Modulation Domain Improved Adaptive Gain Equalizer for Single Channel Speech Enhancement

Abstract: Human speech is the main method for personal communication. During communication speech may get impaired with ubiquitous noise. Enduring interfering noise decreases speech intelligibility and makes speech communication troublesome. To improve the speech quality and intelligibility, speech enhancement is one of the emerging and most used branches of signal processing. For the reduction of noise from speech signals, methods are continuously developed, one among those is the Improved Adaptive Gain Equalizer (IAGE) which is a single-channel speech enhancement method that has particular focus on enhancement of speech instead suppression of noise. Improved Adaptive Gain Equalizer is an enhanced version of the Adaptive Gain Equalizer (AGE). The noise reduction algorithm used in IAGE helps the speech to be amplified according to Signal to Noise Ratio (SNR) estimate in sub bands. Modulation decomposition of the speech signals brought the idea of a modulation system which is useful for modeling of speech and other signals. The purpose of this thesis is to implement the IAGE within modulation system (IMAGE) for speech enhancement. This thesis report present details of the implementation of IAGE in modulation domain. The successful implementation of the system has been validated with different performance measurements, i.e., Spectral Distortion (SD), Signal to Noise Ratio Improvement (SNRI), Mean Optimum Score (MOS) and Spectrogram Analysis. The system was analyzed with male and female speech with noise signals Engine noise (EN), Factory noise (FN) and Gaussian Noise (GN) at 0 dB, 5 dB, 10 dB, -5 dB and -10 dB Signal to Noise Ratio (SNR). MOS has found to be between 4 and 3 for all the test cases. In comparison to IAGE, IMAGE has produced optimal results.