Multiband Delay-Filter Design
In §3.7.5, we derived first-order FDN delay-line filters which
can independently set the reverberation time at dc and at half the
sampling rate. However, perceptual studies indicate that
reverberation time should be independently adjustable in at least
three frequency bands [217]. To provide this degree
of control (and more), one can implement a multiband delay-line filter
using a general-purpose filter bank
[370,500]. The output, say, of each delay
line is split into bands, where
is recommended, and then,
from Eq.
(3.6), the gain in the
th band for a length
delay-line can be set to
![$\displaystyle G^{M_i}(e^{j\omega_kT})\eqsp 10^{-\frac{3M_i}{n_{60}(\omega_k)}} ...
...ln}(10)\,M_i}{n_{60}(\omega_k)} \approxs
1-\frac{6.91\,M_i}{n_{60}(\omega_k)}
$](http://www.dsprelated.com/josimages_new/pasp/img882.png)
![$ n_{60}(\omega)=t_{60}(\omega)/T$](http://www.dsprelated.com/josimages_new/pasp/img883.png)
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Orthogonalized First-Order Delay-Filter Design