Biology Reference
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21kHz
0
White Noise
White Noise
-40
0
21kHz
0
Time
Frequency (Hz)
21kHz
0
Pink Noise
Pink Noise
0
-40
21kHz
Time
0
Frequency (Hz)
Fig. 6.1
Spectrogram and power spectrum of a
white
noise and a
pink
noise
frequency and amplitude modulation. The noise can be distinguished according to
the bandwidth (broad or narrow frequency bands).
Despite the different definitions, a noise is a degraded sound or the summation of
different sounds that create a confused pattern. In both cases it contains a low level
of information. Adopting the three categories of geophonies, anthrophonies, and
biophonies, we can say that the noise is acoustic energy that in turn masks and
interferes one of these three sound source types.
The word noise derives from the latin
nausea
and has different definitions as
stated in the topic by Truax (
1999
): unwanted sound, unmusical sound, any loud
sound or disturbance in any communication system.
An interesting definition of noise is proposed by Dodd (
2001
):
“noise
subjec-
tive sound which we would choose not to listen (i.e. it is subjective sound from
which we would not choose to extract information).”
When is a sound transformed to noise? Generally we refer to noise when we
perceive indistinct and annoying background noise. But also a near-ground sound
that is not identified or is unwanted may be considered a noise.
Noise is a voluntary or involuntary sound that when added to a signal reduces the
capacity of that signal to be correctly perceived and interpreted. In an animal
communication context, the noise is defined as “any factor that reduces the ability
of receiver to detect a signal or to discriminate one signal from another” Brumm
and Slabbekoorn (
2005
).
¼
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