Showing 35 results for Monazzam
S. Farhang Dehghan, M. R. Monazzam, P. Nassiri, Z. Haghighi Kafash, M. Jahangiri,
Volume 3, Issue 3 (12-2013)
Abstract
Introduction: Noise is one of the most common health hazards at the workplaces that can cause not only somatic problems, but also adversely affect mental health. The aim of this study was to investigate and evaluate occupational noise exposure and noise annoyance in one of the petrochemical companies.
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Material and Method: The study population included 47 people working in Administrative and Manufacturing parts of the petrochemical company. First, dosimetry of production workers and noise frequency analysis of Administrative employees were performed. Then, self-report questionnaire for the assessment of noise annoyance at workplace was completed by the subjects. The questionnaire consisted of three parts: scoring of the noise intensity in the workplace, scoring of the noise annoyance in the workplace and determining the feelings and emotions (e.g. fatigue, sleepiness, and concentration problems) that experienced by subjects during the working day.
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Result: The results of noise dosimetry measurements showed that mean eight hour equivalent continuous A-weighted sound pressure level was 86.13 dBA. According to the frequency analysis of office rooms, mean noise level and Preferred Noise-Criteria (PNC) was 69.4 dBA and 62 dB, respectively. The findings of our analysis revealed that 17.9% of administrative staff and 63.2% of manufacturing workers assigned “very high” score to the noise intensity in the workplace. The annoyance score was obtained “very annoyed” by 10% of employees of office section and 42% of manufacturing workers. For noise-related complaints and sensations defined by subjects, 49% of administrative staff and 60% of manufacturing workers marked the “sometimes” and “more” item of the questionary.
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Conclusion: Based on the obtained results of investigating the noise level (objective exposure) as well as the noise annoyance (subjective exposure) at the studied company, it is necessary to adopt the management –technical noise reduction measures at manufacturing sectors as the personal noise exposure and environmental noise exposure and also noise personal exposure of administrative staff can be decreased.
H. Ekhlas, P. Nassiri, M. R. Monazzam, N. Mansouri,
Volume 4, Issue 1 (5-2014)
Abstract
Introduction: Noise is one of hazardous agents of workplaces in industries. Electric industries and power plants are among industries in which noise pollution should be taken into account. This study aimed to develop and verify a statistical model for acoustic wave propagation in an indoor environment for noise related risk reduction management.
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Material and Method: This theoretical-experimental study was performed in a gas power plant with nominal capacity of 648 MW including four gas turbine with nominal capacity of 162 MW. The relations between sound power level and sound pressure level in indoor environments were used for developing the statistical model. Moreover, verification of the obtained data was done by a field inside a turbine hall study using ISO9612 standard method.
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Result: Comparison of results from the field and the theoretical study showed no significant differences. The differences between predicted value and field measurements was, in average, less than 0.5 db. This shows the acceptable accuracy of the presented model in estimating the workplace noise level, according to the real functional conditions of the noise sources.
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Conclusion: The presented model is easy and practical and allows managers to model scenarios of noise pollution reduction in indoor environments, before huge expenses of actual control measures. This method is faster comparing to numerical modeling methods. Furthermore, its accuracy is also acceptable.
M. Naserpour, M. J. Jafari, M. R. Monazzam, H. R. Pouragha Shahneshin, M. Saremi, S. Jam Bar Sang,
Volume 4, Issue 1 (5-2014)
Abstract
Introduction: In the most industrial environment, workers are exposed to noise everyday. Exposure to this physical hazardous agent can cause immediate as well as delayed adverse effects. Cognitive performance decrement is one of the adverse effects of noise exposure which its main consequences is occupational accidents. This study attempted examine the effect of exposure to different levels of noise with harmonic indices of neutral, treble and bass on the cognitive performance.
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Material and Method: In this analytical-descriptive study, the cognitive tests were performed by 33 students, aged 23-35 years. During the tests, participants were exposed to three type of noise including neutral, treble and bass at 4 different levels of 45, 75, 85 and 95 decibels. In order to assess students cognitive performance, continuous performance test (CTP) software was employed, which investigated attrition and reaction time.
