ACTIVE CONTROL OF NOISE TRANSMISSION THROUGH A PANEL INTO A CAVITY .3. EFFECT OF THE ACTUATOR LOCATION

The effect of the location of a point force used to control sound transmission through a panel backed by a cavity has been theoretically analyzed for a single frequency plane-wave incident sound field. Although the simple quadratic relationship between the point force phase and amplitude and the resulting interior noise level is well known, there is no such quadratic relationship between point force location and the resulting minimum achievable sound energy in the cavity. Results obtained here demonstrate that for a particular type of incident sound field, the optimum locations for the actuator producing the point force can be obtained by a global evaluation of the total sound energy in the cavity as a function of actuator location. It is demonstrated that a controller that drives an actuator placed at the optimum location will always produce a better attenuation performance than one that drives a randomly located actuator. It is shown that there might be more than one location at which a single actuator may achieve a similar minimum sound energy level in the cavity. However, the best actuator location is determined by considering other constraints, such as control force amplitude and the structural vibration level.