Communication Theories - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 85

4.11 How to Improve Signaling
The efficiency of a signal largely depends on the internal design and the capacity of
an emitter to separate the signal from background noise.
Signals must be separated by background noise and must be minimized for their
degradation by distance or by interference with the medium (soil, foliage, etc.).
Signals must cope with the environmental conditions and at the same time over-
come the environmental constraints to improve communication.
The signal must evolve to maximize the signal-to-noise ratio, and the simplest
way is to increase the intensity or amplitude of the signal. For instance, males able
to produce a louder song are preferred by females. The signal must contrast with the
background noise, but when background noise is strong evolutionary pressure can
produce a weak signal.
Noise reduction is an important issue in communication strategy; in particular, to
reduce background noise behavior can evolve to send signals from the most
favorable places, times, and seasons, when ambient noise is at the minimum
(Fig. 4.9 ).
Signals produced throughout the day require more energy to mask background
noise, but at night the signals may be weaker in a quieter sonic background. One
main hypothesis for the dawn and dusk chorus (but see Chap. 7 ) resides in a quiet
sonic environment that would improve the diffusion of acoustic performances.
A strategy to increase the signal-to-noise ratio consists of filtering out continuous/
monotonous signals such as background noise. This process is known as habituation.
Fig. 4.9 Distribution of background noise ( < 1,500 Hz) during daytime hours and months
resulting from application of acoustic complexity index (ACI) to sound files recorded at a site in
a Mediterranean maqui (Reproduced from Farina et al. 2013 )