Quadrasonic sound system for two channel transmission

Claim 2

An encoding method for use in a directional sound system wherein at least first, second, third and fourth directional sound signals are respectively coupled to first and second channels to produce first and second channel signals, and the first and second channel signals are decoded into at least four directional audio output signals which are coupled to at least four loudspeakers disposed around a listener in a listening room, said encoding method comprising the steps of: combining said first sound signal at a larger amplitude level, said second sound signal at a smaller amplitude level, said third sound signal at a larger amplitude level, and said fourth sound signal at a smaller amplitude level in such a preselected phase relationship as said third sound signal and said fourth sound signal have substantially a plus 90* phase difference with respect to said first sound signal and said second sound signal, respectively, producing the first channel signal; and combining said first sound signal at a smaller amplitude level, said second sound signal at a larger amplitude level, said third sound signal at a smaller amplitude level, and said fourth sound signal at a larger amplitude level in such a preselected phase relationship as said third sound signal and said fourth signal have substantially a minus 90* phase difference with respect to said first sound signal and second sound signal, respectively, producing the second channel signal.

Claim 3

A signal transmission system comprising: first means for obtaining multichannel signals by picking up sounds produced in a sound room; second means for connection to said first means for composing the multichannel signals into those of fewer channels by combining them; third meanS for for transmitting said signals of fewer channels; fourth means for connection to said third means for converting the signals of fewer channels to those of multichannels by combining them in preselected amplitude and phase relationships; and fifth means for connection to said fourth means for reproducing sounds from the multichannel signals of said fourth means; said first means comprising microphones MFL, MFR, MRL and MRR arranged on the front left and right sides and rear left and right sides of the sound source room so as to obtain four channel signals FL, FR, RL and RR respectively; said second means comprising an encoder having first, second, third and fourth phase shifters connected to receive said signals FL, FR, RL and RR, said first and fourth phase shifters being connected to receive said signals FL and FR respectively so as to shift the phase of said signals FL and FR by a reference angle, and said second phase shifter being connected to receive said signal RL so as to advance the phase of said signal RL within the range of from 45* to 135* relative to output signals of said first and fourth phase shifters, and said third phase shifter being connected to receive said signal RR so as to delay the phase of said signal RR within the range of from -45* to -135* relative to output signals of said first and fourth phase shifters, a first variable attenuator connected between both input terminals of said second and third phase shifters, a second variable attenuator connected between both output or both input terminals of said first and fourth phase shifters, said variable attenuators forming signals having amplitudes proportional to those of the signals supplied thereto with the proportional coefficient ranging within 0 to 1 including 0, a first adder connected to the output terminals of said first and second phase shifters, and a second adder connected between the output terminals of said third and fourth phase shifters, each of said adders producing one of said fewer channel signals as an output.

Claim 4

A signal transmission system comprising: first means for obtaining multichannel signals by picking up sounds produced in a sound room; second means for connection to said first means for composing the multichannel signals into those of fewer channels by combining them; third meanS for for transmitting said signals of fewer channels; fourth means for connection to said third means for converting the signals of fewer channels to those of multichannels by combining them in preselected amplitude and phase relationships; and fifth means for connection to said fourth means for reproducing sounds from the multichannel signals of said fourth means; said first means comprising microphones MFL, MFR, MRL and MRR arranged on the front left and right sides and rear left and right sides of the sound source room so as to obtain four channel signals FL, FR, RL and RR respectively; said second means comprising an encoder having first, second, third and fourth phase shifters connected to receive said signals FL, FR, RL and RR, said first and fourth phase shifters being connected to receive said signals FL and FR respectively so as to shift the phase of said signals FL and FR by a reference angle, and said second phase shifter being connected to receive said signal RL so as to advance the phase of said signal RL within the range of from 45* to 135* relative to output signals of said first and fourth phase shifters, and said third phase shifter being connected to receive said signal RR so as to delay the phase of said signal RR within the range of from -45* to -135* relative to output signals of said first and fourth phase shifters, a first variable attenuator connected between both input terminals of said second and third phase shifters, a second variable attenuator connected between both output or both input terminals of said first and fourth phase shifters, said variable attenuators forming signals having amplitudes proportional to those of the signals supplied thereto with the proportional coefficient ranging within 0 to 1 including 0, a first adder connected to the output terminals of said first and second phase shifters, and a second adder connected between the output terminals of said third and fourth phase shifters, each of said adders producing one of said fewer channel signals as an output.

