure on lipid peroxidation and antioxidant enzymes among workers.

The aim of this study was to measure individual exposure to noise and its effect on the levels of lipid peroxidation and enzymatic antioxidant defense. In this cross-sectional study, 94 male workers working in a food factory in Shahroud, Iran, were selected as the case group and 112 people were also included as the control group. The level of exposure to noise was measured using a dosimeter and the equivalent level was calculated. The levels of malondialdehyde (MDA), catalase (Cat), superoxide dismutase (SOD), and Total AntioxidantCapacity (TAC) were measured in the serum samples of all participants. Independent t test, one-way ANOVA, and multivariate linear regression were used to analyze the data. The levels of MDA, Cat, and TAC were significantly higher in staff exposed to noise than in the controls. The starch and warehouse units' staff were exposed to the highest (99.3 ± 3.23dB) and lowest (77.1 ± 9.68dB) mean levels of sound pressure. Based on the linear regression model, noise exposure level was the most important predictor variable for levels of MDA (β = 0.48, CI 95% = 0.04-0.93), Cat (β = 0.43, CI 95% = 0.05-0.83), and TAC (β = 0.11, CI 95% = 0.06-0.16). Noise exposure increases the production of free radicals. As exposure rate increases, the levels of MDA, Cat, and TAC enzymes increase as well.

Chronic occupational noise exposure: Effects on DNA damage, blood pressure, and serum biochemistry

Noise levels experienced by industrial workers may cause both auditory and non-auditory harmful effects. We have studied the effects of chronic industrial noise exposure on DNA damage, blood pressure, and serum biochemistry in factory workers. Male workers (109 individuals) in three parts of a food factory in Shahroud, Iran were enrolled as the exposed group and male office workers (123 individuals) were the unexposed control group. Noise exposure was measured (dosimetry) and the comet assay was used to evaluate DNA damage in peripheral blood mononuclear cells. Glutathione peroxidase (GPx) and ceruloplasmin (Cp) levels were measured in serum samples. GPx levels, systolic and diastolic blood pressure, and DNA damage were significantly higher in the exposed group than in the control group. However, ceruloplasmin levels were not significantly different. Based on multivariate linear regression analysis, noise exposure was the most important predictor of GPx levels, systolic and diastolic blood pressure, and DNA damage.

Development of an automatic classifier for the prediction of hearing impairment from industrial noise exposure.

The ISO-1999 [(2013). International Organization for Standardization, Geneva, Switzerland] standard is the most commonly used approach for estimating noise-induced hearing trauma. However, its insensitivity to noise characteristics limits its practical application. In this study, an automatic classification method using the support vector machine (SVM) was developed to predict hearing impairment in workers exposed to both Gaussian (G) and non-Gaussian (non-G) industrial noises. A recently collected human database (N = 2,110) from industrial workers in China was used in the present study. A statistical metric, kurtosis, was used to characterize the industrial noise. In addition to using all the data as one group, the data were also broken down into the following four subgroups based on the level of kurtosis: G/quasi-G, low-kurtosis, middle-kurtosis, and high-kurtosis groups. The performance of the ISO-1999 and the SVM models was compared over these five groups. The results showed that: (1) The performance of the SVM model significantly outperformed the ISO-1999 model in all five groups. (2) The ISO-1999 model could not properly predict hearing impairment for the high-kurtosis group. Moreover, the ISO-1999 model is likely to underestimate hearing impairment caused by both G and non-G noise exposures. (3) The SVM model is a potential tool to predict hearing impairment caused by diverse noise exposures.

HYGIENIC ASSESSMENT OF HEALTH RISK FACTORS FOR POPULATION OF MEGAPOLISIS’SATELLITE TOWNS BY THE EXAMPLE OF LENINGRAD REGION

Minor towns with population size of 50-100 thousand people are much rarely studied in regards of the ecological-hygienic assessment of human environment, in spite of the fact that they are characterized by specific ecological problems. The objective of the study was the hygienic assessment of the impact of urban environment on population health status in Tikhvin and Gatchina towns of the Leningrad region. Morbidity rate in the population of Tikhvin and Gatchina in 2005-2015, atmospheric emissions of industrial enterprises, findings on monitoring for both atmospheric air pollution and centralized drinking water supply, as well as motor transport noise levels were studied. Population health risk stipulated by industrial emissions and noise exposure was calculated. Statistical data treatment with correlation analysis of the relationship between environmental pollution indices and population morbidity was carried out. The study revealed increased atmospheric air pollutant concentrations in Gatchina, which might be connected with motor transport effect. Acute non-carcinogenic risk levels resulting from air pollutants are on the borderline of the admissible level, while in Tikhvin town those values are significantly lower. Estimated concentrations of atmospheric pollutants produced by industrial emissions are by 1.5-2 times lower than the actual levels shown by monitoring. Noise levels and predicted health risks in Gatchina are on the borderline of the admissible level, while in Tikhvin they are significantly reduced. The statistically significant gain in the general primary morbidity rate indices due to respiratory diseases in Gatchina town, correlated with atmospheric air pollution, was revealed. Our study showed that despite the presence of large industrial enterprises in studied towns, motor transport proved to be the key factor that forms air pollution and noise load, more typical of large cities.

