Semi-Supervised Sound Source Localization Based on Manifold Regularization

Conventional speaker localization algorithms, based merely on the received microphone signals, are often sensitive to adverse conditions, such as: high reverberation or low signal-to-noise ratio (SNR). In some scenarios, e.g., in meeting rooms or cars, it can be assumed that the source position is confined to a predefined area, and the acoustic parameters of the environment are approximately fixed. Such scenarios give rise to the assumption that the acoustic samples from the region of interest have a distinct geometrical structure. In this paper, we show that the high-dimensional acoustic samples indeed lie on a low-dimensional manifold and can be embedded into a low-dimensional space. Motivated by this result, we propose a semi-supervised source localization algorithm based on two-microphone measurements, which recovers the inverse mapping between the acoustic samples and their corresponding locations. The idea is to use an optimization framework based on manifold regularization, that involves smoothness constraints of possible solutions with respect to the manifold. The proposed algorithm, termed manifold regularization for localization, is adapted while new unlabelled measurements (from unknown source locations) are accumulated during runtime. Experimental results show superior localization performance when compared with a recently presented algorithm based on a manifold learning approach and with the generalized cross-correlation algorithm as a baseline. The algorithm achieves 2° accuracy in typical noisy and reverberant environments (reverberation time between 200 and 800 ms and SNR between 5 and 20 dB).