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JPS528681

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DESCRIPTION JPS528681
o44 original reproduction device ■ Japanese Patent Application No. 49-115303 [phase]
Application No. 45 (1970) October 28 O Japanese Patent Application No. 45-94917 division 0
inventor Takeo Shiga 125 Minato Shiga Kawasaki City Nippon Columbia Co., Ltd. Kawasaki Office
Michio Okamoto Michi-no-sho Doki Sawazawa-no-sho same-committee Ms. Nakatani 0 applicant
Nippon Columbia Co., Ltd. Tokyo 14 14 14 [Awning] agent attorney at Minato-ku Akasaka Tokyo
Kazuhide Yamaguchi
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram for explaining a recording
apparatus for obtaining a signal to be reproduced according to the present invention, and FIG. 2
is a system diagram for explaining a reproduction apparatus of the present invention.
DETAILED DESCRIPTION OF THE INVENTION The present invention is intended to realize fourdimensional three-dimensional reproduction with four channel sources using a two-line
transmission path, and by utilizing the correlation between the sound collection method and the
reproduction signal. The purpose is to obtain a reproduction effect superior to that of the
conventional two-channel reproduction and equivalent to that of the conventional four-channel
reproduction by reproducing from four speakers. The conventional 4-channel reproduction
requires a 4-system transmission system, which makes the apparatus expensive and complicated,
and it is difficult to easily create a reproduced sound field with four sound sources. In view of
such a point, in the present invention, conventional 2-channel recording / reproduction systems
such as tape, record, FM broadcast, etc. are used as they are, and 4-channel reproduction is
simply performed in line [111111] and adjacent speakers behind. It is intended to improve the
stereophonic reproduction effect by supplying a differential signal of a 90-degree phase signal to
the rear speaker to improve the ambiguous reproduced sound of discomfort and localization due
to the 180-degree phase difference reproduced between the two. The present invention will be
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described below with reference to the drawings. FIG. 1 is a system diagram for explaining one
method of obtaining a signal to be reproduced according to the present invention, in which a raw
sound field 1 such as a studio or a hall is picked up with a 4-channel microphone and converted
into a 2-channel. It shows the process. The direct sound reproduced from the sound source in
front is one point for the signal FL in the sound field on the left front and the signal FR in the
sound field on the right front by the two unidirectional microphones 2 and 3 directed to
approximately 45 degrees each other Similarly, the other two unidirectional microphones 4 and
5 respectively pick up the signal BL in the left rear sound field and the signal BR in the right rear
sound field. The forward signals FL and FR are mixed with each other by the mixing amount m by
the mixer 6, while the backward signals BL and BR are mixed with each other by the mixing
amount n by the mixer 7, and the left signal is the right side by the mixing circuit 8, Are mixed
respectively in the mixing circuit 9 and converted into two synthesized signals and R. At this
time, for one of the rear signals BL and BR (BR in the figure), the polarity inverter 10a and the
thread path 10b connected in parallel thereto are mixed through the polarity switch 10c and
then mixed through the polarity inverter 11. Ru. The polarity switching device 10c is positive
polarity (ie, 10b side when it is necessary to pick up the direct sound of the sound source from
the rear with the microphones 4 and 5, and (B) the sound source is only forward and the rear is
indirect In the case of only the sound, it is the reverse polarity, ie, 10a. Thus, [111111] EndPage
obtained from the mixing circuits 8 and 9: 12 signals and R are recorded or carried by a
conventional 2-channel transmission device 12 such as a 2-channel tape recorder, disc record,
FM stereo broadcast, etc. Ru.
