Paragraphs on Noise pollution!
Noise is unwanted sound and covers all sounds which can result in hearing impairment or are harmful to health, or otherwise dangerous.
According to K.E. Maxwell, “Noise is any sound that is not wanted. It is one of the more common forms of atmospheric pollution.”
Noise pollution may be defined as the state of discomfort and restlessness caused to humans by unwanted high intensity sound. More and more noise is created as the modern civilization moves ahead. It has now become a major environmental pollutant especially in urban areas. In 1972, the UN Environment Conference at Stockholm, noise pollution has been accepted as a problem, which needs proper control.
The most popular measure of noise level is the decibel measured by an instrument known as decibel meter. A sound between 0 and 1 decibel is about the weakest that the average human can hear. For testing purposes, 0 decibel is considered to be the threshold of hearing.
A whisper is about 20 decibels and an average speaking voice is about 60 decibels. The loudest sound that a person can stand without discomfort is about 80 decibels. Automobile horns may reach 90 decibels and a jet airplane may have an intensity of about 140 decibels. The levels of common noise are given in Table 9.22 and have also been depicted in Figure 9.19.
Table 9.22 Intensity of Various Sounds:
|Sound Source||Intensity (in decibels)||Response Criteria|
|Soft whisper||30||very quiet|
|Library, bedroom slow radio||30-50||quiet|
|Light auto traffic, air conditioning unit||50-70||intrusive|
|Freeway traffic, freight tram||70-80||annoying|
|Motor cycle, heavy traffic||80-100||very annoying; hearing damage|
|Carrier deck jet operation||140-150||painfully loud|
Actually, loudness alone is not the sole cause of noise problem, although the most apparent characteristic of noise that creates environmental problems. Pitch of the noise also influences the degree of annoyance—the higher the pitch, the greater the annoyance. Similarly, duration of the noise also determines how annoying or irritating noise will be. The degree of noise in an enclosed space or indoors is different from the level of outdoor noise.