Joint modeling of impedance and radiation as a recursive parallel filter structure for efficient synthesis of wind instrument sound
In the context of efficient synthesis of wind instrument sound, we introduce a technique for joint modeling of input impedance and sound pressure radiation as digital filters in parallel form, with the filter coefficients derived from experimental data. In a series of laboratory measurements taken on an alto saxophone, the input impedance and sound pressure radiation responses were obtained for each fingering. In a first analysis step, we iteratively minimize the error between the frequency response of an input impedance measurement and that of a digital impedance model constructed from a parallel filter structure akin to the discretization of a modal expansion. With the modal coefficients in hand, we propose a digital model for sound pressure radiation which relies on the same parallel structure, thus suitable for coefficient estimation via frequency-domain least-squares. For modeling the transition between fingering positions, we propose a simple model based on linear interpolation of input impedance and sound pressure radiation models. For efficient sound synthesis, the common impedance-radiation model is used to construct a joint reflectanceradiation digital filter realized as a digital waveguide termination that is interfaced to a reed model based on nonlinear scattering.