Page 108 - The Master Handbook Of Acoustics

CHAPTER
4

Sound Waves in

the Free Field

ractical acoustic problems are invariably associated with people,
Pbuildings, rooms, airplanes, automobiles, etc. These can generally
be classified either as problems in physics (sound as a stimulus) or
problems in psychophysics (sound as a perception), and often as both.
Acoustical problems can be very complex in a physical sense, for
example, thousands of reflected components might be involved or
obscure temperature gradients might bend the sound in such a way as
to affect the results. When acoustical problems involve human beings
and their reactions, “complexity” takes on a whole new meaning.
Don’t be discouraged if you want a practical understanding of acous-
tics, but your background is in another field, or you have little technical
background at all. The inherent complexity of acoustics is pointed out
only to justify going back to the inherent simplicity of sound in a free field
as a starting point in the study of other types of practical sound fields.

Free Sound Field: Definition

Sound in a free field travels in straight lines, unimpeded and unde-
flected. Unimpeded sound is sound that is unreflected, unabsorbed,
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