Applications of Modal Analysis to Active Control of Sound by Plates

• Main Authors: Wen-Hong Lin, 林文弘
• Other Authors: 陳國在
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/62409296574087238339

碩士 === 國立臺灣大學 === 工程科學及海洋工程學研究所 === 92 === Active control of sound radiation from a vibrating clamped rectangular plate excited by a steady state harmonic PZT is experimentally studied. First, the mechanism of vibrating plate is analyzed numerically. Then the sound power is calculated by summing individual contributions of radiation modes. From the numerical results, different locations of exciting points will have various radiation mode distribution patterns. Thus, it is possible to reduce more sound power by arranging the locations of controlling points to attenuate individual radiation modes. For simplicity, the experiment of this study employs two independent control systems. The first one has a PZT attached to the corner of the plate with a piezoceramic patch as error sensor of vibration. And another PZT is attached to the center of the plate, with a microphone in the radiation field as error sensor of sound pressure. In recent researches, this arrangement of PZT at the center with microphone successfully reduces the sound power of first radiation mode. And the power of other modes can be attenuated by carefully choosing the location of piezoceramic patch error sensor. The experiment results show that this control strategy reduces more sound power than a single control system in lower frequencies.