US3725586A - Multisound reproducing apparatus for deriving four sound signals from two sound sources - Google Patents

Multisound reproducing apparatus for deriving four sound signals from two sound sources Download PDF

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Publication number
US3725586A
US3725586A US00242945A US3725586DA US3725586A US 3725586 A US3725586 A US 3725586A US 00242945 A US00242945 A US 00242945A US 3725586D A US3725586D A US 3725586DA US 3725586 A US3725586 A US 3725586A
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phase
signal
input
signals
sound
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K Iida
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Sony Corp
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Sony Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S5/00—Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation 
    • H04S5/02—Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation  of the pseudo four-channel type, e.g. in which rear channel signals are derived from two-channel stereo signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
    • H04S3/02—Systems employing more than two channels, e.g. quadraphonic of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other

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  • ABSTRACT Left and right sound signals applied to two separate input circuits are each shifted in phase by a predetermined amount by phase shifters and are then supplied to separate output circuits.
  • the left sound signal is also fed through a low pass filter to be combined with the phase shifted right sound signal and this combined signal is supplied to a separate output circuit.
  • the right sound signal is fed through a low pass filter to be combined with the phase shifted left sound signal and this combined signal is also supplied to a separate output circuit.
  • the resultant four outputs give the listener the illusion of naturalness.
  • a multichannel sound system so called a four channel stereo system, providing third and fourth playback channels to an otherwise two-channel system by feeding third and fourth loudspeakers with signals.
  • a stereophonic sound information signal into left and right sound signals defined as L and R, respectively, by a channel separator.
  • the L signal is supplied to a loudspeaker placed on the left-hand side of a listener and in front of him while the R signal is supplied to a loudspeaker positioned on the right-hand side of the listener and in front of him as in a conventional manner.
  • the proposed system further inverts the phase of the L signal to make it a signal L and supplies it to a loudspeaker positioned on the left-hand side of the listener at his back.
  • the R signal is inverted in phase to be R and is supplied to a loudspeaker positioned on the right-hand side of the listener at his back.
  • the signal R is supplied to the left rear loudspeaker while the signal L is supplied to the right rear loudspeaker.
  • a matrix circuit is employed for applying signals L-R and R-L to the loudspeakers at the left-hand and right-hand rear sides of the listener, respectively.
  • a multisound reproducing system comprising a first and a second input circuits for receiving a first and a second signal, respectively, means connected to the first and the second input circuits for separately shifting the phase of the first and the second sound signals by a predetermined amount, means responsive to the phase shifted first and second sound signals for separately reproducing them, means for filtering the first sound signal and for combining it with the phase shifted second sound signal to produce a third sound signal, means for filtering the second sound signal and for combining it with the phase shifted first sound signal to produce a fourth sound signal, and means responsive to the third and the fourth sound signals for separately reproducing them.
  • the phase shifting means is designed to shift their phases by one hundred and eighty degrees with respect to their phases after being filtered by each of the combining means.
  • the system is provided with switches and an additional set of phase shifting circuits connected to the first and the second input circuits forproviding of additional phase shift over the primary phase shifting means.
  • the switches allow the listener to selectively and separately reproduce the third and the fourth sound signals or the output signals from the additional phase shifting circuits, thereby making the system compatible with either stereophonic or quadraphonic sound media, respectively.
  • one object of the invention is to provide a multisound reproducing system in which four independent signals are produced from stereophonic sound signals supplied by two channels and the four independent signals are supplied to at least four loudspeakers.
  • Another object of the invention is to provide a multisound reproducing system for reproducing a sound signal about the circumference of the listener without discomfort to the listener.
  • a further object of the invention is to provide a multisound reproducing system in which a monaural signal is reproduced as a monaural sound positioned in front of a listener.
  • a still further object of the invention is to provide a multisound reproducing system which allows the sound to be positioned in accordance with the frequency which is most sensitive for the listener.
  • Yet another object of the invention is to provide a multisound reproducing system which is compatible with both stereophonic and four-channel reproducing systems.
  • FIG. 1 is a block diagram showing one embodiment of the invention
  • FIGS. 2A, 2B and 2C are graphs for explaining the operation of the embodiment depicted in FIG. 1;
  • FIG. 3 is a plane view of the loudspeaker arrangement of the embodiment of FIG. 1;
  • FIGS. 4A, 4B, 5A and 5B are plane views of the reproduced sound fields for different input signals to the embodiment of FIG. 1, diagrammatically illustrating the directions of the sounds reproduced by the embodiment of FIG. 1;
  • phase versus frequency characteristics of the phase shifter circuits 61 and 62 are illustrated in FIG. 2A and are designated 1116.
  • the phase shift for an incoming signal varies approximately in direct proportion to the logarithm of its frequency from 0 of phase shift to 360 of phase shift.
  • the phase of an incoming signal is shifted I80".
  • the predetermined frequency f6 which is, for example about 400 Hz
  • the phase of an incoming signal is shifted I80".
  • the signals Lf and Rf are inverted in phase when the signals L and R are at thefrequency f6 and have the same phase as the signals L and R at the fringes of the band range.
  • each filter The phase versus frequency characteristic of each filter is depicted by the curve (118 in FIG. 2A.
  • the output signals La and Ra are phase shifted from 0 to 90 in direct proportion to the logarithm of the frequency of the input signals L and R within a band range centered about a frequency f8.
  • the signal La or Ra is shifted by 45 with respect to the signal L or R.
  • the lower end of the frequency range it has the same phase and at the upper end of the frequency range it is phase shifted by 90 with respect to the signal L or R.
  • the signals Lf and Rf are both shifted in phase by equal amounts by the phase shifters61 and 62, respectively, and their amplitudes are constant over the frequency range of the system. Therefore the signals L, R, Lf and Rf are equal with each other in level and the phase difference between the signals Lf and Rf is equal to the phase difference between the signals L and R. It also follows that the sounds S1 and S2 are reproduced with the same phase and the same level from the loudspeakersl and 2, respectively, as shown in FIG. 4A.
  • the signals Lf and Ra are added together to produce the signal Lb.
  • the phase versus frequency characteristics of the phase shifters 61 and 62 and the filters 83 and 84 are such that at a predetermined frequency f7 (which is, for example between 650 to 700 Hz) there is l difference in phase between signals emerging from either of the filters 83 and 84 and signals emerging from either of the phase shifters 61 and 62.
  • f7 which is, for example between 650 to 700 Hz
  • the signal Lb has no signal components near the frequency f7 as illustrated in FIG. 2C by dotted lines.
  • the signal Ra delivered from the filter 83 has an amplitude characteristic as illustrated by the curve A8 in FIG. 2B and as a result the frequency spectrum of the signal Lb has no signal-components near the frequency f7 as illustrated by the solid line curve in the FIG. 2C and is attenuated in its intermediate and high frequency signal components.
  • the main part of the signal Lb is a signal component lower than the frequency f7. Since the signal L is equal in level and phase to the signal R, it
  • the sound S1 is reproduced from the loudspeaker 1 from the signal Lf but there is no sound signal reproduced from the loudspeaker 2 as illustrated in FIG. 4B.
  • the signal Lb derived from the adder circuit 93 contains only the signal Lf which is then reproduced through the loudspeaker 3 as the sound S3 having the same level as the sound S1.
  • the signal Rb from the adder circuit 94 contains only the signal La obtained from the filter 84.
  • the amplitude characteristic of the signal Rb is shown by the curve A8 in FIG. 2B, so that the signal Rb consists primarily of the low frequency signal component of the signal L and the attenuated intermediate frequency signal component thereof.
  • the phase of the signal Rb is also substantially the same as the phase of the signal Lf.
  • the signal Rb is reproduced from the loudspeaker 4 as the sound S4.
  • the reproduced sound S1 from the loudspeaker I and $3 from the loudspeaker 3 are the same in phase and level and the reproduced sound S4 from the loudspeaker 4 contains only the low frequency signal component and the attenuated intermediate frequency signal component of the signal L.
  • the sound image as perceived by the listener 5 is positioned near the loudspeaker 3.
  • the separation for left and right side sounds is effectively kept because the sound S4 contains no high frequency signal component of the signal L and its intermediate frequency signal component is substantially attenuated.
  • the sound image is positioned near the loudspeaker 4 as perceived by the listener 5.
  • the above examples of sound positioning by the reproducing system of the invention indicate that although the signals L and R are normally reproduced by a two channel stereophonic reproducing system as a sound image S evenly distributed in front of the listener (FIG. 5A) the same signals when reproduced by the embodiment of FIG. 1 provide a sound image S which is expanded to surround the listener from his left rear side, around in front of him, to his right rear side (FIG. 5B).
  • the system of the invention is capable of giving'the illusion of a singer standing directly in front of the listener 5 and with musical instruments being played around the listener.
  • a quadraphonic stereo reproducing system has a first input terminal 101 a second input terminal 102 and a first, second, third and fourth output terminals 103, 104, 105 and 106, respectively.
  • a first and a second phase shifter 107 and 108 are connected to the first input terminal 101 and a third and a fourth phase shifter 109 and 110 are connected to the second input terminal 102.