Claim 5

A system according to claim 2 wherein the output signals of said first and fourth phase shifters are of the same phase, the output signal from said second phase shifter has its phase advanced 90* from those of said first and fourth phase shifters, and the output signal from said third phase shifter has its phase delayed 90* from those of said first and fourth phase shifters.

Claim 6

A system according to claim 2 wherein said first means further comprises a microphone MCL disposed at the middle part of the microphones MFL and MRL placed at the front left side and rear left side of said sound source room respectively and another microphone MCR positioned at the middle of the microphones MFR and MRR located at the rear left side and rear right side of said sound source room respectively, thereby forming 6-channel signals FL, FR, RL, RR. CL and CR; and said encoder further includes a fifth phase shifter connected to receive said signal CL to shift the phase of an input by said reference angle, a sixth phase shifter connected to receive said signal CR to shift the phase of an input by said reference angle, a third adder connected to the output terminals of said fifth phase shifter and first adder to combine output signals therefrom, and a fourth adder connected to the output terminals of said sixth phase shifter and second adder to combine output signals therefrom, each of said third and fourth adders producing one of said fewer channel signals as an output.

Claim 7

A system according to claim 4 wherein output signals from said fifth and sixth shifters have the same phase as those from first and fourth phase shifters.

Claim 8

A system according to claim 4 wherein there is connected a first switch in series with said first variable attenuator disposed between terminals of said second and third phase shifters And a second switch in series with said second variable attenuator disposed between terminals of said first and fourth phase shifters.

Claim 9

A system according to claim 10 wherein said fourth means comprises: first and second phase splitters supplied with said fewer channel signals from said third means; combining means connected to said phase splitters for combining output signals of said splitters; and first, second, third and fourth phase shifters connected to said combining means, the output signals from said first and fourth phase shifters being of the same phase, the output signal of said second phase shifter having its phase delayed 90* in phase with respect to those of said first and fourth phase shifters, and the output signal of said third phase shifter having its phase advanced 90* in phase with respect to those of said first and fourth phase shifters.

Claim 10

An encoder system for use in a directional sound system wherein at least four directional audio input signals are respectively coupled to first and second channels to produce first and second channel signals, and the first and second channel signals are decoded into at least four directional audio output signals which are coupled to at least four loudspeakers disposed around a listener in a listening room, said encoder system comprising: first means for coupling a first directional audio input signal at a larger amplitude level to the first channel with a first phase shift amount; second means for coupling a second directional audio input signal at a larger amplitude level to the second channel substantially with said first phase shift amount; third means for coupling a third directional audio input signal at a larger amplitude level to the first channel with a second phase shift amount; fourth means for coupling a fourth directional audio input signal at a larger amplitude level to the second channel with a third phase shift amount; fifth means for coupling said first and second directional audio input signals at smaller amplitude levles to the second and first channels substantially with said first phase shift amount, respectively; and sixth means for coupling said third and fourth directional audio input signals at smaller amplitude levels to the second and first channels with said third and second phase shift amounts, respectively; said second and third phase shift amounts having differences of +45* to +135* and -45* to -135*, respectively, with respect to said first phase shift amount.

