Global active noise control in vibro-acoustic cavities using acoustic sensing

Abstract

This paper proposes a method for global active noise control in vibro-acoustic cavities using acoustic sensing under the presence of both structural and acoustic disturbances. Global active noise control has earlier been carried out by minimizing the acoustic potential energy in the cavity expressed as the sum of squares of the acoustic pressures at discrete microphone locations. However, this approximation though holds well for a rectangular box cavity, is not applicable for the cavities of other shapes. This calls for development of an active noise control method based on the estimation of the acoustic potential energy applicable to the cavities of arbitrary shapes as encountered in practice. Virtual sensing of the acoustic potential energy has been reported in the literature based on measurement of vibration by the structural sensors. However, such approaches are applicable when only the structural disturbances act on the cavity, but cannot be used if the acoustic disturbances are also present in the cavity. This paper presents development of a global active noise control method based on virtual sensing of the acoustic potential energy in the cavity under the presence of structural and acoustic disturbances. Minimisation of the estimated acoustic potential energy through a feedforward control law is developed. Numerical studies on an irregular-shaped vibro-acoustic cavity and a car cavity are presented to evaluate the performance of the proposed technique. The results are also compared with the maximum possible reduction in the acoustic potential energy obtained using the optimal control inputs. The levels of reduction in the acoustic potential energy obtained with the proposed method are found to be close to the maximum possible reduction using the optimal control inputs. The proposed method is then also validated through an experimental study on a rectangular box cavity.