Speech enhancement based on the discrete Gabor transform and multi-notch adaptive digital filters Ergun Erc ßelebi * Department of Electrical and Electronics Engineering, University of Gaziantep, 27310 Gaziantep, Turkey Received 25 July 2003; received in revised form 25 February 2004; accepted 26 February 2004 Available online 12 April 2004 Abstract This paper presents a new method to speech enhancement based on time–frequency analysis and adaptive digital filtering. The proposed method for dual-channel speech enhancement was developed by tracking frequencies of corrupting signal by the discrete Gabor transform (DGT) and implementing multi-notch adaptive digital filter (MNADF) at those frequencies. Since no a priori knowledge of the noise source statistics is required this method differs from traditional speech enhancement methods. Specifically, the proposed method was applied to the case where speech quality and intelligibility deteriorate in the presence of background noise. Speech coders and automatic speech recognition (ASR) systems are designed to act on clean speech signals. Therefore, corrupted speech signals by the noise must be enhanced before their pro- cessing. The method uses a primary input containing the corrupted speech signal while a reference input containing the noise only. In this paper, we designed MNADF instead of single-notch adaptive digital filter and used DGT to track frequencies of corrupting signal because fast filtering process and fast measure of the time-dependent noise frequency are of great importance in speech enhancement process. Therefore, MNADF was implemented to take advantage of fast filtering process. Different types of noises from Noisex-92 database were used to degrade real speech signals. Objective measures, the study of the speech spectrograms and global signal-to-noise ratio (SNR), segmental SNR (segSNR), Itakura–Saito distance measure as well as subjective listing test demonstrated consistently superior enhancement performance of the proposed method over traditional speech enhancement method such as * Tel.: +90-342-3601200x2111; fax: +90-342-3601103. E-mail address: ercelebi@gantep.edu.tr (E. Erc ßelebi). 0003-682X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.apacoust.2004.02.004 www.elsevier.com/locate/apacoust Applied Acoustics 65 (2004) 739–762