Ultrasonics: Some Properties of Inaudible Sound^*

Abstract

THE intensity or loudness of a sound depends upon the extent or amplitude of the vibration set up, and its pitch upon the frequency or number of vibrations per second. Disturbances of the same type as sound waves may be inaudible either because the intensity (loudness) is insufficient or because the ear is deaf to those particular frequencies: the normal range of hearing of a human being extends approximately from 20 to 20,000 vibrations per second.