86
Hans Winkler
8
3
C=4
CD
-o
<::
0
·2
<::
~
·7
·12L-------~------~------~------~------~
0
2
4
6
8
10
Frequency (kHz)
8
3
CD
-o
<::
0
·2
-;;;
:::>
<::
~
·7
C=D
-12
0
2
4
6
8
10
Frequency (kHz)
Fig. 2. Model calculations for frequency-dependent excess attenuation caused by ground
effects. The turbulence constant C (Chessell 1977) differs for the two curves. Based on
Delany-Bazley' s ground model with local reaction assumption and a ground impedance of
200 kPa (grassland) with a 0.1 m porous layer (see Sutherland and Daigle 1997). These
particular calculations are representative for skylarks, Alauda, that feed on the ground
(receiver) and sing high above the ground in a song flight. Top Model for a bird singing at
12 m (about the minimum height observed, Glutz von Blotzheim and Bauer 1985), and
Bottom for a bird singing at 120m
Hans Winkler
8
3
C=4
CD
-o
<::
0
·2
<::
~
·7
·12L-------~------~------~------~------~
0
2
4
6
8
10
Frequency (kHz)
8
3
CD
-o
<::
0
·2
-;;;
:::>
<::
~
·7
C=D
-12
0
2
4
6
8
10
Frequency (kHz)
Fig. 2. Model calculations for frequency-dependent excess attenuation caused by ground
effects. The turbulence constant C (Chessell 1977) differs for the two curves. Based on
Delany-Bazley' s ground model with local reaction assumption and a ground impedance of
200 kPa (grassland) with a 0.1 m porous layer (see Sutherland and Daigle 1997). These
particular calculations are representative for skylarks, Alauda, that feed on the ground
(receiver) and sing high above the ground in a song flight. Top Model for a bird singing at
12 m (about the minimum height observed, Glutz von Blotzheim and Bauer 1985), and
Bottom for a bird singing at 120m