Independent Component Analysis (ICA) is a recently developed technique that in many cases characterizes the data in a natural way. The main application area of the linear ICA model is blind source separation. Here, unknown source signals are estimated from their unknown linear mixtures using the strong assumption that the sources are mutually independent. In practice, separation can be achieved by using suitable higher-order statistics or nonlinearities. Various neural approaches have recently been proposed for blind source separation and ICA. In this paper, these approaches and the respective learning algorithms are briefly reviewed, and some extensions of the basic ICA model are discussed. 1. Introduction A recent trend in neural network research is to study various forms of unsupervised learning beyond standard Principal Component Analysis (PCA). Such techniques are often called nonlinear PCA methods. They can be developed from various starting points, usually leading to different ...

i Abstract This thesis is concerned with the problem of Blind Source Separation. Specifically we considerthe Independent Component Analysis (ICA) model in which a set of observations are modelled by xt = Ast: (1) where A is an unknown mixing matrix and st is a vector of hidden source components attime t. The ICA problem is to find the sources given only a set of observations. In chapter 1, the blind source separation problem is introduced. In chapter 2 the methodof Ensemble Learning is explained. Chapter 3 applies Ensemble Learning to the ICA model and chapter 4 assesses the use of Ensemble Learning for model selection.Chapters 5-7 apply the Ensemble Learning ICA algorithm to data sets from physics (a medical imaging data set consisting of images of a tooth), biology (data sets from cDNAmicro-arrays) and astrophysics (Planck image separation and galaxy spectra separation).

This paper addresses a method of multichannel signal separation (MSS) with its application to cocktail party speech recognition. First, we present a fundamental principle for multichannel signal separation which uses the spatial independence of located sources as well as the temporal dependence of speech signals. Second, for practical implementation of the signal separation lter, we consider a dynamic recurrent network and develop a simple new learning algorithm. The performance of the proposed method is evaluated in terms of word recognition error rate (WER) in a large speech recognition experiment. The results show that our proposed method dramatically improves the word recognition performance in the case of two simultaneous speech inputs, and that a timing eect is involved in the segregation process. Indexing Terms: Blind signal separation, cocktail party speech recognition, dynamic recurrent networks, multichannel signal separation. submitted to Special Issue, Blind Si...