
156 Human factors engineering and ergonomics
where H is the frequency of the sound in cycles per second, F(H) is the
number of times the tonal frequency occurs in the sample, a is a constant of
the distribution that determines the color of the noise, and k is a constant of
no particular consequence.
The noise is designated as pink if |a| = 1 The noise is brown if |a| = 2.
The noise is black if |a| > 2. As the noise changes from pink to black, there
is greater determinism in the source. At the black extreme, we have an
unwavering, sustained, and probably annoying single tone. Colored noise
with |a| < 2 thus indicates that a self- organized process ...