ARP 2600 - Waveform Properties: Amplitude, Frequency, and Shape; Amplitude vs. Volume, Frequency vs. Pitch; Waveform Shape and Timbre;Tone Color

7
X
"Timbre" is the
subjective
quality
of a
tone
which
enables
the listen-
er to
distinguish
between
it and
other
tones
which
may
have the
same
pitch or loudness,
(e.g.
trumpets
and
clarinets
produce
sounds
of differ-
ent
timbres.
)
2.1421
3
We will
use
these
terms
throughout the rest
of
this
manual.
Frequencies
of
less than
1Hz will
generally
be
referred
to
by
their
period
to save
you
the labor of,
say,
translating
".05Hz" into "one
cycle
every
20
seconds".
2.15
CHANGES IN
THE AMPLITUDE
OR
FREQUENCY OF A
PERIODIC
WAVEFORM
ARE, INDEED,
SO
COMMON, AND THEIR
RELATIONSHIP
TO
PERCEIVED
SOUND
SO
CLEAR, THAT
THEY
ARE
NOT
COMMONLY THOUGHT
OF
AS
INVOLVING
CHANGES
IN
THE SHAPE
OF A WAVEFORM
AT
ALL.
2.151 From now
on
we will
follow
this convention.
Changing
the
frequency
or
amplitude of
a
wave will
not
count as a
change
in
its shape.
2.1 51
1
There
is
a
more subtle
reason
than
mere convenience for this
practice. Graphically,
this waveform
can
become this
waveform
by a mere change
of coordinates;
and likewise for turning
this
waveform
into
this
one
#.-
But no
amount
of
graphical transformation
will
turn something
like
this
into
this
;
no change in
mere amplitude or
frequency
or
both
or
change in units of measurement. (The
latter is what we
mean
by
a "change
in
coordinates".)
2.152 CHANGES IN THE SHAPE of an
audio
waveform are
generally
associated
with
CHANGES
IN
THE TONE
QUALITY,
or TIMBRE*
of the sound produced.
(See
2.131).
Since
human
perception
has limits,
there
are possible changes
in
the
shape of
a
waveform
that
might
not
be perceived
by even the
most practiced
ear; but anything that is
perceived
as
a change
in timbre
must
be reflected
in the
waveform
being perceived.
2.1521 Summarizing 2.141,
2.142,
and
2.152 gives us
these
approx-
imate relationships: