In-car noise field analysis and multi-zone noise cancellation quality estimation

The loudspeaker array plays a key role in an active noise cancellation (ANC) system. In most in car ANC systems, the car's pre-installed multimedia loudspeakers are employed as the secondary sources of the ANC system. In this paper, we evaluate the in-car loudspeaker system's capability in multi-zone noise field cancellation by analyzing the simultaneous noise field at multiple control regions inside a car cabin. We show that the average noise power in multi-zone spatial configurations can be expressed using a series of coefficients, and that the noise field can be decomposed into several basis noise patterns. Based on this model, we also estimate the integrated loudspeaker system's maximum noise cancellation capability, which can be used to assist design optimization. Through analyzing the noise field measurements in a car, we show that the car's integrated stereo loudspeaker system can attenuate the in-car noise by approximately 20 dB for the head position of two seats simultaneously, and up to 200 Hz.