CLINICAL AND AUDIOLOGICAL VALUES IN THE EARLY DIAGNOSIS OF HEARING IMPAIRMENTS AND RISK GROUPS AMONG SHIP REPAIR WORKERS

Introduction: The hazardous effect of industrial noise exposure on ship repair workers has been highlighted in a number of studies. However, no data are currently available for studying the effect of noise exposure on the auditory system and general health of ship repair workers. The aim: The study is focused on the early diagnosis of hearing impairments and identifying risk groups among the workers. Materials and methods: It was examined two groups of workers of approximately the same age and length of employment. The Group 1 included workers from the Azov Shiprepair Yard (Mariupol city, Ukraine) who were exposed to workplace noise impact of less than 80 dBA threshold level, the workplace noise level in the Group 2 was above 80 dBA. Audiometric testing was conducted in a sound-treated room using the MA 31 clinical audiometer (Germany). Results: Our findings indicate that all the noise-exposed groups of ship repair workers should be conducted audiometric testing. The hearing levels at the audiometric test frequencies of 4, 6 and 8 kHz, as well as differential thresholds at the audiometric test frequencies of 4 kHz by the Luscher-Zwislocki method should be taken into account. Such complaints as increased annoyance, sleep disorder, tinnitus aurium, hypertension should be considered as most hazardous. Conclusions: We recommend that the ship repair workers undergo routine medical check-ups and systematic prophylactic observation. All these preventive measures will contribute to the early detection of hearing impairments, thereby timely preventing the development and progression of occupational sensorineural hearing loss.

The effect of industrial noise exposure on attention, reaction time, and memory

Noise, a common physical hazard in many workplaces, may affect different aspects of human cognitive function. In this study, the effect of exposure to noise on some aspects of cognitive function was assessed in industrial workers. This was a cross-sectional study on 84 individuals exposed to noise level higher than 85dBA in a metal industry (noise group), comparing a group of workers from the same industry (n = 80) with exposure to noise level lower than 80dBA (control group). The individuals in the noise group were classified as well according to noise intensity into: high exposure (90dBA and higher) and low exposure (between 85 and 90dBA). Selective attention score, divided attention score, selective response time, divided response time, and memory scale were measured before and after work shift. Data were analyzed by SPSS (Ver. 16) using Kolmogorov-Smirnov test, paired t test, Student's t test and Mann-Whitney U test were used to compare mean difference of the variables between two groups. p < 0.05 was considered as significant. All measured cognitive functions were significantly changed after work shift in the noise group and the difference was statistically significant between noise and control group. Exposure to higher noise intensity caused more change in cognitive function. Exposure to noise higher than 85dBA affects some aspects of cognitive function (reaction time, attention and memory).

An assessment of the permissible exposure limit for industrial complex noise exposure

An 8-hr time-weighted average exposure of 85 dBA was adopted as the permissible exposure limit (PEL) by most current international standards for exposure to noise. Using the definition of material hearing impairment (MHI) as the average of hearing threshold levels for both ears exceeded 25 dB at 1, 2, 3, and 4 kHz, NIOSH estimated that the excess risk was 8% for workers exposed to an average noise level of 85 dBA over a 40-year working lifetime. However, this 85 dBA PEL was based on the data that was acquired from workers exposed to steady state (Gaussian) noises. In this study a database of 648 workers (age 36.9 yrs + /- 7.8, exposure duration 12.8 yrs + /- 8.0) exposed to non-Gaussian noises were used to assess the 85 dBA PEL. Among them 222 subjects exposed to noise at level of 80-84 dBA and 426 subjects at 85-89 dBA. Although the average duration of exposure from non-Gaussian database was much less than 40 years, the prevalence of MHI was 16.7% at level of 80-84 dBA and 31.5% at level of 84-89 dBA. The results show that 85 dBA PEL may not well protect hearing for workers exposed to non-Gaussian complex noise exposure.