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Result: The results of this study revealed that exposure to neutral noises with Noise Harmonic Index (NHI) of +3dB at the frequency of 1000 Hz, the maximum percentage of attention (99.88 %) was belonged to Sound Pressure Level (SPL) of 95 decibels. Maximum percentage of attention due to exposure to the treble noise with NIH -105 dB at the noise frequency of 8000 Hz (100%) and bass noise with NIH of 407 dB at the frequency of 500 Hz (99.92%) were belonged to the SPL of 95 and 85 dBA, respectively. Moreover, the result showed that the effect of bass noise with NIH of 4.5 dB and frequency of 500 Hz on reduction of attention were more than treble noise with NIH of -105 dB and frequency of 8000 Hz. Under exposure to neutral noise with NIH of 3 dB and frequency of 1000 Hz, the longest reaction time (2.594 Second) was observed at the SPL of 85 dBA. The longest reaction time for treble noise with NIH of -105 dB and frequency of 8000 Hz (2.786 Second) and for the bass noises with NIH of 4.5 dB and frequency of 500 Hz (2.594 Second) were also belonged to the SPL of 85 and 75 dBA, respectively.
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Conclusion: The results showed that bass noises (frequency of 500 Hz) increased reaction time, in comparison with treble noises (frequency of 8000 Hz).
P. Nassiri, M. R. Monazzam, F. Zivary Delavar,
Volume 4, Issue 1 (5-2014)
Abstract
Introduction: The previous studies have used fibrous absorbents usually in the form of cone-shaped wedges for making anechoic and semi-anechoic chambers which their design and construction have been costly and difficult. The present study aimed to design a semi-anechoic chamber, using rectangular fibrous absorbents and also perform acoustic analysis for it.
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Material and Method: In the present study, which was done at semi-anechoic chamber of the laboratory in Tehran University of Medical Sciences. The reverberation time, the total surface and the absorption surface of the chamber were determined, before and after the design and also they were compared with the target values. Intersection layout of the rectangular fibrous absorbents were design using graphic design software (AutoCAD and 3Ds Max). before design, the reverberation time were measured according to ISO 3382:2000. The reverberation time in redesigned chamber was also calculated through retention time equation (Sabine). Moreover, Sabin’s formula was applied for determining the absorption surface and the total surface of the chamber, before and after the design.
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Result: Before design, the reverberation time in the cut-off frequency of 250 Hz according to ISO 3382:2000 was determined 0.3 second. Moreover, the total chamber surface was 47.97 m2. CAD software estimated at least 253 rectangular absorbents with dimensions of 50×18 cm. After design, the absorption surface and the total chamber surface were obtained 46.32 m2 and92.64 m2, respectively and the reverberation time in the mentioned frequency was 0.07 (s).
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Conclusion: According to the results, it can be concluded that the suggested intersection layout of rectangular fibrous absorbents can be used as a reliable method in order to reduce the reverberation time and to gain lower cut-off frequency for construct a semi anechoic chamber with the high efficiency.
F. Golbabaei , M. Rostami Aghdam Shendi, M. R. Monazzam, M. Hosseini, M. Yazdani Avval,
Volume 5, Issue 2 (7-2015)
Abstract
Introduction: Outdoor workers are exposed to heat from solar radiation and the atmospheric conditions, in addition to the heat from the working process, which is worse by global warming. The purpose of this study was to evaluate heat stress based on wet bulb globe temperature index and also to examine the relationship between WBGT and physiological indices among outdoor workers of Shabestar city.
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Material and Methods: This cross-sectional study was conducted in August 2014. WBGT measurements were taken according to ISO7243 standard in different hours. The physiological response of 53outdoor workers (including heart rate, systolic and diastolic blood pressure, oral temperature, and skin temperature) were measured among9occupationalgroups, including municipal workers, concrete makers, porters, construction and road making workers, stonemasons, farmers, traffic officers, and street vendors.
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Result: The mean WBGT index for all outdoor workers, except for municipal workers, street vendors, traffic officers and stonemason, was greater than threshold limit. The highest average WBGT index was for construction workers and the lowest was for municipal workers (respectively 27 and 26 °C). Moreover, a significant direct association was reported between the WBGT index and physiological parameters (P <0.0001), with the highest correlation coefficient belonged to heart rate (r=0.492).
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Conclusion: According to WBGT index, porters, Concrete makers, construction and road makers, and farmers had the highest exposure at all times of the day while the lowest level was related to municipal workers. What is more, heat stress showed a significant correlation with the study strains. Therefore, it is essential to conduct further research and in order to represent preventive countermeasures for the workers in this field.
