A technique is described for the determination of the first three formant frequencies of a voiced speech signal corrupted by high levels of noise. The technique involves a rough frequency-domain analysis followed by an accurate time-domain statistical analysis. The frequency-domain analysis is performed with a bank of overlapped, shifted, bandpass digital filters chosen to cover the frequency range of the first three formant frequencies. The time-domain analysis involves a calculation of the consistency of the intervals between successive zero-crossings at the output of each filter. As the algorithm proceeds, those filters which contain peaks in the energy spectrum are chosen as a first estimate of the location of the first three formants. The final choice of filter containing each formant is made, in the neighborhood of the first estimate, by choosing that filter with a signal output having the maximum zero-crossing interval consistency. A decision procedure is applied to several calculated parameters to result in a measurement of each of the first three formant frequencies. The results of extensive testing of the method are reported for speech contaminated by high levels of additive white Gaussian noise.

http://ieeexplore.ieee.org/iel6/29/26190/01164571.pdf

A zero-crossing consistency method for formant tracking of voiced speech in high noise levels

In this paper results are presented concerning the use of spectral subtraction for enhancing speech corrupted by additive noise. In this study several variations of the spectral subtraction process have been implemented and tested. The overall results provide insight into the use of spectral subtraction for speech enhancement. As a result of this study, several conclusions are presented regarding spectral subtraction, its effects on noise corrupted speech, and its ability to enhance speech intelligibility and listenability. Finally, the use of spectral subtraction as a preprocessor for speech feature extraction is considered.

Factors Related To Spectral Subtraction For Speech In Noise Enhancement

In this paper a method is proposed to provide enhancement of the intelligibilty of speech which has been contaminated by additive noise. The method is based on the assumption that intelligibility enhancement can be achieved by making use of information directly related to speech intelligibility. A structure which provides the means to implement the method is presented and a discussion of some preliminary results obtained with the method is included.

Adaptive Processing With Feature Extraction To Enhance The Intelligibility Of Noise-Corrupted Speech

Intelligibility enhancement of speech signals in high levels of additive, wideband noise is a problem of significant interest and application. Consequently, a number of speech processing methods have been developed. Although a large number of methods have been proposed, an implementation that significantly increases the intelligibility of speech corrupted by high levels of wideband noise has not been demonstrated. It is the purpose of this paper to review the processing strategies and philosophies used in these methods and to make some observations based on this review that suggest a processing framework for speech intelligibility enhancement in noise. The paper concludes with a description of one implementation of this suggested framework.

Understanding speech corrupted by noise

: This report describes results of an examination of four methods for processing speech so as to enhance its intelligibility in the presence of wideband random noise at the source. The four methods were: (1) INTEL, a method which involves processing in both the first and second order spectral domains; (2) Spectral subtraction, which involves a simple subtraction of the average noise spectrum from the first-order spectrum; (3) Minimum mean square error filtering, which involves filtering speech in such a way as to minimize the mean square error between a signal and its expected value in noise; and (4) Methods based upon suppressing the frequency content of a speech plus noise signal between pitch harmonics of the speech signal. To carry out a study of methods of enhance speech intelligibility in noise, two general-purpose computer processing systems were implemented. The first, a terminal interactive system for generation, analysis, and graphic display of synthetic voiced speech sounds, provided considerable insight into the effect of various processing algorithms upon speech and upon speech in noise. The second computer processing system has been developed for the processing of real speech. It involves use of a DDP-116 data converter and a Honeywell 6000 Computer.

The Development of a Computer Speech Processing System and Its Use for the Study and Development of Processing Methods for Enhancing the Intelligibility of Speech in Noise.

Robert A Curtis

Papers

The Development of a Computer Speech Processing System and Its Use for the Study and Development of Processing Methods for Enhancing the Intelligibility of Speech in Noise.