Studies in Signal Processing Techniques for Speech Enhancement: A comparative study

Speech enhancement is very essential to suppress the background noise and to increase speech intelligibility and reduce fatigue in hearing. There exist many simple speech enhancement algorithms like spectral subtraction to complex algorithms like Bayesian Magnitude estimators based on Minimum Mean Square Error (MMSE) and its variants. A continuous research is going and new algorithms are emerging to enhance speech signal recorded in the background of environment such as industries, vehicles and aircraft cockpit. In aviation industries speech enhancement plays a vital role to bring crucial information from pilot’s conversation in case of an incident or accident by suppressing engine and other cockpit instrument noises. In this work proposed is a new approach to speech enhancement making use harmonic wavelet transform and Bayesian estimators. The performance indicators, SNR and listening confirms to the fact that newly modified algorithms using harmonic wavelet transform indeed show better results than currently existing methods. Further, the Harmonic Wavelet Transform is computationally efficient and simple to implement due to its inbuilt decimation-interpolation operations compared to those of filter-bank approach to realize sub-bands

Active Noise Control using Variable step-size Griffiths’ LMS (VGLMS) algorithm on Real-Time platform

This paper proposes implementation of Griffith’s Variable step-size algorithm for Active Noise Control (ANC) on ADSP-TS201 EZ-Kit Lite. The dual computational units and execution of up to four instructions per cycle which are special features over other processors are best utilized to generate an optimized code. The VGLMS provides improved secondary path estimation and computations involved are marginal as the same gradient is used for step-size computation and coefficient adaptation. The improved secondary path estimate, in turn improves the ANC performance. Further, variable step-size algorithm is used for the main-path to achieve faster convergence. Both for narrowband (fundamental and its harmonics) and broadband noise fields, for a duct the attenuation achieved is 25 dB and 15 dB respectively. The program execution time was only 1.25% for an input sampling rate of 1 KHz which indicates the utility of the special features of the processor considered. Further these features have enabled in bringing down the program memory requirement in the implementation of the algorithm

ACTIVE NOISE CONTROL: ITS IMPLEMENTATION & PERFORMANCE

Active noise control systems based on feedforward approach using filtered-x LMS algorithm for single channel (in a duct) and multi-channel (in an enclosure), are considered. The systems are implemented on a TMS320C30 processor based d_space DSP board and their performances are evaluated. In the case of duct, for the tonal and white noise, a noise reduction of about 32dB and 12dB, respectively are achieved. For a duct with an axial flow fan, using anti-turbulence probes, 7.66dB noise reduction is obtained. For the multi-channel case, a 2 channel system for a typical aircraft cockpit mockup model is considered and a reduction of about 20dB is obtained for a tonal noise

Analytic discrete cosine harmonic wavelet transform(ADCHWT) and its application to signal/image denoising

A new simple and efficient analytic wavelet transform based on Discrete Cosine Harmonic Wavelet Transform DCHWT (ADCHWT) has been proposed and is applied for signal and image denoising. The analytic DCHWT has been realized by applying DCHWT to the original signal and its Hilbert transform. The shift invariance and the envelope extraction properties of the ADCHWT have been found to be very effective in denoising compared to that of DCHWT

Vehicular Ad-Hoc Networks (VANETs) for Vehicle tracking

Vehicular Ad-Hoc networks (VANETs) are self-organized networks built up from moving vehicles, and are part of the broader class of Mobile Ad-Hoc Networks(MANETs). VANETs require the definition of specific networking techniques, whose feasibility and performance are usually tested by means of simulation. The main challenges posed by VANETs simulation are their faithful characterization and physical implementation, logistic difficulties, economic issues and technology limitations make simulation the mean of choice in the validation of networking protocols for VANETs and a widely adopted first step in development of real world technologies. It is quite interesting to bring down complexities of VANETs in realization of their characteristics both in simulation as well as real-time implementation by defining VANETs for a number of vehicles and base-stations for their tracking applications within the geographical scenario specified by the service provider

Analytic discrete cosine harmonic wavelet transform(ADCHWT) and its application to signal/image denoising

A new simple and efficient analytic wavelet transform based on Discrete Cosine Harmonic Wavelet Transform DCHWT (ADCHWT) has been proposed and is applied for signal and image denoising. The analytic DCHWT has been realized by applying DCHWT to the original signal and its Hilbert transform. The shift invariance and the envelope extraction properties of the ADCHWT have been found to be very effective in denoising compared to that of DCHWT

A Dual Tree Complex Discrete Cosine Harmonic Wavelet Transform (ADCHWT) and Its Application to Signal/Image Denoising

A new simple and efficient dual tree analytic wavelet transform based on Discrete Cosine Harmonic Wavelet Transform DCHWT (ADCHWT) has been proposed and is applied for signal and image denoising. The analytic DCHWT has been realized by applying DCHWT to the original signal and its Hilbert transform. The shift invariance and the envelope extraction properties of the ADCHWT have been found to be very effective in denoising speech and image signals, compared to that of DCHWT