Environmental noise remains a complex and fragmented interplay between industrialization, population growth, technological developments, and the living environment. Next to the circulatory diseases and cancer, noise pollution has been cited as the third epidemic cause of psychological and physiological disorders internationally. A reliable and firm relationship between the cumulative health implications with the traffic annoyance and occupational noise has been established. This agenda has called for an integrated, coordinated, and participatory approach to the reliable protection of noise interference. Despite several fragmented policies, legislation and global efforts have been addressed; the noise pollution complaints have been traditionally neglected in developing countries, especially in Malaysia. This paper was undertaken to postulate an initial platform to address the dynamic pressures, gigantic challenges, and tremendous impacts of noise pollution scenario in Malaysia. The emphasis is speculated on the traffic interference and assessment of industrial and occupational noise. The fundamental importance of noise monitoring and modeling is proposed. Additionally, the confronting conservation program and control measure for noise pollution control are laconically elucidated.
Keywords: Environmental noise, industrial, monitoring, occupational noise, traffic
|How to cite this article:|
Yuen FK. A vision of the environmental and occupational noise pollution in Malaysia. Noise Health 2014;16:427-36
| Introduction|| |
Noise is perceived as an environmental stressor and nuisance, from road traffics, railways, airports, industrial sites and domestic activities.  Noise pollution has been synonymous with the urban settlements, industrialization, rapid housing expansions, population growth and technological developments. Environmental noise interferes with the social behavior and manifest in the form of psychological and physiological disorders through a variety of mechanisms. Exposure to a continuous noise of 85-90 dBA could lead to progressive hearing loss and changes of the threshold sensitivities. These annoyance reactions are associated with the degree of magnitude, variety, and severity on the daily activities. [Table 1] summarizes some noise levels commonly observed in the daily life. 
Road transportation noise represents the major contributor responsible to environmental violations, mainly generated by the frictional contact between vehicle and the air, between tires with the road surface, rolling noise of engine at speeds higher than 50 km/h for passenger cars, and at speeds higher than 80 km/h for lorries.  Domestic noise is derived from the premises or installations related to the catering trade (restaurant, cafeterias and discotheques), live or recorded music, sporting events, playgrounds, car parks, domestic animals, ventilation systems, office machines, and home appliances. Meanwhile, offensive industrial noise is a disruptive sound pattern that can generally be classified into continuous machinery noise, high-speed repetitive actions, flow-induced noise, and working tools associated with furnaces, generators and electro-mechanical devices in the working environment.  [Table 2] outlines the maximum permissible sound level (LAeq ) according to the receiving zones. 
|Table 2: The maximum permissible sound level (LAeq) according to the receiving zones|
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The health impacts of noise pollution can be seen as a pyramid in [Figure 1]. These potential implications of noise exposure are numerous, pervasive, persistent, cumulative and augmented synergistically and antagonistically, with corresponding real (economic) and intangible (well-being) losses. An explicit link between environmental noise with the activation of sympathetic and endocrine systems has been witnessed, resulting in the changes of blood pressure, hypertension, peripheral vasoconstriction and cardiovascular disease.  Scientific evidence  has proposed that chronic aircraft noise exposure may impair reading comprehension and long-term memory among children whereas high noise level of industrial settings is subjected to nausea, headaches, argumentativeness and modulation of mood and anxiety [Figure 2]. Epidemiological studies have shown that irregular traffic noise of 45 dBA has been interlinked to the interference of daily activities, sleeping, rest, study, communicating, and adverse health implications such as frustration, lower tolerance, and changes of blood compositions.  Specifically, road traffic annoyance is a major culprit with reported negative symptoms of hearing loss, gastric secretion, pituitary and adrenal gland stimulation, suppression of the immune response, and female reproduction and fertility failures. Scientific evidences have suggested that these interactive impacts of multiple noises showed greater effects than simply summing the individual stressors, with chronic sympathetic arousal or states of helplessness. 
