A sound wave is a pressure wave in the audible range. It originates at the sound source, for example the loudspeaker, and propagates in solid, liquid and gaseous materials. Sound waves can be radiated spherically or directionally and are subject to diffraction, refraction, reflection and absorption.
The speed at which sound waves propagate is the speed of sound. It depends on the consistency of the medium and is 5,000 m/s in metals and 330 m/s in air. The speed of sound is strongly dependent on temperature.
The frequencies of sound audible to humans range from 20 Hz, corresponding to a very low-pitched sound, to 20 kHz, for extremely high-pitched sounds. The sound wavelengths calculated from this range from 17 m for a 20 Hz vibration to 1.7 cm for a 20 kHz vibration. The loudness-dependent perception of sound waves is reflected in the hearing characteristics.