| 摘要 |
<p>1522599 Stereophonic sound reproduction DOLBY LABORATORIES Inc 30 Oct 1975 [16 Nov 1974] 49724/74 Heading H4R The gain of a centre channel signal derived from left and right signal channels including delays is enhanced relative to the left and right signals when they show substantial correlation. A speech signal, intended for reproduction at the centre stage of an auditorium has high correlation in the left and right channels and leads to the centre loudspeaker level being relatively increased to harden the central image. The delays ensure the centre channel signal is heard first to enhance this effect. The gain controls and/or gain controlling stage may be restricted to the speech band by filters. In Fig. 5 the larger of the rectified left and right signals is compared 59 with a signal representing phase correlation 55 between L and R to derive a control signal which, if above a threshold 60, is used to adjust the gains of amplifiers 30, 31 Fig. 3. For centre speech signals all channel gains reduce to 1 whilst for uncorrelated signals the left and right channel gains are 0À747 and centre channel gain is 1À340. Sum and difference comparison techniques may be used and the gain change instantaneous or gradual.</p> |
