US3892918A - Sound signal converting apparatus for use in a four channel stereophonic reproduction system - Google Patents

Sound signal converting apparatus for use in a four channel stereophonic reproduction system Download PDF

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Publication number
US3892918A
US3892918A US355420A US35542073A US3892918A US 3892918 A US3892918 A US 3892918A US 355420 A US355420 A US 355420A US 35542073 A US35542073 A US 35542073A US 3892918 A US3892918 A US 3892918A
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channel
signal
signals
output
level
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US355420A
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Susumu Takahashi
Ryosuke Ito
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Sansui Electric Co Ltd
Lyondell Chemical Technology LP
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Sansui Electric Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/86—Arrangements characterised by the broadcast information itself
    • H04H20/88—Stereophonic broadcast systems
    • H04H20/89—Stereophonic broadcast systems using three or more audio channels, e.g. triphonic or quadraphonic
    • 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

Definitions

  • two-channel signals L and R being stored in a recording medium are each composed as follows:
  • LF left-front sound signals RF right-front sound signals LB left-back sound signals RB right-back sound signals A a constant or matrix coefficient having a value of about 0.4
  • a sound signal-converting apparatus or decoder reproduces from the signals L and R shown in the above equation (1) the following four-channel signals LF], RF], LBl and RB] mainly consisting of signals corre sponding to said L and R signals.
  • the aforementioned matrix four-channel system has the drawback that separation between signals of the adjacent channels is very poor.
  • a stereophonic record is manufactured for the matrix four-channel sys tem.
  • most customary practice is to localize the sound image of low pitch musical instruments such as a bass or drum at the center between the left-front channel and the right-front channel. at the center between the left-back channel and the right-back channel or both centers.
  • the sound image of high pitch musical instruments such as a trumpet is localized at the center between the left-front channel and leftback channel. at the center between the right-front channel and right-back channel or both centers.
  • the prior art matrix four-channel system fails to enable a listener distinctly to feel the location of the sound image of low or high pitch musical instruments due to poor separation between signals of the adjacent channels.
  • a sound signal-converting apparatus including matrix circuit means for reproducing four-channel signals on four output channels by combining two channel signals is characterized in that the matrix circuit means includes means for varying the mixing ratio of two channel signals according to their frequencies.
  • Separation characteristics of the reproduced four channel signals by the sound signal-converting apparatus of the invention are characterized in that with rcspect to a medium frequency. separation between the front and back channels and separation between the left and right channels are substantially equal to each other; with respect to a low frequency. separation between the left and right channels is lowered, whereas separation between the front and back channels is enhanced; and with respect to a high frequency. separation between the front and back channels is lowered. whereas separation between the left and right channels is enhanced.
  • an impedance circuit including resistors and capacitors are connected in series with a separate resistor between the input terminals receiving two channel signals to deliver desired additively combined signals from the junction of the impedance circuit with the separate resistor.
  • the capacitors whose impedance varies with the frequencies of signals supplied thereto change the mixing ratio of two channel signals according to their frequencies.
  • subtractively combined output signals there are connected a similar impedance circuit and a separate resistor between the input terminals of two channel signals having opposite polarities.
  • signals representing the sum and difference of two channel signals there are also produced signals representing the sum and difference of two channel signals.
  • the difference signals are mixed with the sum signals through a filter or capacitor which increasingly attenuates the level of signals as they fall in frequency.
  • the sum signals are mixed with the difference signals through a filter or capacitor which attenuates the level of signals more prominently as they decrease in frequency.
  • FIG. I is a circuit diagram of a sound signalconverting apparatus according to an embodiment of this invention.
  • FlG. 2 shows a pattern of reproduced low frequency signals obtained by the sound signal-converting apparatus of FIG. 1'
  • FIG. 3 indicates a pattern of reproduced high fre quency signals produced by the apparatus
  • FIG. 4 is a block diagram of a sound signalconverting apparatus according to another embodi ment of the invention.
  • FIG. 5 is a concrete circuit diagram of the apparatus of FIG. 4.
  • FIG. 1 illustrating an embodiment of this invention.
  • a first matrix circuit Ml for reproducing the signal LFl by additive combination of the signals L and R includes serially con nected resistors 13 and 14 having an equal value, for example, kohms; a reactive impedance element 15 such as a capacitor of. for example. 5.000 picofarads connected parallel with the resistor 13 and exhibiting a relatively low impedance at a higher frequency than a predetermined frequency.
  • a second matrix circuit M2 for reproducing the signal RF] by additive combination of the signals L and R includes serially connected resistors 18 and 19; a ca pacitor 20 connected parallel with the resistor 19, a series circuit connected parallel with the resistor 19 and including a capacitor 21 and a resistor 22.
  • the junction of the resistors l8 and I9 is connected to an output terminal 38 for deriving the signal RFl through a phase shifter 37.
