LOUDNESS -----
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1) It is subjective quantity. This means that a sound may be loud for one person and may be faint for another person.
2) It cannot be measured as it is just sensation that can be only felt.
3) Loudness is measured in decibel (dB).
4) Loudness depends upon sensitivity of one's ears.
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INTENSITY ------
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1) It is objective physical quantity. It means that it doesn't vary person to person.
2) It can be measures as a physical quantity.
3) Intensity of any sound is measured in watts per square meter. (W/m^2)
4) It doesn't depend upon sensitivity of one's ears.
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