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The traditional cosine-modulated filter banks design method have some disadvantages, such as the necessary and sufficient conditions for a perfect reconstruction of the filter banks are strict, at the same time the nonlinear optimization algorithms fall down to local minimum easily and itpsilas operation is complicated. A new method is proposed in this paper. The method can be used to improve modulation...
In this paper, we show that the whole echo path in an FXO varies sharply and suddenly because multiple switches involved in a call could not be active at the same time. An echo canceller adapting the echo path, therefore, will have poor performance. We then present an echo cancellation system consisting of two echo cancellers: one is a fixed echo canceller canceling the echo from the switch inside...
This paper applies Gabor expansion to passive noise reduction of speech signals. The Gabor expansion with Gaussian prototype function has a property that its time and frequency product is minimal. The property makes the noise-only segment more clearly and the noise estimate more robustly. When a Gabor component contains noise only, the constant weight is applied to the component, and when a Gabor...
Surrounded noises degrade both audio and video qualities in a multimedia environment. This paper applies Gabor expansion to passive noise reduction of speech signals. The noise reduction method and performance via Gabor expansion are studied. The Gabor expansion with Gaussian prototype function has a property that its time and frequency product is minimal. The property makes the noise-only segment...
This paper presents new conditions equivalent to the traditional conditions for existence of frames constructed in the joint time-frequency (JTF) domain and based on biorthogonal functions. In addition to addressing existence of frames, we discuss computation techniques for dual frames based on these equivalent conditions. The equivalent conditions facilitate theoretical analysis of frames. For...
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