  • the phase shifter 108 provides a phase difference of 90 with respect to the phase shifter 107 and a phase shifter 109 provides a phase difference of 90 with respect to the phase shifter l 10.
  • Quadraphonic signals supplied to the first and second input terminals 101 and 102 are encoded to comprise signals LT and RT from, for example, four original sound informational signals LF, RF, LB and RB.
  • the composite signal LT consists of three components LF, 0.7LB and 0.7RB.
  • the signals LF and 0.7RB have the same phase whereas the signal 0.7LB is 270 different in phase from the signal LP.
  • the other composite signal RT similarly consists of three components RF, 0.7RB and 0.7LB.
  • the signal 0.7LB is 180 out of phase with the signal RF and the signal 0.7RB is 90 out of phase with the signal RF.
  • loudspeaker (not shown) is connected to the output terminal 106 and is placed at the right front side of the listener to reproduce a sound having the signal RF as its main component.
  • the composite signal LT supplied to the first input terminal 101 is also fed to the second phase shifter 108 where is is shifted in phase 90 with respect to the output of the first phase shifter 107.
  • the phase-shifted composite signal from the phase shifter 108 is supplied through a resistor 120 to an adder circuit 121 where it is combined with the output from the phase shifter 110 supplied to the adder 121 through a resistor 122.
  • the output from the adder circuit 121 is fed through a phase inverter 123 to a fixed contact b of a single pole, double throw switch 124.
  • the moving contact c of the switch 124 is connected to the input of a power amplifier 126" whose output is supplied to the output terminal 104.
  • the signal LB derived at the output terminal 104 has the components LB 0.7LF 0.7RF. It has the same phase as the signal LB but is 90 out of phase with the signal 0.7LF and is out of phase with the signal 0.7RF.
  • the output terminal 104 is connected to a loudspeaker (not shown) placed at the rear right hand side of the listener.
  • the composite signal RT is also supplied to the phase shifter 109 where it is phase shifted by 90 with respect to the output signal from the phase shifter 110.
  • the phase-shifted composite signal from the phase shifter 109 is supplied through a resistor 130 to an adder circuit 131 where it is combined with the output signal from the phase shifter 107 which is supplied to the adder 131 through a resistor 132.
  • the output signal from the adder circuit 131 is supplied directly to a fixed terminal b of a single pole, double throw switch 134.
  • the contact arm c of the switch 134 is connected to the input of a power amplifier 136 which has its output connected to the output terminal 105.
  • the signal RB derived at the output terminal 105 contains the signal components RB 0.7LF 0.7RF. It has the same phase as the signals RB and 0.7LF but is 270 out of phase with the signal 0.7RF.
  • the terminal 105 is connected to a loudspeaker (not shown) which is positioned at the rear right hand side of the
  • the output side of the phase shifter circuit 110 is connected through a resistor 157 to the adder circuit 154.
  • the signals from the low pass filter 151 and the phase shifter circuit 110 are combined by the adder and its output signal is connected to the terminal a of the switch 134.
  • the output side of the phase shifter 107 is connected to the adder circuit 156 through a resistor 158.
  • the signals from the low pass filter 152 and from the phase shifter circuit 107 are combined in the adder circuit 157 and its output is connected to the fixed terminal a of the switch 124.
  • the movable contacts c, which are ganged together, of the two switches 124 and 134 are connected to their respective fixed contacts a then the stereophonic signals L and R supplied to the input terminals 101 and 102 are reproduced as the signals LF and RF at the output terminals 103 and 106 while the respective signals LB and RB are derived at the output terminals 104 and 105 to achieve an effect similar to that described with respect to the embodiment of FIG. 1. It should be noted that in this mode of operation the phase shifters 107 and 110 are employed.
  • phase shifting circuits 108, 109 and 110 are similarly constructed and an explanation of their construction is omitted for the sake of simplicity. Since the phase shifters 108 and 109 are used for phase shifting signals by with respect to the signals passed through the phase shifters 107 and 110, the value of the capacitors and resistors connected between the leads of the transistors of the phase shifters 108 and 109 are selected to be different from those of the capacitors and the resistors connected to the transistors of the phase shifters 107 and 110.
  • the low pass filter 151 comprises a resistor 151R connected between the input terminal 101 and one lead of a capacitor 151C. The other lead of the capaci tor 151C is connected to the circuit ground. The output from the low pass filter 151 is taken from the connection point between the resistor 151R and the capacitor 151C.