  • a third matrix circuit M3 for reproducing the signal LBl by subtractive combination of the signals L and R includes an inverter 23 and resistors 24 and 25 all con nected in series. a capacitor 26 connected parallel with the resistor 25, a series circuit connected parallel with the resistor 25 and including a capacitor 27 and a resistor 28. The junction of the resistors 24 and 25 is connected to an output terminal 40 for deriving the signal LBl through a phase shifter 39.
  • a fourth matrix circuit M4 for reproducing the signal RBI by subtractive combination of the signals L and R includes an inverter 29 and resistors 30 and 31 all connected in series. a capacitor 32 connected parallel with the resistor 31. and a series circuit connected parallel with the resistor 3
  • the capacitors and resistors included in the second, third and fourth matrix circuits M2, M3 and M4 have the same values as those included in the first matrix M1.
  • the phase shifters 3S and 37 have the same phase-shifting characteristics over the entire audible frequency range.
  • the phase shifter 39 has a phase-shifting characteristic which is displaced 90 relative to those of the phase shifters and 37, while the phase shifter 41 has a 4 phase-shifting characteristic which is displaced relative to those of the phase shifters 35 and 37.
  • the capacitor [5 has a large impedance while the capacitor 16 serially connected to the resistor 17 has a small impedance. Therefore. the resultant impedance of the impedance circuit including the resistors l3 and I7 and capacitors l5 and I6 is determined substantially by the parallel resistance (about 4 kohms) of the resistors 13 and 17.
  • both capacitors l5 and 16 exhibit a large impedance. so that the abovementioned resultant impedance is substantially defined by the resistor [3.
  • signals of high frequency For signals of medium frequency.
  • the capacitor l5 has a far smaller impedance than the resistors l3 and 17, so that the resultant impedance is substantially determined by the impedance of the capacitor 15. This resultant impedance is negligibly small as compared with the value of the resistor 14 l0 kohms) serially connected to the impedance circuit.
  • the im pedance circuits of the second, third and fourth ma trices M2, M3 and M4 have the same property as that of the first matrix Ml.
  • four-channel reproduced signals obtained by the decoder of FIG. 1 from the two channel signals L and R having a medium frequency may be expressed as follows:
  • the two channel signals L and R having a low frequency of less than 200 Hz provide four-channel signals substantially as shown below:
  • FIG. 2 A reproduction pattern obtained in the above case is shown by solid lines in FIG. 2. As apparent from this figure. separation between the left and right channels is decreased. whereas separation between the front and back channels is increased. In the case of low frequency signals, there takes place front-back stereophonic reproduction wherein the stereophonic reproduction of low frequency signals is carried out between the centers between the front and back channels, with the image of sounds from a low pitched musical instru ment localized at the front and/or back center.
  • the two channel signals L and R having a high frequency of more than 5 kHz provide four-channel signals substantially as indicated below:
  • a decoder causes matrix circuits additively or subtractively to combine signals of the two channels in different degrees according to their frequencies, namely, enabling low frequency two channel signals to be combined in a larger ratio than medium frequency signals. and high frequency two channel signals to be combined in a smaller ratio than the medium frequency signals.
  • Matrix circuits 5] and 52 provide sum signals L R and different signals L R from the two channel signals L and R respectively.
  • the difference signals L R and sum signal L R are supplied to a first and a second level-varying means 53 and 54 which increasingly attenuate the lev els of signals as they fall in frequency.
  • the sum signal L R and an output signal from the first level-varying means 53 are mixed by a first mixer 55 to form the reproduced signal LFl, and then conducted to a phase shifter 61 of the same type the phase shifter 35 of FIG. I.
  • the output signal from the first Ievel-varying means 53 is also supplied to a second mixer 57 through a phase inverter 56 to be mixed with the sum signal L R for formation of the reproduced signal RF].
  • An output signal from the second mixer 57 is transmitted to a phase shifter 62 of the same type as the phase shifter 37 of FIG. I.
  • the difference signal L R and an output signal from the second level-varying device 54 are conducted to a third mixer 58 and then to a phase shifter 63 of the same type as the phase shifter 39 of FIG. I.
  • the difference signal is also transmitted to a fourth mixer 60 through a phase inverter 59 to be mixed with an output signal from the second levelvarying means 54 for formation of the reproduced signal RBI.
  • An output signal from the fourth mixer 60 is supplied to a phase shifter 64 of the same type as the phase shifter 41 of FIG. I.
  • the embodiment of FIG. 4 enables signals of two channels to be mixed in different ratios according to their frequencies in the embodiment of FIG. I.
  • the first and second level-varying means 53 and 54 may each consist of a filter or capacitor which increasingly attenuates the level of input signals as they decrease in frequency.
  • the sound signal-converting apparatus whose arrangement is schematically illustrated in the block diagram of FIG. 4 may be devised in a variety of forms. one concrete form being presented in FIG. 5.
  • the matrix circuit 51 for producing the sum signal L R includes resistors 71 and 72 of the same value connected in series between the input terminals receiving the two channel signals L and R. the sum signal L R being delivered from the junction of the resistors 71 and 72.
  • a matrix Circuit 52-1 for providing a first difference signal L R includes a serial circuit consisting of resistors 73 and 74 of the same value and a phase inverter 75 for Inverting the polarity of the signal R, the first difference sig nal L R being obtained from the junction of the resistors 73 and 74.
