Bending nearfield compensation in the context of vibroacoustic active control

Abstract

The efficiency of passive methods for noise reduction decreases at low frequency. In this frequency range active structural acoustic control (ASAC) can reduce sound radiation of structures by controlling their vibration usually using piezoelectric or electrodynamic transducers. Besides its global effect on the structure, a bending nearfield is observed, depending on the actuator type. In some ASAC strategies as in the virtual impedance approach, actuators and sensors are collocated. Although it does not affect the radiation of the structure, the local bending strongly modifies the transfer function between transducers. A method is proposed in order to identify and compensate it. The global part of the vibratory field is extracted by cancelling the contribution of higher order modes approximated as a stiffness. After compensation, the signal from the sensor is much more representative of the radiation and nearly independent of the nature and the size of the actuator.