Claim 11

An encoder system for use in a directional sound system wherein at least four directional audio input signals are respectively coupled to first and second channels to produce first and second channel signals, and the first and second channel signals are decoded into at least four directional audio output signals which are coupled to at least four loudspeakers disposed around a listener in a listening room, said encoder system comprising: first means for coupling a first directional audio input signal at a larger amplitude level to the first channel with a first phase shift amount; second means for coupling a second directional audio input signal at a larger amplitude level to the second channel substantially with said first phase shift amount; third means for coupling a third directional audio input signal at a larger amplitude level to the first channel with a second phase shift amount; fourth means for coupling a fourth directional audio input signal at a larger amplitude level to the second channel with a third phase shift amount; fifth means for coupling said first and second directional audio input signals at smaller amplitude levles to the second and first channels substantially with said first phase shift amount, respectively; and sixth means for coupling said third and fourth directional audio input signals at smaller amplitude levels to the second and first channels with said third and second phase shift amounts, respectively; said second and third phase shift amounts having differences of +45* to +135* and -45* to -135*, respectively, with respect to said first phase shift amount.

Claim 12

An encoder system according to claim 8 wherein said first to fourth means include first, second, third and fourth phase shifters, respectively, the phase shifting characteristics of said first and second phase shifters being substantially equal to each other, and the phase shift characteristics of said third and fourth phase shifters having differences of +45* to +135* and -45* to -135*, respecitvely, with respect to the phase shift characteristics of said first and second phase shifters.

Claim 13

An encoder system according to claim 8 wherein each of said fifth and sixth means includes resistor means.

Claim 14

An encoder system according to claim 10 wherein each of said resistor means of said fifth and sixth means includes a variable resistor.

Claim 15

An encoder system according to claim 10 wherein each of said fifth and sixth means includes a manually operable switch connected in series with said resistor means.

Claim 16

An encoder system according to claim 9 wherein said third and fourth phase shifters have phase shift characteristics of about +90* and -90* differences with respect to those of said first and second phase shifters respectively.

Claim 17

An encoder system according to claim 8 including: seventh means for coupling to said first channel a fifth directional audio input signal desired to be located midway of a pair of loudspeakers disposed around the listener to which said first and third directional audio input signals are desired to be coupled respectively; and eighth means for coupling to said second channel a sixth directional audio input signal desired to be located midway of another pair of loudspeakers to which said second and fourth directional audio input signals are desired to be coupled respectively.

Claim 18

An encoder system according to claim 14 wherein said seventh means includes means for introducing a predetermined phase shift amount to said fifth directional audio input signal, and said eighth means includes means for introducing a predetermined phase shift amount to said sixth directional audio input signal.

Claim 19

An encoder system according to claim 8 wherein said first directional audio input signal is one which is desired to be coupled mainly to a first loudspeaker disposed at front-left side of the listening room, said second directional audio input signal to a loudspeaker disposed at front-right side, said third directional audio input signal to a loudspeaker at rear-left side, and said fourth directional audio input signal to a loudspeaker disposed at rear-right side.

Claim 20

An encoder system for use in a directional sound system wherein at least four directional audio input signals are respectively coupled to first and second channels to produce first and second channel signals, and the first and second signals are decoded into at least four directional audio output signals which are coupled to at least four loudspeakers disposed around a listener in a listening room, said encoder system comprising: first means for coupling a first directional audio input signal at a larger amplitude level to the first channel with a first phase shift amount; second means for coupling a second directional audio input signal at a larger amplitude level to the second channel substantially with said first phase shift amount; third means for coupling a third directional audio input signal at a larger amplitude level to the first channel with a second phase shift amount; fourth means for coupling a fourth directional audio input signal at a larger amplitude level to the second channel with a third phase shift amount; fifth means for selectively coupling said first and second directional audio input signals at smaller amplitude levels to the second and first channels substantially with said first phase shift amount, respectively; sixth means for selectively coupling said third and fourth directional audio input signals at smaller amplitude levels to the second and first channels with said third and second phase shift amounts, respectively; seventh means for coupling to said first channel a fifth directional audio input signal desired to be located midway between a pair of ludspeakers disposed around the listener to which said first and third directional audio input signals are desired to be coupled respectively; and eighth means for coupling to said second channel a sixth directional audio input signal desired to be located midway between another pair of loudspeakers to which said second and fourth directional audio input signals are desired to be coupled respectively; said second and third phase shift amounts having differences of + 45* to + 135* and - 45* to - 135*, respectively, with respect to said first phase shift amount.

