A time-frequency ε -filter (TF ε -filter) is an advanced ε -filter applied to complex spectra along the time axis. It can reduce most kinds of noise while preserving a signal that varies frequently such as a speech signal. The filter design is simple and it can effectively reduce noise. It is applicable not only to small amplitude stationary noise but also to large amplitude nonstationary noise. However, when the filter is applied to the noise that varies much frequently along the time axis, TF ε -filter cannot reduce noise without the signal distortion. This paper introduces an advanced method for noise reduction that applies ε -filter to complex spectra not only along the time axis but also along the frequency axis labeled cross TF ε -filter. It can reduce the noise where the neighboring frequency bins have similar powers. To show the effectiveness of the proposed method, some comparative experiments are also given, such as the performance of noise reduction and the robustness concerning input signal-to-noise ratio and parameter changes.
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