This paper introduces hexaphonic distortion as a way of achieving harmonically rich guitar distortion while minimizing intermodulation products regardless of playing style. The simulated hexaphonic distortion effect described in this paper attempts to reproduce the characteristics of hexaphonic distortion for use with ordinary electric guitars with mono pickups. The proposed approach uses a parallel comb filter structure that separates a mono guitar signal into its harmonic components. This simulates the six individual string signals obtained from a hexaphonic pickup. Each of the signals are then individually distorted with oversampling used to avoid aliasing artifacts. Starting with the baseline of the distorted mono signal, the simulated distortion produces fewer intermodulation products with a result approaching that of hex aphonic distortion.

In the context of efficient sound synthesis by digital waveguides, we present a novel methodology for joint modeling of string instrument body radiativity and driving-point bridge admittance functions, as obtained from experimental data. From our modeling framework, aimed at simulation of guitar and bowed string sound, here we focus on the body of the instrument and leave aside the strings. First, a modal decomposition of the measured bridge admittance is obtained by means of a novel frequency-domain algorithm for optimization of recursive digital filters in parallel form. Then, from extracted modal parameters, the radiativity, and admittance functions are modeled by projecting measurements over a common modal basis, enforcing passivity of the two-dimensional admittance model by means of semidefinite programming. We propose a formulation that enables the joint realization of bridge reflectance and sound radiativity as a lumped delay line termination in which a single bank of resonant filters is shared among all string reflection and body radiation outputs. Our approach provides efficient means to model two-dimensional (2-D) bridge reflectance, 2-D string-string coupling, sound radiation with an arbitrary number of outputs, and (implicitly) vibrational energy loss from the bridge transmittance to nonradiating modes and dissipation.

We present a technique to iteratively optimize poles of a recursive digital filter in parallel form. Only exposing the poles as the variables to optimize, we employ a linearly constrained gradient descent routine in which the numerical estimation of the error gradient involves first obtaining the zeros by projecting the target response over a basis of responses defined by the pole positions at a given step. Example fits are presented for exponentially decaying white noise and measured violin radiativity filters.

Force-feedback interaction with a bowed string model can suffer critically from noise in the velocity signal derived from differentiating position measurements. To address this problem, we present a model for bowed string interaction based on a position-constraint friction. We validate the proposed model by comparing to previous work using off-line simulations, and show measurements of interaction on haptic hardware. This noise-free excitation signal leads to cleaner string motion than previous models, thereby improving the quality of force and audio synthesis in the presence of noise.

This paper introduces an analysis/synthesis scheme for the reproduction of sounds generated by sustained contact between rigid bodies. This scheme is rooted in a Source/Filter decomposition of the sound where the filter is described as a set of poles and the source is described as a set of impulses representing the energy transfer between the interacting objects. Compared to single impacts, sustained contact interactions like rolling and sliding make the estimation of the parameters of the Source/Filter model challenging because of two issues. First, the objects are almost continuously interacting. The second is that the source is generally unknown and has therefore to be modeled in a generic way. In an attempt to tackle those issues, the proposed analysis/synthesis scheme combines advanced analysis techniques for the estimation of the filter parameters and a flexible model of the source. It allows the modeling of a wide range of sounds. Examples are presented for objects of various shapes and sizes, rolling or sliding over plates of different materials. In order to demonstrate the versatility of the approach, the system is also considered for the modeling of sounds produced by percussive musical instruments.