What is loudness?
Loudness is the human impression of the strength of a sound. The loudness of a noise does not necessarily correlate with its sound level. Loudness level of any sound, in phons, is the decibel level of an equally loud 1kHz tone, heard binaurally by an otologically normal listener. Historically, it was with a little reluctance that a simple frequency weighting “sound level meter” was accepted as giving a satisfactory approximation to loudness. The ear senses noise on a different basis than simple energy summation, and this can lead to discrepancy between the loudness of certain repetitive sounds and their sound level. A 10dB sound level increase is considered to be about twice as loud in many cases. The sone is a unit of comparative loudness with 0.5 sone=30 phons, 1 sone=40 phons, 2 sones=50 phons, 4 sones = 60 phons etc. The sone is inappropriate at very low and high sound levels where subjective perception does not follow the 10dB rule. Loudness level calculations take account of “mas