M. R. Monazzam Esmaielpour, F. Golbabaei, F. Khodayari, K. Aazam,
Volume 5, Issue 3 (9-2015)
Abstract
Introduction: Heat is one of the hazardous physical agents in the workplace. Exposure to heat and consequent thermal stress influence workers productivity in addition to adverse health effects. The aim of this study was to determine the heat stress induced productivity loss related to different tasks of farmers in Darreh Shahr city, during summer.
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Material and Method: This cross-sectional study was conducted in summer, 2014, among farmers in Darreh Shahr city. After determining the sample size, farmers’ activities were determined using hierarchical task analysis (HTA), and WBGT measurements were done according to the ISO7243. Metabolism was estimated by the ISO8996. Following, the type of activities were identified according their required metabolism. Knowing WBGT and workload and using the work capacity model, the productivity loss in different tasks and ultimately total productivity loss were calculated.
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Result: The mean WBGT activities for plowing, terracing, planting seeds, watering, fertilizing, weeding, spraying, and harvesting were 29.98 °C, 31.28 °C,30.66 °C,31.39 °C,31.99 °C,31.75 °C,31.08 °C, and 30.3 °C, respectively. WBGT values were higher than the permissible level provided by ISO7243 in all farming activities. Maximum value of WBGT was belonged to fertilizing activity (31.99 °C) and the lowest value was for plowing (29.98 °C). ANOVA test results did not show a significant difference in WBGT at head, waist, and ankle height. The highest and lowest amount of productivity loss was estimated respectively for weeding and plowing activities. The total productivity loss for farming was calculated 69.3 percent in an hour which is due to high physical activity, working outdoor, with exposure to direct solar radiation, and consequent heat stress imposed to workers.
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Conclusion: Productivity is a factor which is affected by the workplace heat stress. According to results of the present research, the amount of productivity is reduced in different tasks due to heat and this reduction is exacerbated by increase in temperature and might impact the local economy. Thus, further studies are needed to improve the working conditions.
M. Abbasi, M. R. Monazzam Esmaielpour, A. Akbarzadeh, S. A. Zakerian, M. H. Ebrahimi,
Volume 5, Issue 3 (9-2015)
Abstract
Introduction: Installation of wind turbines in residential areas due to their unique sound characteristics may cause noise annoyance. Noise annoyance can increase the risk of health problems and sleep disturbance. Thus, this study was conducted to assess the effect of wind turbine noise annoyance on sleep disturbance among the Manjil wind farm workers.
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Material and Method: All the Manjil wind farm workers have been divided into three groups according to their noise exposure levels, including maintenance, security, and administrative workers. The equivalent A weighted noise levels were measured for each of the study working groups, using ISO 9612 standard method. Information related to the noise annoyance and sleep disturbance were determined by ISO15666 standard and the Epworth Sleepiness Scale, respectively. Data were analyzed using R software.
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Result: Findings of ANOVA and Kruskal-Wallis statistical tests showed that noise annoyance and sleep disturbance were statistically different among workers with various occupational, age, and work experience groups. Also, noise annoyance and sleep disturbance had a significant association in a way that regardless of the effects of other variables, it can be stated that for every one unit increase in noise annoyance, 0.26 units will be added to the amount of sleep disturbance.
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Conclusion: In this study, workers with more wind turbine noise annoyance had more sleep disturbance. Therefore, in addition to the direct effects of noise on sleep disturbance, it can indirectly exacerbate sleep disturbances.
Mahdi Asghari, Parvin Nassiri, Mohammad Reza Monazzam, Farideh Golbabaei, Hossein Arabalibeik, Ali Akbar Shamsipour, Armin Allahverdy,
Volume 7, Issue 1 (4-2017)
Abstract
Introduction: To evaluate heat stress in the workplace different indices are used. But, none of these measures have been widely accepted. The aim of this study was to determine effective criteria in selecting a heat stress index and weighting of these criteria.
Material and Method: This study is a qualitative study that was designed and conducted within 10 stages. In the current study, effective criteria for choosing a heat stress index was determined by using Delphi technique and expert’s opinions (30 people), and then the fuzzy analytic hierarchy process was used for weighting and prioritization of these criteria.