  • a matrix circuit 52-2 for producing a second difference signal R L includes a serial circuit consisting of resistors 76 and 77 of the same value and a phase inverter 78 for inverting the polarity of the signal L, the second difference signal R L being delivered from the junction of the resistors 76 and 77.
  • the embodiment of FIG. 5 eliminates the necessity of providing the phase inverters 56 and 59 of FIG. 4 because two different signals L R and R L which are opposite in polarity are produced.
  • the sound signal-converting apparatus of this invention was applied in converting two channel signals including a plurality of channel signals to the plural channel signals.
  • the present sound signal-converting apparatus can be used intact with the stereophonic signals obtained from the conventional two-channel stereophonic phonographic records, magnetic tape or FM stereophonic broadcasting.
  • the sound signalconverting apparatus of the invention is not limited to the aforesaid embodiments, but may be applied with any other modifications or Changes, provided they fall within the scope of the claims of the invention.
  • a sound signal-converting apparatus including matrix circuit means for reproducing first, second, third and fourth founchannel output signals by additively combining two channel input signals in first and second ratios to produce said first and second output signals. respectively, and subtractively combining said two channel input signals in third and fourth ratios to produce said third and fourth output signals. respec tively.
  • said matrix circuit means includes means for varying each of said first, second, third. and fourth mixing ratios from a first ratio when both two channel input signals are at one frequency to a second higher ratio when both two channel input signals are at a second higher frequency.
  • a sound signal converting apparatus for reproducing four output signals from first and second channel signals comprising:
  • first level varying means connected to receive the difference signals for varying the level thereof according to the frequency thereof;
  • second level varying means connected to receive the sum signal for varying the level thereof according to the frequency thereof;
  • a sound signal converting apparatus according to claim 2 wherein said first and second level varying means are operative to attenuate the levels of the difference and sum signals, respectively, as the frequencies thereof fall.
  • each of said first and second level varying means includes a capacitor.
  • a sound signal-converting apparatus for reproducing on four output channels four-channel signals from first and second channel signals, comprising:
  • fourth means for subtractively combining said first channel signal with said second channel signal in a predetermined ratio of said first channel signal to said second channel signal for channel signals of the medium frequency, in a larger ratio than said predetermined ratio for channel signals of the lower frequency and in a smaller ratio than said predetermined ratio for channel signals of the higher frequency to produce a fourth output signal.
  • said first means includes an impedance circuit including reactive impedance elements for coupling said first channel signal to the first output channel, and a resistor for coupling said second channel signal to the first output channel
  • said second means includes an impedance circuit including reactive impedance elements for coupling said second channel signal to the second output channel, and a resistor for coupling said first channel signal to the second output channel
  • said third means includes an impedance circuit including reactive impedance elements for coupling said first channel signal to the third output channel, and a resistor for coupling said second channel sig nal of opposite polarity to the third output channel
  • said fourth means includes an impedance circuit including reactive impedance elements for coupling said second channel signal to the fourth output channel. and a resistor for coupling said first channel signal of opposite polarity to the fourth output channel.
  • said impedance circuits include a parallel arrangement including a first resistor, a first ca pacitor and a serial circuit of a second resistor and a second capacitor, respectively.
  • a sound signal-converting apparatus further including means for producing a sum signal by additively combining said first and second channel signals and for producing first and second difference signals having the opposite polarities by sub tractively combining said first and second channel signals;
  • said first means includes means for coupling said sum signal to the first output channel and means for coupling said first difference signal to the first output channel, the latter means including levelvarying means for increasingly attenuating the level of said first difference signal as its frequency falls;
  • said second means includes means for coupling said sum signal to the second output channel and means for coupling said second difference signal to the second output channel, said latter means including level-varying means for increasingly attenuating the level of said second difference signal as its frequency falls;
  • said third means comprises means for coupling said first difference signal to the third output signal and means for coupling said sum signal to the third output channel, said latter means including level-varying means for increasingly attenuating the level of said sum signal as its frequency falls;
  • said fourth means has means for coupling said second difference signal to the fourth output channel and means for coupling said sum
  • a sound signal-converting apparatus wherein said level-varying means include a capacitor, respectively.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Stereophonic System (AREA)
  • Stereo-Broadcasting Methods (AREA)
US355420A 1972-05-02 1973-04-30 Sound signal converting apparatus for use in a four channel stereophonic reproduction system Expired - Lifetime US3892918A (en)

