Physics: Difference between revisions

Most are familiar with the properties of one type of sound source – the spherical-wave source – because virtually every loudspeaker is an example of this type. But there are two other types: the cylindrical-wave source, and the plane-wave source. These sources are named for the shapes of the sound waves they produce, and each has significantly different properties:

:* A spherical-wave source is shaped like a typical loudspeaker. Spherical sound waves expand in three dimensions – like an expanding sphere: out, left and right, and up and down.  

:* A cylindrical-wave source is shaped like a line. To produce cylindrical waves at musical frequencies the source must be high, about six feet (two meters), or higher. Cylindrical waves expand in two dimensions only – out and to the sides but not up or down (assuming the source is oriented vertically, like a flagpole).

:* A source capable of producing plane waves is itself planar, or sheet-like, in shape. To produce plane waves at musical frequencies the plane-wave source must be large, about six feet square (two meters square), or larger. Plane waves travel in only one direction, or dimension: out, but not to the sides or up and down.