Time-domain numerical modeling of brass instruments including nonlinear wave propagation, viscothermal losses, and lips vibration

TL;DR

This paper presents a comprehensive time-domain numerical model of brass instruments that includes nonlinear wave propagation, viscothermal losses, and lips vibration, validated through extensive simulations showing effects on sound timbre and playability.

Contribution

It introduces a novel coupled modeling approach combining the Menguy-Gilbert model with a lips vibration model, incorporating viscothermal losses via local memory variables.

Findings

Nonlinear wave propagation significantly affects sound timbre.

Viscothermal losses influence the sound envelope and frequency.

Lips vibration modeling impacts playability and frequency control.

Abstract

A time-domain numerical modeling of brass instruments is proposed. On one hand, outgoing and incoming waves in the resonator are described by the Menguy-Gilbert model, which incorporates three key issues: nonlinear wave propagation, viscothermal losses, and a variable section. The non-linear propagation is simulated by a TVD scheme well-suited to non-smooth waves. The fractional derivatives induced by the viscothermal losses are replaced by a set of local-in-time memory variables. A splitting strategy is followed to couple optimally these dedicated methods. On the other hand, the exciter is described by a one-mass model for the lips. The Newmark method is used to integrate the nonlinear ordinary differential equation so-obtained. At each time step, a coupling is performed between the pressure in the tube and the displacement of the lips. Finally, an extensive set of validation tests is successfully completed. In particular, self-sustained oscillations of the lips are simulated by taking into account the nonlinear wave propagation in the tube. Simulations clearly indicate that the nonlinear wave propagation has a major influence on the timbre of the sound, as expected. Moreover, simulations also highlight an influence on playing frequencies, time envelopes and on the playability of the low frequencies in the case of a variable lips tension.