Civil Engineering Reference
In-Depth Information
sin
2
πma
D
sin
2
πna
k
0
a
2
sin
θ
D
−
∞
2
D
2
φ(L)a
2
+
Z
m,n
(B)
π
4
m
2
n
2
k
0
D
sin
θ
2
π
m
=
1
n
=
0
,
±
1
,
±
2
...
−
(9.85)
The added external length
ε
e
can be evaluated in the same way as for circular apertures.
The dependence on the incidence angle of
ε
e
can be neglected and Equation (9.31) can
be used at oblique incidence. The impedance
Z
in the free air close to the facing is
given by
1
s
[
Z(B
)
+
jωρ
0
(ε
e
+
d)
]
Z
=
(9.86)
References
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Cahiers
du Centre Scientifique et Technique du B atiment
,
31
, 1 - 15.
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Applied Acoustics
,
13
, 43 - 55.
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Field Theory of Guided Waves
, McGraw-Hill, New York
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,
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.,
36
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1037 - 61.
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J. Acoust. Soc. Amer
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J. Acoust. Soc.
Amer
.,
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J. Acoust. Soc. Amer
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23
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J. Acoust. Soc. Amer
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42
,
6 - 17.
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.
