Noise is often defined as “unwanted sound”, but this definition is subjective because of the fact that one man’s sound may be another man’s noise. Again the better definition of noise is: “wrong sound, in the wrong place, at the wrong time”. Noise has become a very important “stress factor” in the present environment.
Noise has two important properties:
- Frequency: The human ear can hear frequencies from about 20-20,000 Hz, but can change according to the subject.
|Sound levels of some noise
|Source of noise||
Sound level (dB)
|2||Music on radio||85|
|4||Speech on radio||80|
|7||Speech, 2-3 people||73|
Acceptable noise levels (dBA)
Park’s Textbook of Preventive and social medicine