Robustness of a chaotic modal neural network applied to audio-visual speech recognition

We stabilized a chaotic Modal Neural Network (MNN) for the purpose of robust speech recognition. A Modal Neural Network is an Artificial Neural Network system which includes two levels of information processing. The first level is trained to store and retrieve some acoustic and visual patterns. The different states of this network, which represent the sound classes in a task of speech recognition, are called modes and are supposed to chaotically evolve when speech recognition is performed in adverse environments. The control of the chaotic behavior of the different modes constitutes the second level. An external signal, taken from a visual input such as the lip-opening parameters of the speaker is applied to stabilize an acoustic modal network of which the modes are moved from an initial position to a target position. The addressed task is the audio-visual recognition of the 10 French vowels, perturbed by some noises. The Perceptual Linear Predictive analysis applied to the speech signal of the 10 vowels outputs some vectors formed by 5 spectral parameters. They are in turn fed into a Modal Neural Network implemented as a feedforward network. When the noise level increases, the classes stored by the acoustic MNN exhibit a chaotic behavior which is stabilized by the signal given by the visual path. We show that in an uncooperative environment, a chaotic modal neural network stabilizes well.