Electrical audio signal processing systems and devices – Binaural and stereophonic – Broadcast or multiplex stereo
Patent
1981-05-28
1983-11-15
Hickey, R. J.
Electrical audio signal processing systems and devices
Binaural and stereophonic
Broadcast or multiplex stereo
381 1, H04H 500
Patent
active
044157681
ABSTRACT:
Right and left FM stereo signals are combined to form an L plus R value and subtracted to produce an L minus R value. The L minus R value is passed through a high-pass filter which mutes the high frequency portion of the signal only when the amplitude of the signal is low. This is recombined with the L plus R signal to provide a 2L output. A similar process is followed to produce a 2R output.
The two left and right outputs are combined and then passed through a mono to stereo converter to produce two phase-shifted signals. These are in turn selectively delayed and passed through respective band pass filters to mute signal portions between approximately five hundred to one thousand Hz. The combined signals, prior to being converted back to a stereo signal are directed through a second band pass filter to mute the frequency portions other than the five hundred to one thousand Hz level, and these are recombined with the rest of the signal.
To diminish the harmful effect of reflected radio waves, the left input is directed to several time delay devices, each having a different time delay, and these outputs are directed to a coincidence circuit that compares the several time delay signals with the main signal. When the coincidence circuit detects the similarity of one of the time delay signals with a component in the main input, the coincidence circuit produces a similar time delay signal, which is inverted and fed back to the main output to cancel out the reflected component in the main output.
REFERENCES:
patent: 2227057 (1940-12-01), Blumlein
patent: 3124649 (1964-03-01), Pflager et al.
patent: 3943293 (1976-03-01), Bailey
patent: 4029906 (1977-06-01), Takahashi
patent: 4032717 (1977-06-01), Mallon
patent: 4047224 (1977-09-01), Yamaguti
patent: 4216353 (1980-08-01), Fish, Jr.
patent: 4303800 (1981-12-01), De Freitas
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