Question

What is meant by the ‘loudness’ of a sound? How is it related to the intensity?

Answer 1

Loudness is an aural sensation, i.e., a physiological rather than a physical phenomenon. It increases with intensity but the relation between the two is not linear, i.e., the ear does not recognize a sound, having twice the intensity of another, as twice as loud. In fact loudness (L) of a sound and its intensity (I) are related as L = k log (I/I₀). Here I/I₀ is the intensity level of the sound or the ratio between its intensity I and the zero of intensity or the threshold intensity I₀ and k, a constant of proportionality depending upon the unit chosen.