Results: Analyzing the completed questionnaires by the experts and according to the percentage of respondents, 11 criteria were finally selected. “Simplicity” criteria by %76.6 had the highest percentage of response. But, the relative weight of this criteria was 0.041, and had the lowest weight after the “low cost” criteria. The criteria relating to the “Standard” item was 0.141as the highest relative weight.
Conclusion: It can be concluded that the first step to have a reliable and accurate measurement is to choose a proper and correct index. Based on specialists and expert’s opinions, standardization of the index is the most important selection criteria. Other criteria that must be considered were accuracy, reliability and good correlation with the physiological strain indices.
Parvin Nassiri, Mohammad Reza Monazzam, Farideh Golbabaei, Aliakbar Shamsipour, Hossein Arabalibeik, Marzieh Abbasinia, Masoumeh Chavoshi, Mehdi Asghari,
Volume 7, Issue 2 (6-2017)
Abstract
Introduction: Heat stress is caused by many factors such as individual factors, environmental factors, and management factors. Individual risk factors can decrease the heat tolerance, and play an important role in heat stress disorders incidence. The aim of this study was to review individual parameters influencing the thermal stress and review the preceding studies.
Material and Method: In this review study sites such as Web of Science, Scopus, Pubmed, Iran Medex, Magiran, Google Scholar and SID databases were used for search. The keywords included heat stress, personal factors and heat exposure. The period of 1995 to 2015 was investigated, and finally 75 original articles were identified.
Result: At the individual level, exposure with a single risk factor may reduce the workers’ heat tolerance; while exposure with a combination of several risk factors probably synergistically increases the risk of heat-related disorders. Individual risk factors include age, gender, obesity, fatigue, race, and previous heat disorders and dehydration. In addition, some diseases (such as cardiovascular disease, diabetes and infectious diseases) or use of certain drugs or alcohol can reduce the heat tolerance.
Conclusion: It is necessary to pay attention to the mentioned items when selecting workers in the hot environments. Also, due to the lack of awareness and knowledge of workers, it is necessary to provide appropriate training programs to reduce the effects of heat stress.
Mohammad Reza Monazzam Esmaielpour, Fereydoon Laal, Fereshte Majlessi, Rohollah Fallah Madvari, Abbas Rahimi Foroushani, Alireza Fallah Madvari,
Volume 7, Issue 4 (12-2017)
Abstract
Introduction: The use of hearing protective devices (HPDs) is the last way for noise control. It is important to know the information about the duration time using these devices to ensure protetion effectiveness. The aim of this study was to investigate the effect of increasing duration time of the using of the devices on hearing loss in tile industry workers with application of the BASNEF education model.
Material and Method: Task Base Method (TBM) and ISO9612(2009) standard methods through a noise dosimeter device were used to exmine workers’ noise exposure level when they didn’t used of HPDs. Actual performance of HPDs was determined by using the NIOSH standard before and after training intervention and measuring time of use and protection device type. Data were analyzed using SPSSVv19 and conducting t-test and ANCOVA statistical tests.
Result: Before training intervention, the actual noise level for case workers was 89.76 dBA. On the contrary, this value was 84.04 dBA for after intervention, with a significant difference with control group (P<0.0001) using ANCOVA analysis. In control group, the actual level of noise has not changed because this group has not received any training.
Conclusion: The results revealed that, based on BASNEF education model, duration time of using hearing protection devices is effective on increasing their function and performance.
Athena Rafieepour, Parvin Nasiri, Omid Giahi, Mohammad Reza Monazzam Esmaeilpour, Abolfazl Zakerian, Farough Mohammadian,
Volume 7, Issue 4 (12-2017)
Abstract
Introduction: Exposure to vibration as one of the consequences of industrial noise or the use of vibration generators can cause discomfort, reduce the efficiency and level of safety in workplaces. Therefore, in this study, the effect of whole body vibration on individual’s mental performance and response time was investigated.
Material and Method: In this study, 40 male students of Tehran University of Medical Sciences were selected randomly and divided into two 20 subjects groups. Each group participated in two Pegboard Board and Math Calculations tests. Subjects in each stage of test were exposed to whole body vibration with acceleration in 0.8 and 1.1 m/s2 as well as background mode without vibration and were investigated response time and mental performance.