The signal recorded or conveyed to the 2-channel transmission device 12 as described above is
reproduced by the reproduction device shown in FIG. The combined signal from the 2-channel
transmission device 12 and R are applied to the wide band phase shifters 13 and 14 and the left
signal (L + 90 °) whose phase is advanced by 90 degrees and the right signal (R-90 °) delayed
by 90 degrees. ) Are added together in a summing circuit 15 to obtain a 90 ° phase-shifted L
and R difference signal B, which is reproduced from the rear speaker 16. Also, the signals LO0
and RO 'which are not phase-shifted are reproduced from the speaker 17 and the right speaker
18 respectively, and at the same time a part thereof is added by the summing circuit 19 to obtain
the sum signal F is reproduced from the front speaker 20. Ru. [111111] Furthermore, in the
recording field of Fig. 1, there is a sound source only in the front, and from the back, in the case
of only reverberation and other indirect sounds, the polarity switch 10 has reverse polarity and
passes through the 10a side to output the channel transmission device 12. Equation (5 × 6) is
taken out for. [111111] Here, the phase shift of the rear signal B by 90 ° means that the sound
image localization at the rear of the (BL × BR) component in the equation (4) is BL and −BR acid
of the equations (1) and (2). This is to prevent the components from being obscured, and this 90
° phase shift causes the localization of the rear reproduction sound image to be steady. When a
sound wave emitted from a sound source at a certain fixed position on the rear directly enters
the microphones 4 and 5, the electric signal waveforms of the two microphone outputs BL and
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BR are mutually correlated or rv 11 111 m here 21 Indicates a playback sound field. In the above
recording / reproducing apparatus, the signals FL, FR, BL, and BR of 4-channel source are output
to the four speakers 20, 17, 16, and 18 respectively in the following combinations: Reproduced
as B, R. That is, when there is a sound source forward and backward in the recording field of FIG.
1, the polarity switch 10 passes through the 10b side if it is positive, and the following lX2 signal
is taken out at the output of the channel transmission device 12 . L = FL + mFR × BL × nBR
························ (1) R = mFL + FR-nBL-BR · · · · · · · (2) Further, if L 十 R = F and L−R = B in the
reproduction system of FIG. 2, (3 × 4) is obtained. [111111] R-= mFL + FR-nBL x BR (6)
Furthermore, in the reproduction system of Fig. 2, L x R = F, L If it is -RB, (7 x 8) will be obtained.
The musical tone signal is canceled or attenuated by the calculation operation (BL-BR) of
[111111] et al. (3), and the rear signal is not reproduced from the front speaker by (3) and (4). It
will be played from the rear speaker. On the other hand, reverberant sound consists of the
synthesis of multi-dimensional reflections from all surfaces, such as walls, ceilings, floors, etc., in
the sound recording field, and the sound emitted from a certain sound source is the two single
directivity points behind. In the case of incident on the property my, crophones 4 and 5, the
electric output signal waveforms BL and BR respectively have rllllllEndPage of the acoustic
reflection path traced, and it can be said that there is almost no correlation in the phase
amplitude from the difference. Therefore, if there is no sound source at the rear and the signal
picked up from the rear is a reverberation, the calculation operation of (BL-BR) does not hold and
there is no cancellation or attenuation, so in equation (8) Even reverberant sound can be
reproduced to give the listener a sense of presence that wraps around the body, which is an
important element in the 4-channel stereo effect. As apparent from the equations (1) to (4) or (5)
to (8), in the playback sound field 21, the acoustic signals FL, FR, BL, BR of the raw sound field 1
are applied to four speakers. Is well blended, and a realistic sound field with no sense of absence
between the speakers is reproduced without losing the sense of localization. Also, in order to
maximize the sound reproduction effect according to the position of the sound source and the
microphone and the acoustic conditions such as the studio or the hall, it is possible to adjust the
mixing amount m and fi to adjust the localization and the realism. [1111111 The playback device
shown in FIG. 2 is made by distributing by studio mixing not only the signals recorded by the
microphone arrangement of FIG. 1, but also the individual instruments often used in conventional
stereo recording. It is clear that good sound effects can be obtained with the 4 channel program
source.
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