An Interference Cancellation Method Using Fixed Beamformer and Adaptive Filter in Car Environment

In-car speech interactive system usually requires to selectively be controlled by one or more person in the vehicle. Beamforming is often introduced to deal with this case by using microphone array. However, most of the beamforming methods like fixed beamformer, Minimum Variance Distortionless Response (MVDR) and Generalized Sidelobe Canceller (GSC) show limited performance when two or more passengers speak simultaneously. Speech recognition pass rate will be severely degraded by the residual interference. And in car environment, speaker's location is previously known and relatively fixed, so an optimized interference cancellation method is proposed to separate desired signal from interferences. The proposed method consists of two parts, beamforming by using multiple fixed beamformer and optimized joint adaptive filter. The proposed beamforming method can provide better reference signal with less desired signal component compared with conventional beamforming method. Thus, by utilizing a powerful adaptive filter, residual noise and interference can be further suppressed with acceptable speech distortion. Simulation and real car experimental results show significant improvement on signal to noise plus interference ratio (SINR) and character error rate (CER).