Result: In the present study, the mean response time to the manual Purdue Pegboard test in the vibrational acceleration of 0.0, 0.8 and 1.1 m/s2 with a decreasing trend was 197.55 ± 2.7, 176.25 ± 5.38 and 177.58 ± 2.92, respectively, which results in a significant reduction in the accuracy of the test. Also, the results showed that whole body vibration does not affect mental performance in shallow levels. But, in the intermediate and deep levels, this difference is statistically significant (p <0.001).
Conclusion: Based on the results, whole body vibration is an effective factor in individual’s response time and mental performance, which can lead to a reduction in the accuracy of the work.
Masoumeh Lotfi, Mohammad Reza Monazzam Esmaielpour, Nabeioallah Mansouri, Saeid Ahmadi,
Volume 8, Issue 2 (6-2018)
Abstract
Introduction: Using diesel generators is necessary for activities like welding in construction sites and it is often accompanied with noise pollution. The aim of this study was to evaluate noise pollution induced by diesel generators in construction activities in one of the districts of Tehran city.
Material and Method: In this descriptive study, 14 construction sites were selected for the evaluation of noise pollution in Tehran, district 4. Background and diesel generators sound pressure level were measured in accordance with BS 5228(2015) and noise guidance in the area around the construction sites. Diesel generators sound pressure level at 4 points and also the audio frequency analysis, one meter away from the device was measured at a random locations around it. TES-1358, Type 2(Taiwan) sound level meter was used to measure sound pressure level and calibration was performed before and after noise measurement. The validated Noise annoyance questionnaire adopted from ISO15666 standard, completed by the residents. T test, correlation and analysis of variance was performed to analyze data using SPSS software ver. 22.
Result: The mean equivalent sound level of diesel generators background noise were respectively 76 ± 4.05 dB(A) and 46.2 ± 1.09 dB(A) around the construction sites. Diesel generators noise around the construction sites was higher than the noise limit (background noise plus 5 dB)(P Value <0.05). The highest (95.3 ± 0.33 dBA) and lowest (90.9 ± 0.63 dBA) average sound pressure level was related to Benz355 and Perkins generators. One-way ANOVA statistical analysis showed significant differences in the average sound pressure level of various diesel generators between the devices (P Value <0.05). The mean sound pressure level among 190 sound monitoring stations in the interior parts of the construction sites were about 81.11 ± 4.6 dB(A). The experienced noise annoyance was evaluated higher than the average by 73.4 percent of residents. Residents’ noise annoyance and noise level around construction sites were significant using Pearson correlation (R=0.486, P value <0.05). Dominant noise frequency and associated sound pressure level of diesel generators were measured 63 Hz and 84.4 dBA, respectively.
Conclusion: Diesel generators noise in the area around the construction sites was higher than the environmental noise limit and it was accompanied with abundant noise annoyance for residents around these construction sites. Therefore, due to the lack of environmental rules related to construction industry noise pollution in Iran, assessment and approving of such rules is essential to reduce noise annoyance in urban areas.
Masoumeh Sadri Khanlou, Mohammadreza Monazzam, Kamal Azam, Alireza Mortezapour, Seyed Abolfazl Zakerian,
Volume 9, Issue 3 (9-2019)
Abstract
Introduction: Nearly a third of people work in jobs that use voice to be part of their work. Teachers as the largest group of professional vocal users, are at risk of vocal disorders. The aim of this study was to investigate the effect of different risk factors on vocal disorders in teachers.
Material and Methods: This is a cross-sectional and descriptive-analytic study that was conducted on 73 primary and secondary male and female school teachers in Saveh in 2017 by random sampling. The researcher-made questionnaire on risk factors affecting verbal disorders with the aim of identifying risk factors and a Voice Handicap Index (VHI) questionnaire (30 items) aimed at evaluating verbal disorders and symptom questionnaire were used in this study. All of them have been shown to be valid and reliable in previous studies. Data were analyzed using t-test and chi square statistical tests by SPSS ver.24.
Results: The reliability of the researcher-made questionnaire on the risk factors affecting vocal disorders was confirmed by Cronbach’s alpha (0.736) and its validity was confirmed by the experts regarding the adequacy of the number of questions, the lack of ambiguity and the assessment of content fitness. According to our gathered data, vocal disorders were observed in 55% of the teachers. Also the results showed the rate of vocal disorders in female teachers is far higher than male teachers. Functional disturbance of vocal cords and allergy as general risk factors, teaching tools and poor air quality as environmental risk factors and inadequate vocal rest and job stress as occupational risk factors contributed to increasing vocal disorders in teachers. Among the symptom associated with verbal disorders in teachers, vocal fatigue and hoarseness were more common in comparison with other symptoms.
