Specifications

®
A Short Introduction To Equalizers And Acoustics
Magazine reviewers and audio system owners spend much
time critically appraising speakers and other stereo components.
Unfortunately, a phenomenon that has a very large effect upon
sound is not easily judged or changed. That effect is the ACOUS-
TICS of the environment in which you are listening.
Room acoustics is a complicated subject about which entire
textbooks have been written. We simply want you to be aware of
a few basics that have a direct effect on real time audio analysis.
As you probably learned in
junior high school, sound trav-
els in waves. In a stereo sys-
tem, these waves are created
by the speakers. Like waves
in a pond created by a splash,
sound waves emanate from
the transducers (speakers) and
spread out into the room. If
your room were innitely big,
that’s all there would be to it.
But just as waves in a pond
reach the bank and reect
back, sound waves bounce
off walls, ceilings, and oors,
reecting, reinforcing and
canceling each other as shown
in the gure above. Since sound is energy, the way it reects
depends upon the angle of the surface, the type of material and
the frequency of the sound wave. Because your listening position
is likely to be towards the back of the Free Field waves shown in
the diagram, you also get part of the reected Reverberant Field
as well.
Now we add the next set of complications: Different frequen-
cies of sound have different wave lengths (a function of frequency
and the speed of sound). Each frequency’s wavelength contributes
differently to the Free and Reverberant Fields because they are
different sizes. For example, a 32 Hz bass note has a wavelength
of 35 FEET, while a 16,000 Hz note has a wavelength just under a
tenth of an inch. Tiny treble waves can be caught and neutralized
by draperies, carpeting, upholstered furniture and gangs of indo-
lent Persian cats…while gigantic bass waves simply slosh back
and forth in the room.
Introduction To
Equalizers And
Acoustics
16
Room interaction