A physically-based impact model – already known and exploited in the field of sound synthesis – is studied using both analytical tools and numerical simulations. It is shown that, for some regions of the parameter space, the trajectories of discretized systems may drift from analytically-derived curves. Some methods, based on enforcing numerical energy consistency, are suggested to improve the accuracy and stability of discrete-time systems.

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This paper investigates the properties of a recently proposed physical model of nonlinear tension modulation effects in a struck circular membrane. The model simulates dynamic variations of tension (and consequently of partial frequencies) due to membrane stretching during oscillation, and is based on a more general theory of geometric nonlinearities in elastic plates. The ability of the nonlinear membrane model to simulate real-world acoustic phenomena is assessed here through resynthesis of recorded membrane (rototom) sounds. The effects of air loading and tension modulation in the recorded sounds are analyzed, and model parameters for resynthesis are consequently estimated. The example reported in the paper show that the model is able to accurately simulate the analyzed rototom sounds.

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Spectral subtraction is a method for restoration of the spectrum magnitude for signals observed in additive noise, through subtraction of an estimate of the average noise spectrum from the noisy signal spectrum. In this paper we show that, starting from the known minimum mean-square error (MMSE) suppression rules of Ephraim and Malah and under the same modeling assumptions, a simpler suppression filtering rule can be found. Moreover, we demonstrate its performances and compare its computational costs with respect to the reference rule of Ephraim and Malah. This result permits a real time implementation of the exposed theory with an efficient algorithm on the DSP TMS320 C6713B.

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