Claim 21

An encoder system for use in a directional sound system wherein at least four directional audio input signals are respectively coupled to first and second channels to produce first and second channel signals, and the first and second signals are decoded into at least four directional audio output signals which are coupled to at least four loudspeakers disposed around a listener in a listening room, said encoder system comprising: first means for coupling a first directional audio input signal at a larger amplitude level to the first channel with a first phase shift amount; second means for coupling a second directional audio input signal at a larger amplitude level to the second channel substantially with said first phase shift amount; third means for coupling a third directional audio input signal at a larger amplitude level to the first channel with a second phase shift amount; fourth means for coupling a fourth directional audio input signal at a larger amplitude level to the second channel with a third phase shift amount; fifth means for selectively coupling said first and second directional audio input signals at smaller amplitude levels to the second and first channels substantially with said first phase shift amount, respectively; sixth means for selectively coupling said third and fourth directional audio input signals at smaller amplitude levels to the second and first channels with said third and second phase shift amounts, respectively; seventh means for coupling to said first channel a fifth directional audio input signal desired to be located midway between a pair of ludspeakers disposed around the listener to which said first and third directional audio input signals are desired to be coupled respectively; and eighth means for coupling to said second channel a sixth directional audio input signal desired to be located midway between another pair of loudspeakers to which said second and fourth directional audio input signals are desired to be coupled respectively; said second and third phase shift amounts having differences of + 45* to + 135* and - 45* to - 135*, respectively, with respect to said first phase shift amount.

Claim 22

An encoder system according to claim 17 wherein each of said fifth and sixth means includes a series connection of a manually operable switch and a resistor means.

Claim 23

An encoder system according to claim 18 wherein said resistor means includes a variable resistor.

Claim 24

An encoder system according to claim 17 wherein said first to fourth means include first, second, third and fourth phase shifters, respectively, the phase shift characteristics of said third and fourth phase shifters having differences of + 45* to + 135* and - 45* to - 135*, respectively, with respect to the phase shift characteristics of said first and second phase shifters.

Claim 25

An encoder system according to claim 20 wherein said first and second phase shifters have phase shift characteristics substantially equal to each other, and said third and fourth phase shifters have phase shift characteristics of about + 90* and - 90* differences with respect to those of said first and second phase shifters respectively.

Claim 26

An encoder system according to claim 17 wherein said seventh means includes means for introducing into said fifth directional audio input signal a phase shift amount which substantially equals said first phase shift amount, and said eighth means includes means for introducing into said sixth directional audio input signal a phase shift amount which substantially equals said first phase shift amount.

Claim 27

An encoder system according to claim 17 wherein said first directional audio input signal is one which is desired to be coupled mainly to a first loudspeaker disposed at front-left side of the listening room, said second directional audio input signal to a loudspeaker disposed at front-right side, said third directional audio input signal to a loudspeaker at rear-left side, and said fourth directional audio input signal to a loudspeaker disposed at rear-right side.

