Speech signal noise reduction by EMD

Abstract

In this paper, a speech signal noise reduction based on a multiresolution approach referred to as Empirical Mode Decomposition (EMD) [1] is introduced. The proposed speech denoising method is a fully data-driven approach. Noisy signal is decomposed adaptively into oscillatory components called Intrinsic Mode Functions (IMFs), using a temporal decomposition called sifting process. The basic principle of the method is to reconstruct the signal with IMFs previously thresholded using a shrinkage function. The denoising method is applied to speech with different noise levels and the results are compared to wavelet shrinkage. The study is limited to signals corrupted by additive white Gaussian noise.

Ica & wavelet as a method for speech signal denoising

“…To solve these problems linear filters are generally used as they are easy to implement. But these are not effective when σ is not known [1]. So based on this other approaches has been proposed.…”

“…Noisy signal can be expressed as (1) where s( t ) is the speech signal free of noise , n ( t ) is noise whose distribution is obeyed by N(0,1), σ is the variance. The aim or the goal is to get a denoised signal estimation.…”

Speech denoising by Adaptive Weighted Average filtering in the EMD framework

“…The major advantage of the EMD is that the basis functions are derived from the signal itself. The EMD is also used in speech denoising [8]. In fact, speech signal noise reduction is a well known problem in signal processing.…”

“…To overcome the drawbacks of the wavelet method, two strategies for noise reduction have been proposed in [8]: EMD associated with filtering is efficient for relatively low noise level and when associated with thresholding is attractive in particular for relatively high noise level. However, in [8], only signals corrupted by additive white Gaussian noise are considered.…”

“…However, in [8], only signals corrupted by additive white Gaussian noise are considered. In this paper, an adaptive denoising scheme associating EMD with the ACWA filter is proposed.…”