Parallel Body Filterbank Design

In [66], a method is described for producing a parallel bank of fourth-order IIR body filters from an arbitrary starting impulse response. Initially, the body impulse is approximated by the impulse response of a fourth-order IIR filter using an algorithm of second author Cheng; the method is said to pick out the most resonant modes of the sampled impulse response, and fourth-order sections were found experimentally to best characterize the resonant modes of the guitar body. The impulse response of the filter so designed is subtracted from the measured impulse response to form a residual impulse response which is given again to the IIR design algorithm. This process is repeated to obtain a parallel bank of fourth-order filters, plus a final residual which is discarded. In the present context, the final residual should be incorporated at least qualitatively into the string excitation signal, or else the method should be applied only to the total parametric impulse response computed by other means and separated from the nonparametric impulse response by inverse filtering.