Claim 28

For use with a directional sound system wherein, at an encoder side at least four directional audio input signals are utilized to produce first and second channel signals, and a first directional audio input signal at a larger amplitude level is coupled to a first channel with a first phase shift amount, a second directional audio input signal at a larger amplitude level is coupled to a second channel substantially with said first phase shift amount, a third input signal at a larger amplitude level is coupled to said first channel with a second phase shift amount, a fourth input signal at a larger amplitude level is coupled to said second channel with a third phase shift amount, said first and second input signals at smaller amplitude levels are coupled to said second and first channels substantially with said first phase shift amount respectively, and said third and fourth input signals at smaller amplitude levels are coupled to said second and first channels with said third and second phase shift amounts respectively, and, at a decoder side, said first and second channel signals are utilized to produce at least four directional audio output signals for coupling to at least four loudspeakers disposed around a listener in a listening room first, second, third and fourth audio output signals each including predominately corresponding one of said first, second, third and fourth audio input signals respectively, and being coupled to the respective loudspeakers through first, second, third and fourth output channels respectively, said decoder comprising: first means for coupling said first channel signal at a larger amplitude level and said second channel signal at a smaller amplitude level to said first output channel with a fourth phase shift amount, which substantially corresponds to said first phase shift amount introduced into said first and second directional audio input signals respectively; second means for coupling said second channel signal at a larger amplitude level and said first channel signal at a smaller amplitude level to said second output channel with said fourth phase shift amount; third means for coupling said first channel signal at a larger amplitude level and said second channel signal at a smaller amplitude level to said third output channel with a fifth phase shift amount substantially corresponding to said third phase shift amount introduced into said fourth audio input signal and a sixth phase shift amount substantially corresponding to said second phase shift amount introduced into said third audio input signal respectively; and fourth means for coupling said second channel signal at a larger amplitude level and said first channel signal at a smaller amplitude level to said fourth output channel with said sixth and fifth phase shifts amounts respectively.

Claim 29

For use with a directional sound system wherein, at an encoder side at least four directional audio input signals are utilized to produce first and second channel signals, and a first directional audio input signal at a larger amplitude level is coupled to a first channel with a first phase shift amount, a second directional audio input signal at a larger amplitude level is coupled to a second channel substantially with said first phase shift amount, a third input signal at a larger amplitude level is coupled to said first channel with a second phase shift amount, a fourth input signal at a larger amplitude level is coupled to said second channel with a third phase shift amount, said first and second input signals at smaller amplitude levels are coupled to said second and first channels substantially with said first phase shift amount respectively, and said third and fourth input signals at smaller amplitude levels are coupled to said second and first channels with said third and second phase shift amounts respectively, and, at a decoder side, said first and second channel signals are utilized to produce at least four directional audio output signals for coupling to at least four loudspeakers disposed around a listener in a listening room first, second, third and fourth audio output signals each including predominately corresponding one of said first, second, third and fourth audio input signals respectively, and being coupled to the respective loudspeakers through first, second, third and fourth output channels respectively, said decoder comprising: first means for coupling said first channel signal at a larger amplitude level and said second channel signal at a smaller amplitude level to said first output channel with a fourth phase shift amount, which substantially corresponds to said first phase shift amount introduced into said first and second directional audio input signals respectively; second means for coupling said second channel signal at a larger amplitude level and said first channel signal at a smaller amplitude level to said second output channel with said fourth phase shift amount; third means for coupling said first channel signal at a larger amplitude level and said second channel signal at a smaller amplitude level to said third output channel with a fifth phase shift amount substantially corresponding to said third phase shift amount introduced into said fourth audio input signal and a sixth phase shift amount substantially corresponding to said second phase shift amount introduced into said third audio input signal respectively; and fourth means for coupling said second channel signal at a larger amplitude level and said first channel signal at a smaller amplitude level to said fourth output channel with said sixth and fifth phase shifts amounts respectively.

Claim 30

A decoder system according to claim 24 wherein said seventh and sixth phase shift amounts have difference of - 45* to - 135*, and + 45* to + 135*, respectively, with respect to said fourth phase shift amount.

Claim 31

A decoder system according to claim 25 wherein said fifth and sixth phase shift amounts have differences of substantially 90* and + 90* with respect to said fourth phase shift amount respectively.