According to the World Health Organization (WHO), approximately 10 million of adults and 5.2 million of children in the United States are suffering from the irreversible noise-induced hearing impairment, and 250 million populations worldwide are exposed to the dangerous levels of environmental noise daily.  In spite of the disrupting interference of environmental noise are well-documented, these noise levels complaints have been traditionally taken for granted in developing countries, especially in Malaysia. In this sense, this narrative review attempts to address the dynamic pressure, key challenges, and confronting mitigating measures of noise management practices in Malaysia. Within this framework, the environmental annoyance of transportation noise, assessment of occupational and industrial noise, and implementation of noise monitoring and modeling are elucidated. Besides, the conservation program and control measures for the promotion of best noise management practices are outlined.
| Annoyance and Interference of Transportation Noise|| |
Traffic noise, defined as undesirable annoyances related to the rapid growth of towns, cities and population, has been recognized as a serious threat to the quality-of-life in most industrialized nations.  This pervasive form of noise pollution is routinely generated by the transportation sources, mainly motor vehicles, aircrafts and railway trains.  In particular, highway traffic has been cited as the most widespread source of noise, and the most prevalent cause of interference worldwide. The discomfort related to the continuous noise exposure may create an unpleasant condition, and hinder the hospitality on the point duty officers, toll plaza employees, and residential communities of the surrounding area.
A study of noise exposure on point duty officers in Kuala Lumpur has been conducted by Thomas et al.  from April 2002 to March 2003. Sound level measurements were taken 3 times a day on 32 points, which were divided into four zones. The sound level meter was omni directional to the source of traffic at the height of 1.5 m above ground and 3 m away from the traffic personnel according to the requirements of ISO 1996. The individual susceptibility to noise induced hearing loss (NIHL) was determined, and a questionnaire was designed on the working experience, number of working hours, knowledge of occupational safety and health (OSH), knowledge and usage of personal protective equipment (PPE), background of residence, numbers of visits and problems of hearing loss to 130 respondents.
Based on the field measurements, the traffic noise levels were between 75 and 85 dBA in general, and occasionally, it reached 90 dBA due to the heavy traffic volume. Besides, 80% of the traffic personnel who underwent audiometric evaluation showed sensor neural hearing loss, while 70% were found to have NIHL, characterized by a dip at 4 kHz on an audiogram. The incidence was higher among those who served a longer duration, mainly ascribed to the noise exposure from the use of fire-arms.  Results from the questionnaires detected that >90.8% of the respondents spent >5 h a day on point duty, without the provisions of hearing protectors and education on OSH and the Factories and Machinery Act. The findings alerted the suitably use of hearing protection equipment, discouraged the working duration for 4 h in a stretch, and recommended audiometric tests and hearing conservation program (HCP) for all personnel exposed to high-level noises.
Similarly, Nadaraja et al.  have attempted to determine the overall noise level in Serdang Raya, Malaysia, with a view to look into the residents' perceptions and awareness about the noise problem on their sleep disturbance. The noise level measurement was conducted using the continuous day night sampling method.  The types and quantity of vehicles that passed through the area were recorded, and a questionnaire survey comprised of 11 questions regarding the socioeconomic and demographic data, level of annoyance, activities and evaluation on the sleeping disturbance was carried out on the basis of randomized sampling method. It is visible that motor vehicles constituted the dominant source of traffic noise, with 37,000 vehicles passed by the residential area.
