The Big Read: Assembling the Popular Canon

Linear Discriminative Analysis techniques have been used in pattern recognition to map feature vectors to achieve op- timal classification. Kernel Discriminative Analysis(KDA) seeks to introduce non-linearity in this approach by map- ping the features to a non-linear space before applying LDA analysis. The formulation is expressed as an eigen- value problem resolution. Using a different kernel, one can cover a wide class of nonlinearities. In this paper, we de- scribe this technique and present an application to a speech recognition problem. We give classification results for a connected digit recognition task and analyze some existing problems.

2009

The robustness of phoneme classification to white Gaussian noise and pink noise in the acoustic waveform domain is investigated using support vector machines. We focus on the problem of designing kernels which are tuned to the physical properties of speech. For comparison, results are reported for the PLP representation of speech using standard kernels. We show that major improvements can be achieved by incorporating the properties of speech into kernels. Furthermore, the high-dimensional acoustic waveforms exhibit more robust behavior to additive noise. Finally, we investigate a combination of the PLP and acoustic waveform representations which attains better classification than either of the individual representations over a range of noise levels.

2000

We describe a new method for phoneme sequence recognition given a speech utterance. In contrast to HMM-based approaches, our method uses a kernel-based discriminative training procedure in which the learning process is tailored to the goal of minimizing the Levenshtein distance between the predicted phoneme sequence and the correct sequence. The phoneme sequence predictor is devised by mapping the speech utterance along with a proposed phoneme sequence to a vector-space endowed with an inner-product that is realized by a Mercer kernel. Building on large margin techniques for predicting whole sequences, we are able to devise a learning algorithm which distills to separating the correct phoneme sequence from all other sequences. We describe an iterative algorithm for learning the phoneme sequence recognizer and further describe an efficient implementation of it. We present initial encouraging experimental results with the TIMIT and compare the proposed method to an HMM-based approach.

2001

The aim of discriminant feature analysis techniques in the signal processing of speech recognition systems is to find a feature vector transformation which maps a high dimensional input vector onto a low dimensional vector while retaining a maximum amount of information in the feature vector to discriminate between predefined classes. This paper points out the significance of the defini- tion of the classes in the discriminant feature analysis technique. Three choices for the definition of the clas- ses are investigated: the phonemes, the states in context independent acoustic models and the tied states in context dependent acoustic models. These choices for the classes were applied to (1) stan- dard LDA (linear discriminant analysis) for reference and to (2) MIDA, an improved, mutual information based dis- criminant analysis technique. Evaluation of the resulting linear feature transforms on a large vocabulary contin- uous speech recognition task shows, depending on the technique, ...

Phoneme classification is investigated for linear feature domains with the aim of improving robustness to additive noise. In linear feature domains noise adaptation is exact, potentially leading to more accurate classification than representations involving non-linear processing and dimensionality reduction. A generative framework is developed for isolated phoneme classification using linear features. Initial results are shown for representations consisting of concatenated frames from the centre of the phoneme, each containing f frames. As phonemes have variable duration, no single f is optimal for all phonemes, therefore an average is taken over models with a range of values of f . Results are further improved by including information from the entire phoneme and transitions. In the presence of additive noise, classification in this framework performs better than an analogous PLP classifier, adapted to noise using cepstral mean and variance normalisation, below 18dB SNR. Finally we propose classification using a combination of acoustic waveform and PLP log-likelihoods. The combined classifier performs uniformly better than either of the individual classifiers across all noise levels.

IEEE Transactions on Audio, Speech, and Language Processing, 2000

This work proposes methods for combining cepstral and acoustic waveform representations for a front-end of support vector machine (SVM) based speech recognition systems that are robust to additive noise. The key issue of kernel design and noise adaptation for the acoustic waveform representation is addressed first. Cepstral and acoustic waveform representations are then compared on a phoneme classification task. Experiments show that the cepstral features achieve very good performance in low noise conditions, but suffer severe performance degradation already at moderate noise levels. Classification in the acoustic waveform domain, on the other hand, is less accurate in low noise but exhibits a more robust behavior in high noise conditions. A combination of the cepstral and acoustic waveform representations achieves better classification performance than either of the individual representations over the entire range of noise levels tested, down to −18dB SNR.

2012 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2012

Modeling the second-order statistics of articulatory trajectories is likely to improve the performance in classifying phone segments compared to using only linear combinations of MFCCs. Nevertheless, the extremely high dimensionality of the feature space spanned by a combination of monomials of degree-1 and degree-2 makes it difficult to effectively exploit the discriminative information in the full covariance matrix. This paper proposes a novel algorithm, dubbed Knowledge-based Quadratic Discriminant Analysis (KnQDA), for reducing the number of dimensions of the space spanned by degree-1 and degree-2 monomials by using phonetic knowledge for selecting the set of degree-2 monomials that are most likely to improve classification. KnQDA seeks a trade-off between overfitting and undertraining, which further improves the learnability. Binary classifications on all pairs of phones in TIMIT show the effectiveness of the proposed method, especially on those phone pairs that overlap strongly in the linear feature space.

2005

In this paper we use kernel-based Fisher Discriminants (KFD) for classification by integrating this method in a HMM-based speech recognition system. We translate the outputs of the KFD-classifier into conditional probabilities and use them as production probabilities of a HMM-based decoder for speech recognition. To obtain a good performance also in terms of computational complexity the Recursive Least Squares Algorithm (RLS-Algorithm) is enforced. We train and test the described hybrid structure on the Resource Management Corpus (RM1).

2003

This work discusses the improvements which can be expected when applying linear feature-space transformations based on Linear Discriminant Analysis (LDA) within automatic speechrecognition (ASR). It is shown that different factors influence the effectiveness of LDA-transformations. Most importantly, increasing the number of LDA-classes by using time-aligned states of Hidden-Markov-Models instead of phonemes is necessary to obtain improvements predictably. An extension of LDA is presented, which utilises the elementary Gaussian components of the mixture probability-density functions of the Hidden-Markov-Models' states to define actual Gaussian LDAclasses. Experimental results on the TIMIT and WSJCAM0 recognition task are given, where relative improvements of the error-rate of 3.2% and 3.9%, respectively, were obtained.

2003