Claim 32

For use with a directional sound system wherein, at an encoder side at least four directional audio input signals are utilized to produce first and second channel signals, and a first directional audio input signal is coupled to a first channel with a first phase shift amount, a second directional audio input signal is coupled to a second channel substantially with said first phase shift amount, a third input signal is coupled to said first channel with a second phase shift amount, a fourth input signal signal is coupled to said second channel with a third phase shift amount, predetermined amplitude levels of said first and second input signals are coupled to said second and first channels substantially with said first phase shift amount respectively, and predetermined amplitude levels of said third and fourth input signals are coupled to said second and first channels with said third and second phase shift amounts respectively, and, at a decoder side, said first and second channel signals are utilized to produce at least four directional audio output signals for coupling to at least four loudspeakers disposed around a listener in a listening room first, second, third and fourth audio output signals substantially corresponding to said first, second, third and fourth audio input signals respectively, and being coupled to the respective loudspeakers through first, second, third and fourth output channels respectively, said decoder comprising: first means including coupling means for coupling said first channel signal with a predetermined amplitude level of said second channel signal, and a first phase shifter connected to the output of said coupling means; second means including coupling means for coupling said second channel signal with a predetermined amplitude level of said first channel signal, and a second phase shifter connected to the output of said coupling means; third means including coupling means for coupling said first channel signal with substantially a 180* out-of-phase predetermined amplitude level of said second channel signal, and a third phase shifter connected to the output of said coupling means and having a phase shift characteristic of -45* to - 135* with respect to those of said first and second phase shifters; and fourth means including coupling means for coupling said second channel signal with substantially a 180* out-of-phase predetermined amplitude level of said first channel signal, and a fourth phase shifter connected to the output of said coupling means and having a phase shift characteristic of + 45* to + 135* with respect to those of said first and second phase shifters.

Claim 33

For use with a directional sound system wherein, at an encoder side at least four directional audio input signals are utilized to produce first and second channel signals, and a first directional audio input signal is coupled to a first channel with a first phase shift amount, a second directional audio input signal is coupled to a second channel substantially with said first phase shift amount, a third input signal is coupled to said first channel with a second phase shift amount, a fourth input signal signal is coupled to said second channel with a third phase shift amount, predetermined amplitude levels of said first and second input signals are coupled to said second and first channels substantially with said first phase shift amount respectively, and predetermined amplitude levels of said third and fourth input signals are coupled to said second and first channels with said third and second phase shift amounts respectively, and, at a decoder side, said first and second channel signals are utilized to produce at least four directional audio output signals for coupling to at least four loudspeakers disposed around a listener in a listening room first, second, third and fourth audio output signals substantially corresponding to said first, second, third and fourth audio input signals respectively, and being coupled to the respective loudspeakers through first, second, third and fourth output channels respectively, said decoder comprising: first means including coupling means for coupling said first channel signal with a predetermined amplitude level of said second channel signal, and a first phase shifter connected to the output of said coupling means; second means including coupling means for coupling said second channel signal with a predetermined amplitude level of said first channel signal, and a second phase shifter connected to the output of said coupling means; third means including coupling means for coupling said first channel signal with substantially a 180* out-of-phase predetermined amplitude level of said second channel signal, and a third phase shifter connected to the output of said coupling means and having a phase shift characteristic of -45* to - 135* with respect to those of said first and second phase shifters; and fourth means including coupling means for coupling said second channel signal with substantially a 180* out-of-phase predetermined amplitude level of said first channel signal, and a fourth phase shifter connected to the output of said coupling means and having a phase shift characteristic of + 45* to + 135* with respect to those of said first and second phase shifters.

Claim 34

An encoder system according to claim 27 wherein said third and fourth phase shifters have phase shift characteristics of substantially plus 90* and minus 90* differences with respect to those of said first and second phase shifters respectively.

Claim 35

A decoder system according to claim 27 further including means for varying a relative amplitude ratio between said first and second channel signals which are coupled to each of said first to fourth output channels.

Claim 36

A decoder system according to claim 27 wherein saId first to fourth loudspeakers are respectively disposed in the listening room at front-left side, front-right side, rear-left side and rear-right side of the listener.