programming with max/msp - Virtual Sound

Chapter 3P - Noise generators, filters, and subtractive synthesis
Note that the spectrum of pink noise, unlike white noise, is gradually
attenuated as frequencies get higher, and that this attenuation (as we know
from Section 3.1T) is 3 dB per octave.
Reconstruct the simple patch shown in the figure and listen carefully to the
difference between pink noise and white noise. Which of the two seems more
pleasant (or maybe just less unpleasant), and why?
Add an oscilloscope (scope~) to the two patches just built, remembering
to set the “Calcount - samples per pixel” 3 attributes in the Value tab of the
Inspector, and observe the difference between the waveforms of pink noise
and white noise.
In Figure 3.5, we see these two waveforms side-by-side.
Fig. 3.5 Waveforms of white noise and pink noise
Without bogging down in technical details, you can see that while white noise
is basically a stream of random values, pink noise is generated using a more
complex algorithm in which a sample, although randomly generated, cannot
stray too far from the value of its predecessor. This results in the “serpentine”
waveform that we see in the figure. The behavior of the two waveforms demonstrates
their spectral content: when the difference between one sample and
the next is larger, the energy of the higher frequencies in the signal is greater. 4
As you know, white noise has more energy at higher frequencies than pink
noise.
Another interesting generator is rand~, which generates random samples
at a selectable frequency and connects these values using line segments (as
shown in Figure 3.6). Unlike noise~ and pink~, which each generate random
samples on every tick of the DSP “engine” (producing a quantity of samples
in one second that is equal to the sampling rate), with rand~ it is possible to
choose the frequency at which random samples are generated, and to make
the transition between one sample value and the next gradual, thanks to linear
interpolation.
3 We explained this attribute in Section 1.2P.
4 To understand this assertion, notice that the waveform of a high sound oscillates quickly, while
that of a low sound oscillates slowly. At equal amplitudes, the difference between succeeding
samples for the high frequency case will be larger, on average, than for the low frequency case.
from “Electronic Music and Sound Design” Vol. 1 by Alessandro Cipriani and Maurizio Giri
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