An analytically tractable framework is presented to describe mechanical and neural processing in the early stages of the auditory system. Algorithms are developed to assess the integrity of the acoustic spectrum at all processing stages. The algorithms employ wavelet representations, multiresolution processing, and the method of convex projections to construct a close replica of the input stimulus. Reconstructions using natural speech sounds demonstrate minimal loss of information along the auditory pathway. Close inspection of the final auditory patterns reveals spectral enhancements and noise suppression that have close perceptual correlates. The functional significance of the various auditory processing stages is discussed in light of the model, together with their potential applications in automatic speech recognition and low bit-rate data compression. >

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Auditory representations of acoustic signals

A common sequence of operations in the early stages of most sensory systems is a multiscale transform followed by a compressive nonlinearity. The authors explore the contribution of these operations to the formation of robust and perceptually significant representation in the early auditory system. It is shown that auditory representation of the acoustic spectrum is effectively a self-normalized spectral analysis, i.e., the auditory system computes a spectrum divided by a smoothed version of itself. Such a self-normalization induces significant effects such as spectral shape enhancement and robustness against scaling and noise corruption. Examples using synthesized signals and a natural speech vowel are presented to illustrate these results. Furthermore, the characteristics of auditory representation are discussed in the context of several psychoacoustical findings, together with the possible benefits of this model for various engineering applications. >

Self-normalization and noise-robustness in early auditory representations

The acoustic features of speech sounds in a model of auditory processing: vowels and voiceless fricatives

This paper presents the effectiveness of perceptual features and iterative clustering approach for performing both speech and speaker recognition. Procedure used for formation of training speech is different for developing training models for speaker independent speech and text independent speaker recognition. So, this work mainly emphasizes the utilization of clustering models developed for the training data to obtain better accuracy as 91%, 91% and 99.5% for mel frequency perceptual linear predictive cepstrum with respect to three categories such as speaker identification, isolated digit recognition and continuous speech recognition. This feature also produces 9% as low equal error rate which is used as a performance measure for speaker verification. The work is experimentally evaluated on the set of isolated digits and continuous speeches from TI digits_1 and TI digits_2 database for speech recognition and on speeches of 50 speakers randomly chosen from TIMIT database for speaker recognition. The noteworthy feature of speaker recognition algorithm is to evaluate the testing procedure on identical messages of all the 50 speakers, theoretical validation of results using F-ratio and validation of results by statistical analysis using 2 χ distribution.

Text Independent Speaker Recognition and Speaker Independent Speech Recognition Using Iterative Clustering Approach

Speech has evolved as a primary form of communication between humans. The advent of digital technology, gave us highly versatile digital processors with high speed, low cost and high power which enable researchers to transform the analog speech signals in to digital speech signals that can be scientifically studied. Achieving higher recognition accuracy, low word error rate and addressing the issues of sources of variability are the major considerations for developing an efficient Automatic Speech Recognition system. In speech recognition, feature extraction requires much attention because recognition performance depends heavily on this phase. In this paper, an effort has been made to highlight the progress made so far in the feature extraction phase of speech recognition system and an overview of technological perspective of an Automatic Speech Recognition system are discussed.

Review of Feature Extraction Techniques in Automatic Speech Recognition

The perceptually based linear predictive (PLP) speech analysis method is applied to isolated word automatic speech recognition (ASR). Low dimensionality of the PLP analysis vector, which is otherwise identical in form to the standard linear predictive (LP) analysis vector, allows for computational and storage savings in ASR. We show that in speaker-dependent recognition of the alpha-numeric vocabulary, the PLP method in VQ-based ASR yields similar recognition scores as does the standard ASR system. The main focus of the paper is on cross-speaker ASR. We demonstrate in experiments with vowel centroids of two male and one female speakers that PLP speech representation is more consistent with the underlying phonetic information than the standard LP method. Conclusions from the experiments are confirmed by superior performance of the PLP method in cross-speaker isolated word recognition.

K. Tsuga

Papers

Perceptually based processing in automatic speech recognition