Enhance Low-frequency Suppress

Usually the generalized sidelobe canceller (GSC) beamformer requires additional highpass pre-filtering due to insufficient suppression of low frequency directional interference, and it deteriorates the bandwidth quality of speech enhancement, especially for small size microphone array. This paper proposes a new GSC beamformer with multiple frequency dependent norm-constrained adaptive filters (FD-NCAF), which combine bin-wise constraint in low frequency band and norm constraint in high frequency band, to improve the performance of the adaptive interference canceller (AIC) for low frequency interference. Simulation on five testing signals shows that directional response of the proposed beamformer is less sensitive to the spectrum of interference than the full-band GSC. In the experiments based on real recordings, when the cut-off frequency of highpass pre-filtering extended to lower frequency, the residual directional interference of the full-band GSC will be increased by 3.37dB, while that of the proposed beamformer will be increased by only 0.95dB. Therefore, the passband of the proposed GSC beamformer can be extended without loss of performance.