  • the low pass filter 152 comprises a resistor 152R connected between the input terminal 102 and one lead of a capacitor 152C. The other lead of a capacitor 152C is connected to the circuit ground. The outputfrom the low pass filter 152 is derived from the connection point between the resistor 152R and the capacitor 152C.
  • a multisound reproducing system comprising a first input circuit for receiving a first sound signal, a second input circuit for receiving a second sound signal, a first phase shifting circuit connected to the first input circuit for shifting the phase of the first sound signal by a predetermined phase angle, a second phase shifting circuit connected to the second input circuit for shifting the phase of the second input signal by a predetermined phase angle, means responsive to the phase shifted first input signal for producing a first output, means responsive to the phase shifted'second input signal for producing a second output, a first filter circuit for filtering the first input signal, a second filter circuit for filtering the second input signal, means for combining the filtered first input signal with the phase shifted second input signal and for producing a third signal, means for combining the filtered second input signal with the phase shifted I first input signal to produce a fourth signal, means responsive to the third signal for producing a third output and means responsive to the fourth signal for producing a fourth output.
  • a multisound reproducing system as recited in claim 1 further comprising a third phase shifting circuit connected to the first input circuit for shifting the phase of the first input signal by a predetermined angle with respect to the output signal from the first phase shifting circuit and a fourth phase shifting circuit connected to the second input circuit for shifting the phase of the second input signal by a predetermined angle with respect to the output signal from the second phase shifting circuit.
  • a multisound reproducing system as recited in claim 6 further comprising switching means connected to the outputs of the third and the fourth phase shifting circuits and to the outputs of the means for producing the third signal and the means for producing the fourth signal for selectively transmitting the third and the fourth signals or the phase shifted signals from the third and the fourth phase shifting circuits to the means for producing the third and the fourth outputs.

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  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
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  • Stereophonic System (AREA)
US00242945A 1971-04-13 1972-04-11 Multisound reproducing apparatus for deriving four sound signals from two sound sources Expired - Lifetime US3725586A (en)

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JP (1) JPS5119761B1 (nl)
CA (1) CA969867A (nl)
DE (1) DE2217740A1 (nl)
FR (1) FR2132897B1 (nl)
GB (1) GB1367191A (nl)
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US3885101A (en) * 1971-12-21 1975-05-20 Sansui Electric Co Signal converting systems for use in stereo reproducing systems
US3892918A (en) * 1972-05-02 1975-07-01 Sansui Electric Co Sound signal converting apparatus for use in a four channel stereophonic reproduction system
US3919480A (en) * 1973-11-29 1975-11-11 Sony Corp Decoding apparatus for reproducing four separate information signals
US3969588A (en) * 1974-11-29 1976-07-13 Video And Audio Artistry Corporation Audio pan generator
DE2616762A1 (de) * 1975-04-17 1976-10-21 Japan Broadcasting Corp Einrichtung zum spreizen eines klangfeldes
US4053711A (en) * 1976-04-26 1977-10-11 Audio Pulse, Inc. Simulation of reverberation in audio signals
US4167651A (en) * 1977-09-20 1979-09-11 O. C. Electronics, Inc. Mixing two signals derived from an audio source without oscillation
US4191852A (en) * 1978-05-16 1980-03-04 Shin-Shirasuna Electric Corporation Stereophonic sense enhancing apparatus
US4219696A (en) * 1977-02-18 1980-08-26 Matsushita Electric Industrial Co., Ltd. Sound image localization control system
US4303800A (en) * 1979-05-24 1981-12-01 Analog And Digital Systems, Inc. Reproducing multichannel sound
US4352953A (en) * 1978-09-11 1982-10-05 Samuel Emmer Multichannel non-discrete audio reproduction system
US4403112A (en) * 1981-05-18 1983-09-06 Modafferi Acoustical Systems, Ltd. Phase shift low frequency loudspeaker system
US4567607A (en) * 1983-05-03 1986-01-28 Stereo Concepts, Inc. Stereo image recovery
US4748669A (en) * 1986-03-27 1988-05-31 Hughes Aircraft Company Stereo enhancement system
