Biology Reference
In-Depth Information
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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