- Murray Campbell
- and Clive Greated
A pattern of vibration spatially distributed through a medium. An example of a medium of great importance in musical instruments is the stretched string. Three types of wave can exist in a string: a transverse wave, in which the particles of the string vibrate in a direction perpendicular to the string axis, a longitudinal wave, in which the string particles vibrate along the string axis, and a torsional wave, in which the string particles rotate about the string axis. All three types of wave can be generated by bowing a string, although the transverse waves normally dominate the acoustic behaviour of a bowed string. Transverse and torsional waves cannot be supported by a gaseous medium, so that only longitudinal waves are present in the air column of a wind instrument.
In a travelling wave the vibration pattern travels through the medium with a characteristic speed (the wave velocity); fig.1a shows three successive views of a transverse wave travelling from left to right on a string. When a travelling wave is reflected back on itself, a standing wave is set up; fig.1...