Comparison of the collected data showed that the noise level has exceeded the standards and guidelines in day and night time limit permitted by WHO, and regulations of Australia, Germany, Japan, Korea, Philippines and Malaysia [Table 3].  Surprisingly, findings from the society survey revealed that >70% of the respondents considered the traffic flow was light or tolerable, while only a small proportion of them reported traffic noise interference, where these respondents woke up more often, experienced worse sleeping quality and felt sleepy during their daytime job. This scenario was primarily attributed to most of the residents, who were staying there for >19 years to get used with the traffic noise, and had adapted it as part of their living environment. The survey outcome also outlined the hope of the respondents to enjoy a peaceful, quitters and conducive living environment. The study highlighted the necessity to promote awareness about the risks of daily exposure to noise disturbance and implementation of proper noise control measures such as erection of effective noise barriers by the local authorities.
|Table 3: Recommended noise level standards and guidelines by WHO and selected countries|
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The discomfort related to the continuous exposure of traffic noise at the Sungai Besi Toll Collection Plaza, located at Seri Kembangan, Selangor among the highway toll plaza employees, highway maintenance and repair crews, and highway inspector has been explored by Azmi et al.  The potential of noise exposure was assessed using sound level meter and noise dosimeter according to the National Institute of Occupational Safety and Health (NIOSH) occupational exposure sampling strategy manual and ISO 9612 Acoustic-Guidelines,  at 20 toll booths for 5 days. The questionnaire survey that divided into four sections, demographic, workplace information, perception toward noise and symptoms of potential NIHL was participated by 71 workers. Result illustrated that majority of the toll tellers were at a high risk of NIHL, and annoyance from chronic exposure to sound levels hazardous of hearing. The mean continuous equivalent level mean maximum level and mean peak level for noise exposure were identified at 79.2 ± 1.4, 107.8 ± 3.6, and 136.6 ± 9.9 dBA, respectively. The study suggested the installation of noise monitoring program, hearing protection devices (HPDs), training, audiometric testing, application of engineering and administrative control, and enforcement of Environmental Quality (Motor Vehicle Noise) Regulations. The findings could be extended to other toll plazas that experienced high traffic volume and the hazard of noise exposure.
Transverse roadway strip (TRS) is a common approach alerts the road users to a roadway changing environment, by generating excessive vibration, pulsating or impulse noise, similar to the sound of knocking a hammer, firecrackers or an explosion. Accordingly, Haron et al.  have evaluated the external noise produced by the installation of rumble strips in Kg. Batu 30 of Pengkalan Raja, Pontian, Johor, a rural settlement area with a population in 60 native houses, and to anticipate the annoyance response due to the installation of TRS. A Pulsar sound level meter and a sound level calibrator were applied for the noise level measurement at locations with and without the installation of TRS throughout the investigation. The equivalent continuous equal energy level (LAeq ), applied to the impulse or fluctuating noise level, and the statistical levels L10 , L50 , and L90 , the percentile levels exceeding 10%, 50% and 90% of the elapsed time respectively were measured. Results revealed that the traffic noise index increased drastically with the presence of TRS, recorded the LAeq , L10 , L50 , and L90 levels of 82, 78, 73, 54, and 67 dBA, respectively. The findings ascertained a strong annoyance of the installation to the community, which prompted vigorous actions and complaints from the local residents.
Meanwhile, Fadhil et al.  have examined the acceptable noise levels for the expansion of Batu Berendam Airport, Malacca to the community of the surrounding area. The proposed site is currently a domestic airport and serves as the center for Malaysian Flying Academy since 1987. On the stage of expansion, this airport will be complemented with modern aeronautical devices while the terminal complex will be reconstructed by a new 7,000 m 2 terminal equipped with international standard amenities. Noise sampling was carried out within the radius of 3 km from the airport, particularly within a residential district to obtain baseline noise information at three consecutive periods, morning, afternoon and evening. The noise levels were measured at every 5 min using a digital sound level meter, where the environmental noise parameters, the equivalent sound level (Leq ) and day-night sound level (Ldn ) were recorded.
Result showed that the expected annoying noise level, generated from the fixed-wing aircraft and ground operations, is greater than the WHO guideline limit. To resolve with the above requirements, the design of takeoff and landing lengths, which would affect the safety of the aircraft operations and neighboring community, need to be carefully developed based on the actual flight tests and operational data. Additionally, the implementation of appropriate buffer zones, including the noise barriers and site design, must be relocated according to the growing air traffics, number of airlines and corporate jets operations.
