Sound
strictly the sensation which results from the stimulating action of atmospheric or other vibrations upon the aural nerves. Beyond ourselves it has no existence, it is purely subjective, and as a sensation must be carefully distinguished from the vibratory motion which is one of the necessary conditions of its existence. Further, the existence of this vibratory motion is itself conditioned by two things-a distributing cause and a suitable medium for transmitting the disturbance to the ear. The study of these in all their possible relations constitutes the science or theory of sound. Sounds are usually classified under the two heads of noises and musical sounds. A musical sound is caused by a regular series of succeeding each other at precisely equal intervals of time; if these conditions are not fulfilled, the sound is a noise.