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Rapid urbanization and industrialization eventhough facilitate our lives, leads to various forms of environmental pollution. This paper presents the results obtained in a study on environmental noise pollution in the city of Salem. Road traffic noise has been a major contributor to the annoyance, which is substantiated by the result of continuous monitoring of noise equivalent levels (Leq) at a number of silence, residential, commercial, industrial zones and road intersections. In conclusion, the noise pollution of the city is wide spread throughout most of its area, where measured noise levels are similar to those commonly observed in cities that do not have mitigation programmes. Public participation, education, traffic management, structural designing play a major role in noise management
Noise, road intersections
Noise has become an alarming issue due to ever growing population and inevitable developmental activities throughout the globe, which poses cumulative stress to all biotic entities. The increase in population and the number of circulating vehicles have led to an increase in the urban noise levels (Calixto et al., 2003). The need for study regarding the urban noise pollution and its consequences for the environment have motivated various researchers on the problem in several countries (Burgess, 1977; Zheng, 1996; Yoshida and Osada, 1997; Ravichandran et al, 1997, 1998; Arana and Garcia, 1998; Suksaard et al, 1999; Abdel-Raziq et al, 2000; Zeid et al, 2000; Kanakasabai et al, 2002 Jorge et al, 2004) .The continuous exposure of the workers to high noise levels can cause Noise Induced Permanent Threshold Shift (NIPTS) in their hearing (Sharma et al .,1998), damages the ear drum and ossicles causing deafness (Kudesia and Tiwari, 1993). The objective of the present research was to show the noise level measurements in different zones of the city and to bring in focus how far the people are unaware and expose to it.
Salem district is geographically situated at about 11°39’ N Latitude and 78°12’E Longitude and is about 241m above the mean sea level except Yercaud hills. It has an area of about 7905.38 Km2 with 38,96,388 inhabitants. Entire district comprises of a hard rock terrain of Archean age with the principal rock type of granite and a semi-arid weather. It is assessable by National Highways 7 and 47, that connects major part of the state and the country. It has major industrial units like Steel Authority of India Limited (SAIL), Tamil Nadu Magnesite Limited (TANMAG) and many Sago units. Because of such importance, population rapidly increases and flooded with vehicular traffic throughout the day. As a result, noise has become a part of the city.
The ambient noise levels were monitored in selected silence, residential, commercial, Industrial zones and road intersections of the city and compared with the ambient noise standards promulgated by Central Pollution Control Board (CPCB). The noise level measurements were recorded using a precision sound level meter-TES 1350 with a measuring range between 35-130dB. The instrument was calibrated before the measurements were recorded. A distance of 2m from the source has been maintained during measurements (Prabhakara Murty and Sudharshan Reddy, 1996). In each location, adequate number of samples was made with one-minute time interval between two subsequent readings (Edison et al., 1999). The noise levels are recorded both during peak (0800 to 1000 and 1700 to 1900 hours) and non-peak (1000 to 1700 hours) timings of the day (Vishwanath and Anantha murthy, 2003) in road intersections and commercial areas.
From these measurements, the minimum sound pressure level Lmin, the maximum sound pressure level Lmax was observed. However, to quantify the variability of noise during each measurement, the percentiles L90 and Leq were also calculated (Michael, 1991).
The city of Salem is divided into four zones, each of them with a particular noise emission limit. The allowable limit for each zone in particular can be observed in Table 1 .The locations covering silence, residential, commercial, industrial zones and road intersections and the results are summarized in the Tables 2 to 6.The noise in these areas is usually composite in nature and generated from many sources near and far with no particular sound predominant.