The effects of transportation noise to the traffic employees and local residents are summarized in [Table 4]. Comparison of these studies addressed an urgency to promote the awareness, knowledge of OSH, attitude, and practice on PPEs. Additionally, the implementation of noise monitoring program, training, audiometric testing, application of engineering and administrative control, and enforcement of environmental quality regulations were suggested. The external annoyance from the installation of rumble strips and expansion of the airport was highlighted. These findings are important at both society and the individual level in regulating in an efficient planning of road traffic activity to secure minimum comfort to the affected populations.
|Table 4: The annoyance of transportation noise to the traffic employees and local residents|
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At the global level, the abatement of traffic and construction noise has been more effective in the United States, with the establishment of Noise Control Act, Aircraft Noise Policy and Aviation Noise Abatement Policy.  These regulations aimed primarily to protect the residents at the peak traffic hour LAeq of 67 dB. In the European countries and cities, various directives regarding noise emissions from different sources, such as motor vehicles, railway systems, aircraft, household appliances, and outdoor machinery have been applied to draw strategic noise maps for the assessment of noise from major transport infrastructures and in communities with >100,000 inhabitants.  In Japan, the environmental quality standards for noise has been implemented against all types of traffic noise sources,  and in Australia, environment protection acts and environment protection policies are regulated to prescribe the maximum noise levels for different classes of motor vehicles with specifications for testing procedures.  Until date, the community noise ordinances and global noise policies are being revised in many parts of the world to incorporate more stringent noise limits and criteria. Even though some successful reduction of road vehicles and aircraft noise has been witnessed, the corresponding reduction of receiver noise values has not been apparent, due to the growing population, traffic and citizen's requirements for a better quality-of-life. 
| Assessment of Industrial and Occupational Noise|| |
Occupational safety and health is a cross-disciplinary subject concerning the safety, health care and welfare engaged in an employment or working environment.  Industrial and occupational noise is a pervasive hazard with many adverse effects, including elevated blood pressure, reduced performance, sleeping difficulties, annoyance and stress, tinnitus, NIHL, and temporary threshold shift.  In the perspective, a perception survey on the public attitudes and level of awareness regarding the odor, noise and visual impact of sewage treatment plants has been carried out in selected areas in Selangor, and the Federal Territory of Kuala Lumpur.  The study was conducted for a period of 2 weeks, where 225 of households were interviewed in 22 different housing estates, with majority of the respondents had at least primary education, and 84.9% had at least secondary education. A wide range of topics related to the reasons, feelings and complaints about living in the vicinity of sewage treatment plants were questioned. Several housing developers were interviewed to obtain a wider purview of the actual situation. It was discovered that industrial noise, emitted by electrical motors and pumps, aerators, rotating discs and splashing of water, from the sewage plants appeared to be a profound psycho-environmental factor affecting the public's acceptance, and nuisance to the nearby residents. A startling finding of the perception survey was the low level of awareness, where 30% of the respondents could not even identify the sewage treatment systems, while 59% of them were either unsure about the purpose of the treatment system.
Similarly, Malakahmad et al.  have identified and accessed the existing occupational hazards at a local sewage treatment plant for total population of 11,500 through Occupational Health and Safety Management System, and properly managed the identified hazards based on a systematic approach. The data were collected via review of literatures, questionnaire distributions, interviews with experts, site inspection and observation. Report of accident investigations, statistics, published documents, regulations and code of practice were reviewed. Chemical safety data sheet and material safety data sheet, which provide information on hazardous materials, control measures first-aided and emergency responses were considered.
