Apparatus for reproducing quadraphonic sound

Claim 2

Signal decoding apparatus for decoding first and second composite signals LT and RT respectively containing dominant signals Lf and Rf in phase with each other and each including two subdominant signal components Lb And Rb in quadrature relationship, with said Lb and Rb components in one of said composite signals leading and lagging, respectively, the Lb and Rb components in the other composite signal, and with one of the Lf and Rf signals in phase with its respective associated Rb and Lb component and the other in phase opposition with the said associated component, said apparatus comprising, in combination: decoder means including first and second input terminals to which said first and second composite signals are respectively applied and at least two all-pass phase-shifting networks connected to respective ones of said input terminals, said phase-shifting networks being operative to shift the phase of one of said composite signals relative to the other by substantially 90* thereby to position the Lb and Rb components in one of the relatively phase-shifted first and second composite signals either in phase coincidence or in phase opposition with corresponding components in the other relatively phase-shifted composite signal, signal-combining networks for combining said relatively phaseshifted first and second composite signals to derive third and fourth composite signals respectively containing dominant signal components Lb and Rb which are in phase with each other and each including two subdominant signal components Lf and Rf, and means for applying composite signals respectively containing said signal components Lf, Rf, Lb and Rb as predominant components to first, second, third and fourth signal amplitudemodifying means, respectively, for reproduction over four corresponding sound-reproducing devices; control circuit means operative in response to at least said relatively phase-shifted first and second composite signals to detect whether said relatively phase-shifted first and second composite signals contain substantially equal amplitude signal components in phase coincidence or in phase opposition and to produce a first control signal operative when applied to said first and second signal amplitude-modifying means to enhance the gain thereof when said first and second composite signals do not contain said signal components Lb and Rb either in phase or in phase opposition and to produce a second control signal operative when applied to said third and fourth signal amplitude-modifying means to enhance the gain thereof when said third and fourth composite signals do not contain substantially equal signal components either in phase or in phase opposition, a logic circuit connected to said first and second input terminals operative to compare the sum and the difference of said first and second composite signals and to produce a third control signal when the sum exceeds the difference and to produce a fourth control signal when the difference exceeds the sum, and means for combining said first and third control signals and applying the combined control signal to said first and second signal amplitude-modifying means to control the gain thereof, and means for combining said second and fourth control signals and applying the combined control signal to said third and fourth signal amplitude-modifying means to control the gain thereof.

Claim 3

Apparatus in accordance with claim 1, wherein said combining means includes circuit means connected to said control circuit means and to said logic circuit and operative to select the larger of said first and said third control signals, and means for applying the larger of said control signals to said signal amplitude-modifying means.

Claim 4

Apparatus in accordance with claim 2 wherein said combining means is an OR circuit.

Claim 5

Signal-decoding apparatus for decoding first and second composite signals LT and RT respectively containing dominant signals Lf and Rf in pHase with each other and each including two subdominant signal components Lb and Rb in quadrature relationship, with the Lb and Rb components in one of said composite signals leading and lagging, respectively, the Lb and Rb components in the other of said composite signals, and with one of the Lf and Rf signals in phase opposition with its respective associated Rb or Lb component and the other in phase with the said associated component, the apparatus including: phase-shifting means operative to shift the phase of one of said composite signals relative to the other by substantially 90* thereby to position the Lb and Rb components in one of the relatively phase-shifted first and second composite signals either in phase coincidence or in phase opposition with corresponding components in the other; signal-combining networks for combining said relatively phase-shifted first and second composite signals to derive third and fourth composite signals respectively containing dominant signal components Lb and Rb which are in phase with each other and each including two subdominant components Lf and Rf; first, second, third and fourth gain control means connected to receive composite signals respectively containing said signal components Lf, Rf, Lb and Rb as predominant components; a control circuit operative in response to said relatively phase-shifted first and second composite signals to produce a first control signal operative when applied to said first and second gain control means to enhance the gain thereof when said first and second composite signals do not contain substantially equal signal components either in phase or in phase opposition and to produce a second control signal operative when applied to said third and fourth gain control means to enhance the gain thereof when said third and fourth composite signals do not contain substantially equal signal components either in phase or in phase opposition; a logic circuit connected to receive and operative to compare the sum and the difference of said first and second composite signals and to produce a third control signal when the sum exceeds the difference and to produce a fourth control signal when the difference exceeds the sum; and means for combining the control signals from said control circuit with the control signals from said logic circuit for producing fifth and sixth control signals for application to the said gain control means to control the gain thereof.

