Loudness of Sound

Two sounds of exactly the same measured intensity need not be perceived as equally loud. The sound of a balloon bursting inside a silent, closed room, for example, is perceived as very loud, whereas the identical burst occurring amid the background noise of a busy market is barely noticed -- even though the actual physical intensity of the sound produced by the burst is the same in both cases. While it is true that increasing the intensity of a sound generally does increase its perceived loudness, intensity alone is not the whole story: the listener's own internal, subjective experience of "how loud" a sound seems -- which depends heavily on the sensitivity of that particular listener's ear, and varies noticeably from one person to another -- is what is actually called loudness. Loudness is therefore formally defined as the degree of sensation of sound produced in the ear, or equivalently the perception of sound by the listener; unlike intensity, which is a fixed, objective property of the sound wave itself, loudness is inherentl …