US4910778A (en) * 1987-10-16 1990-03-20 Barton Geoffrey J Signal enhancement processor for stereo system
US4910779A (en) * 1987-10-15 1990-03-20 Cooper Duane H Head diffraction compensated stereo system with optimal equalization
US4975954A (en) * 1987-10-15 1990-12-04 Cooper Duane H Head diffraction compensated stereo system with optimal equalization
US5034983A (en) * 1987-10-15 1991-07-23 Cooper Duane H Head diffraction compensated stereo system
US5136651A (en) * 1987-10-15 1992-08-04 Cooper Duane H Head diffraction compensated stereo system
US5386473A (en) * 1994-01-21 1995-01-31 Harrison; Robert W. Passive surround sound circuit
US5524053A (en) * 1993-03-05 1996-06-04 Yamaha Corporation Sound field control device
US5661808A (en) * 1995-04-27 1997-08-26 Srs Labs, Inc. Stereo enhancement system
US5666422A (en) * 1994-05-18 1997-09-09 Harrison; Robert W. Remote speaker for surround-sound applications
US5912976A (en) * 1996-11-07 1999-06-15 Srs Labs, Inc. Multi-channel audio enhancement system for use in recording and playback and methods for providing same
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Cited By (68)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3885101A (en) * 1971-12-21 1975-05-20 Sansui Electric Co Signal converting systems for use in stereo reproducing systems
US3892918A (en) * 1972-05-02 1975-07-01 Sansui Electric Co Sound signal converting apparatus for use in a four channel stereophonic reproduction system
US3919480A (en) * 1973-11-29 1975-11-11 Sony Corp Decoding apparatus for reproducing four separate information signals
US3969588A (en) * 1974-11-29 1976-07-13 Video And Audio Artistry Corporation Audio pan generator
DE2616762A1 (de) * 1975-04-17 1976-10-21 Japan Broadcasting Corp Einrichtung zum spreizen eines klangfeldes
US4053711A (en) * 1976-04-26 1977-10-11 Audio Pulse, Inc. Simulation of reverberation in audio signals
US4219696A (en) * 1977-02-18 1980-08-26 Matsushita Electric Industrial Co., Ltd. Sound image localization control system
US4167651A (en) * 1977-09-20 1979-09-11 O. C. Electronics, Inc. Mixing two signals derived from an audio source without oscillation
US4191852A (en) * 1978-05-16 1980-03-04 Shin-Shirasuna Electric Corporation Stereophonic sense enhancing apparatus
US4352953A (en) * 1978-09-11 1982-10-05 Samuel Emmer Multichannel non-discrete audio reproduction system
US4303800A (en) * 1979-05-24 1981-12-01 Analog And Digital Systems, Inc. Reproducing multichannel sound
US4403112A (en) * 1981-05-18 1983-09-06 Modafferi Acoustical Systems, Ltd. Phase shift low frequency loudspeaker system
US4567607A (en) * 1983-05-03 1986-01-28 Stereo Concepts, Inc. Stereo image recovery
US4748669A (en) * 1986-03-27 1988-05-31 Hughes Aircraft Company Stereo enhancement system
US4910779A (en) * 1987-10-15 1990-03-20 Cooper Duane H Head diffraction compensated stereo system with optimal equalization
US4975954A (en) * 1987-10-15 1990-12-04 Cooper Duane H Head diffraction compensated stereo system with optimal equalization
US5034983A (en) * 1987-10-15 1991-07-23 Cooper Duane H Head diffraction compensated stereo system
US5136651A (en) * 1987-10-15 1992-08-04 Cooper Duane H Head diffraction compensated stereo system
US4910778A (en) * 1987-10-16 1990-03-20 Barton Geoffrey J Signal enhancement processor for stereo system
US5524053A (en) * 1993-03-05 1996-06-04 Yamaha Corporation Sound field control device
US5386473A (en) * 1994-01-21 1995-01-31 Harrison; Robert W. Passive surround sound circuit
US5666422A (en) * 1994-05-18 1997-09-09 Harrison; Robert W. Remote speaker for surround-sound applications
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US5892830A (en) * 1995-04-27 1999-04-06 Srs Labs, Inc. Stereo enhancement system
US5661808A (en) * 1995-04-27 1997-08-26 Srs Labs, Inc. Stereo enhancement system
US6597791B1 (en) 1995-04-27 2003-07-22 Srs Labs, Inc. Audio enhancement system
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US5970152A (en) * 1996-04-30 1999-10-19 Srs Labs, Inc. Audio enhancement system for use in a surround sound environment
US5912976A (en) * 1996-11-07 1999-06-15 Srs Labs, Inc. Multi-channel audio enhancement system for use in recording and playback and methods for providing same
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Also Published As

Publication number Publication date
FR2132897B1 (nl) 1978-03-03
CA969867A (en) 1975-06-24
GB1367191A (en) 1974-09-18
NL172815C (nl) 1983-10-17
JPS5119761B1 (nl) 1976-06-19
IT951373B (it) 1973-06-30
FR2132897A1 (nl) 1972-11-24
NL172815B (nl)
NL7204910A (nl) 1972-10-17
DE2217740A1 (de) 1972-10-26

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