Conclusion: Due to the prevalence of vocal disorders in half of the teachers and the impact of general, environmental and occupational risk factors, it is necessary to identify and control the risk factors of vocal disorders in teachers. It can also be concluded that teachers can enjoy a healthy voice by considering the principles of ergonomics and occupational health.
Marziye Pirani, Mohammad Raza Monazzam, Seyed Qasem Pourjandaghi,
Volume 11, Issue 1 (3-2021)
Abstract
Introduction: Reducing noise pollution has become an essential issue due to the increase in public concern and also social demands for a better lifestyle. Using sound absorption materials is a preferred method to reduce the noise pollution. Undesirable properties of pure polyurethane such as poor absorption of mechanical energy in narrow frequency ranges can be improved by providing polymeric nanocomposites. The main purpose of this study is to synthesize the polyurethane nanocomposite foams in order to improve its acoustic properties.
Material and Methods: At the first steage, pure polyurethane foam was synthesized using the pre-polymer method. Afterwards, nanocomposite foams were synthesized with different mass fractions of Nano silica. The cellular morphology of prepared nanocomposite foams was investigated by scanning electron microscopy (SEM (.Utilizing a two-microphone impedance tube, sound absorption coefficient (α) was calculated in the frequency ranges of 100 Hz to 1600 Hz in order to investigate the acoustic properties of the new absorbant.
Results: According to the microscopic investigations, morphology of the cells changed after adding silica nanoparticles. Also, the cell sizes were observed to be decreased by increasing the amount of silica nanoparticles. Furthermore, the acoustic analysis of nanocomposite foams indicated that the sound absorption increased by enhancing the load of silica nanoparticles.
Conclusion: In the current study, the effect of silica nanoparticles additive amount on acoustic properties of the polyurethane-based nanocomposite was investigated. Our findings depicted that the polyurethane-based nanocomposites were able to promote the sound absorption coefficient.
Aysa Ghasemi Koozekonan, Mohammad Reza Monazzam Esmaeilpour, Saba Kalantary, Ali Karimi, Kamal Azam, Farideh Golbabaei,
Volume 11, Issue 1 (3-2021)
Abstract
Introduction: The skin, can be exposed to harmful factors like ultraviolet radiation (UV). Exposure to this physical hazardous agent could be contributed to pigmentation, erythemas, early aging, skin cancer, and DNA damage. The aim of this study, therefore, was to fabricate the polyacrylonitrile (PAN) nanofibers with the UV protection property by the use of various concentrations of titanium dioxide (TiO2) nanoparticles.
Material and Methods: The PAN nanofibers (10%wt) containing 0, 1, 5, 10 and 15% wt of TiO2 nanoparticles were produced using electrospinning method. The morphological propertis of nanofibers were studied by scanning electron microscopy (SEM) and the functional groups were investigated by Fourier transform infrared spectrophotometer (FTIR). The UV protection property of nanofibers was studied by measuring UV transmittance as well as calculating UV protection factor (UPF).
Results: The results showed that the diameter and morphological characteristics of nanofibers are different at various concentrations of TiO2 and increasing the concentration of TiO2 has resulted to an increase in nanofibers diameter. The analysis of FTIR results showed that TiO2 nanoparticles have been successfully loaded on nanofibers for UV protection purposes. The findings clarified that nanofibers loaded with TiO2 could increase the UV protection property up to 15%.
Conclusion: Totally, our findings show the successful fabrication of UV-protective nano webs using TiO2 nanoparticles. the new combination used in nano matcould protect employees from UV radiation.
Sepideh Keyvani, Mohammadreza Monazzam Esmaielpour, Fatemeh Fasih-Ramandi, Akbar Ahmadi Asour, Malihe Kolahdouzi, Zahra Hashemi,
Volume 11, Issue 3 (9-2021)
Abstract
Introduction: The acoustic performance of natural fiber adsorbents has been investigated in numerous studies. A part of these materials show a poor adsorption within the frequency range of less than 1000 Hz. In the present study, attempts were made to investigate the effect of layout sequence of double-layered composites consisting of natural and synthetic fibers on improving the acoustic adsorption coefficient of natural fiber in the low-frequency range (63 to 1000 Hz) using the numerical finite element method.
