effect of noise on human performance: a clinical trial

Noise is defined as unwanted or meaningless sound that apart from auditory adverse health effects may distract attention from cues that are important for task performance. Human performance is influenced by many job-related factors and workplace conditions including noise level. To study the effect of noise on human performance. The participants included 40 healthy male university students. The experimental design consisted of 3 [sound pressure level] x 3 [noise schedule] x 2 [noise type] factors. To investigate occupational skill performance, some specific test batteries were used: 1] steadiness test, 2] Minnesota manual dexterity test, 3] hand tool dexterity test, and 4] two-arm coordination test. Time duration of test completion was measured as speed response; to determine error response, the time taken during committing an error by participants while performing a task was measured. Speed response obtained from the 4 tests in combined conditions of noise schedule, harmonic index, and sound pressure level was highest for [intermittent, treble, 95 dB], [continuous, treble, 95 dB], [continuous, treble, 85 dB] and [intermittent, treble, 95 dB], respectively. Treble noise was found significant in reducing human performance; also, intermittent noise, especially at high pressure levels, was responsible for worsening environmental conditions during performing a task

[Introducing the standard and chart to measure and control the motorcycle noise level]

Sound of motorcycles plays an important role in noise pollution in big cities. This is due to the lack of national law or standards to control the noise of domestic and also imported motorcycles. This study tries to introduce a practical limit value in different stage of motorcycle life cycle by assessing their noise pollution. First the motorcycles noise standards at different countries were studied and they were compared with the results from noise level of 622 motorcycles in 3 different groups. The sample volume in each group corresponds to the amount of their annual production rate. Then using statistical tests, a limit was determined in which 90% of the domestic motorcycles can be covered. The limit is proposed as the standard for domestic motorcycle noise. The limit for motorcycles of groups 1, 2 and 3were 84, 86 and 87 dB [A], respectively in the TA stage. For the COP stage [Conformity of Production], the limit increases according to certain formula. In the end, a flowchart was proposed as a standard method for measuring the sound of motorcycles in the TA and COP stages was proposed. Noise level of the domestic motorcycles is at least 9 dB [A] higher than the noise limit value of European motorcycle. If European limit value is considered for producing the national motorcycle, 90% of them will get out of production cycle and this would not be practical

[Evaluation of noise pollution and possibility of its control in a petrochemical plant]

This study was conducted to assess noise pollution in one of the petrochemical complex and take practical measures to reduce it. The companyis located in site 4 of Mahshahr Special Economic Zone. In the first phase of the research, environmental noise was measured to determine the noise levels in the different sections of the plant and also identify the main sound sources.Then, using the basic acoustic knowledge, a formula has been proposed as an index of noise control priority to select one section of the plant as the first priority for controlling noise. The main sound source of the selected section was known by referring to noise maps and contours and finally its acoustic properties were analyzed. The results showed that safety; caution and danger areas of the plant under study were 16.7%, 74.5% and 8.8% respectively and a major part of the danger zone [about 54%] was related to unit Air. Noise level in 24 percent of the caution zone ranged from 80 to 85 dBA and also it was above 90 dBA in 33.4% of danger areas. Compression section which was located in unit Air was known as first priority based on Noise Control Priority Index. Dryer machines were the main sound source in this section

Extremely low frequency magnetic flux densities measured near hospital in Tehran

The ever increasing rate of power consumption has led to an increase in public exposure to extremely low frequency magnetic fields [ELF-MFs] and brought severe concerns about their health effects. Considering previous studies and the facts about potential health effects of these fields, the present study aimed to evaluate the ELF-MF flux densities from power distribution lines near hospitals in Tehran. ELF-MF measurements were performed according to IEEE standard procedures-Std 644-1994 near the hospitals entrances using HI-3604 Power Frequency Field Strength Measurement System during three different time periods [i.e. 12-3 AM, 9-12 AM, 6-9 PM]. The results were analyzed using One-Way ANOVA Test. Mean, minimum, and maximum values of ELF-MF flux densities were 0.165 +/- 0.08 microT, 0.018 microT, 0.52 microT, respectively. There were no statistically significant differences in ELF-MF flux densities neither among different hospital groups nor among different time periods. The ELF-MF flux densities from power distribution lines around Tehran hospitals were much less than the standards values, implying that it can be considered only in epidemiological studies. In fact, in the case of powerful sources, magnetic field intensity is declined rapidly by distance and is limited to a few meters around the sources. This subject is considered as one of the main reasons for contradictory results in previous studies. Results of the present study can be used as a part of hospital patients' exposure to quantify the total exposure levels of patients as a critical and sensitive group in Tehran hospitals

