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Acoustic signals are used for long-range communication in many animals
from insects to birds and mammals. Long-range signals are used primarily
by males to advertise and defend their home ranges or territories or to
attract mates.
During transmission over long distances, the structure of signals becomes
progressively degraded. At the position in which a receiver makes a
decision to respond, the characteristics of signals can differ markedly
from those at the source. This degradation impairs extraction of
information coded in the signal but also allows receivers to assess the
distance (range) of the signaler.
Auditory distance assessment (called 'ranging') is particularly important
in territorial species as the optimal initial response often depends on
the distance of the signaler. Perception of distance is comparatively
well studied in animals but this
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work is not well integrated with information from related fields such as
sound perception in animals or humans.
Here we review recent advances in studies of distance estimation and
relate these to fundamental issues in sound transmission and sound
perception. We consider the different components of signal degradation
and how they can be measured in a perceptually meaningful way. We discuss
limitations on the perception of degradation and the possibility that
signalers might send deceptive information about their actual distance
from a receiver.
By integrating studies of auditory distance perception and studies of
sound perception in animals and humans, we provide a framework for
understanding the evolutionary implications of sound degradation in
communication.
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