14 August 2015
Time: 2:00 - 3:00pm
Venue: ITL Top Floor Meeting Room
Gaussian processes for audio modelling
Richard E. Turner
University of Cambridge, Department of Engineering
In this talk I will present a theoretical framework that links a set of widely used methods from signal processing to statistical inference procedures. This result will then be used as a conceptual springboard to improve upon the classical methods.
I will begin by giving a brief tutorial on Gaussian processes, which are probability distributions over infinite dimensional functions. I will then describe a simple family of probabilistic models for audio that utilise Gaussian processes in which optimal inference corresponds to the short-time Fourier transform (STFT), spectrogram, filter bank, and wavelet representations of signals. The framework allows us to use modern techniques from statistical inference to improve upon these classical signal processing methods. I will show two examples where such an approach has borne fruit. In the first example we use an inferential extension of the Hilbert method to produce high-quality approaches to joint amplitude and frequency modulation of signals. The new approach is uncertainty-aware and therefore noise robust which results in fewer artifacts. In the second example we extend the STFT into an adaptive time-frequency analysis using a hierarchical probabilistic model. The parameters of the new representation, including the channel centre-frequencies and bandwidths, can be learned directly from the signal. The adaptive representation can be used to remove noise from signals and to impute missing data. Surprisingly, the method is an excellent model for naturally occurring audio textures such as howling wind, falling rain, and running water.
Richard Turner received the M.Sci. degree in Physics from the University of Cambridge, UK and the Ph.D. degree in Computational Neuroscience and Machine Learning from the Gatsby Computational Neuroscience Unit, UCL, UK. Following his PhD, he held an EPSRC Postdoctoral research fellowship which he spent at both the University of Cambridge and the Laboratory for Computational Vision, NYU, USA. He now holds a Lectureship in the Computational and Biological Learning Lab, Department of Engineering, University of Cambridge, UK. His research interests include machine learning for signal processing and probabilistic models of perception.