| 摘要 |
<p>In a transmitting and reproducing system for a plurality of audio information signals consisting of an encoding stage for encoding first, second, third and fourth audio information signals into two channel signals each of which has a based band channel and modulated carrier channel, wherein said encoding stage includes means for selecting at least three of said first, second, third and fourth audio information signals and for combining them in presented amplitude and phase relationships so as to form said base band channel, means for selecting at least one of said first, second, third and fourth audio information signals, and means for modulating a carrier signal with a selected signal derived from said selecting means and for converting a modulated signal into a vestigial side band so as to form said modulated carrier channel, and a reproducing stage for reproducing four output signals corresponding to said first, second, third and fourth audio information signals, respectively, wherein said reproducing stage includes means for separating said modulated carrier channel from said base band channel, means for detecting said selected signal from said modulated carrier channel, and matrixing means for combining said signals contained in said base band channels with said signal contained in a demodulated signal to obtain said four output signals, in which said system further includes a first noise reduction circuit connected to an input stage of said modulating means in said encoding stage so as to compress the signal in a predetermined frequency range, and a second noise reduction circuit connected to an output stage of said demodulating means in said reproducing stage so as to expand the detected signal in said predetermined frequency range, said predetermined frequency range corresponding to a signal side band range in said vestigial side band.</p> |