Noise levels measured at some of the silence zone locations consists of collectorate, hospital, park and educational institutions varied between 61.8 to 72.78 dB(A), exceeding the standard level of 50dB (A) as shown in Fig. 1. In K.N.Rao hospital and govt. Arts College the Leq of 69.77 and 61.8 dB(A) is observed. For silence zone locations, proper designing and acoustic planning of the building is essential. One is to orient the building axis perpendicular to the direction of the roadway and then to locate the noise sensitive rooms at the end of the building. In case of hospitals, operation theatres and intensive care units could be located at the farthest end. Use of horns, loud speakers and bursting of crackers must be banned in these places (Shasthri et al., 1996)
The Lgq in residential areas ranged between 66.6 to 70.83dB(A)The noise environment is alarming due to higher noise levels than the established standards as shown in Fig.2. All the five locations had Leq values greater than 65dB(A). It is observed that the residential location (Fairlands) near the central bus stand is exposed to comparatively higher noise levels. In contrast, the Swarnapuri Annexe shows low levels. This is due to its location away from the main road and the attenuation due to houses shielding the location. Developing green belt in these zones will bring down the noise levels within the limits (Siddique and Shamin, 1998).
Measurement in commercial centers was also carried out to assess the impact on community. The Leq was in the range of 80.26 to 92.3dB(A) in peak hours and 69.93 to 81.85dB (A) in non-peak hours. The L90 values are greater than 60dB(A) throughout the day. The encroachments of the vendors and small businessmen causes traffic congestion with frequent hooting. Consequently, people are exposed to high noise levels. It is observed that all the areas exceed the CPCB standards as found in Fig. 3.
The Leq noise levels in the industrial zones vary from 84.95 to 94.32dB (A). The observed noise levels were more than the standard permissible limit of 75dB(A) and these are illustrated in the Fig. 4. The L90 of 83.1dB(A) is observed in TANMAG, which clearly indicate the high levels of occupational noise exposure. Noise reduction is imperative to protect workers from permanent hearing loss. This can be effected through insulation of the source, better maintenance of machinery and exhaust mufflers. The hearing conservation programme, by undertaking periodic hearing tests, can identify workers who have high susceptibility to noise induced hearing loses.
The noise generated through traffic activities was also assessed at main road intersections of the city. The participation of vehicles in traffic flows leads to a steady state urban noise that causes sleep disturbances, annoyance and interference to communication. The Leq values ranges from 89.98 to 93.5 dB(A) in peak hours and 78.78 to 87.57dB(A) in non-peak hours. In practice (Mitani and Ohta, 1986), the Leq is very widely used since it allows a simple quantification of noises that may often vary in a highly non-stationary manner. The observed noise levels are very high and illustrated in the Fig.5. Since the vehicles flowing through different directions wait in signal with running engines, road intersections are always encountered with high noise levels. So the traffic policemen are highly affected.
For obtaining the reaction of the public in different localities of the city, a survey was conducted by questionnaire method. In all 200 respondents selected at random, the following results were obtained.
38% of the public felt that heavy trucks were the main source of noise pollution. 90% of the public conveyed that the level of noise is increasing day-by-day. 96% felt that unplanned urbanization and lack of awareness have resulted in increased noise pollution. 34% have ringing effect in their ear and 16% consulted ENT specialist. 70% felt that they live in a noisy environment.
This research looks at the possibilities for real time control of noise pollution. It is concluded that the environmental noise pollution problem caused by the traffic vehicles is the main cause of urban noise levels. The inhabitants living in these areas are bound to suffer from health problems and low life quality. From the technical point of view, it is necessary to take several measures in order to reduce the noise levels. In order to do so, measures should be considered as follows:
* Reduction of speed limits, mainly near residential areas, schools and hospitals.
* Incentives may be given to the vehicle manufactures to develop new systems in order to reduce sound power emissions. Removal of encroachments and banning the use of air horns within the city limits.
Among all things that can be done to relieve the environmental noise pollution problem in the city of Salem, the most effective one is to promote awareness of the population about the risks of daily exposure to high noise levels. Noise abatement is less of a scientific problem but primarily a policy problem, and this is not yet understood in Salem as well as in Tamilnadu.