Question

State the unit of loudness. How is it related to energy level of sound?

Answer 1

Loudness:

1. The degree of sensation produced in the ear by a sound is called its loudness. We can distinguish a loud sound from a feeble sound on the basis of its loudness
2. The loudness of sound is measured in units bel (B) and decibel (dB), where
   1 decibel (dB) = $\frac{1}{10}$bel (B)
3. The unit of loudness is named after the scientist 'Alexander Graham Bel' who invented the telephone.
4. A normal person can just hear a sound whose energy level is 10^-12 watts/m².
5. The loudness corresponding to this energy level is taken as the reference level and is called 0 dB. If the energy level is 10^-11 W/m² (i.e., 10 times the reference level), loudness is taken to be 10 dB.
6. If the energy level is 10^-10 W/m² (i.e., 100 times the reference level), loudness is taken to be 20 dB, and so on.