The extraordinary functionalities of acoustic metamaterials have led to the realization of wave manipulation techniques previously regarded as impossible with deep subwavelength structures. Unfortunately, since much of metamaterials’ properties originate from the resonance phenomenon, the novel functionalities are necessarily restricted to narrow frequency ranges; yet broadband is usually a necessity in practical applications. Recently, breakthroughs in the designed integration strategy have overcome the narrow frequency limitation and showed that some functionalities, such as sound absorption, can be made to be tunable in accordance with the target absorption spectrum. Such designed integration scheme has already led to the formation of a Hong Kong startup company, Acoustic Metamaterials Group (AMG), which has achieved mass production capability of the designed prototypes, and of a French startup company, Metacoustic, which proposes acoustic and vibration solutions consisting in metaporous and metaporoelastic layers. In this project, we would like to extend the previous success in acoustic absorption to open a new frontier in room acoustics, by constructing walls that can passively switch from a totally absorbing to a spatially modulated reflection phase, by utilizing resonances to tune the impedance of the walls. Such change can significantly alter the audio experience of a room, from anechoic-like to the audio feel of a larger room than it is in reality. Traditionally, acoustic wall constructs are static and achieve only one functionality. Moreover, they are efficient at high frequencies but results in bulky and heavy structures at low frequencies. This project aims at designing deep subwavelength re-configurable acoustic metamaterials for altering the room acoustics. We intend to draw on the combined expertise of the Hong Kong and French teams to prove experimentally the effectiveness of such a system in two demonstration rooms, one in Hong Kong and one in Le Mans. The two demonstration rooms will use different integration approaches and different resonators (Fabry-Pérot resonators for the Hong Kong team, and Helmholtz resonators for the Le Mans team) in achieving the same goal. The research and development experience of both teams in theory, simulation, sample fabrication, and implementation will be enriched through each others’ approaches, as well as through mutual visits and student exchanges.
Both teams will collaborate with AMG and Metacoustic in this project. AMG’s role will be to provide space for the demonstration room in Hong Kong, while the PI, Co-I and students in Hong Kong and in Le Le Mans will design, fabricate and test the acoustic metamaterials in collaboration with AMG and Metacoustic. We envision new commercial opportunities with the successful completion of this project.
Monsieur Jean-Philippe Groby (LABORATOIRE D'ACOUSTIQUE DE L'UNIVERSITE DU MANS)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
LAUM LABORATOIRE D'ACOUSTIQUE DE L'UNIVERSITE DU MANS
HKUST Hong Kong University of Science and Technology
HKBU Hong Kong Baptist University
AMG Acoustic Metamaterials Group
Help of the ANR 588,188 euros
Beginning and duration of the scientific project: January 2019 - 48 Months