Occupational Noise Exposure to Masonry Saw Cutting Materials

Despite a widespread recognition of the impacts of noise on hearing and other aspects of health, noise exposure in industry remains a significant problem, especially in the construction industry where noise exposure levels of workers are high, especially due to the use of manual equipment and machines used in constructions sites. The masonry saw is a portable power tool widely used in construction in small cuts and finishes for floors, tiles, bricks and woods. It stands out for versatility, lightness and its ergonomics. As part of efforts to identify sources of noise pollution from construction, a noise exposure is developed here for the occupational assessment from masonry saws, which are electric cutters that are commonly used in the industry. Different building materials commonly used in Brazil are used with the masonry saw in their conditions of loading and operation. The proposed methodology evaluates the noise generated during cutting with equipment in accordance with ISO 3744:2010 which specifies methods of measuring sound pressure levels on a surface enveloping the noise source in an environment that approximates an acoustic free field over a reflecting plane and the standard ISO 9612:2009 which specifies an engineering method for measuring workers' exposure to noise in a working environment and calculating the noise exposure level. The cutting of different building materials was louder than the disengaged saw. The highest observed sound pressure level was 106.9Â dB(A) at operator ear and 99.1 dB(A) at 2 meters from the source. The smallest difference observed between the cutting and disengaged saw was 7.8Â dB(A). Noise generated by the saw was quantitatively assessed. An occupational analysis illustrates that the sound levels generated in operations exceeded the tolerances permitted without protection. The subject is relevant to anticipating risks in the workplace in activities with the masonry saw cutting various building materials. Noise excess removal in the workplace is not just a legal responsibility of the companies, as it is also involved with the market interests of an organization. The safer and healthier a workplace is, the fewer probabilities of absenteeism, accidents and low performance, and consequently, cost savings will be achieved. This study also contributes to the analysis of occupational noise generation, considering the difficulties in obtaining previously reported values of the sound spectrum of masonry saws.

What can 35 years and over 700,000 measurements tell us about noise exposure in the mining industry?

Objective: To analyse over 700,000 cross-sectional measurements from the Mine Safety and Health Administration (MHSA) and develop statistical models to predict noise exposure for a worker. Design: Descriptive statistics were used to summarise the data. Two linear regression models were used to predict noise exposure based on MSHA-permissible exposure limit (PEL) and action level (AL), respectively. Twofold cross validation was used to compare the exposure estimates from the models to actual measurement. The mean difference and t-statistic was calculated for each job title to determine whether the model predictions were significantly different from the actual data. Study sample: Measurements were acquired from MSHA through a Freedom of Information Act request. Results: From 1979 to 2014, noise exposure has decreased. Measurements taken before the implementation of MSHA’s revised noise regulation in 2000 were on average 4.5 dBA higher than after the law was implemented. Both models produced exposure predictions that were less than 1 dBA different than the holdout data. Conclusion: Overall noise levels in mines have been decreasing. However, this decrease has not been uniform across all mining sectors. The exposure predictions from the model will be useful to help predict hearing loss in workers in the mining industry.

Asymmetrical Hearing Loss in Cases of Industrial Noise Exposure: A Systematic Review of the Literature.

Asymmetrical hearing thresholds are common in people claiming compensation for noise-induced hearing loss (NIHL). When present and otherwise unexplained, there is some controversy as to whether such asymmetry can be attributed to occupational noise exposure. In this review, our main objectives were to collate the overall prevalence of this finding in subjects with NIHL, and further, to provide a balanced argument regarding causality. MEDLINE, CINAHL, EMBASE, Cochrane, Google Scholar. No date or language restrictions. A systematic review of the literature was performed and data on noise exposure, pure tone audiometry, and lateralized hearing outcomes were reviewed. Newcastle-Ottawa (N-O) criteria were employed to assess quality of studies where applicable. N/A CONCLUSION:: Six studies met the inclusion criteria giving a total of 4,735 individual cases with NIHL. Asymmetrical hearing loss accounted for between 2.4% and 22.6% of NIHL cases (L-R difference >15 dB for any frequency 0.5-8 kHz). However, the overwhelming majority of subjects in this review have symmetrical hearing loss when adjusted for other significant variables, e.g., age, sex, and binaural hearing deterioration. Subjects considered for noise exposure remuneration were men (94.3% SE ± 2.7), aged 52.9 years (inter-quartile range, 46.1-58.4), and from a broad range of industrial backgrounds. Future research will be needed to establish the influence of other factors such as smoking status, exposure to chemical agents, specific drugs, or genetic predisposition.