Assessment of noise induced psychological stresses on printery workers

The purpose of this study was to assess the relationship between psychological stresses and noise stresses on printery workers in Tehran, Iran. Hence, 267 workers were randomly selected. The Leq and Lmax were measured and the psychological stresses such as depression, anxiety, aggression and job satisfaction were also studied by the relevant questionnaires. The data were statistically analyzed by Pearson correlation test. The results demonstrated that there was no significant statistical relationship between noise and psychological stresses. In addition, by using Spearman regression method, the influence of variables such as age, gender and job history on psychological stresses caused by Leq and Lmax was studied and the results only revealed that the aggression caused by Leq increased in young personnel [P=0.02] as well as, anxiety caused by Lmax increased accompanied by increasing the job history and age of the workers [P=0.002 and P=0.007]. Therefore, more variables must be taken into consideration to judge about noise induced psychological stresses in workplaces

[Performance of PRD welled surfaces in T shape noise barriers for controlling environmental noise]

There is a considerable notice in the use of noise barriers in recent years. Noise barriers as a control noise solution can increase the insertion loss to protect receivers. This paper presents the results of an investigation about the acoustic efficiency of primitive root sequence diffuser [PRD] on environmental single T-shape barrier. A 2D boundary element method [BEM] is used to predict the insertion loss of the tested barriers. The results of rigid and with quadratic residue diffuser [QRD] coverage are also predicted for comparison. It is found that decreasing the design frequency of PRD shifts the frequency effects towards lower frequencies, and therefore the overall A-weighted insertion loss is improved. It is also found that using wire mesh with reasonably efficient resistivity on the top surface of PRD improves the efficiency of the reactive barriers; however utilizing wire meshes with flow resistivity higher than specific acoustic impedance of air on the PRD top of a diffuser barrier significantly reduces the performance of the barrier within the frequency bandwidth of the diffuser. The performance of PRD covered T-shape barrier at 200 Hz was found to be higher than that of its equivalent QRD barriers in both the far field and areas close to the ground. The amount of improvement compared made by PRD barrier compared with its equivalent rigid barrier at far field is about 2 to 3 dB, while this improvement relative to barrier model "QR4" can reach up to 4- 6 dB. Employing PRD on the top surface of T-shape barrier is found to improve the performance of barriers compared with using rigid and QRD coverage at the examined receiver locations

Factors affecting road traffic noise annoyance among white-collar employees working in Tehran

The effect of personal and attitudinal factors, noise level, hearing status and psychological traits on traffic-related noise annoyance among white-collar employees working in Tehran has been carefully analyzed. This survey has been conducted by interviewing 495 citizens working in non-manufacturing industries in Tehran, using questionnaires, Weinstein noise sensitivity scale, Beck's depression, Buss and perry's aggression, Zung's anxiety, job satisfaction and Eysenc's personality inventory. These citizens were office workers or store employees. Noise annoyance was determined both by numerical-based questionnaire criterion and by verbal index. Personal information, attitudinal factors and hearing conditions were determined using a general questionnaire. The amount of workplace noise the participants were exposed to was directly measured at their workplaces. It was revealed that among personal factors, age [p=0.030], marital status [p=0.004], residential period [p=0.001] and wealth [p=0.04] were related to noise annoyance. Attitudinal factors including sensitivity to noise [p=0.001], individual's opinion on the need to control the noise [p=0.000] and individuals' assessment of the amount of the workplace ambient noise [p= 0.000] were found to have relationship with noise annoyance. No meaningful relationship was seen between the equivalent noise level [p=0.879] and statistical noise level of L90 [p=0.909]. The present study revealed that among all effective factors involved in noise annoyance, attitudinal factors had the most significant role in this regard

