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Noise
& Distortion In simple PA
Systems, it is possible to work with
just one microphone, one amplifier and
one speaker. However, for more
complicated setups, it might be
necessary to alter the sound slightly.
For example, karaoke sets add echo to
the voice before pumping the sound to
the loudspeaker. Also, you may want to
add a voice-over to music, just like a
DJ speaking over music. It is overkill to do
all this at a signal level powerful
enough to drive speakers. To process
audio signals that have come straight
from the microphone would not be a good
idea either, as the signal is barely a
trickle of current. It would be like
gathering a few scraps of hieroglyphs
from an archeological dig and trying to
write a thesis on what the Egyptians
thought of Barney the Dinosaur in
ancient times. Not only will you have to
add a lot of (probably erroneous)
information, it will probably be
completely different from the truth. |
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Erroneous sound
signals are called noisy, because that's how
they will sound. You can often hear this
in badly tuned radios as static crackles
or a quiet hiss in the background. This
arises because your radio is not set up
to receive all the audio information to
give you a clear sound. |
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| Distortion
also damages sound signals. This arises
when the equipment producing the sound
cannot adequately handle the sounds to
give you a fair representation of what
it is supposed to sound like. The most
well known example is probably of the
Distorted Guitar, the kind of sound
produced by heavy metal guitarists. That
grungy, grating sound used in guitar
solos is interesting, but I'm pretty
sure that's not what a guitar actually
sounds like. A twang on a guitar string
produces a twang, not a Deep Purple
power chord. |
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That previous
example also shows that Distortion and
Noise are not always undesirable. They
can be manipulated to good use. Clipping is a form of distortion. Clipping occurs when a sound signal's voltage increases past a point that the equipment cannot output. As such, instead of maintaining the real waveform of a sound, the sound is abruptly truncated where equipment meets its limits. This can sometimes cause the grating-guitar sort of sound. Read
more on page 3 |
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