Noise pollution is a major problem confronting the environment and it people. The problem has existed since years, however, in the recent decades urbanization combined with development of transport and industry has begun to severely plague the society. In most developed countries noise pollution is omnipresent, though much emphasis in not given towards its effect and control. Across the globe, urban population is greatly affected due to noise pollution, with the rates especially higher for the metropolitan cities.
Some of the predominant sources of noise pollution are road traffic, jet planes, garbage trucks, construction equipment, manufacturing processes, and lawn mowers (Birgitta and Lindvall, 1995). The roar of the aircraft, thunder of heavily laden trucks and thumps and whines of industry broadcast these noisy and unwanted sounds into the air (WHO, 2001). Such unwanted noise is not only annoying or disturbing but also pose health hazard and are hampering economic development. Noise pollution is problem faced by developed and developing countries alike.
According to Kapoor and Singh (1995), the effects of noise are so annoying and worrisome that in certain countries it considered next to crime. In China, till third century B. C. , noise has been used for torturing and punishing criminals with dangerous crime record. Bond, (1996) estimates that 16% of people in Europe are exposed to 40 dB or more of traffic noise in their bedrooms accounting for disrupted sleep. Initiative steps have been taken by various countries to keep the noise level under control.
In the United States an initiative has been taken to create sites where human-caused noise pollution will not be tolerated (Geary, 1996). The laws of Netherlands do not permit construction of houses in areas where 24-hour average noise levels exceed 50dB. According to the Noise Act in Great Britain, the local authorities are empowered to confiscate any equipment that can cause excess noise. In addition, people who create excess noise at night are also fined heavily.
Very recently, many countries are looking towards ‘porous asphalt’ technology as a good strategy to curtail traffic noise by up to 5dB (Singh and Davar, 2004). Impact on Health The response of the human ear to sound depends both on the sound frequency (measured in Hertz, Hz) and the sound pressure, measured in decibels (dB). A normal ear in a hale and healthy young person can sense sounds with frequencies from 20 Hz to 20 000 Hz and speech frequency ranges from 100 to 6000 Hz (WHO, 2001). Noise pollution is a deliberate and restrained killer which has become a hazard to quality of life.
Even moderately low levels of noise negatively affect human health, causing hypertension, disrupt sleep and hinder cognitive development in children. According to Bond (1999) excessive noise could result in permanent impairment of memory or a psychiatric disorder. Haphazard use of vehicle horn and widespread use of loud speakers in Indian social and religious ceremonies cause various health hazards in urban populations. Associated problems are deafness, nervous breakdown, mental disorder, heart troubles and high blood pressure, head-aches, dizziness, inefficiency and insomnia (Bhargawa, 2001).
Singh (1984) observed that the workers exposed to elevated noise levels have a greater frequency of circulatory problems, cardiac diseases, hypertension, peptic ulcers, and neurosensory and motor impairment. WHO (2001) estimates that about 120 million people worldwide are estimated to have disabling hearing difficulties. The reports also that estimates more than half citizens of Europe reside in noisy environment and in the USA the number of people exposed to occupations noise level above 85 dB increased from 9 million in 1981 to 30 million in 1990.
In Germany and other developed countries as many as 4 to 5 million working people are exposed to noise levels of 85 dB or more (WHO, 2001). This has resulted in noise-related hearing impairment. Risks of permanent medical conditions, such as hypertension and ischemic heart disease are also higher in communities exposed to noise pollution for an extended period. In adults and in children it adversely affects reading, memory, attentiveness and problem solving performances. Noise above 80 dB may increase aggressive behavior provoke annoyance responses and changes in social behavior (WHO, 2001). Sources of Noise Pollution
Community noise High volumes of sound coming from open-air concerts, discotheques, motor sports events etc are non-industrial sources and are categorized as community noise. This is also termed as environmental, residential or domestic noise. The major indoor sources are ventilation systems, office machines, home appliances and neighbors. Other typical sources of neighborhood noise are restaurants, cafeterias, live or recorded music, sports, playgrounds, car parks, barking dogs. In the recent decades there has been a continued growth in transport systems such as highways, airports and railways.
This has further accelerated the generation of more noise. Road traffic is another key source of noise in metros. Nagi et al. (1993) observed that household equipment and appliances produce noise level that sometimes reaches up to 97 dB which is more than double the acceptable (45dB) noise level. Several countries have policies on community noise arising from rail, road, construction sites and industrial plants. These policies are based on emission standards. However, very few regulations are available on neighborhood community noise.
This is perhaps due to difficulties with its classification, measurement and control strategies. Ultimately lack of sufficient knowledge of noise pollution effects on people prevents further action to prevent and control this environmental problem. Occupational noise Noise is a common occupational hazard in several workplaces. The major sources of noise that damages hearing are impact processes, material handling and industrial jets. Air jets — widely used, for example, for cleaning, drying, power tools and steam valves –can generate sound levels of 105 dB.
Sources of noises in industrial machinery and processes are multi-various. These include: rotors, gears, turbulent fluid flow, impact processes, electrical machines, internal combustion engines, pneumatic equipment, drilling, crushing, blasting, pumps and compressors (WHO, 2001). In addition, the emitted sounds are reflected from floors, ceiling and equipment. Exposure rate is also another parameter to be greatly considered. WHO (2001) estimates that in a cigarette factory in Brazil workers involved in compressed air cleaning were exposed to sound levels equivalent to 92 dB for 8 hours.
The sound levels of saws can be as high as 106 dB in the woodworking industry. In industries such as foundries, shipyards, breweries, weaving factories, paper and saw mills average sound level ranges between 92 and 96 dB. The recorded peak values were between 117 and 136 dB (WHO, 2001). Occupational exposure limits spells out the utmost tolerable sound pressure levels and exposure duration times to which workers may be repetitively exposed without undesirable effect or impairment on hearing and their ability to comprehend normal speech.
WHO (2001) estimates that an occupational exposure limit of 85 dB for 8 hours should defend the majority of people against a permanent hearing mutilation induced by noise after 40 years of occupational exposure. Control Noise-induced hearing impairment is certainly avoidable. This is possible by protection against perilous noise exposure by means proper hazard prevention and control programs in residential communities and occupation places as well. Noise pollution can be effectively management by several strategies.
Firstly, the design and technology of industrial machinery and equipments could be changed to minimize the noise levels. Noise emission levels should be declared on the machineries. This would permit prospective buyers to select the least hazardous equipment and also to calculate the noise impact at workplaces and to further help with noise-control planning (WHO, 2001). When the cost is worked, making noise-generating processed quieter is 10 times less expensive than to make a barrier to screen the noise. The dangers of noise should be recognized upfront, even before workers start complaining of hearing impairments.
Secondly, noise levels can be lessened by the use of noise-control enclosures such as absorbers, silencers and baffles and by the use of personal protective equipment, such as earmuffs. Use of noise barriers may help control noise. The third strategy is to defend receptors of sound by protective shields. This can be done by proper insulation of buildings, body and window planes made sound proof. Nevertheless, where technical processes are inadequate, noise exposure may be lowered by putting-off the time spent in noisy environment or alternatively by scheduling noisy operations outside normal shifts or at remote and distant locations.
Apart from these strategies, it is quite necessary for the worker to have a clear understanding and knowledge on the machineries and the way to handle them. Noise pollution being a social problem, educating the public proves to be a good alternative. Singh and Davar (2004) suggest that sheer ignorance about the deleterious effects of noise pollution emerges to be a prime factor hindering to reduce and control its levels. Hence an essential element of noise control programs should include education and training of the workers and local public.