8
subjective changes in perceived...
correspond to
physical
changes
in the...
VOLUME
PITCH
TIMBRE
or
TONE
COLOR
AMPLITUDE
FREQUENCY
WAVESHAPE or
FREQUENCY-SPECTRUM
. .
.
of the
perceived vibration.
This is
worth remembering because,
as
we
have
emphasized
elsewhere,
synthesizers
work
with
the qualities listed in
the right-hand column
for the
sake of our perception of those
listed
in the left-hand column;
anyone who uses a synthesizer regularly
must
be able to
translate
eas-
ily
from the language
of
volume,
pitch, and
timbre,
to
the language
of amplitude, frequency, and waveshapes. This section
of the manual
is intended
to get you started
on this
sort
of translation back
and forth
2.153 The
OSCILLATORS in
any
synthesizer
generate one
or
more of
these simple periodic waveforms:
SINE
,
SAWTOOTH
.SQUARE ,TRIANGLE
,
and
PULSE
2.154 A NOISE GENERATOR produces an APERIODIC
waveform
(see
section
2.14212)
of completely RANDOM pattern.
2.1
541
A random
voltage
has
very interesting properties. You
can
think of
it
statistically as
a
waveform
in
which your chances
of finding
any
particular frequency are equal
to your chances
of finding any other
frequency. Strictly
speaking
this sort of a
waveform
is
called WHITE
NOISE,
by analogy
with white
light:
it
contains
all frequencies
just
as
white light contains all
colors.
2.1542 Human ears tend
to
give undue prominence (for reasons we
needn't go into
here)
to
the
higher
frequencies in a
WHITE NOISE
sig-
nal, so that it sounds
like
steam escaping from a radiator. If
a
white
noise signal
is slightly FILTERED to produce a noise whose
frequency
content
SOUNDS MORE
EQUAL TO HUMAN EARS,
it is called
PINK NOISE. Pink noise
sounds
like
NIAGARA FALLS.
2.1543
From
the statistical point of view, what happens
when
white
#
noise
is FILTERED
is simply that
the
odds
on finding
any
particular
frequency in the noise waveform become
heavily weighted in favor of
some certain
RANGE OF FREQUENCIES. This
range
is
called the
BANDWIDTH of the filtered noise.
Thus
we
can talk about wideband
HOl^S
•
•
•
•
•
•
PINK. N
(Si
t
ft
R£.F.u£v6i
•
MO
^c
Rfcf.weve^
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