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

A time-domain numerical modeling of brass instruments is proposed. On one hand, outgoing and incoming waves inside the resonator are described by the Menguy-Gilbert model, which incorporates three key features: nonlinear wave propagation, viscothermal losses, and a variable section. The nonlinear propagation is simulated by a finitevolume scheme with flux limiters, well-suited for 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 optimally combine 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 numerical 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.