compact model for predicting road traffic noise

Noise is one of the most important sources of pollution in the metropolitan areas. The recognition of road traffic noise as one of the main sources of environmental pollution has led to develop models that enable us to predict noise level from fundamental variables. Traffic noise prediction models are required as aids in the design of roads and sometimes in the assessment of existing, or envisaged changes in, traffic noise conditions. The purpose of this study was to design a prediction road traffic noise model from traffic variables and conditions of transportation in Iran. This paper is the result of a research conducted in the city of Hamadan with the ultimate objective of setting up a traffic noise model based on the traffic conditions of Iranian cities. Noise levels and other variables have been measured in 282 samples to develop a statistical regression model based on A-weighted equivalent noise level for Iranian road condition. The results revealed that the average L[Acq] in all stations was 69.04 +/- 4.25 dB[A], the average speed of vehicles was 44.57 +/- 11.46 km/h and average traffic load was 1231.9 +/- 910.2 V/h. The developed model has seven explanatory entrance variables in order to achieve a high regression coefficient [R[2]=0.901]. Comparing means of predicted and measuring equivalent sound pressure level [L[Acq]] showed small difference less than -0.42 dB[A] and -0.77 dB[A] for Tehran and Hamadan cities, respectively. The suggested road traffic noise model can be effectively used as a decision support tool for predicting equivalent sound pressure level index in the cities of Iran

Contribution of quadratic residue diffusers to efficiency of tilted profile parallel highway noise barriers

This paper presents the results of an investigation on the acoustic performance of tilted profile parallel barriers with quadratic residue diffuser [QRD] tops and faces. A 2D boundary element method [BEM] is used to predict the barrier insertion loss. The results of rigid and with absorptive coverage are also calculated for comparisons. Using QRD on the top surface and faces of all tilted profile parallel barrier models introduced here is found to improve the efficiency of barriers compared with rigid equivalent parallel barrier at the examined receiver positions. Applying a QRD with frequency design of 400 Hz on 5 degrees tilted parallel barrier improves the overall performance of its equivalent rigid barrier by 1.8 dB[A]. Increase in the treated surfaces with reactive elements shifts the effective performance toward lower frequencies. It is found that by tilting the barriers from 0 to 10 degrees in parallel set up, the degradation effects in parallel barriers is reduced but the absorption effect of fibrous materials and also diffusivity of the quadratic residue diffuser is reduced significantly. In this case all the designed barriers have better performance with 10 degrees tilting in parallel set up. The most economic traffic noise parallel barrier which produces significantly high performance, is achieved by covering the top surface of the barrier closed to the receiver by just a QRD with frequency design of 400 Hz and tilting angle of 10 degrees. The average A-weighted insertion loss in this barrier is predicted to be 16.3 dB [A]

[Occupational noise exposure evaluation in drivers of bus transportation of Tehran City]

Noise in large cities is considered by the World Health Organization to be the third most hazardous type of pollution. Buses are an interesting object of study in the theme of noise pollution. They are at the same time a source of urban environmental [traffic] noise and occupational noise exposure source for drivers. The object of this study is Occupational noise exposure evaluation in drivers of bus transportation of Tehran city. Noise levels in 90 buses were sampled in three separate sub-sample including [1]30 Ikaroos buses [2]30 Man buses [3]30 Shahab buses, which were selected by simple random sampling. Noise exposure level was normalized to a nominal 8-h working day [LEX, 8h]. Simultaneous Octave Frequency Analysis were measured and sound intensity level [SIL] for bus drivers were calculated. Results, which are obtained from separate buses were compared together and too with standard levels. the normalized noise exposure levels [LEX, 8h] in Ikaroos bus drivers[82dB A] were higher than that of in Man bus drivers [77/6dB A] and this Values were higher than that of in Shahab bus drivers[75dB A].SIL values for Ikaroos bus drivers were higher than other that of other bus drivers. Results obtained of Frequency Analysis showed that age of buses in mid frequencies ws a meaningful on noise increase. Results showed that type and age of buses were effective factors in drivers' noise exposure levels [LEX, 8h], which was consistent with previous studies in this field