Material and Methods: In this study, the finite element method and the Johnson-Champoux-Allard model in COMSOL software version 5.3a were used to investigate the acoustic performance of the double-layered composites consisting of natural and synthetic adsorbents. The acoustic absorbers under study included date palm fiber, polyurethane foam and cellular rubber. Each double-layered composite included a date palm fiber with 10mm in thickness and a synthetic adsorbent (polyurethane foam or cellular rubber) with 10mm in thickness. In sum, four double-layered composite structures with different layouts of adsorbents in each structure were studied.
Results: The location of natural fiber can play a critical role in the acoustic performance of the double-layered composite structures such that comparing the studied double-layered composites revealed that when the natural fiber was the first layer exposed to the normal sound in the double-layered composites with 20mm in thickness, the trend of acoustic performance was approximately the same as the single-layered composite of natural fiber with 20mm in thickness; but in the composite structures, when the synthetic adsorbent was the first layer exposed to the sound, the trend of acoustic absorption was improved.
Conclusion: On the basis of the results, the double-layered composite structure with a higher-density and lower-porosity upper layer showed a better acoustic absorption trend than the single-layered composite including the natural adsorbent.
Milad Abbasi, Mohammad Reza Monazzam, Mansour Shamsipour, Hossein Arabalibeik,
Volume 11, Issue 4 (12-2021)
Abstract
Introduction: There are several generic and specific models to assess the individual job performance (IJP). While these methods may provide the valuable information, none of them cover the complexity and wide range of the behaviors which express the IJP. This review study aimed to identify all existing models and incorporate them to achieve a comprehensive conceptual model to assess the IJP.
Material and Methods: Databases such as PubMed, Scopus, Embase, and ProQuest were systematically searched to meet the study’s goals. Moreover, references to relevant publications were examined. Finally, suitable publications were discovered and analyzed using the inclusion and exclusion criteria.
Results: The results of Search in databases, including PubMed, Scopus, Embase, and ProQuest, showed that 12754 articles were found in the initial search. After removing duplicate and unrelated articles, finally, 155 eligible articles were selected. Based on full-text screening, 10 studies were excluded, and 5 studies were not accessible. Finally, by checking the references mentioned in the selected articles, 4 more eligible articles which were not retrieved in the search strategy were added; finally, 61 articles were selected to be reviewed. Ninteen articles were related to the general models, and 19 articles addressed job-specific assessment models. The remaining 23 articles described other existing models.
Conclusion: To evaluate IJP, a heuristic structure was developed based on the literature research. These dimensions were selected because they can accommodate all of the preceding models’ dimensions. They also include any behaviors that may have an impact on IJP.
Haniyeh Ekhlas, Hamidreza Pouragha, Mohammadreza Monazzam, Ramin Mehrdad, Parisa Bahrami, Mojgan Zaeimdar,
Volume 11, Issue 4 (12-2021)
Abstract
Introduction: Previous studies have been conducted on the effects of exposure of industrial workers to high levels of noise and their association with mental health or exposure of people to harmful levels of environmental noise. In this study, we investigated the association between moderate noise levels and the symptoms of depression, anxiety, and stress in non-industrial workers.
Material and Methods: This study is a Cross-Sectional study that was conducted using the enrollment phase data of the Tehran University of Medical Sciences Cohort (TEC) study. The study population consisted of 3899 workers of Tehran University of Medical Sciences who were employed in seven occupational groups of the university, Office Workers, Healthcare workers, technical personnel, services workers, security guards, and radiology-radiation units. Exposure to moderate noise level was examined using the Leq10min index, and the Depression Anxiety Stress Scales were examined on the mentioned population by DASS-42 questionnaires.