Result revealed that biological hazards (38.4%) showed the highest rate of exposure, followed by physical (34.6%) and chemical hazards (27.0%) in a descending order. Interestingly, excessive noise, generated by the applications of pumps for wastewater flow, and blowers for air supply constituted the major on-site risk, with the Leq of 94.2 dBA. This observation is vulnerable to auditory effects, which include both hearing loss and speech interference and psychological/sociological impacts such as annoyance, and sleeping interference. Implementation of sound absorbers indicated that the existing noise (94.2 dBA) was reduced to 92.1 dBA and 90.6 dBA by the application of carpet and cardboard, respectively. The findings highlighted the unsafe conditions encountered by the wastewater treatment plant operators.
The wooden furniture manufacturing industry is the fastest growing subsector in Malaysia, both in terms of workforce employment and foreign exchange earnings. The noise annoyance emancipating from the wood machining processes, specifically structural vibration of machine frames, aerodynamic turbulence of the rotating tools and dust, and wood chips extraction systems remains a debatable concern among the wood manufacturing workers.  Accordingly, a study has been carried out to determine the dust, noise and chemical solvents exposure, and to identify the extent of hearing damage among the wooden furniture industry workers from 30 selected factories, in the South East Asian region, Malaysia, Thailand, Indonesia and Vietnam.  It was conducted over a period of 9 months between March and November, 2009, with the assistance of national furniture trade associations in seven distinct parts. Noise-level measurements were performed using a calibrated portable sound level meter, complying with BS6504. The possible noise-induced hearing problems were quantified by audiometric tests, with the aid of audio-chambers in the range of 500-8000 Hz, for 500 Hz intervals.
Results revealed that 43% of the factories workers were exposed to the noise level higher than the recommended permissible limit, with 25.8% of them had a slight handicap with permanent threshold shift between 30 and 40 dBA, while 8.9% of the workers showed a significant handicap with permanent threshold shift >40 dBA. Rough milling department, which involved heavy-duty operations, molding, ripping, and planning was regarded as the major noise contributor, recorded the highest noise-level of 130 dBA. The study also demonstrated that low attention was concentrated to the application of hearing protective devices. The finding could be tailored to be a reliable representative of the wooden furniture manufacturing industries on the regional scale. The responsibility to enforce and ensure the compliance of effective law within the wooden manufacturing factories was highlighted.
Meanwhile, a structured survey was undertaken to examine the determinants of workers' safety climate, including noise exposure in the Malaysian wooden furniture industry.  The relationship between the safety practices, safety level, and the primary health and safety concerns within 30 wooden furniture manufacturing factories was evaluated. The five-part structured analysis, safety climate and safety precautions, safety practices, safety level, and health and safety issues enabled the identification of primary risk factors among the factory workers. The study strengthened the essential need of human resource practices, consultations and safety management system, as advocated by the ISO 18000 scheme. More specifically, commitment to safety knowledge and trainings had illustrated a statistically significant impact to drive for an improving of safety, productivity and quality.
The electronics industry developed coincided with the New Economic Policy and Industrialization Strategy in the early of 1970s. Till 1980s, it has been pointed out that the incidence rate of occupational illness among the semiconductor workers was three folds higher than the general manufacturing industries. Chee and Rampal  have attempted to identify the health problems commonly experienced by the workers on 24 semiconductor factories listed in two geographical clusters, Bayan Lepas, Penang and Selangor, selected from the Malaysian Industrial Development Authority list. The self-administered survey on socio-demographic characteristics, physical working conditions, chemical usage, and health problems took place in the allocated factories between July 1999 and March 2000. A total of 968 women workers, aged between 18 and 54 years, were participated in this study. Noise exposure (39.6%) was cited as the most confronting physical hazards, reported a significant association with the self-reported stress, irregular menstruation and dysmenorrhea among the manufacturing workers.
