Designing a traffic noise prediction model for highways in iranian megacities [case study: Ahvaz City]

One of the important factors in urban construction designs is noise prevention. According to results of this study [2011-2012], a suggested model is presented for traffic noise compatible to conditions in Ahvaz. Data was colleted to design a model from totally 112 measuring stations, 4 weekdays and 2 intervals as rush hours, yielding to a total number of 1344 traffic noise measurements [L] and the effective factors from traffic load, speed of vehicles, environmental and dimensional factors of roads. In the next step, based on desired overall structure, using analytical and experimental modeling strategies, several Regression multi-variables were tested on data in order to design a model. The model designed for Ahvaz consists of 9 inputs with high clarification coefficient [R[2]=0.92] and correlation coefficient [R= 0.95]. Due to precision and minuteness of designing as well as the number of inputs, the model can be a suitable one to define half- hour equal level for traffic noise and estimation of noise pollution in Ahvaz

[ study on heat stress and its risk assessment in a steel factory]

A glance at different occupations and production processes showed that one of the important and popular occupational health problems in the workplace is improper climate conditions such as hot environments .In this condition the core body temperature may increase and cause some diseases, occupational accidents and reduction of efficiency. The purpose of this study is determination of heat stress and its risk assessment in a steel factory. In order to survey heat stress, a cross-sectional study was conducted in a steel factory in Ahwaz in the autumn season and WBGT index was used as a standard method for heat stress measurement. After measurement of WBGT index, the results were compared to ACGIH_TLV. In the second stage, for the assessment of probable heat hazard, psychometric conditions of work place along with some other parameters like work load, kind of occupation, distance between workplace and rest areas, water consumption and uses of personal protective devices were taken into account In this area, it was tried to determine the existence of improper probable heat condition with regard to priority and necessity for modifications. After measurement in production process, other workshops and administrative office, the data were compared to ACGIH standards .The results showed that the workplace had acceptable climate conditions from heat stress with 81.1%and there were no acceptable climate conditions with 18.9%which is above TLV. The workplaces heat risk assessment showed that their conditions with 14.3%, 49.3% and 36.4% were in level one to three respectively. Although the fall season in regions such as Khuzestan is cooler than summer, but employment in industries such as steel due to its exothermic process, a threat to the health of these kinds of workers. The heat conservation planning should not only be limited to the summer season. More research in the spring and even winter are recommended.

[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

[Survey of noise exposure and permanent hearing loss among Shadris spinning factory workers of Yazd using Task Base Method [TBM]]

During last decades one the hazardous agents on workers health has been workplace noise. The aim of this study was to investigate the level of noise exposure in different jobs and noise induced permanent threshold shift in relation to noise level and work experience. This is a cross-sectional and descriptive study that performed among total workers. Dosimetry was done for determination of accurate noise exposure level during an eight-hour s shift for each job group. Audiometry was performed in a standard acoustic room by the audiologist. The obtained data was analyzed by means of SPSS software. Mean of age was 36.58 +/- 6.76 [19-52 years] and minimum, maximum and mean of work experience were 1, 18, 11.08 +/- 5.47 respectively. Mean of hearing loss was 15.38 +/- 8.63 in right ear and 16.31 +/- 9.51 in left ear and total hearing loss was 14.72 +/- 8.33. A significant relationship was also identified between noise intensity and work experience with hearing loss. Findings of this study indicated that there is a high prevalence of noise pollution in different parts of workplace. Considering the obtained results, that shows positive effect of noise and work experience on hearing loss, the necessity of improvement of control and protection measures is of prime importance

[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

[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

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]

relationship between the worker's safety attitude and the registered accidents

Millions of workers are the victims of different kinds of accidents every year throughout the world. The purpose of this study was to investigate the relationships between safety attitude and occurrence of the occupational accidents. This investigation was a cross-sectional study performed in a gas refinery in south of Iran in 2008. Sample size of this study was 176 people. To determine the value of worker's safety attitude a validated 5 degrees questionnaire was used. Different statistic analyses including Chi-square, t-test and Logistic Regression were used by Spssll.5 to analyze the data. The Cronbachs alpha coefficient was found to be 0.97 in this investigation. In the study population, the average age was 31.67[ +/- 5.89], the average work experience was 5.65 [ +/- 4.29] and the average of the safety attitude was 188.52[ +/- 14.84] and only 28.7% were injured through accidents. The relationship between safety attitude of the workers and the accidents occurred was significant [P< 0.0001]. The relationship between safety attitude of the workers and the accidents occurred was significant, although the relation was not significant for graduate workers. No significant relationship was found between safety attitude and accident in accordance with worker's age and work experience

On the application of partial barriers for spinning machine noise control: a theoretical and experimental approach

Noise is one of the most serious challenges in modern community. In some specific industries, according to the nature of process, this challenge is more threatening. This paper describes a means of noise control for spinning machine based on experimental measurements. Also advantages and disadvantages of the control procedure are added. Different factors which may affect the performance of the barrier in this situation are also mentioned. To provide a good estimation of the control measure, a theoretical formula is also described and it is compared with the field data. Good agreement between the results of filed measurements and theoretical presented model was achieved. No obvious noise reduction was seen by partial indoor barriers in low absorbent enclosed spaces, since the reflection from multiple hard surfaces is the main dominated factor in the tested environment. At the end, the situation of the environment and standards, which are necessary in attaining the ideal results, are explained

Sound field diffusivity at the top surface of Schroeder diffuser barriers

Reactive barriers are one of the most promising and novel environmental noise barriers. In this case using Schroeder diffusers [e.g. quadratic residue diffusers] on the top surface of the T-shape barrier was shown to significantly improve the performance of absorbent T-shape barriers. The reasons behind the high performance of diffuser barriers are considered in this investigation. A question about the diffusivity behavior of Schroeder diffusers when they are utilized on the top of barrier was raised. Diffusion coefficients of a diffuser in different conditions at some receiver locations were predicted by using a 2D boundary element method. It was found that the diffusion coefficient of diffuser at the top of barrier is so small that the diffusivity of the structure is almost the same as rigid T-shape barrier. To find the barrier's cap behavior, the total field above the top surface of profile barriers was also predicted. It was found that the lowest total energy is at the receiver side of the cap very close to the top surface, which could demonstrate the effect of top surface on absorbing the energy as wave transfers from source edge toward the receiver side of the cap. In this case the amount of minimum total energy depends on the frequency and the configuration of the top surface. A comparison between the reductions of total field at the source side of the cap with the improvements of barrier's performance was also done. It was shown that the amount of decrease in total field compared to that of an absorbent barrier "Ref" is directly associated to the amount of improvement in the insertion loss made by the diffuser barrier compared to the "Ref" barrier in the wide area on the ground at the shadow zone. Finally it was concluded that the diffuser on the top of barrier does not act as a diffuser and a kind of similarity between the contribution of diffuser and absorbent material on the top of T-profile barrier is seen