Question

Defination of ' Bel ' and ' Phon ' ?

Answer 1

By definition, the number of phon of a sound is the dB SPL of a sound at a frequency of 1 kHz that sounds just as loud. This implies that 0 phon is the limit of perception, and inaudible sounds have negative phon levels. Thephon unit is not an SI unit in metrology

bel - Computer Definition. In physics, a measure of comparative power ratio, or relative loudness. In other words, a unit of power ratio. The number of bels is the decimal logarithm of the power ratio, which is expressed mathematically as follows: B = log 10 (P 1 /P 2 ) where B = Bel, and P 1 and P 2 are power levels.

Answer 2

Bel:
a unit used in the comparison of power levels in electrical communication or of intensities of sound, corresponding to an intensity ratio of 10 to 1.
Phon:
a unit of the perceived loudness of sounds.