Virtual Sensing Active Noise Control System with 2D Microphone Array for Automotive Applications

Virtual sensing techniques are used in Active Noise Control (ANC) system to shift the silent zone away from the physical error microphone as it causes inconvenience to the user in many applications. The present virtual sensing ANC configuration uses 1D microphone array as error microphone, which is placed very close to the silent zone. The noise cancellation and shifting of the silent zone is controlled by the microphone array geometry, beam-forming technique and the virtual sensing algorithm. In this paper, we propose a virtual sensing ANC system using 2D microphone array for capturing the error. A dual beam-forming technique is proposed considering the direction of arrival of the noise and anti-noise for the effective cancellation of noise in the silent zone. A circular microphone array with central element is used and amplitude shading technique is applied to shape the beam pattern. Using the proposed 2D microphone array and dual beam forming technique, a feed forward virtual sensing ANC system using FxLMS adaptive algorithm is built and simulations are performed with two automotive noises (truck and car) as primary input noise. Fixing the array radius, the number of array elements and the virtual distance is varied to calculate the noise cancellation at the silent zone. A high noise cancellation of 11.6dB and 10.99dB is achieved for the truck and car noise respectively with a virtual distance of 16cm. Compared to linear array, circular array performs better with increase in virtual distance. It gives 2dB increase in noise cancellation for car noise and 6.1dB increase for truck noise when the virtual distance is 64cm.