[Noise induced hearing loss in Zanjan dentists]

There are many chemical, physical and biological hazards which are threatening the dentists' health. In this study we assessed the effect of noise on Zanjan dentists hearing loss as one of the dentistry physical hazards. This cross sectional study was performed on all zanjan dentists in 2006-7. All dentists were examined by audiometer [CA76 and AC40]. The exclusion criteria were hearing accidents and diseases. The data were statistically analyzed by T test [alpha =0.05]. Noise induced hearing loss was observed in most cases. Left ear was more susceptible than right ear. The men had more hearing loss than the women. [P value on Freq 8000[HZ]= 0.001]. Deutists with seniority of 10 years and over had more hearing loss than who have seniority of less than 10 years [P value on Freq 8000[HZ]= 0.004]. The dentists in the age of 40 years old and over had more hearing loss than the ages below 40 year [P value on freq 8000 HZ in the left ear = 0.007, in the right ear = 0.019]. Left ear had more hearing loss than right ear. Noise induced hearing loss in extra-speech frequencies was more than speech frequencies. The noise frequency of dental equipments was between 70 to 105 db. Noise induced hearing loss which has threatened the dentists' health is an incurable problem that must be prevented. Regular audiometric exam, use of hearing protection devices and also the occupational health regulations must be implemented for dentists in order to reduce the risk of noise induced hearing loss

Risk assessment of workers exposed to noise pollution in a textile plant

In order to assess the risks associated with worker's hearing loss, due to exposure to noise pollution, at the Boroujerd Textile Factory a cross sectional study was conducted. 60 workers from the Spinning and Weaving workshops and official staff were randomly selected as case and control groups and their hearing were tested by audiometry. The audiometric results revealed that amongst workers being exposed to the noise pollution in the Spinning and Weaving Workshops there is a distinct increase in the number of cases of hearing loss at high frequencies. There also appears to be a slight bias towards hearing loss in the left ear, in preference to the right in addition, those who have worked for longer than 16 years are subjected to hearing loss even at low frequencies conversely, the office workers [the control group] seem to suffer little or no hearing loss at low frequencies at all, but after approximately 10 years of service there may be some hearing loss, but only at higher frequencies, which could be attributed to presbycusis. Also, the t-test [statistical hypothesis test] results verified the significant difference among both groups at high frequencies. The questionnaire results indicated that workers feel symptoms such as headache, no sense centralization, excitement, nervousness, vertigo. Hence, controlling procedures seem to be essential to protect workers from noise disorders

Road traffic noise model

The recognition of road traffic noise as one of the main sources of environmental pollution has led to develop models that enable to predict noise level from fundamental variables. Traffic noise prediction models are required as aids for designing roads and highways. In addition, sometimes are used in the assessment of existing or envisaged changes in traffic noise conditions. In this paper a statistical modelling approach has been used for predicting road traffic noise in Iranian road conditions. The study was performed during 2005-2006 in Hamadan city, in the west of Iran. The data set consisted of 282 noise measurements. The entire data set was utilized to develop a new model for Iranian condition using regression analysis. The developed model has twelve explanatory variables in order to achieve a proper fit for measured values of L[eq] [r[2]= 0.913]. The proposed road traffic noise model can be effectively used as a decision support tools for prediction of traffic noise index of L[eq[30min]], in Iran's cities

Reliability analysis of traffic noise estimation in highways of Tehran by Monte Carlo simulation method

This study was aimed to examine the reliability of traffic noise estimate and measurement techniques in highways of Tehran, capital of Iran. The multiple regressions showed that the traffic flow and the distance from the effective source position are the most important factors to estimate the L10 [1h]. Traffic flow, traffic composition in terms of heavy vehicles and traffic speed are identified as the key factors influencing the generation of traffic noise. The new equations for estimating the noise descriptor L10 was calibrated on the basis of noise measurements. The effects of the key factors on L10 [1h] were examined by the sensitivity analysis and it was found that traffic flow, distance from the effective source position, traffic composition and traffic speed had the most sensitivity on traffic noise, respectively. The probability distribution for each of the key factors was derived with the use of the survey data. The reliability of the traffic noise estimates was obtained from the combined probability distribution of the key factors by Monte Carlo simulation method. This study showed that there was no significant difference between estimated noise by calibrated CoRTN calculation of road traffic noise and measured noise level. The reliability analysis gives the traffic noise estimates with a particular probability or vice versa

