Acoustic metamaterials (AMMs) and metasurfaces (AMSs) are engineered structures aimed at achieving unprecedented acoustic properties not available in nature. They are usually made of periodically arranged sub-wavelength resonators. Since the passive resonant units present inherent limitations such as narrow frequency bandwidth of operation, active control concepts, with features of tunability and reconfigurability, have received a surge of interests in AMMs and AMSs designs. Moreover, nonlinearities can offer more degrees of freedom for manipulating waves, allowing thus a richer and diverse set of non-trivial acoustic phenomena.

Very recently, based on the linear active impedance control scheme that has already been developed in the laboratory, a novel nonlinear control approach was proposed. Such control, applied to sub-wavelength electroacoustic resonators, is proved capable of triggering nonlinear effects at low sound pressure thresholds, thereby improving sound absorption in the low frequency range. This preliminary result allows the validation of the defined nonlinear control approach, however further study needs to be performed in a view to improving experimental method and developing other types of nonlinear controls.

Thus, the project will consist of:

  • developing experimental program for automatically performing the time domain measurements in need.

  • estimating and assessing (both numerically and experimentally) the absorption performance of the achieved nonlinear resonator, when it is connected or not to a tube.

  • characterizing the effect of the tube length in the final absorption results.

  • if time allows, proposing and studying other types of feasible nonlinear control schemes.

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

Prerequisites: Acoustics, Electroacoustics

Learning outcome: linear and nonlinear active control for acoustics, acoustic measurement, Matlab programming.

Context: Theory/Physical Simulations (25%), measurement (75%)