Jean-Philippe Groby Senior Researcher at CNRS/Directeur de Recherche CNRS. Habilitation à Diriger des Recherches. Leader of the team «Acoustic Materials»(one of the three research teams of the Laboratory LAUM). Chair of the Technical Committee «Acoustic Materials»of the European Acoustics Association (EAA). Associate editor of npj acoustics. Mailing address: Laboratoire d'Acoustique de l'Université du Mans (LAUM), UMR6613 CNRS, Avenue Olivier Messiaen, F-72085 LE MANS Cedex 9 France. Phone: +33 2 43 83 36 70 email: Jean-Philippe.Groby@univ-lemans.fr French citizen Born, 16th August 1979

Acoustic Waves in Periodic Structures, Metamaterials, and Porous Media: From Fundamentals to Industrial Applications, N. Jimenez, O. Umnova, and J.-P. Groby, (Editors), Topics in Applied Physics, 444 pages, Springer, Cham (2021). ISBN: 978-3-030-84299-4 DOI: https://doi.org/10.1007/978-3-030-84300-7 This book delivers a comprehensive and up-to-date treatment of practical applications of metamaterials, structured media, and conventional porous materials. With increasing levels of urbanization, a growing demand for motorized transport, and inefficient urban planning, environmental noise exposure is rapidly becoming a pressing societal and health concern. Phononic and sonic crystals, acoustic metamaterials, and metasurfaces can revolutionize noise and vibration control and, in many cases, replace traditional porous materials for these applications. In this collection of contributed chapters, a group of international researchers reviews the essentials of acoustic wave propagation in metamaterials and porous absorbers with viscothermal losses, as well as the most recent advances in the design of acoustic metamaterial absorbers. The book features a detailed theoretical introduction describing commonly used modelling techniques such as plane wave expansion, multiple scattering theory, and the transfer matrix method. The following chapters give a detailed consideration of acoustic wave propagation in viscothermal fluids and porous media, and the extension of this theory to non-local models for fluid saturated metamaterials, along with a description of the relevant numerical methods. Finally, the book reviews a range of practical industrial applications, making it especially attractive as a white book targeted at the building, automotive, and aeronautic industries.

Subwavelength broadband perfect absorption for unidimensional open-duct problems, Adv. Mater. Technol., 2201909, 2023, by Y. Meng, V. Romero-García, G. Gabard, C. Bricault, S. Goudeé, and J.-P. Groby.

Abstract: Passive metamaterials provide efficient solutions for sound absorption in the low-frequency regime with deep subwavelength dimensions. They have been extensively applied in unidimensional reciprocal problems considering that an incident wave is either reflected or transmitted at the outlet boundary. However, the generalized problem with impedance boundary condition is not well understood yet. This work presents a general design methodology of metamaterial absorbers for open-duct problems, which is a special case of impedance outlet boundary encountered in broad practical applications, for example, noise-attenuation problems in heat ventilation and air conditioning systems. By properly using monopolar point scatterers made of arrays of Helmholtz resonators, the design process is significantly simplified; the transfer matrix modeling is sufficiently accurate to describe the acoustic response of the system. A single monopolar point scatterer is insufficient to attenuate both the reflected and radiated waves; a frequency-dependent maximum absorption exists and is derived analytically. To go beyond this absorption bound and achieve perfect absorption, at least two point scatterers are necessary. Specific designs are provided and validated experimentally for maximum or perfect absorption, either at single frequencies or over specific frequency bands.
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Underwater metamaterial absorber with impedance-matched composite, Science Advances, 8: eabm4206, 2022, by S. Qu, N. Gao, A. Tinel, B. Morvan, V. Romero-García, J.-P. Groby, and P. Sheng.

Abstract: By using a structured tungsten-polyurethane composite that is impedance matched to water while simultaneously having a much slower longitudinal sound speed, we have theoretically designed and experimentally realized an underwater acoustic absorber exhibiting high absorption from 4 to 20 kHz, measured in a 5.6 m by 3.6 m water pool with the time-domain approach. The broadband functionality is achieved by optimally engineering the distribution of the Fabry-Perot resonances, based on an integration scheme, to attain impedance matching over a broad frequency range. The average thickness of the integrated absorber, 8.9 mm, is in the deep subwavelength regime and close to the causal minimum thickness of 8.2 mm that is evaluated from the simulated absorption spectrum. The structured composite represents a new type of acoustic metamaterials that has high acoustic energy density and promises broad underwater applications.
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Virtual visit of the temporary exhibition À l'image du son, Le Mans Sonore - Biennale Internationale du Son, 22 Jan.- 17 Feb. 2022.

Virtual visit of the temporary exhibition Acoustics and Beyond at the University of Coimbra's Museum of Science, 21 Feb.- 31 Oct. 2020.