The decibel scale derives from the smallest perceivable change in loudness.

Evidence

The factor of 10 arises because this makes the result a number in which an integer change is approximately equal to the smallest change that can be perceived by the human ear. A factor of 10 change in the power density ratio is called the bel; in Equation 1.18 this would result in a change of 10 in the outcome. The integer unit that results from Equation 1.18 is there­ fore called the decibel (dB). It represents a 10 10 change in the power den­ sity ratio, that is, a ratio of about 1.26. — David Howard, Jamie Angus, coustics and Psychoacoustics, 167

Categorization

• DEFINE: Explains why the decibel unit is calibrated to perceptual just-noticeable difference — the bel/decibel naming and the 1.26 power ratio.