Whereas, a survey has been conducted to investigate the relationship between environmental factors, workstation design (heat, noise and lighting) that influents the job satisfaction and discomfort level among 210 operators in four automotive manufacturing companies in Malaysia.  The questionnaires comprised 67 Likert-type multiple choice items,  that divided into five sections: Demographic, discomfort level, satisfaction factors, workstation design, and working environment. The gathered information illustrated that 58.3% of the respondents were exposed to high level of noise, with the correlation, r = 0.441. The study suggested the importance to establish a balance between the job satisfaction and employees' health and safety.
The environmental noise scenario and impact analysis of four different industrial projects in Malaysia: Petronas refinery extension project MG-3, Janamanjung power station in Perak, roller compacted concrete plant in Semenyih and co-generation plant in Melaka have been presented to establish the existing background noise level, and to identify the significant noise sources during the operations.  Noise level measurements were carried out on 16-17 th April, 2003, and the LAeq noise levels at these monitoring stations varied between 45.2 and 76.2 dBA during day-time, and 42.8-56.0 dBA during night-time. These findings are representative of the typical noise impacts from the industrial development project in Malaysia. In the same vein, Zolfagharian et al.  have conducted a structured interview with 15 construction professionals, aimed at prioritizing the frequency and severity of environmental impacts across the residential buildings in Malaysia. Construction activities were identified as the second contributory sources of noise pollution. The findings outlined the need of effective plans to promote the awareness and knowledge of construction practitioners, and implementations of noise control strategies by construction of barriers, and application of noise protective tools.
[Table 5] depicts the assessment of industrial and occupational noise for different industries. Comparison of the research findings indicated that occupational exposure to industrial noise is dependent on a variety of determining parameters, particularly type of industry, workplace-specific factors, including facility and process, raw materials, machinery, tools, engineering and work practice controls, the use of personal protective devices, and duration of the interference. Today, excessive occupational noise exposure is a pervasive hazard with considerable social, physiological and economic implications.  In the United States, >30 million of workforces are exposed to the time-weighted average sound levels of above 85 dBA.  In the European Union, 28% of workers surveyed reported that at least one-fourth of the time, they are occupationally exposed to noise loud enough that they would have to raise their voices to hold a conversation.  Despite a statistical summary on the industrial noise exposure for most developing and non-industrialized countries is not available, high occupational noise exposure levels have been reported in 17 studies conducted in 12 countries in South America, Africa and Asia. 
|Table 5: The assessment of industrial and occupational noise for different industries|
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Accordingly, NIOSH has recommended a national framework for the effective reduction of workplace noise and more targeted hearing loss preventive programs specific to the characteristics of these industries and occupation groups:
- Initial and annual audits of procedures,
- Assessment of noise exposures,
- Engineering or administrative control of noise exposures,
- Audiometric evaluation and monitoring of workers' hearing,
- Use of hearing protectors for exposures >85 dBA,
- Education and motivation of workers, and
- Good record keeping. 
| Environmental Noise Monitoring and Modeling|| |
Today, the development of computational monitoring and mathematical simulation related to the transportation or propagation of noises, and associated with the complexity of sources, receivers or predictive models, have become a challenging issue for improving public health and quality of life. Noise prediction models play a vital role to assess the contemporary changes of traffic, railway, airport, factory or design schemes of town planning. A study took a closer look into the background noise level and dominant noise sources in several selected locations in Malaysia, has been carried out by Ismail et al.  at Lahad Datu to present the noise scenario for East Malaysia, JanaManjung, Perak to represent the West Peninsular Malaysia, Tangga Batu, Melaka to represent Mid-West Peninsular Malaysia, Terengganu to represent East Peninsular Malaysia, and Lido, Johor to represent South Peninsular Malaysia.
Baseline sound levels were monitored for two different periods, day-time and night-time readings, and noise descriptors, such as L10 , L90 and Leq were recorded. West Peninsular Malaysia (Janamanjung Perak) illustrated the highest day and night-time Leq of 75.5 dBA, while Mid-West Peninsular Malaysia (Tangga Batu, Melaka) noted the lowest day and night-time Leq , 55.0 and 53.1 dBA, respectively. These data are useful as a reference and guideline for future regulations on noise limit to be implemented for the urban areas in Malaysia. The analysis would benefit the researchers and policy makers, especially for those who involve directly with the noise pollution of environmental impact assessment (EIA) with the Department of Environment, Malaysia.
