SCALE EFFECT ANALYSIS FOR THE VIBRO-ACOUSTIC PERFORMANCE OF A MICRO-PLATE

Micro electromechanical system (MEMS) is an electromechanical device of microscale, in which micro-plate is the most typical structure. Its acoustical and mechanical properties influence the design of MEMS significantly. The vibroacoustic performance of simply supported micro-plate subjected to simultaneous stimulation of sound pressure and gas film (squeeze film) damping force is analyzed theoretically, the latter induced by the vibration of a micro-plate having similar size. By applying the Cosserat theory and the Hamilton principle, micro scale effects due to characteristic length and Knudsen number are taken into account. The governing equations are subsequently solved using the method of multiple Fourier transform to quantify sound transmission loss (STL) across the micro-plate. In the frequency domain, the effects of squeeze film under different circumstances (e.g., different characteristic lengths and Knudsen numbers, different vibration frequencies and amplitudes) on STL are investigated systematically. This work demonstrates the great influence of micro-scale effects, as well as vibration, on STL. Decreasing the vibration amplitude and increasing the distance between micro-plates lead to better performance of sound transmission. Results presented in this study provide useful theoretical guidance to the practical design of micro-plates in MEMS.