Investigation of spatio-temporal networks for temporal sequence recognition

Pao Yue-kong Library Electronic Theses Database

Investigation of spatio-temporal networks for temporal sequence recognition

 

Author: Ko, Tat Leung
Title: Investigation of spatio-temporal networks for temporal sequence recognition
Degree: M.Sc.
Year: 1996
Subject: Automatic speech recognition
Neural networks (Computer science)
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: vi, 82 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1219799
URI: http://theses.lib.polyu.edu.hk/handle/200/4164
Abstract: This investigation is to verify the effectiveness of applying spatio-temporal approach in the area of temporal sequence recognition, in particular, speech recognition. Speech recognition is fundamentally a pattern classification task. Its objective is to take an input pattern, the speech waveform, and classify it as one of a set of spoken words, phrases, or sentences. The Spatio-temporal Pattern (STP) can be defined as a time-correlated sequence of spatio patterns. With spatio-temporal network, the speech data of a single word can be allocated into a series of time frames. Each time, the data in a specified time frame will be sent to the network for processing. This can reduce the complexity of the network and the processing time. One of the advantages of spatio-temporal network is that the network can be constructed dynamically, thus simulating the effect of training. One of its disadvantages is that different words with same ending may result in ambiguous results. In addition, Recurrent Neural Networks (RNNs) were applied to recognize the speech data by using the Real Time Recurrent Learning (RTRL) algorithm which is a gradient following learning algorithm for completely recurrent networks running in continuous sampled time. The merit of RTRL algorithm is its ability to process input data continuously without any requirement for a fixed, or even unbounded epoch length. Its drawback is that it requires a great deal of computation on each update cycle, and it is non local. From the results obtained, for both algorithms, the accuracy of recognition is about 75%. We have found that, the spatio-temporal networks are more suitable for speech recognition for the same speaker, whilst RTRL algorithm is more appropriate for speech recognition for multiple speakers. In order to increase the accuracy, for spatio-temporal networks, we found that the number of time frames for each word should be more or less the same. For the RTRL algorithm, it is better to use minimum squared errors instead of slope differences to determine how close the network output curve is to the desired output curve.

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