By Maxwell Pereira
NOISE HAS been defined variously. Physically, 'Noise is a complex sound with little or no periodicity. Acoustically, 'Noise is defined as a signal that bears no information and whose intensity varies randomly and in time. Psychologically. Noise is any sound which is unpleasant or unwanted'. Commonly, it is the last definition that affects and touches every soul.
Increasing urbanization has led to mounting volumes of noise. Intruding upon the quality of life and privacy of urban dwellers. The annoyance and discomfort caused by noise at time assume serious proportion meriting urgent attention. Consequently, the seminar on Noise Pollution organized recently in Delhi by the Department of ENT and the Centre for Occupational and Environmental Health of Maulana Azad Medical College in association with AASOCHAM could not have come a day early.
Noise can cause interference in speech and in the enjoyment of audio and television programmes. It can cause disturbance in the studies and intellectual pursuits.
Noise is conventionally measured in terms of the pressure measured in terms of the pressure of the sound wave. All government authorities and international standards specify exposure levels in terms of decibels applicable over an eight-hour exposure with peak exposure level. Noise in cities is a result of a number of activities and factors such as road traffic, aircraft. Railways and industrial and constructional works. Widespread prevalence of high intensity levels of sound from all these activities in our environment is termed as noise pollution.
Without going into the wide gamut of noise sources, let me herein tackle noise emanating from road traffic. The generation of noise from the automobile machinery as well as the widespread and often unnecessary use of horns is a major contributor to the level of ambient noise in most cities today. It is the traffic personnel who are the most exposed to this menace throughout the day. Also persons who works in establishment at various important crossing and commuters on the road also suffer the ill effect Detrimental effects of traffic noise can be under 3 major groups-the subjective effects the behavioural, and physiological Subjective effects are annoyance, disturbance, dissatisfaction, bother and noisiness. These are difficult to measure precisely because a wide variation can exist among subjects in describing what level of sound causes them annoyance and discomfort. Behavioural effects cover interference with sleep. Speech or any general task Noise wakens up people - especially children or impairs quality of sleep and its duration. Disturbance in sleeps is common high noise areas in which it also takes longer time to fall off to sleep and there are greater chances of waking up. Noise can cause interference in speech and in the enjoyment of audio and television programmes. It can cause disturbance in the studies and intellectual pursuit. It can upset balance between stress and recuperation and thus cause chronic fatigue, reduced efficiency and in increased incidence of ailment.
Physiological effects are those that startle or cause fright phenomenon and can result in harmful effects on various part of the body Exposure to Noise can raise blood pressure, accelerate heart rate, contact blood vessels of the skin increase muscular tension and at extremely high levels and long periods of exposure, it may produce deafness.
Noise caused by road traffic can be that - from various parts of the vehicle, that contributed by the interaction between vehicle and road surface, and noise dependant on the speed, flow or density of traffic. Also the vehicle itself, with its elements that contribute being engine (Power unit. Especially during acceleration), the inlet and the exhaust; propulsion and transmission including gears and breaks, the load factor in the vehicle and also door slamming.
Motorcycles and Scooters are generally noisier than passenger cars. Commercial trucks are major source of noise because of the large horse power of the diesel engine and the heavy loads they carry and as vehicle grow older and then mechanical conditions deteriorate, them noise condition deteriorate, then noise condition becomes more. In tyre /road - surface interaction smooth surfaces generally produce less noise than rough ones Grooves cement concrete payments are at times a source of annoying noise to the neighborhood. And wet surfaces contribute too.
As traffic volume (flow) increases, the noise level inevitably rises. Higher Speeds cause higher noise levels. At lower speeds, the influence of engine and transmission noise is predominant - at high speeds the tyre - surface interaction assumes greater important Noise levels increase during acceleration.
Control of traffic noise can be considered with changes vehicle design, changes in tyres or road surfaces elimination of noisier vehicles; modification in traffic operations and designing streets, building and areas that produce less noise. Changes in tyre - tread design and composition can reduce noise. Smoother surfaces result in less noisier roads but this has simultaneously to be balanced against the required skid resistance factor of the tyres too. And legislative measures can prevent old vehicles from being used on roads.
Some measures possible in traffic operations are - re-routing of commercial vehicles and buses to the extent possible from predominantly residential areas; providing bypasses on Ring Roads to siphon off traffic entering the town; providing synchronized traffic signals at street crossing to reduce the stop and go traffic flow and consequently eliminating acceleration noise; and prohibiting the blowing of horns by proper signages and enforcement strategies as was done by Delhi Traffic Police earlier this year banning honking at signalized junctions.
The Central Motor Vehicle Rules - 1989 require a motor vehicle to be fitted with an electric horn for purpose of warning only. And specifies against the use of any multi -toned horn or other sound producing device giving an unduly harsh, shrill or alarming noise Ambulances, fire engines, salvage vehicles or those of police and motor vehicles department are permitted the use of such sound signals (sirens) as may be approved by the authority. Every motor vehicle is required to be fitted with a silencer to reduce as far as practicable the noise that would otherwise escapes from exhaust gases. The Rules of the Road Regulations - 1989 further prohibit a driver from sounding the horn needlessly or continuously or violate the silence zone regulations or drive a vehicle that creates noise when in motion and against driving a vehicle with a muffler causing alarming sounds.
Noise levels above 80dB are considered detrimental to healthy hearing. And for normal tension free conversation one requires a background noise level of <55dB. However, noise standards prescribed in the CMVR for petrol driven two wheelers is 80 dB (A). for passenger cars and other petrol driven vehicles -82 dB (A). For passengers or LCVs including three wheeled vehicles with diesel engines upto 4000 Kgs.- 85 dB (A), for passengers commercial vehicles above 4000 and upto 12000 Kgs. 89 dB (A. Compared to this, the acceptable noise levels prescribed in USA by the Federal Highway Administration are for parks and open spaces, the exterior limits to be not above 60dB (A) For residential areas within the buildings -55 dB (A) and outside the buildings - 70 dB (A) and for other developed areas 75 dB (A).
The Delhi Traffic Police in 2000 launched 2,11,177 prosecutions against those blowing pressure horns and violating Silence Zone restrictions. The corresponding figure for 2001 is 1,91,546 And up to end of April 2002. While 60,663 were similarly prosecuted another 15,727 faced challans for honking at signalized junctions too.
© copyright : Maxwell Pereira
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