Loud voice heard from 1m. Intensity of sound reaching ear is -
LOUDNESS: Loudness or intensity depends upon the amplitude of the vibrations which initiated the noise. The loudness of noise is measured in decibels (dB). When we say that sound is 60 dB, it means that it is 60 dB more intense than the smallest distinguishable noise or the "reference" sound pressure, which is understood to be 0.0002 microbar or dynes/cm2 . A dyne is 1/1000,000th of atmospheric pressure. Normal conversation produces a noise of 60-65 dB; whispering, 20-30 dB; heavy street traffic, 60-80 dB; and boiler factories, about 120 dB. A daily exposure up to 85 dB is about the limit people can tolerate without substantial damage to their hearing. Ref: Park 25th edition Pgno: 779
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Environment and health