Biological monitoring of mercury exposure in dentists of Tehran

In order to assess the risk for mercury poisoning in dentists, urine specimens were collected and analysed from 250 dentists [190 male, 60 female]. Subject data and pertinent health symptoms were asked via a questionnaire. The results indicate that the mean and standard deviation of mercury values were 51.3 +/- 38.0 micro g/L, while 27.2% of dentists had levels within normal limits [0-19 micro g/L]. The results also showed that values for general practitioners tended to be higher, but was not significant for the specialists. The data demonstrated that there is an association between health symptoms pertinent to mercury poisoning and urine mercury values above 50 micro g/L

effect of noise-induced hearing loss on dentists

This paper presents noise problems associated with the use of air-turbine drills in dental practice. Two hundred and fifty dentists [male and female] were randomly selected from the faculty of dentistry as well as the dentists who worked private in Tehran. The results indicated that the mean value of sound pressure level produced by the high-speed drills was 69.1 db. Most of the energy from the drills lied in the high frequency range, 6000- 8OOO Hertz. Audiological evaluations showed that the loss of hearing in all age groups and years in dental practice lie in 6000 Hertz which has a positive correlation with the value of sound pressure level in this frequency. The hearing loss in the right ear of women was slightly higher than the left one, while this was not true in men. The hearing loss in the female group was greater than In male group

Determination of the optimum heat stress index at a foundry

This paper presents a case study to determine the efficiency of the currently used heat stress indices in correlation with wet bulb globe temperature [WBGT] as a permissible index at a foundry plant and to evaluate the extent of the physiological responses such as heart rate and body temperature in correlation with heat stress indices. The field consisted of a foundry plant where a shift work was in operation. The results indicated that wet globe temperature [WGT], corrected effective temperature [CET], and predicted four-hour sweat rate [P4SR] indices have the best correlation with WBGT index respectively, and P4SR and CET indices correlate well with physiological responses more successfully than WBGT does in hot-dry conditions, CET index gives the best correlation with body temperature while P4SR is the most accurate with the heart rate

Combined effects of heat, stress and shift work on physiological parameters in foundry workers

In order to investigate the combined effects of shift work and heat stress on the physiological parameters, such as heart rate [HR] and body temperature [BT], a hot-dry working environment was investigated for 53 workers in foundry workshops. In this study Wet Bulb Globe Temperature index [WBGT] was measured and along with that simultaneously heart rate and oral temperature were checked in 3 shifts. The results indicated that the physiological responses of workers changed whenever the shift changed and the responses were increased by a corresponding increase in heat stress, index

Production of activated charcoal sampler tubes for sampling air contaminants

The importance of the use of activated charcoal tubes for sampling gases and vapors is very well-known. For producing these tubes in the country, their production started in the laboratory of the department of occupation al health using activated charcoal, polyurethane foam and glass wool and consequently two types of foamed and foamless tubes were produced. To investigate the quality of the raw materials used, 186 tubes were exposed to various proportions of solutions of different volumes of known percentages of four compounds of benzene, toluene, O-xylene and P-xlene. The adsorption of various parts of sampler tubes was done by a chemical method using CS2 and the final analysis was done by gas chromatography. The results obtained show that the amount of the above named compounds adsorbed by glass wool and foam in comparison to the activated charcoal isn't significant [respectively P<0.001 and P,0.05]. Also the experiments don's show any significant differences between the total amount of adsorbed chemicals by charcoal in the back-up layer and the sample layer of the foamed tube and the amount adsorbed in the foamless tube, when treated with various compounds [P,0.001]. Considering the equal adsorption of both types of tubes and the advantage of foamed tubes in controlling the time duration and the flow rate of sampling, the foamed type was recommended for production and use