NETtalk (artificial neural network)

NETtalk-Back-propagation

NETtalk is a significant early project in the field of artificial intelligence (AI) and neural networks. Developed in the mid-1980s by Terry Sejnowski and Charles Rosenberg, NETtalk was designed to demonstrate the potential of artificial neural networks in simulating the process of human learning, specifically in the domain of speech. It was one of the first systems to show how a network of simple units could learn complex patterns and behaviors, such as the pronunciation of English text, through machine learning techniques.

Overview

NETtalk's primary function was to convert written text into phonetic or spoken output. The system was trained using a supervised learning algorithm on a dataset comprising English text paired with their phonetic transcriptions. Through the training process, NETtalk learned to generalize from the examples it was given, enabling it to produce the phonetic pronunciation of words it had not encountered during its training phase.

Architecture

The architecture of NETtalk is based on a multi-layer feedforward neural network. It consists of three layers: an input layer, a hidden layer, and an output layer. The input layer receives encoded representations of characters from the text to be pronounced. The hidden layer processes these inputs, and the output layer generates the corresponding phonetic transcription.

- Input Layer: The input to NETtalk consists of a sliding window of seven characters from the text, centered on the character to be pronounced. This window allows the network to consider the context of surrounding characters, which is crucial for determining the pronunciation of English words. - Hidden Layer: The hidden layer contains a number of units (neurons) that enable the network to learn complex patterns in the data. The exact number of units can vary, but the original NETtalk system used 80 hidden units. - Output Layer: The output of the network is a set of phonemes, the basic units of sound in speech. NETtalk was designed to output a phoneme corresponding to the central character in the input window.

Learning Algorithm

NETtalk was trained using the backpropagation algorithm, a method that allows the network to adjust its weights based on the error between its predicted output and the actual output. Through repeated iterations over the training data, NETtalk gradually improved its ability to predict the correct phonemes for given text inputs.

Impact and Legacy

NETtalk made a significant impact on the field of artificial intelligence and neural networks. It demonstrated the feasibility of using neural networks for complex pattern recognition tasks, such as speech. The project helped to revive interest in neural network research during the 1980s, a period that saw increased skepticism towards the potential of AI.

Furthermore, NETtalk laid the groundwork for subsequent research in neural networks and machine learning, influencing the development of more sophisticated models and algorithms. Its success illustrated the importance of context in language processing and contributed to the understanding of how neural networks can be applied to problems in natural language processing (NLP) and speech recognition.

See Also

• Artificial neural network
• Machine learning
• Natural language processing
• Speech recognition
• Backpropagation