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? 44 former stereo transmission system ? Japanese Patent Application No. 46-55655 [phase]
Application No. 46 (1971) published on July 27 closed 48-22202 @ Akira 48 (1973) March 20 0
inventor Fujita Hisashi Tokyo Metropolitan Tokyo Meguro District 12 Senso 2nd Suisho Dou
Wakukuri Nagura City Shoujaku City 6th 6th 3450 Applicants Japan Broadcasting Association
Tokyo Broadcasting System Tokyo 2 Shibuya 2 ward Jinnan 2 2 1 [present] Attorney Attorney
Sugimura Hidehiro One person (The applicant has a license available. Detailed Description of the
Invention The present invention is also audiometrically compatible when making a four-way
stereo signal compatible with monophonic and two-way stereo signals and reducing the number
of transmission channels to be received to improve the signal-to-noise ratio. The present
invention relates to a four-way stereo signal transmission system in which a single carrier wave
multiplexes transmission without damaging the original stereo effect. In general, four-way stereo
signals are supplied to the front left and right, rear left and right speakers (each. It consists of
Rtltr). Since each signal, R, l, r, is generally independent, the usual concept requires four
independent channels to transmit these signals. In addition, in the case of four-way stereo
broadcasting using radio waves, there is a limit to the combination of the front and rear left and
right signals in each channel in terms of compatibility with conventional broadcasting.
Conventionally, four channels are used when transmitting a four-way stereo signal, for example,
as shown in the frequency spectrum of FIG. 1, when four-way stereo broadcasting is performed
using one radio wave of four-channel multiplex modulation for four-way stereo signal. When the
pilot signal for the subcarrier is ? C (for example, 19 kHz), the signal CI-L + R + f + r is for the
first channel, the signal C2- (LR + 4r) sin2?ct for the second channel, and the signal C3 for the
third channel. The lower channel or the entire sideband of the signal C4 = (L?R?1 + r) 5 in
4?ct is accommodated in the fourth channel. As described above, in the case of performing fourway stereo broadcasting by radio waves, in the case of long distance reception, the S / N of the
fourth channel first decreases. The reason for this is that the 4th channel's S / N is 22 = 4 or 6
dB, because the subcarrier is theoretically twice the frequency of the 3rd, [111111] EndPage:
2nd channel. This is because the S / N decreases, and the 6 dB S / N decrease is 4 times (for
example, 50 W requires 200 KW as the fourth channel) in the transmission power. A difference
of about% rank appears in sound quality hearing evaluation.
Thus, on the receiving side, the demodulated output C1) C2, C3 and C4 is passed through a
matrix to restore a four-way stereo signal, so the reception sound quality is dominated by the
transmission channel of the lowest S / Na (Na: audio noise). To be reduced. The object of the
present invention is to restore 4-ary stereo signal completely using signal of 4 channels normally
and to prevent S / N decrease when the received electric field is weak and the S / N decreases. It
excludes the channel but loses almost no physical or psychological effect of the 4-way stereo
sound (the 4-way stereo signal is restored so that it can be listened, and it is compatible with
monophonic and binary stereo. In order to be able to be heard by the user, the four-way stereo
signal is appropriately combined and transmitted through one channel of four-channel
multiplexing, and the sound quality of the four-light stereo is related to the realism and S / N at
the receiving side. It is to propose a four-way stereo signal transmission system which can be
selected. The present invention combines the left signal and right signal R on the front side and
the left signal 1 and right signal r on the rear side to form a four-way stereo signal and sums (L +
R) and (JL + r) and difference signals (L) respectively. C2- (1 + g) by forming -R) and (JL-r), and
changing the level of the sum signal (L + R) and the difference signal (L-R) of the front surface by
a rate of 1?l (o <1?I <1) (L?R) + (L?r) C3 = (1?g) (L + R) (JL + r) C, ? (1 + g) (L?R) ? (J?r)
Signals C1, C2, C3 and C4 By transmitting the signals C1 and C2 to restore compatible
monochrome signals when receiving only the signal C1, and restore compatible binary stereo
signals when receiving the signals C1 and C2, and Receive C2 and C3 Sometimes, it is
characterized in that the four-way stereo signal is disturbed (restoration is made possible, and
when the signals C1, C2, C3 and C4 are received, the four-way stereo signal can be restored in
terms of hearing). If only the signal C1 among the signals C1 to C4 is received, it is possible to
listen to a monophonic signal consisting of an aurally equal sum of LtRtJ-tr when ? is set as
small as possible. If double numbers C1 and C2 are received and these signals C1 and C2 are
passed through a matrix circuit to perform the following operation, (CI + C2) / 2-L + JL-? R = ?
(CIC 2) / 2-R + rtL-R ' Signals L 'and W are obtained, and good binary stereo sound can be heard,
with the left and right signals ?,' Fe 'being the sum of the left and right signals respectively.
