The sound is a physical phenomenon that stimulates the sense of hearing, in human beings hearing takes place whenever the vibration of frequencies between about 15 to 20,000 hertz reach the inner ear. Hence, noise pollution can define as an unpleasant and unwanted sound.
Noise may define as any sound that can produce an undesirable effect to living especially human either physiologically or may interfere with personal, social or group activities or work or communication or rest or recreation or sleep. Thus, the noise measured by the sound level meter.
Unit of Noise Pollution Measurement
It is the wounding energy transferred per second from the sources (sound) to the air. Power express in watts (W).
Sound Power Level Lw
The sound power in watts converted to decibel scale is called the sound power level.
The amount of air pressure fluctuation created by the source of the sound.
Sound pressure expressed as Pascal. A healthy young person can hear sound pressure is low pressures as low as 0.00002Pa.
Sound Pressure Level (SPL)
Sound pressure converted to the decibel scale is called sound pressure level.
Decibel (dB) used in environmental noise pollution as a measure of sound power level, sound intensity level, and sound pressure level.
Furthermore, the sound pressure ratio expressed on a logarithmic scale. This logarithmic scale takes care of a wide range of sound power, intensity, and pressure.
dB = 10* log (A/A0)
In general, dB of the quantity A, relative to the reference quantity A0 defined as above.
Daytime: 6 am to 9 pm
Night time 9 pm to 6 am
Noise Rating System
A noise may consist of different type of sound with different pressure levels operating for different time intervals.
The frequency of this sound may vary. So, the combined resultant impact of different sound pressure lasting different periods works out by using some statistical measures as LN and Leq system.
The LN Concept
The parameter LN is a statistical measure indicating how frequently a particular sound level exceeded.
The value of LN will represent the sound pressure level that will exceed for N% of the gauging time.
The Leq concept
The Leq defined as the constant noise level, which over a given time, expands the same amount of energy, as extended by fluctuating levels over the same time.
Sources of Noise Pollution
Following are the primary sources of noise pollution
- Traffic sources
- Industrial sources
- Constructional sources Other miscellaneous sources
Noise created by various means of transport like trucks, tractors, buses, trains, airplanes, etc. are the traffic-related source of noise pollution. It may be in the form of:
- Horn of vehicles
- Raise of accelerator
- The car with the damaged silencer
- Noise produced by a diesel car will be more than that provided by a petrol car.
- A jet aircraft will produce more noise than a propeller type of aircraft.
Noise is the essential by-product of industry, its intensity and nature are dependent upon the type of production.
Industrial noises usually produced by:
- Reciprocating or rotating machinery
- Cutting of materials, grinding
- Blow hammers
- High pressure and high-velocity gases, etc
- Sounds produce by various constructional activities are:
- Rock crusher for production of aggregate
- Pile driving equipment
- Boring and drilling equipment
- Road rollers
- Materials handling by conveyers
- Rock blasting
Other miscellaneous sources
- In the residential area – the loud voice of T.V., music systems, radio, etc
- Public address system – public functions, Navratri festival etc.
- Sirens – Police van, industries, ambulance
- Military sources – noise of bomb, grenade explosion, tanks other vehicles, missiles etc.
- Use of crackers during Diwali and other celebrations.
- Shouting of hawkers at marketplaces
- Playing of children at the playground.