Chair: Prof Wim Desmet, Catholic University of Leuven, belgium.

Prof. Zhiyu Yang, Hong Kong University of Science and Technology

Acoustic and elastic metamaterials based on decorated membrane resonators, principles and applications

After some fifteen years of research and development, in addition to further the understanding of fundamental physics, membrane-type elastic meta-materials have evolved into three types of functional devices, namely sound blocking, sound absorption, and vibration damping. These devices are compact, lightweight, broad band, can be made with all metallic components so as to function in extreme environments. These devices are also easy to install. Current research activities include working on the application of these devices in a wide range of areas, such as residential and commercial building sound proof walls and floors/ceilings, trains, motor vehicles, ships, aircraft, highway and railway noise control, factories, construction machinery, power plants, etc…

Prof. José Sánchez-Dehesa, Universitat Politècnica de València, Spain

Noise attenuation by arrays of sound absorbers: Theory and experiment

The application of periodic distributions of sound scatterers, named as sonic crystals, for the attenuation of broadband noise will be addressed. Starting with the simple mechanism of reflecting sound due to the acoustic band gaps due to the periodicity, barriers whose attenuation performance is produced from the combination of two physical mechanisms will be presented. These two mechanisms are: the absorption by the scattering units and the reflectance due to the periodicity. It will be shown that efficient noise barriers can be developed by using only three rows of micro-perforated units. Furthermore, optimisation algorithms will be used in the design of noise barriers are capable of attenuating specific broadband noise.

Prof. Massimo Ruzzene, Georgia Institute of Technology, US

Linear and Nonlinear Internally Resonating Metamaterials for Vibration and Noise Control

Meta-materials consist of engineered microstructural assemblies that exhibit superior properties in comparison to less-composed or naturally-occurring materials. Their unusual wave properties include band-gap behaviour, response directionality, left-handedness, and negative acoustic refraction, among others. These features, and their application for the design of acoustic filters, waveguides, logic ports, and ultrasonic transducer arrays, motivate the investigation of elastic wave propagation in micro-structured media. The talk illustrates the band gap and directional properties of periodic media, as defined by their ability to direct waves in preferential direction and at specified frequencies. Such properties are first illustrated on simple spring-mass systems, and subsequently demonstrated in complex structural lattices operating in linear and nonlinear deformation regimes. In addition, periodic arrays of electromechanical resonators and lattices that undergo topological changes resulting from structural instabilities are discussed as examples of adaptive meta-materials. Tunable local resonating systems and local instabilities are investigated as effective means to provide the considered periodic assemblies with adaptive band-gaps and wave steering characteristics, which are very effective for vibration and noise control.