That is, when ? is selected as% in accordance with 4-way stereo reproduction to be described
later, this is crosstalk of 50% detection limit in the case of 2-channel stereo, and does not cause
deterioration in quality as 2-way stereo. Next, when each output {square root over (R)}, R ?, JII, r
? is obtained by demodulating the triples C1, C2, C3 and passing through a matrix circuit and
performing the following calculation, EndPage: 2 [111111] Although crosstalk between the four
channels is equal to the coefficient ratio of each signal component, as described later, when
selecting the value of ? to an appropriate value, preferably%, the signal of only three channels is
sufficient. It is possible to perform four-way stereo reproduction with a four-way stereo effect.
Next, in order to receive the four signals C1tC2 and CatC4 and restore the original signal, the
matrix circuit performs the following operation. In this case, the signal can be restored to the
original signal except for the coefficient of H, and as described later, if the value of the coefficient
? of the signal or R is appropriately selected and a matrix of four signals is performed, for
example, Also, when the value of ? is selected to be the above-mentioned%, it is possible to
reproduce a four-way stereo which is almost the same as the original sound. In each of the above
four reception modes (monophonic, binary stereo, quaternary stereo), the recovered signal has a
crosstalk count as a function of ? added, but if an appropriate numerical value is given to ? It is
three in defining a form that is optimal and compatible in terms of hearing. Now, assuming that
when receiving signals C1, C2 and C3, if ?-?, in four-way stereo reproduction using these
signals C1, C2 and C, crosstalk in each direction is 10 dB, and the front by crosstalk on the front
With the exception of the effects of Hearing on sound quality and directionality except for the
effect of-can fully preserve the original sound effect, but the front stereo effect is lacking. Since
the sensitivity of crosstalk on the front and back or the back is less than half the sensitivity of
crosstalk on the front as judged from the results of experiments based on human hearing
[111111] [111111], the crosstalk on the front, back, and the back is 18dB It is most desirable at
this point to replace it with crosstalk on the front. Now, assuming that ?-%, five crosstalks as
shown in the figure are distributed to the reproduced sound from the four speakers SL, 5R9S ?
and Sr arranged in the left and right front and back of the listener 1 in FIG. It is equivalent to the
50% detection limit of crosstalk in stereo, and there is no particular problem on the front and
back, the back, and it is possible to reproduce a 4-way stereo with a sufficient 4-way stereo
When receiving four signals C1 and C2tC3tC4, complete restoration is obtained except for
crosstalk of -15dB on the front side, but if there is a need to improve crosstalk on the front side,
add k to biphasic antiphase, or signal C1 or C2 , C3 and C4 in the next added / subtracted value
signal Fe, i /, r / ?OCI + ?OC2 + ?OCa + ?oC4 = L'?0CI-?OC2 + ?0Ca-?oC4-* "OCI + ?OC2
+" OCa + ?Oc, -J "?0Ct-?0C2-?0Ca-? ? By replacing the front crosstalk with the back
crosstalk using C4-r ', the front crosstalk is improved to less than 30 dB in the former case at ?
=%, and the front crosstalk in the latter case. Cross talk on the back side is 1-15 dB. In this way,
the crosstalk on the front can be completely eliminated in the sense of hearing. As described
above, when the original sound field is constructed by restoring the signal transmitted according
to the present invention, a level difference is provided to the combination of the front and back
signals, and crosstalk between the side and the back is replaced with crosstalk on the front. Even
if the stereo effect is reduced to some extent due to savings, hearing problems will occur
(restoration of the 4-way stereo signal in good condition will result in 0, and the fourth channel
will be added as well to improve crosstalk) A perfect original sound field can be reproduced by
performing back and forth crosstalk reversal by difference reception. As described above,
according to the present invention 4-ary stereo signal transmission method [111111] EndPage:
3, it is completely compatible with monophonics in radio waves and ░ binary stereo
broadcasting, and then with full sound field effect on hearing sense. If the original stereo
broadcast can be performed and the S / N of the fourth channel is poor in long distance
reception (the reception sound quality in this case is dominated by S / Na), the fourth if
necessary. It is possible to use a channel (a total of three channels can receive a sound having a
sufficient four-way stereo effect, and the operation on the transmission side for this does not
cause any problems to mono and stereo receivers. Therefore, for example, when performing fourchannel stereo broadcasting of one radio wave of four channels with the configuration as shown
in the modulation signal spectrum of FIG. 1, for example, the S / N of the fourth channel
corresponds to the second and third channels as described above. The% rank difference in the 5step sound quality evaluation caused by a 6 dB reduction as compared can be sufficiently
improved by the present invention (the difference between the S / N detection limit and the
allowance is about 10 dB). Thus, the present [111111] invention has the advantage that the
reception of the fourth channel can be stopped by the strength of the received electric field and
the sound quality can be improved with little harm to the S / N improved aural effect on the
audibility. Have.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a frequency spectrum diagram for explaining
the transmission format of a conventional four-way stereo signal, and FIG. 2 is a three-channel
diagram showing the relationship between the arrangement of four-way stereo speakers and the
amount of crosstalk between the left, right, front and back of the listener. It is a diagram shown
about the case of (epsilon)-% by reception. 1
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Cited Reference Special Opening and Closing 47-41207 [1111111 EndPage: ?
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