Claim 6

Signal-decoding apparatus for decoding first and second composite signals LT and RT respectively containing dominant signals Lf and Rf in pHase with each other and each including two subdominant signal components Lb and Rb in quadrature relationship, with the Lb and Rb components in one of said composite signals leading and lagging, respectively, the Lb and Rb components in the other of said composite signals, and with one of the Lf and Rf signals in phase opposition with its respective associated Rb or Lb component and the other in phase with the said associated component, the apparatus including: phase-shifting means operative to shift the phase of one of said composite signals relative to the other by substantially 90* thereby to position the Lb and Rb components in one of the relatively phase-shifted first and second composite signals either in phase coincidence or in phase opposition with corresponding components in the other; signal-combining networks for combining said relatively phase-shifted first and second composite signals to derive third and fourth composite signals respectively containing dominant signal components Lb and Rb which are in phase with each other and each including two subdominant components Lf and Rf; first, second, third and fourth gain control means connected to receive composite signals respectively containing said signal components Lf, Rf, Lb and Rb as predominant components; a control circuit operative in response to said relatively phase-shifted first and second composite signals to produce a first control signal operative when applied to said first and second gain control means to enhance the gain thereof when said first and second composite signals do not contain substantially equal signal components either in phase or in phase opposition and to produce a second control signal operative when applied to said third and fourth gain control means to enhance the gain thereof when said third and fourth composite signals do not contain substantially equal signal components either in phase or in phase opposition; a logic circuit connected to receive and operative to compare the sum and the difference of said first and second composite signals and to produce a third control signal when the sum exceeds the difference and to produce a fourth control signal when the difference exceeds the sum; and means for combining the control signals from said control circuit with the control signals from said logic circuit for producing fifth and sixth control signals for application to the said gain control means to control the gain thereof.

Claim 7

Apparatus in accordance with claim 4, wherein said control circuit is operative to produce first and second control signals, and said logic circuit is operative to produce third or fourth control signals depending upon whether the sum exceeds the difference of the first and second composite signals, or vice versa, and wherein said combining means comprises means for adding the third and fourth control signals to the first and second control signals, respectively.

Claim 8

Apparatus in accordance with claim 4, wherein said combining means includes a circuit connected to said control circuit and to said logic circuit and operative to select the larger of the control signals produced by the control circuit and the logic circuit, and means for applying the larger of the signals to said gain control means.

Claim 9

Apparatus for reproducing on four sound-reproducing devices four directional audio information signals respectively designated Lf, Rf, Lb and Rb contained in first and second composite signals respectively containing to the extent they are present dominant Lf and Rf component signals, and each including to the extent they are present sub-dominant Lb and Rb component signals, with said Lb and Rb component signals in one of said composite Signals in substantially quadrature relationship with the corresponding component signals in the other of the composite signals, the combination comprising: decoding circuit means including first and second pairs of all-pass phase-shifting networks connected to receive said first and second composite signals, respectively, a first phase-shifting network of each pair being operative to shift the phase of the applied signal by a predetermined reference angle and a second phase-shifting network of each pair being operative to shift the phase of the applied signal by an angle differing from said reference angle by substantially 90*, signal-combining networks for combining the relatively phase-shifted first and second composite signals from the first phase-shifting network of one of said pairs and from the second phase-shifting network of the other of said pairs to derive third and fourth composite signals respectively containing dominant signal components Lb and Rb which are in phase with each other and each including two subdominant signal components Lf and Rf, signal-coupling means connected to receive and operative to couple composite signals respectively containing said signal components Lf, Rf, Lb and Rb as their predominant components to respective ones of first, second, third and fourth sound-reproducing devices, said signal-coupling means including signal amplitude-modifying means for separately adjusting the amplitude of the composite signal applied thereto, a control circuit operative in response to relatively phase-shifted first and second composite signals from the first phase-shifting network of one of said first and second pairs of phase-shifting networks and from the second phase-shifting network of the other pair to produce a first control signal operative when applied to said first and second signal amplitude-modifying means to enhance the gain thereof when said first and second composite signals do not contain substantially equal signal components either in phase or in phase opposition or a second control signal operative when applied to said third and fourth signal amplitude-modifying means to enhance the gain thereof when said third and fourth composite signals do not contain substantially equal signal components either in phase or in phase opposition, a logic circuit connected to receive and operative to compare the sum and the difference of the first and second composite signals and to produce at least one of third and fourth control signals depending upon whether the sum exceeds the difference, or vice versa, and means for combining the first or the second control signals from said control circuit with the third or the fourth control signals, respectively, from said logic circuit for producing fifth and sixth control signals for application to said first and second and to said third and fourth signal amplitude-modifying means, respectively, to control the transmission characteristic thereof.

