Speech enhancement using soft thresholding with DCT-EMD based hybrid algorithm

This paper introduces a new speech enhancement method using soft thresholding with a Discrete Cosine Transform (DCT) and Empirical Mode Decomposition (EMD) based hybrid algorithm. Soft thresholding for DCT-enhancement is a powerful method for enhancing the noisy speech signal in a wide range of signal-to-noise ratios (SNRs). However, due to the thresholding criteria a significant amount of noise is left in the enhanced signal. EMD is applied here to remove the remaining noise components. Due to the frequency characteristics of the intrinsic mode functions (IMFs), the noise components are mainly centered in the lower order IMFs. Therefore, it is possible to successfully identify and remove the remaining noise. The experimental results show that the proposed hybrid method is significantly more effective in removing the noise components from the noisy speech signal; thus giving better results in output SNR and quality compared to recently reported techniques.