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Statistical Energy Analysis is extensively used framework for predicting the transmission of vibration and sound through complex structures. The prediction of noise and vibration levels in such structures depends on precise estimation of three parameters viz. modal densities, the damping loss factors and the coupling loss factors between the subsystems. Damping is usually characterized by the amount of energy dissipated and the most common measure of this dissipation is damping loss factor. This paper describes the effect of materials used for plate on damping loss factor. The experimental results of conventional and composite plates are compared. Damping loss factor has been determined by Half-power bandwidth method for the plates.

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This review article summarises the mechanism of the acoustic energy harvester or converter which includes the compact structure of the piezoelectric element, electromagnetic transducer and Helmholtz resonator; different shapes of Helmholtz resonators, piezoelectric cantilever, acoustic metamaterial-based approach, electrostatic transduction method, auxetic structure of material and other techniques. The recently established methods of acoustic energy harvesting and converting mechanisms; devices are carefully reviewed, and their results are compared and listed in the table. The technique of energy conversion by using acoustic metamaterial will tend to be more efficacious due to its complexity and the structure. Even in the few noise attenuation applications, more metamaterial is used, where, with the help of the conversion mechanism, the noise or sound energy can be converted into electrical energy for small electronic applications. It is demonstrated that the acoustic energy-conversion technique will become an essential part of the environmental energy harvesting research field.

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