Development of composite plate for compact silencer design

A compact flow-through plate silencer is constructed for low frequency noise control using new reinforced composite plates. The concept comes from the previous theoretical study [L. Huang, Journal of the Acoustical Society of America 119 (2006) 2628-2638] which concerns a clamped supported plate enclosed by rigid cavities. When the grazing incident sound wave comes and induces the plate into the vibration, it will radiate sound and reflect sound. Such sound reflection causes a desirable noise reduction from low to medium frequency with wide broadband. The structural property of the very light plate with high bending stiffness is very crucial element in such plate silencer. In this study, an approach to fabricate new reinforced composite panel with light weight and high flexibility to increase the bending stiffness is developed in order to realize the function of this plate silencer practically. The plate silencer can be constructed in more compact size compared with the previous two-plate silencer with two rectangular cavities and the performance with the stopband of the range from 229 to 618 Hz, in which the transmission loss is higher than 10 dB over the whole frequency band without flow or with flow at the speed of 15 m/s, can be achieved. The experimental data also proves that the non-uniform clamped plates with thinner ends perform very well. To implement the use of such silencer practically in controlling noise at different dominant frequency ranges, a design chart has been established for searching the optimal bending stiffness and corresponding stopband at different geometries.