Electroacoustic resonators are devices comprising (at least) one electrodynamic loudspeaker and an electronic instrumentation (feedback based on pressure/velocity sensing, shunt with a synthetic electrical load). This control allows to significantly modify the acoustic impedance presented by the moving part (namely the membrane) of the loudspeaker, eg. by increasing/lowering the mechanical resistance, or by reducing the effective mass and stiffness, leading in interesting properties in terms of acoustic waves reflection. The usual applications are mainly sound absorption at low frequencies (“electroacoustic absorbers”), either in ducts or in room.

We aim at investigating the application of this technique to wind instruments control, in particular to develop a prototype of active mute. The main interest of the active mute is to mute the sound without altering the intonation. Indeed, the control of the acoustic impedance at the duct termination colours the instrument's sound, as the timbre results from the natural harmonic series of the instrument due to the boundary conditions. A second interest in the active mute is that it might facilitate the playability of the instrument, the emission being potentially made difficult by the obstructing object.

The expected work will consist in designing a full numerical model of a trombone (which we will first assimilate to a straight cylindrical duct of variable length), equipped with an active mute based on the electroacoustic resonator concept. Several control techniques will be assessed resulting in the selection of components (loudspeaker, eventual sensor(s)) and the optimal control strategy. A prototype of active mute will then be built and tested in laboratory conditions.

Profile: Electrical engineering, Micro-engineering, Physics, Mechanics

Prerequisites: Electroacoustique (BA5) or Audio Engineering (MA1)

Context: Theory (20%), design (60%), experiments (20%)