Attack transients in a clarinet model with time-varying blowing pressure
Abstract
Reed instruments are modelled as self-sustained oscillators driven by the pressure inside the mouth of the musician. A set of non-linear equations connects the control parameters (mouth pressure, lip force) to the system output, usually considered as the mouthpiece pressure. Clarinets can then be studied as dynamic systems, their steady behaviour being dictated uniquely by the values of the control parameters. Considering the resonator as a lossless straight cylinder is a dramatic yet common simplification that allows for simulations using non-linear iterative maps. Many important aspects such as the kind of regime (static, oscillating), values of amplitude and periodicity have been predicted from such an approach. However, the existing studies focus mainly on the steady state, disregarding important features such as the attack transient. This presentation discusses transient behaviour of these simplified clarinet models when the control parameters follow simple laws of variation with time. In this case, unexpected behaviour can occur, such as bifurcation delays, meaning that oscillations do not start when the mouth pressure reaches the threshold value predicted by static bifurcation theory. This behaviour will be described and an analytical expression of the early attack transient state will be proposed.
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