The term "acoustic beamforming," when applied to loudspeaker
audio reproduction, refers to the ability to direct audio waves
in a particular direction other than the loudspeakers typical
radiation pattern. An ideal loudspeaker acts as a piston-type
source set in an infinite baffle and has a radiation pattern
that is dependent upon the frequency being reproduced relative
to the speaker disk radius. The degree of acoustic sound beaming
is related to the ratio of the radius of the loudspeaker piston
to the wavelength of the sound. At low frequencies, the
loudspeaker's sound spreads out evenly in all directions in
front of the speaker. This is the reason you can set a subwoofer
at almost any location in the front of a room and hear it
equally well from anywhere else in the room. As the frequency is
increased, the radiation pattern becomes more focused in front
of the speaker, increasingly becoming a narrowing cone shaped
pattern around an axis perpendicular to the loudspeaker face.
The sound pressure level is str