Real time feedforward active noise control using virtual sensors

Abstract

Active noise control (ANC) is a potential solution for low frequency tonal noise in vehicular cabin interiors. While ANC can significantly reduce low frequency noise at a microphone error sensor, the zone of attenuation may be so small that a nearby observer might not experience any improvement at all. However, it is also possible to reduce the noise specifically at the observer location, by using a forward prediction 'virtual microphone'. Pressure can be estimated (and hence minimised) at the observer location by extrapolating the signal from a number of remote microphones. Publications by the authors to date have presented the results from either control simulation models or post processed control examples where the potential for control is evaluated mathematically using experimental data. This paper presents the re-sults of real time control using a feedforward controller and two types of 'virtual' error sensor in a free field.