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.