Noise models are established to assess the degree of noise annoyance for a given projected road, highway, railway, airport, factory or town planning. Since 1950s, traffic noise prediction models were designed to estimate the single vehicle sound pressure, based on a constant speed experiments. The earliest road traffic noise model was given in the Handbook of Acoustic Noise Control.  With the help of computer graphic programs, the predicted noise levels can be presented by a noise exposure map.
According to the diffused-field theory, Abdullah and Nor  have developed an adaptive three-dimensional Gauss-Legendre Quadrature technique to simulate the propagation of outdoor noise from sources with variable shapes and power distribution. The method takes into the account of geometry of a defined sound source, and produces appropriate contours conforming to the shape of sources. The noise sources are modeled as an array of point sources, in the form of lines, planes and three-dimensional blocks. The simulation is accepted to represent the real scenario, with the overall level difference <±1.2 dB. This mathematical approach has been successfully implemented in a number of EIA studies in Malaysia.
The inferences drawn about the noise-working efficiency relationship are often referred to the actual surveys, but not supported by the mathematical formalism. This underlines the need to model the cause-effect relationships in the context of noise-working efficiency linkages. A fuzzy model for predicting the effects of noise pollution as a function of noise level, time exposure and age of the operators has been presented.  The noise level of grass trimmer, equipment widely used in the maintenance of grass areas in Malaysia was measured, and the age, time exposure, task, and performance of 300 workers for three interval time, 2, 5, and 8 h respectively, were recorded. The modeling system was proposed into four sequential steps: Identification of input and output variables, selection of input and output variables, determination of the functions for input and output variables, and formation of the set of IF-THEN rules. The result was visualized in the form of graphs, and compared with the safe exposure limit recommended for the industrial workers. The findings inferred that the working efficiency depends on the time exposure in related to the age and noise level, where the reduction follows a logarithmic behavior in the noise range of 85-115 dBA. These studies outlined the prominent role of noise monitoring and modeling systems as a convenient way for predicting the effects of noise pollution, and yields a real-value output from the on-site monitoring information.
In short, a proper modeling of noise production is a powerful tool for the effective simulation of the behavior of acoustic waves in the external environment. Independent of the bases of available data, which are sometimes very limited, and of the choice of calculation method for reliable prediction of changing environment, noise prediction models constitute an essential toolbox that deeply validate the propagation, sources' characterization, dose-effect correlation, or qualitative and quantitative determination of the acoustic noise. , These growing numerical models have been effectively applied to a number of different situations in which noise pollution must be analyzed, predicted or reduced.
| Conservation Program and Control Measures|| |
In Malaysia, the HCP was introduced under the Noise Regulation 1989,  with the main objectives to protect industrial workers from noise exposure and prevent NIHL. HCP was divided into seven major sections, the government policy and owner policy, noise exposure monitoring, noise control, providing HPD, audiometric program and treatment, training program and record keeping. Although the enactment of Noise Regulation has been enforced for >14 years, the industries' compliance toward HCP remains unknown.
In the perspective, a cross-sectional study has been conducted from July 2003 to September 2003 among 167 industries registered to the Department of Occupational Safety and Health, Negeri Sembilan, with the main objectives to determine the factors influencing HCP, and to assess their compliance to HCP.  The survey also aimed to identify the association between HCP with the prevalence of hearing impairment and standard threshold shift. Data were collected by self-administered questionnaires about the socio-demographic status, type of industry, ownership, number of employees, duration of operation and formation of the Occupational Safety and Health Committee. It was found that only 41.3% of these industries were fully complied to the program, with most industries were least compliant in using engineering or administrative controls. The results were in according to the hypotheses that the compliance is higher among industries, which are owned by the foreign investors, with at least 150 workers, shorter duration in operation, and hire officers in charge of HCP as compared to the opposite groups. The study strengthened the importance of HCP, as an effort to tackle with the hearing problems among the industrial workers. The findings could be applied as a reference to improve the enforcement of policies and regulations by the relevant authority.
