Measurement 

 A decibel is the standard for the measurement of noise. The zero on a decibel scale is at the threshold of hearing, the lowest sound pressure that can be heard, on the scale acc. To smith, 20 db is whisper, 40 db the noise in a quiet office. 60 db is normal conversation, 80 db is the level at which sound becomes physically painfull.

The Noise quantum of some of the cities in our country indicate their pitch in decibel in the nosiest areas of corresponding cities, e.g. Delhi- 80 db, Kolkata - 87,Bombay-85, Chennai-89 db etc.

On the basis of measurement noise pollution can be divided into following type

Sounds of normal conversation:
Sound Intensity: 40-60 db
Health Hazard: Sound, less than 80 db, is safe for the ear. 

Sounds emanting from tape recorders or an orchestra:

Sound Intensity   : 70 db
Health Hazard   : It is safe for ear.

Sounds of heavy traffic: 

Sound Intensity: 90 db
Health Hazard:  Constant hearing of sound, greater than 80 db, causes temporary hearing loss and if they are not treated immediately, causes permanent impairment. 

Sounds of pneumatic drills and other machines:

Sound Intensity   : 100 db
Health Hazard:   Constant hearing causes temporary hearing loss and if they are not treated immediately, causes permanent impairment. 

Sounds of aircraft engine: 
Sound Intensity: 100-200 db
Health Hazard   : Higher noise level of 160 db cause total deafness, rupturing eardrums, damaging inner ear. It also causes high blood pressure, ulcer in stomach, palpitation, nervous problems, irritation, anger, and affects pregnant women’s embryo.


Sounds of rockets during take off:
Sound Intensity: 200 db
Health Hazard:   It is dangerously causing total deafness by rupturing the eardrums and damaging the inner ear. It also causes high blood pressure, ulcer in stomach, palpitation, nervous problems, irritation, anger and affects pregnant women’s embryo.


 

Table depecting various sound levels