Biology Reference
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Fig. 7.3 Three network models to explain the function of dawn and dusk choruses in birds.
I Broadcast network: an individual sends intended signals to two or more neighbors. II
Eavesdropping network: two individuals are in active reciprocal connection and two or more
other individuals eavesdrop the circulating information. III Interactive network: all the individuals
are contemporary senders and receivers of direct intended signals and in turn are eavesdropping
(Adapted with permission from Burt and Vehrencamp 2005 )
The variation in sound intensity with distance can be expressed by the equation
I 0
r 2 e
I
¼
α v þ α c þ α d þ α r þ α m
ð
Þ
r
This expression can be converted to decibel attenuation in sound level (assuming
a reference level of 1 m from the source), and the foregoing expression can be
converted in the following equation:
N
¼
20log r
þ β v þ β c þ β d þ β r
ð
Þ
r
þ β t r
þ β m r
þ β D r
ð
r s
Þ
where
r
¼ distance between the source and the receiver, and
α
and
β
(where
β ¼
) are the absorption coefficients corresponding to the different
mechanisms of atmospheric attenuation
β v ¼
4.343
α
viscosity,
β c ¼
heat conduction,
β d ¼
molecular diffusion,
β r ¼
thermal
radiation
β t r
represents the attenuation caused by scattering of sound from atmospheric
turbulence
β m r
¼
¼
the attenuation caused by atmospheric moisture content
represents attenuation from the curvature of the soundpath by
wind velocity or temperature gradient
β D ( r
r s )
¼
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