Noise-Induced Stress Assessment by Salivary Cortisol Measurement

Background: Noise exposure is known as a risk factor for hearing loss and one of its effects is noise-induced stress. Cortisol as a stress hormone is used in noise-induced stress assessments. Objectives: The aim of this study was to measure and compare saliva cortisol concentrations in the morning and evening in normal work day and rest day in both case and control groups and to assess the association between industrial noise exposure and salivary cortisol concentrations in the two groups. Patients and Methods: This study included 200 male participants (100 industrial workers and 100 office employees). Morning and evening saliva samples were collected at 7 AM and 4 PM respectively. Noise exposure levels were assessed by sound level meter and noise dosimeter. All measurements were performed in two days; rest day and then in working day. Descriptive statistics, paired and independent sample t-test and regression analysis were used with α = 0.05. Results: There was no significant difference between morning salivary cortisol concentrations in the two groups on the rest and work days. A significant higher level was observed comparing evening cortisol concentrations in work day with rest day in worker group, but this was not observed in the control group. The evening cortisol in the working day in worker group was significantly higher than control group. Conclusions: Our study revealed that industrial noise exposure with levels higher than 80 dBA has a significant effect on salivary cortisol elevation.

Noise Pollution in Metalwork and Woodwork Industries in the Kingdom of Saudi Arabia

This study was conducted in metalwork and woodwork industries in Jeddah Industrial Estate. The purpose of this study was to assess the magnitude of industrial noise exposure and to propose remedial actions. Noise was measured at different times of a day in 28 randomly selected factories and workshops. Results indicated that noise levels varied according to the type and size of a factory, and the type and number of machines used. Mean noise levels in metalwork factories were higher than those in woodwork factories. The highest noise levels were observed while manufacturing cans and forming steel reinforcement for concrete, where noise levels exceed 90 dB(A). All mean noise levels in all studied metalwork factories and in 50% of studied woodwork industries were higher than the standard level of 85 dB(A).

The value of a kurtosis metric in estimating the hazard to hearing of complex industrial noise exposures

A series of Gaussian and non-Gaussian equal energy noise exposures were designed with the objective of establishing the extent to which the kurtosis statistic could be used to grade the severity of noise trauma produced by the exposures. Here, 225 chinchillas distributed in 29 groups, with 6 to 8 animals per group, were exposed at 97 dB SPL. The equal energy exposures were presented either continuously for 5 d or on an interrupted schedule for 19 d. The non-Gaussian noises all differed in the level of the kurtosis statistic or in the temporal structure of the noise, where the latter was defined by different peak, interval, and duration histograms of the impact noise transients embedded in the noise signal. Noise-induced trauma was estimated from auditory evoked potential hearing thresholds and surface preparation histology that quantified sensory cell loss. Results indicated that the equal energy hypothesis is a valid unifying principle for estimating the consequences of an exposure if and only if the equivalent energy exposures had the same kurtosis. Furthermore, for the same level of kurtosis the detailed temporal structure of an exposure does not have a strong effect on trauma.

Effect of cigarette smoking on noise-induced hearing loss in workers exposed to occupational noise in China

Excessive exposure to high noise level environments has the potential to cause noise-induced hearing loss (NIHL), and cigarette smoking has also been shown to have a potential adverse effect on hearing. The aim of this study was to determine whether smoking interacts with noise in the development of hearing loss, and if so, the extent of the contribution from smoking on NIHL. A cross-sectional study was designed to assess the effect of smoking on NIHL in 517 male workers (non-smokers: N = 199; smokers: N = 318) exposed to a high-level industrial noise environment in China. Shift-long temporal waveforms of the noise that workers were exposed to for evaluation of noise exposures, and audiometric threshold measures were obtained on all selected subjects. The subjects used hearing protection devices only within the last 1-2 years. The results suggest that smoking has an adverse effect on NIHL in workers exposed to high level industrial noise, i.e., the median high frequency hearing thresholds were significantly greater in smokers than non-smokers exposed to noise for more than 10 years. This effect was observed at 4.0 and 6.0 kHz. Smoking did not have an adverse effect on NIHL in workers exposed to noise less than 10 years. Multivariate regression analysis revealed that the odds ratio (OR) for high frequency hearing loss (i.e., hearing threshold greater than 40 dB at 4.0 kHz) were 1.94 for smokers in comparison to non-smokers. The results suggest that: (1) smokers have a higher risk of developing high frequency hearing loss than non-smokers with a similar occupational noise exposure, and (2) the interaction between cigarette smoking and high-level noise exposure may be additive. There is a need to develop and analyze a larger database of workers with well-documented exposures and smoking histories for better understanding of the effect of smoking on NIHL incurred from high-level industrial noise exposures. A better understanding of the role of smoking may lead to its incorporation into hearing risk assessment for noise exposure.

