Spatial noise cancellation inside cars: Performance analysis and experimental results

A loudspeaker array is a key component in active noise cancellation (ANC) systems. Most in-car ANC systems utilize the car's own integrated loudspeakers to cancel the noise due to engine and other sources. In this paper, we evaluate the integrated loudspeakers' noise cancelling capabilities by analyzing the in-car noise field and the loudspeaker responses. We show that the average noise power in a spatial region can be expressed using a series of coefficients, and that the noise field can be decomposed into several basis noise patterns. Through analysing the measurements in a car, we show that the car's built-in loudspeakers are capable of attenuating the driving noise by up to 30 dB for frequencies up to 500 Hz within a spherical region of 10 cm radius.