Supervision: Maxime Volery

Project type: Semester project (master) Master thesis

Finished

Metamaterials are engineered materials with a subwavelength structure that enables extraordinary propagation and manipulation of waves. In acoustics, they can be achieved by stacking "unit-cells", composed of acoustic channels and cavities, or emplyoing elastic membranes. Current developments using electroacoustic transducers as unit-cells, connected to an active impedance control device (denoted here "electroacoustic metamaterials"), allow for a wide range of acoustic behaviors : depending on the electrical load applied to the loudspeaker, its acoustic properties, such as reflection, absorption and transmission, can be altered. A first concept of such "electroacoustic metamaterial" unit-cell has been developped in the laboratory that allows controlling the transmission or reflection coefficients at a loudspeaker diaphragm in a 1D waveguide, achieving unitary transmission or reflection coefficients with controllable phase shifts. This unit-cell concept is the first step towards the realization of an active acoustic metasurface for various applications.

An acoustic metasurface can be defined as a 2D arrangement of acoustic unit-cells, used as an interface with an acoustic field. Used in transmission/reflection, it can allow transmitting/reflecting sound beams towards prescribed (preferred) directions.

The purpose of this project is to develop a prototype of active acoustic metasurface, composed of several electroacoustic metamaterials unit cells arranged either in 1D configuration (along one direction) or in 2D (over the whole surface), depending on targeted applications. One of the main expected research outcome of this project is the assessment of the acoustic behavior of sound fields subject to such acoustic metasurface, and the performance in controlling the transmitted/reflected sound waves with respect to phase/direction. The metasurface will consist of a planar arrangement of electroacoustic transducers, with their own active impedance control units, to achieve the targeted applications.

The project will then consist in:

• defining use-cases for assessing the performance of the metasurface (in a 1D arrangement or in a 2D arrangement);
• setting a simulation platform (on Comsol Multiphysics) to model the 3D behaviour of the metasurface and optimizing the design depending on the application;
• building a prototype for experimental assessement/validation;
• setting the experimental facilities and experimentally assessing the acoustic performance;

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

Prerequisites: Acoustics, Electroacoustics

Learning outcome: active control for acoustics, COMSOL Multiphysics, acoustic measurement

Context: Theory/Physical Simulations (50%), design (25%), measurement (25%)