Industrial noise exposure and salivary cortisol in blue collar industrial workers

Measuring non-auditory effects of noise such as stress-inducing ones have become of interest recently. Salivary cortisol has become a popular measure in stress research. So, assessing noise-induced stress via saliva cortisol evaluation can present a bright future in non-invasive exposure assessment methods. This study had 3 goals: (1) Assess and compare saliva cortisol concentrations in the morning and evening in normal work day and leisure day in industrial workers, (2) assess the relationship between industrial noise exposure and salivary cortisol concentrations, and (3) assess the possibility of using salivary cortisol as a possible marker of noise-induced stress. This study included 80 male participants working in 4 different parts (painting, assembling lines, casting, and packaging) of a household manufacturing company. Morning and evening saliva samples were collected at 7.00 am and 4.00 pm, respectively. Noise exposure levels were assessed by sound level meter and noise dosimeter. All measurements occurred in two days: One in leisure day and other in working day. Descriptive statistics, paired sample t-test, and regression analysis were used as statistical tools of this study with P < 0.05. On the leisure day, morning salivary cortisol (geometric mean [GM], 15.0; 95% CI, 12.0 to 19.0 nmol/L) was significantly higher than evening cortisol (GM, 5.2; 95% CI, 4.2 to 6.3 nmol/L) (P < 0.05). Also, on the working day, morning salivary cortisol (GM, 14.0; 95% CI, 11.25 to 18.0 nmol/L) was significantly higher than evening cortisol (GM, 8.0; 95% CI, 6.5 to 10.0 nmol/L) (P < 0.05). No significant difference was obtained for morning cortisol levels between leisure day and working day samples (P = 0.117). But, for evening cortisol concentrations, a strong significant difference was noted leisure day and working day (P < 0.001). The evening cortisol in the working day correlated significantly with noise exposure > 80 dBA. Our study revealed that industrial noise, with levels > 80 dBA, has a significant effect on salivary cortisol elevation.

The use of the kurtosis metric in the evaluation of occupational hearing loss in workers in China: Implications for hearing risk assessment

This study examined: (1) the value of using the statistical metric, kurtosis [β(t)], along with an energy metric to determine the hazard to hearing from high level industrial noise environments, and (2) the accuracy of the International Standard Organization (ISO-1999:1990) model for median noise-induced permanent threshold shift (NIPTS) estimates with actual recent epidemiological data obtained on 240 highly screened workers exposed to high-level industrial noise in China. A cross-sectional approach was used in this study. Shift-long temporal waveforms of the noise that workers were exposed to for evaluation of noise exposures and audiometric threshold measures were obtained on all selected subjects. The subjects were exposed to only one occupational noise exposure without the use of hearing protection devices. The results suggest that: (1) the kurtosis metric is an important variable in determining the hazards to hearing posed by a high-level industrial noise environment for hearing conservation purposes, i.e., the kurtosis differentiated between the hazardous effects produced by Gaussian and non-Gaussian noise environments, (2) the ISO-1999 predictive model does not accurately estimate the degree of median NIPTS incurred to high level kurtosis industrial noise, and (3) the inherent large variability in NIPTS among subjects emphasize the need to develop and analyze a larger database of workers with well-documented exposures to better understand the effect of kurtosis on NIPTS incurred from high level industrial noise exposures. A better understanding of the role of the kurtosis metric may lead to its incorporation into a new generation of more predictive hearing risk assessment for occupational noise exposure.

The use of the kurtosis metric in the evaluation of industrial noise exposures.

Data from a chinchilla model of noise-induced hearing loss will demonstrate the value of using the statistical metric, kurtosis, along with an energy metric to evaluate complex industrial noise environments for hearing conservation purposes. Complex noises are non-Gaussian noises consisting of a combination of Gaussian continuous noise and noise transients, either impacts or noise bursts. Chinchillas were exposed to an interrupted and intermittent 97-dB sound pressure level broadband, non-Gaussian noise for 8 h/day for 3 weeks. The experimental noises were designed to model an industrial exposure. Groups of animals with 8/group were exposed to 1 of 12 different complex noise environments having a fixed spectrum and energy but with different temporal structures achieved by varying the transient peak, interval, and duration histograms. Preliminary results show that (1) hearing and sensory cell loss increase with increasing kurtosis despite a fixed energy; (2) at a given value of kurtosis, hearing trauma is invariant with respect to changes in the temporal structure of the noise exposure. A metric such as the kurtosis may be a necessary adjunct to spectral energy in the evaluation of industrial noise exposures for the purposes of hearing conservation. [Research supported by NIOSH Grant R01 OH 002317.]