Stereo width control using interpolation and extrapolation of time-frequency representation

This paper presents a method to control the stereo stage width to provide additional functionality to a stereophonic sound-field recording/reproduction system that uses two microphones and two loudspeakers. The proposed method interpolates or extrapolates the time-frequency representations of the left and right stereo signals according to the desired scaling magnification. A mathematical analysis is introduced that clarifies the scaling ability of the proposed method. Listening tests using a stereo signal consisting of a mixture of two speech signals with different time-lags are performed. The results indicate that the two stereo signals yield almost the same aural impression when the scaling magnification is under two and the following two requirements are satisfied. 1) The time-lags in the stereo signal are scaled strictly before mixing. 2) The time-lags are scaled approximately by the proposed method after mixing. The listening tests also clarified the superiority of the proposed method in terms of the sound quality with respect to conventional methods.