Definition, Measurement, and Generation of Structure-Borne Sound

Abstract

Many of the acoustic events that reach our ear—such as the sound of a violin, the squeaking of brakes, or a noisy conversation in the next apartment—are either produced or conducted by vibrating solid bodies. That field of physics which deals with the generation and propagation of (usually very small) time-wise varying motions and forces in solid bodies, as well as with the associated sound radiation, is called “structure-borne sound”. The word “sound” indicates that the audible frequency range—that is, the range between about 16 Hz and 16000 Hz—is of primary interest. Vibrations and waves at lower frequencies generally belong to the fields of mechanical vibrations or seismics, whereas those at higher frequencies belong to ultrasonics. However, the aforementioned frequencies are not to be considered as absolute limits; for example, structure-borne sound at 50 or 100 Hz may often be treated merely as mechanical vibrations with a finite number of degrees of freedom, and many of the measurement techniques suitable for determining the properties of materials in the structure-borne sound region also are applicable at ultrasonic frequencies.