Meanwhile, Wong et al.  have organized a low cost and simple ergonomic intervention for occupational health and safety (OHS) improvement on a conventional line (CL) in a semiconductor factory in Malaysia. A validated questionnaire, on the employees' demographic data (age, gender and service years), work-shift (morning, afternoon or night) and job scope (wire-bonding, die-bonding, molding, plating, trim-form or testing) was designed on the basis of Sinclair's  and Sekaran's  guidelines. The auditory assessment was conducted to determine the extent of noise production while direct observation provides an insight into the effectiveness of those interventions. Results showed that the operators were exposed to the noise disturbance higher than 90 dBA for the 8-h shift. The interventions introduced the integration of noise insulating covers, personal protection devices, and installation of an elevated platform and extra exhaust fans. These interventions have successfully rectified the workers' OHS and better working environment. The finding could be empirically applied in other semiconductor/electronics factories, particularly among industrially developing countries (IDCs) that share the similar manufacturing processes.
Zulkifli et al.  have advanced an investigation to examine the potential of coir fiber in replacing synthetic and mineral based fibers for sound control applications. The effects of porous layer backing and perforated plate on sound absorption coefficient were evaluated. The samples were tested at the acoustic lab of Faculty of Engineering and Built Environment, National University of Malaysia, according to the ASTM E 1050-98 international standards. Experimental results showed that coconut coir fiber with perforated plate gave higher value at lower frequencies of 600-2,400 Hz. The optimum value for coconut coir fiber with perforated panel was around 0.94-0.95 at the frequency range of 2,600-2,700 Hz. The finding demonstrated the feasibility of this innovative sound absorption panel for real practical application, due to their renewable, nonabrasive, cheaper, abundantly availability and environmental friendly as compare to the synthetic based materials.
Conclusively, the establishment of noise conservational amendment, education, training, operations and motivational programs, including the consistent use of engineered controls and personal hearing devices, administrative scheduling to limit noise exposure, and reliable prediction on the dangers of noise propagation is a protective compliance to improve the knowledge, attitudes, and practice for environmental and occupational noise pollution control.  To further encourage the conservational capabilities, a new alliance between the government and consensus organizations, Occupational Safety and Health Administration, NIOSH, and National Hearing Conservation Association associated with individual perceptions of vulnerability, seriousness of the hearing loss threat, and OSH for the development of good hearing health and best management practices should be promoted. 
| Conclusion|| |
The commencement of the 21 st century represents a global pressure towards the tremendous impacts of rapid urbanization, population growth, environmental noise and the natural environment. Compelling evidence has identified the adverse impacts of environmental and occupational noise on the health of the global population. This narrative review evaluates the distribution of noise pollution problem in Malaysia. Results from the survey, monitoring, short term and longitudinal studies have positioned the noise pollution scenario in Malaysia at a critical level. This highlighted the resurgent need of practical solutions by the government, non-governmental organizations and educational institutions to generate a healthy working and living environment. The plan espouses the organization of environmental awareness and conservative program, enforcement of environmental protection rules, and the establishment of EIA prior to projects approval. Conclusively, more integrated actions and practical strategies should be pursued systematically to underpin the inter-agency collaboration, public engagement and innovation, which are paramount towards building a sustainable future.
| Acknowledgments|| |
The authors acknowledge the financial support provided by Universiti Sains Malaysia under the Short Term Grant scheme (Project No. 304/PPSK/61312127).
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Foo Keng Yuen
Environment and Occupational Health Programme, School of Health Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]