Page 260 - The Master Handbook Of Acoustics

CHAPTER
10

Reflection of Sound

f a sound is activated in a room, sound travels radially in all direc-
Itions. As the sound waves encounter obstacles or surfaces, such as
walls, their direction of travel is changed, i.e., they are reflected.

Reflections from Flat Surfaces

Figure 10-1 illustrates the reflection of waves from a sound source
from a rigid, plane wall surface. The spherical wavefronts (solid lines)
strike the wall and the reflected wavefronts (broken lines) are returned
toward the source.
Like the light/mirror analogy, the reflected wavefronts act as
though they originated from a sound image. This image source is
located the same distance behind the wall as the real source is in front
of the wall. This is the simple case—a single reflecting surface. In a
rectangular room, there are six surfaces and the source has an image
in all six sending energy back to the receiver. In addition to this,
images of the images exist, and so on, resulting in a more complex sit-
uation. However, in computing the total sound intensity at a given
receiving point, the contributions of all these images must be taken
into consideration.
Sound is reflected from objects that are large compared to the
wavelength of the impinging sound. This book would be a good
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