Results: The results showed that the prevalence of severe to very severe symptoms of depression, anxiety and stress were 8.2, 7.9, and 11% respectively. Also, it was observed that 14.5% of the participants of the study were exposed to noises of more than 70 dB(A). Furthermore, the results indicated that the highest average noise was equal to 71.3 dB(A) for the technical staff group, and the lowest value with an average of 59.1 dB(A) was recorded for the office workers group. The symptoms of severe to very severe depression was associated with exposure to noises above 70 dB(A) (OR:5.22) anxiety (OR:1.16), stress (OR:1.17) and socioeconomic status (OR:1.84). The severe to very severe anxiety was associated with stress (OR: 1.25). On the other hand, the symptoms of severe to very severe stress was associated with variables of age (OR:0.99), gender (OR:0.46), socioeconomic status (OR:1.52), having job management position (OR:0.81) and having healthcare working job (OR:0.65).
Conclusion: Regarding the obtained results of the present study, it was concluded that exposure to moderate noise levels had positive and significant association with depression in non-industrial workers. In non-industrial work environments, exposure to moderate noise levels is and can be independently associated with depression.
Monireh Khadem, Elham Kazemi Rad, Mohammad Reza Monazzam Esmaeilpoor, Maryam Mirzaei Hotkani, Sajjad Mozaffari, Amir Abbasi Garmaroudi,
Volume 12, Issue 1 (3-2022)
Abstract
Introduction: One of the most important complications of exposure to noises is changes in the gene expression patterns. Irreversible damage to the inner ear, such as noise-induced hearing loss (NIHL), is caused by tissue damage and changes in the gene expressions in the auditory system. Changes in the GJB2 gene expression pattern lead to autosomal deafness at different loci. The present study aims to evaluate the GJB2 gene expression in cochlear tissue exposed to white noise.
Material and Methods: In this study, ten male Westar rats were divided into two experimental (W1, W2) groups of six rats and a control (normal) group of four rats. Two experimental groups were exposed to constant white noise in the frequency range of 100-20000 Hz and the sound pressure level of 118-120 dB. In order to study the histology and gene expression, after a cochlea biopsy, the histological tests, RNA extraction, cDNA synthesis, and qRT-PCR analysis were performed.
Results: The results showed that the transcript level of GJB2 was significantly decreased in both experimental groups W1 and W2 by 0.02 and 0.12-fold, respectively (p <0.05). Also, the results of the histological study showed that cochlear tissue was more seriously damaged in the W1 group than W2.
Conclusion: It can be concluded that a significant reduction in the GJB2 gene expression and irrevocable damage to auditory nerve ganglion and Reissner membrane (vestibular membrane) caused changes in the gene expression patterns in cochlear tissue and developed the risk of non-syndromic sensorineural hearing.
Azar Mehrabi Matin, Mahsa Alefi, Mohammad Reza Monazzam, Adel Mazloumi, Kamal Azam,
Volume 12, Issue 1 (3-2022)
Abstract
Introduction: The noise could affect some aspects of human health, including the cognitive performance. In addition to sound pressure level and exposure time, the psychoacoustic features of noise may cause destructive effects on humans. A few recent studies have been conducted on effect of sound quality on cognitive performance. This study aims to find the noise loudness and sharpness levels as the most destructive effects on human cognitive performance.
Material and Methods: This was a cross-sectional study on 10 male students of Tehran University of Medical Sciences. The Noises were generated in two channels that the left channel produced the pink noise as a background noise. The pink noise loudness and sharpness were 19.7 sone and 2.49 acum, respectively. The right channel generated noises with different loudness and sharpness levels the noise loudness ranged from 8.87 to 67.9 sone and the noise sharpness ranged from 1.07 to 6.4 acum. Finally, ten noises with different loudness and sharpness were applied. The students were exposed to ten different types of noise and a silent condition. The Mathematical Problem Solving Task (MPST) test was performed to assess cognitive performance. The reaction time and the accuracy rate were measured after 5 minutes of noise exposure. Data were analyzed by SPSS (ver. 22). P< 0.05 was considered as significant level.
Results: The mean reaction time and the mean accuracy rate increased with the sharpness level. However, alteration in the loudness and sharpness levels had no significant effect on the speed and accuracy of students. Performance speed increased in noise 3 with the highest loudness (L=67.9, SH=1.07) in comparison with the silent condition (p-value=0.05). The mean accuracy rate in exposure to the noise 9 reduced in comparison with silence (p-value=0.04)
Conclusion: Different levels of psychoacoustic features had no significant effect on the cognitive performance parameters. Although, the accuracy rate and the reaction time decreased in noises 9, the sharpest noise, and 3, the loudest noise, in comparison to the silence, respectively.
