Electrical audio signal processing systems and devices – Binaural and stereophonic – Pseudo stereophonic
Patent
1988-03-14
1989-06-20
Isen, Forester W.
Electrical audio signal processing systems and devices
Binaural and stereophonic
Pseudo stereophonic
381 1, H04S 100
Patent
active
048415723
ABSTRACT:
A stereo image enhancement system, in which difference signal components in relatively quieter difference signal frequency bands are boosted to provide an improved stereo image, is provided with a stereo input that is synthetically derived from monaural signal (L+R). Simulated sum (L+R).sub.s and simulated difference (L-R).sub.s signals are provided from a monaural input (L+R) by sending the input through a phase shifter and splitter (12) that provides 0.degree. and 90.degree. outputs with a constant 90.degree. phase separation between the two at all audio frequencies. The leading one of the two output signals from the phase shifter is employed as a simulated sum signal, and the other as a simulated difference signal. The simulated difference signal has different frequency components, each delayed by different amounts relative to corresponding components of like frequency of the simulated sum signal. This provides an effective synthetic difference signal, with both sum and difference signals being suitably filtered to provide an improved pair of synthetically derived stereo sum and difference signals (L+R).sub.s, (L-R).sub.s as inputs to an image enhancement circuit.
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Dickey, "Outputs of Op-Amp Networks have fixed phase difference", pp. 129, 130 of Designers Casebook.
Hughes Aircraft Company
Isen Forester W.
Karambelas Anthony W.
Szabo Joseph E.
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