Low frequency approximation of T-network
In the case where the wavelength is large compared to the tube length, it is possible to replace the impedance terms of the T-network
and
by terms obtained via the first order development of the tangent and sinus functions. Knowing that
, thus,
where
and
.
is the acoustic mass of a length of tube
(
) and
is the compliance of a length of tube
(
).
The equivalent network at low frequencies is given below.
