Abstract:

In this paper, analytical and experimental results of an investigation of active control of sound radiated from cylinders are presented. The aluminum cylinder is 1 m in length, 25 cm in diameter, and 2.4 mm in thickness with two rigid endcaps at both ends. The excitation is a bandlimited random noise encompassing the first five modes of the cylinder and the control actuators are surface mounted piezoceramic transducers. Since it is desired to integrate the error sensors into the structure, the recently developed structural acoustic sensing (SAS) approach is extended to cylindrical coordinates and implemented using 12 accelerometers mounted on the cylinder. The SAS approach provides time-domain estimates of far-field radiated sound at predetermined radiation angles. The controller is a 3x3 filtered-x LMS paradigm implemented on a TMS320C30 DSP. The results show excellent global control of the radiated sound over the frequency bandwidth of excitation. The SAS approach is shown to yield similar performances as error microphones located in the far field. [Work supported by the Office of Naval Research.]