Patent
1980-03-12
1981-12-29
Robinson, Thomas A.
H04R 500
Patent
active
043084230
ABSTRACT:
A stereo enhancement system utilizes a difference signal derived from the left and right stereo channels in which the difference signal is delayed, amplified, and then added into the appropriate channels to cancel left/right speaker mixing at the listener's ears, thereby to improve stereo separation without center region distortion. Depending on the amplification level of the difference signal, an increase in the perimeter sound over that produced at the central region gives a "wrap around" effect with only two speakers by increasing the volume of only the left/right directional sound components relative to centrally located sounds which have no left/right directionality. In order to compensate for the angle between the listener and the speakers, a continuously variable delay is provided in the 100 microsecond -1 millisecond range by the utilization of a serial-analog delay bucket brigade device. Ultrashort delays are created, in one embodiment, by utilizing equal delays in the left and right stereo channels. The difference signal is then delayed by an amount equal to either of the two initial delays plus the amount of desired delay. When serial analog delay devices are utilized, the clock rate of the delay line used for the difference signal is made slightly lower than the clock rate of the delay lines utilized in initially delaying the left/right signals, thereby to provide for ultrashort delayed difference signals. Off-center listener positions are accommodated by a further continuously variable delay line in one or the other of the left and right channels.
REFERENCES:
patent: 3249696 (1966-05-01), Van Sickle
patent: 3697692 (1972-10-01), Hafler
patent: 3849600 (1974-11-01), Ohshima
patent: 3892624 (1975-07-01), Shimada
patent: 4087629 (1978-05-01), Atoji et al.
patent: 4239937 (1980-12-01), Kampmann
"On the Advanced Stereophonic Reproducing System, `Ambience Stereo`"; Sakamoto et al., Audio Engrg. Soc. Preprint 1361, May 2, 1978.
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