Claim 10

Apparatus for reproducing on four sound-reproducing devices four directional audio information signals respectively designated Lf, Rf, Lb and Rb contained in first and second composite signals respectively containing to the extent they are present dominant Lf and Rf component signals, and each including to the extent they are present sub-dominant Lb and Rb component signals, with said Lb and Rb component signals in one of said composite Signals in substantially quadrature relationship with the corresponding component signals in the other of the composite signals, the combination comprising: decoding circuit means including first and second pairs of all-pass phase-shifting networks connected to receive said first and second composite signals, respectively, a first phase-shifting network of each pair being operative to shift the phase of the applied signal by a predetermined reference angle and a second phase-shifting network of each pair being operative to shift the phase of the applied signal by an angle differing from said reference angle by substantially 90*, signal-combining networks for combining the relatively phase-shifted first and second composite signals from the first phase-shifting network of one of said pairs and from the second phase-shifting network of the other of said pairs to derive third and fourth composite signals respectively containing dominant signal components Lb and Rb which are in phase with each other and each including two subdominant signal components Lf and Rf, signal-coupling means connected to receive and operative to couple composite signals respectively containing said signal components Lf, Rf, Lb and Rb as their predominant components to respective ones of first, second, third and fourth sound-reproducing devices, said signal-coupling means including signal amplitude-modifying means for separately adjusting the amplitude of the composite signal applied thereto, a control circuit operative in response to relatively phase-shifted first and second composite signals from the first phase-shifting network of one of said first and second pairs of phase-shifting networks and from the second phase-shifting network of the other pair to produce a first control signal operative when applied to said first and second signal amplitude-modifying means to enhance the gain thereof when said first and second composite signals do not contain substantially equal signal components either in phase or in phase opposition or a second control signal operative when applied to said third and fourth signal amplitude-modifying means to enhance the gain thereof when said third and fourth composite signals do not contain substantially equal signal components either in phase or in phase opposition, a logic circuit connected to receive and operative to compare the sum and the difference of the first and second composite signals and to produce at least one of third and fourth control signals depending upon whether the sum exceeds the difference, or vice versa, and means for combining the first or the second control signals from said control circuit with the third or the fourth control signals, respectively, from said logic circuit for producing fifth and sixth control signals for application to said first and second and to said third and fourth signal amplitude-modifying means, respectively, to control the transmission characteristic thereof.

Claim 11

Apparatus in accordance with claim 7, wherein said last-mentioned means comprises means for adding the third and fourth control signals to the first and second control signals, respectively.

Claim 12

Apparatus in accordance with claim 7, wherein said last-mentioned means includes a circuit connected to said control circuit and to said logic circuit and operative to select the larger of the control signals produced by the control circuit and by the logic circuit, and means for applying the larger of the signals to said signal amplitude-modifying means.

Claim 13

Apparatus in accordance with claim 7, wherein said logic circuit includes first and second summing junctions each connected to receive both of said first and second composite signals and operative to produce sum and difference signals, respectively, first and second logarithmic amplifiers connected to receive and operative to amplify said sum and difference signals, respectively, and third and fourth summing junctions each connected to receive both of said amplified sum and difference signals and operative to produce at least one of said third and fourth control signals depending upon whether the sum of the first and second composite signals exceeds the difference of the first and second composite signals, or vice versa.

Claim 14

Apparatus for reproducing four individual audio information signals respectively designated Lf, Rf, Lb and Rb contained in first and second composite signals respectively containing to the extent they are present dominant Lf and Rf component signals and each including to the extent they are present sub-dominant Lb and Rb component signals with a phase-shift angle of substantially 90* between said Lb component signals and between said Rb component signals, the combination comprising: decoding circuit means connected to receive said first and second composite signals and operative in response thereto to derive third and fourth composite signals respectively containing predominant Lb and Rb component signals and each including sub-dominant Lf and Rf component signals, first, second, third and fourth signal amplitude-modifying means respectively connected to receive and operative to couple said first, second, third and fourth composite signals to respective ones of first, second, third and fourth sound-reproducing means, a logic circuit connected to receive and operative to compare the sum and the difference of said first and second composite signals and to produce a first control signal when the sum exceeds the difference and to produce a second control signal when the difference exceeds the sum, and means for applying said first control signal to said first and second signal amplitude-modifying means, and means for applying said second control signal to said third and fourth signal amplitude-modifying means.

Claim 15

Apparatus for reproducing four individual audio information signals respectively designated Lf, Rf, Lb and Rb contained in first and second composite signals respectively containing to the extent they are present dominant Lf and Rf component signals and each including to the extent they are present sub-dominant Lb and Rb component signals with a phase-shift angle of substantially 90* between said Lb component signals and between said Rb component signals, the combination comprising: decoding circuit means connected to receive said first and second composite signals and operative in response thereto to derive third and fourth composite signals respectively containing predominant Lb and Rb component signals and each including sub-dominant Lf and Rf component signals, first, second, third and fourth signal amplitude-modifying means respectively connected to receive and operative to couple said first, second, third and fourth composite signals to respective ones of first, second, third and fourth sound-reproducing means, a logic circuit connected to receive and operative to compare the sum and the difference of said first and second composite signals and to produce a first control signal when the sum exceeds the difference and to produce a second control signal when the difference exceeds the sum, and means for applying said first control signal to said first and second signal amplitude-modifying means, and means for applying said second control signal to said third and fourth signal amplitude-modifying means.

Claim 16

Apparatus in accordance with claim 11, wherein said logic circuit includes first and second summing junctions to each of which both said first and second composite signals are applied and operative to produce sum and difference signals, respectively, first and second logarithmic amplifiers connected to receive and operative to amplify said sum and difference signals, respectively, and means connected to receive said amplified sum and difference signals and operative to produce one or the other of said first and second control signals depending upon whether the amplified sum signal exceeds the amplified difference signal, or vice versa.