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JP47043991A JPS5210364B2 (enrdf_load_stackoverflow) 1972-05-02 1972-05-02

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US (1) US3892918A (enrdf_load_stackoverflow)
JP (1) JPS5210364B2 (enrdf_load_stackoverflow)
DE (1) DE2322145C2 (enrdf_load_stackoverflow)
GB (1) GB1395477A (enrdf_load_stackoverflow)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3971890A (en) * 1975-02-10 1976-07-27 Cbs Inc. Method and apparatus for quadraphonic enhancement of stereophonic signals
US3997725A (en) * 1974-03-26 1976-12-14 National Research Development Corporation Multidirectional sound reproduction systems
US4081606A (en) * 1975-11-13 1978-03-28 National Research Development Corporation Sound reproduction systems with augmentation of image definition in a selected direction
US4799260A (en) * 1985-03-07 1989-01-17 Dolby Laboratories Licensing Corporation Variable matrix decoder
US5046098A (en) * 1985-03-07 1991-09-03 Dolby Laboratories Licensing Corporation Variable matrix decoder with three output channels
WO2002052896A3 (en) * 2000-12-22 2002-10-31 Koninkl Philips Electronics Nv Multi-channel audio converter
US20060150047A1 (en) * 2004-12-30 2006-07-06 Wolfgang Nikutta Apparatus and method for generating a high-frequency signal
WO2005070097A3 (en) * 2004-01-09 2006-10-19 Masonware Partners Llc Passive surround sound adapter

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4915401A (enrdf_load_stackoverflow) * 1972-05-19 1974-02-09
JPS61235498A (ja) * 1981-01-26 1986-10-20 エチル・ペトロレウム・アデイテイブス・インコーポレーテッド 燃料および潤滑油用添加剤
ES2127135B1 (es) * 1997-04-23 1999-11-16 Lera Jose Maria Lopez Sistema de audicion.

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3725586A (en) * 1971-04-13 1973-04-03 Sony Corp Multisound reproducing apparatus for deriving four sound signals from two sound sources
US3745252A (en) * 1971-02-03 1973-07-10 Columbia Broadcasting Syst Inc Matrixes and decoders for quadruphonic records
US3786193A (en) * 1971-07-19 1974-01-15 Sony Corp Four channel decoder with variable mixing of the output channels
US3813494A (en) * 1970-06-08 1974-05-28 Columbia Broadcasting Syst Inc Quadraphonic reproducing system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3813494A (en) * 1970-06-08 1974-05-28 Columbia Broadcasting Syst Inc Quadraphonic reproducing system
US3745252A (en) * 1971-02-03 1973-07-10 Columbia Broadcasting Syst Inc Matrixes and decoders for quadruphonic records
US3725586A (en) * 1971-04-13 1973-04-03 Sony Corp Multisound reproducing apparatus for deriving four sound signals from two sound sources
US3786193A (en) * 1971-07-19 1974-01-15 Sony Corp Four channel decoder with variable mixing of the output channels

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3997725A (en) * 1974-03-26 1976-12-14 National Research Development Corporation Multidirectional sound reproduction systems
US3971890A (en) * 1975-02-10 1976-07-27 Cbs Inc. Method and apparatus for quadraphonic enhancement of stereophonic signals
US4081606A (en) * 1975-11-13 1978-03-28 National Research Development Corporation Sound reproduction systems with augmentation of image definition in a selected direction
US4799260A (en) * 1985-03-07 1989-01-17 Dolby Laboratories Licensing Corporation Variable matrix decoder
US5046098A (en) * 1985-03-07 1991-09-03 Dolby Laboratories Licensing Corporation Variable matrix decoder with three output channels
WO2002052896A3 (en) * 2000-12-22 2002-10-31 Koninkl Philips Electronics Nv Multi-channel audio converter
KR100909971B1 (ko) 2000-12-22 2009-07-29 코닌클리케 필립스 일렉트로닉스 엔.브이. 다중-채널 오디오 변환기
WO2005070097A3 (en) * 2004-01-09 2006-10-19 Masonware Partners Llc Passive surround sound adapter
US20060150047A1 (en) * 2004-12-30 2006-07-06 Wolfgang Nikutta Apparatus and method for generating a high-frequency signal

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Publication number Publication date
DE2322145A1 (de) 1973-11-08
JPS5210364B2 (enrdf_load_stackoverflow) 1977-03-23
JPS495601A (enrdf_load_stackoverflow) 1974-01-18
DE2322145C2 (de) 1986-03-27
GB1395477A (en) 1975-05-29

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