This paper describes a novel sound source separation method for a robot that needs to cope with dynamically changing noises in the real world. The sound source separation method, Geometric Source Separation (GSS), is promising because it has high separation performance and requires low computational cost. One of the most important factors in GSS performance is a step-size parameter to update a separation matrix which is generally used for extracting a target sound source. A fixed value that was obtained empirically is commonly used as the step-size parameter. However, in the real world, the surrounding environment changes dynamically. Thus, conventional GSS with a fixed step-size parameter sometimes results in poor separation results, or divergence of the separation matrix. Another important factor is the weight parameter, which adjusts the balance between geometric errors and separation errors and also affects performance. If this parameter is set to a small value, GSS becomes similar to a Blind Source Separation method, by which the output signal may contain errors based on indefinite source amplitudes and orders. In contrast, if this parameter is set to a large value, GSS becomes similar to a delay-and-sum Beamforming method, which does not have high separation performance. GSS gives good performance when the parameters are tuned to an optimum value, which changes according to the environment. We propose two effective methods that can be used for general BSS's. One is an adaptive step-size parameter control method. By using this method, the step-size and the weight parameters are automatically set to optimum values and are able to adapt to environmental changes. The other is an optima controlled recursive average method for correlation matrix estimation. This method can improve the estimation of a separation matrix, and achieve high separation performance. We evaluated the proposed GSS algorithm with an 8ch microphone array embedded in Honda ASIMO. Experimental results showed that the proposed method improved sound source separation even in dynamically changing environments.
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