Absorption of low-frequency sound by a resonant metasurface Seminar

Logan Schwan 1, Olga Umnova 2 and Claude Boutin 3

1 LAUM, Universite du Maine, France

2 Acoustics Research Centre, University of Salford, UK

3 ENTPE, Universite de Lyon, France

In collaboration with S.Taherzadeh and K. Attenborough (Open University, UK)

The work is devoted to theoretical and experimental investigation of a resonant acoustic metasurface for total sound absorption at low frequencies. An equivalent admittance model is developed using the two-scale asymptotic homogenization method. Based on the model, the metasurface is built and tested in both impedance tube and anechoic chamber. The metasurface is composed of a regular array of spherical Helmholtz resonators with internal neck and is more than 25 times thinner than the wavelength of the absorbed sound. It is shown that: (a) the total absorption of a plane wave normally or obliquely incident on the surface can be achieved by tuning the design of the resonators and their arrangement on the backing; and (b) the design is robust enough to achieve high absorption levels even when the incident wave is not plane and the metasurface has dimensions of the order of the wavelength. Other applications, such as enclosure mode control and sound absorption by curved arrays, are also discussed. (The work is supported by EPSRC, project EP/K037234/1)