Adaptive line enhancer-based beat noise suppression for FM radio in motor vehicle

In FM-radio on motor vehicles, there exists an interference called as a beat noise which is caused by equipped electronic control units. We propose a method which suppresses a beat noise using VAD (Voice Activity Detection) and ALE (Adaptive Line Enhancer). The ALE adaptively eliminates the beat noise in noise-only segments obtained by VAD. The ALE whose coefficients are automatically fixed when the variance of the ALE estimation error becomes sufficiently small in noise-only segments. In speech existence segments, the fixed ALE is used. Since the proposed ALE is automatically fixed after convergence, it can reduce speech degradation caused by misjudgement of VAD. Unfortunately, the ALE often adds a pseudo beat noise in speech existence segments. Thus, when the variance of the output signal is greater than the variance of the input signal, we remove the ALE. Simulation results show that the proposed method improves SNR in comparison to a conventional method.