Loudness, Its Definition, Measurement and Calculation

O U D N E S S is a psychological term used to describe the magnitude of an auditory sensation. Although we use the terms "very loud," "loud," "moderately loud," " s o f t " and " v e r y soft," corresponding to the musical notations ff, /, mf, p, and pp, to define the magnitude, it is evident that these terms are not at all precise and depend upon the experience, the auditory acuity, and the customs of the persons using them. If loudness depended only upon the intensity of the sound wave producing the loudness, then measurements of the physical intensity would definitely determine the loudness as sensed by a typical individual and therefore could be used as a precise means of defining it. However, no such simple relation exists. The magnitude of an auditory sensation, t h a t is, the loudness of the sound, is probably dependent upon the total number of nerve impulses that reach the brain per second along the auditory tract. It is evident that these auditory phenomena are dependent not alone upon the intensity of the sound but also upon their physical composition. For example, if a person listened to a flute and then to a bass drum placed at such distances that the sounds coming from the two instruments are judged to be equally loud, then the intensity of the sound at the ear produced by the bass drum would be many times t h a t produced by the flute. If the composition of the sound, t h a t is, its wave form, is held constant, but its intensity at the ear of the listener varied, then the loud* Jour.