Even though these waveforms do not look like noise, they are synthesized noise. By frequency
modulating the oscillators in a ring a multitude of signals are created just like those found in noise.
However, unlike random noise this synthesized oscillator noise can be manipulated in several ways,
e.g. varying the frequency (illustration above) or varying the degree of frequency modulation
(illustration below). In other words, this noise can be played with and noise with varying bandwidth
can be created (resonance effect).
NOISE GENERATOR
There are three noise outputs; white (wide band, unfiltered), red (lowpass filtered with 12 dB/octave)
and low frequency noise (slow random).
In the illustration below white noise and red noise is shown on the left side and spectrum density
on the right side.
RING FREQUENCY MODULATION, VARIABLE FM LEVEL, OSCILLATOR1/SINUS out
O
U
TP
U
T
(V
ol
ts
)
3.00
4.00
5.00
6.00
7.00
8.00
Time (milliseconds)
dB
V
rm
s
0.0
-10.0
-20.0
-30.0
-40.0
-50.0
-60.0
-70.0
-80.0
-90.0
1.0k
3.0k
5.0k
7.0k
9.0k
11.0k 13.0k 15.0k 17.0k 19.0k
Frequency (Hz)
WHITE NOISE SYNTHESIS
BAND-PASS NOISE SYNTHESIS
dB
V
rm
s
0.0
-10.0
-20.0
-30.0
-40.0
-50.0
-60.0
-70.0
-80.0
-90.0
1.0k
3.0k
5.0k
7.0k
9.0k
11.0k 13.0k 15.0k 17.0k 19.0k
Frequency (Hz)
30
40
50
60
70
80
O
U
TP
U
T
(V
ol
ts
)
Time (milliseconds)
WHITE NOISE
RED NOISE
39
RING MODULATOR
The multiplier, even popularly called the ring modulator is a very useful sound processor for the
creation of sounds with non-harmonic overtones and undertones such as bell and wood sounds.
The ring modulator multiplies the amplitude of two incoming signals. This results in two sine-formed
signals with the difference and sum frequencies of the incoming signals. For example, if
the incoming frequencies are 1000 Hz and 200 Hz, two signals with the same amplitude are created
(multiplier gain = 1), one at 800 Hz and the other at 1200 Hz, i.e. the sum and difference of 1000 Hz
and 200 Hz. The fundamental tones are suppressed. However, the real ring modulators is not so
perfect so that there will always be residual products and the fundamental tones cannot be completely
suppressed. The illustration below shows typical outputs from the ring modulator.
