JPS58190199A - Pseudo stereo system - Google Patents

Abstract

PURPOSE:To obtain a wide sound image without producing a bias, by obtaining two types of acoustic signals which perform at least at a part of frequency band an inrement of frequency for the phase difference between both acoustic signals, a consecutive increment or decrement of the frequency or the increment and decrement alternately and repetitively. CONSTITUTION:A phase shifter 10 has the phase frequency characteristics with which the phase shift quantity increases and decreases in response to the frequency. A pseudo stereo signal is obtained by converting directly an input acoustic signal into an output 1 and converting an output acoustic signal of the shifter 10 into an output 2 respectively. For the frequency characteristics of the shifter 10, it is possible to have a monotonous increment and a monotonous decrement alternately and repetitively once for the phase shift quantity over the entire circumference frequency band. The decrement characteristics of the phase shift quantity given from the shifter 10 is set at a value with which the correlative coefficient gamma between both ears is set at 0 or a value close to 0 between the outputs 1 and 2. Thus the maximum degree of spread is obtained for a stereo sound image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for transmitting a single-channel acoustic or audio signal to a two-channel speaker or one handphone for a stereo effect, i.e., psychologically eliminating the presence of the sound. Pseudo-stereo type VC that gives a sense of expansion of the Ti image
In particular, the present invention is designed to provide a sense of spread of a sound image with good frequency characteristics and no bias.

This sound-like stereo system can be applied to an ordinary monaural receiver to obtain a stereo effect, applied to an ordinary television receiver to listen to stereo sound, or applied to a monaural cassette player or disc player. Effective for playing stereo sound. For this reason, various pseudo-stereo systems have been proposed in the past for VC systems. The following three methods are the main ones, but each has its own drawbacks.

(1) <L-shaped filter method The operating principle is that a single-channel acoustic signal is divided into one channel by complementary comb-shaped filters whose pass frequency bands are alternately changed to *.

These divided two-channel signals are placed as left and right sound sources, giving a broader sound image as a whole. Depending on the frequency spectrum of the sound source, the sound image may be biased to either the left or right side, and the sound image of the extra instruments during performance may be biased to the left or right side.
Also, the frequency response is flat and I-engineered (・Therefore, the sound quality is worse than the original sound!).

(2) / 8chroeder method / This method was proposed by M, ) L, 8chroeder in the United States around 1970, and its operating principle is as shown in Fig. 1, from the microphone 101 as a sound source. ! The frequency band of the signal is divided into a plurality of bands by bandpass filters 10 to 10 NK, and the phase of each 'Jf division band is changed to a phase shifter 103-/~103-uN Vc.
By alternately inverting the signal to +/2 and -/K and creating a phase difference of 1π/J and 1π/λ between the left and right channels for each divided band, the sound image is expanded.
C supply. (1) < Same as L-type filter method <1
There is a drawback that the frequency spectrum of the divided bands causes IC bias in the spread of the sound image, and a clear spread of the sound image cannot be achieved.

(5) Reverberant sound addition method The operating principle is to delay the original sound with reverberant sounds with different frequency characteristics to form a co-channel acoustic signal with different reverberation characteristics.

Try to expand the sound image. Since residual phonographs without the original sound VC are added with different mantissas on the left and right sides, there is a drawback that the sound quality differs from the original sound.

As mentioned above, the conventional pseudo-stereo type VC has drawbacks such as movement of the sound image due to the distribution of the frequency spectrum and loss of quality due to the addition of reverberation to the original sound VC.

In addition, according to the results of the inventors' investigation of sound image spread r using white noise, the sound image spread feeling becomes maximum when the binaural correlation coefficient γ becomes 0, and r - When , @ becomes small, and 1′ at the height of r=1/! When the h image was moved far away, D, S, γ--l, a VCH image between the VC and cochlea was produced, but no reverberation occurred.

The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, and to utilize the results of the above-mentioned studies to obtain a wide sound image without causing bias, and to create a pseudo 7 television system.

In other words, as an example of the pseudo-stereo system of the present invention, as described later, the input original sound-signal is set as a one-phase frequency characteristic, and as the frequency increases, the V
While repeating C, the increasing and decreasing phase shifter is guided to the phase shifter that presents without delay, and the output signal of the phase shifter and the original sound 1
No. 6 is used as a pseudo-stereo sound source.

That is, according to the present invention, from a single acoustic signal, the phase difference between them increases and decreases continuously as the frequency increases, and then decreases to JIIl'O. The present invention is characterized in that it forms an acoustic signal with an oscillating angle in which the oscilloscope is alternately repeated in at least a part of the frequency band, and a stereo sound source is constructed using these oscilloscope acoustic signals.

If the sound signals constituting the pseudo-stereo No. 111 formed by the method of the present invention are supplied to two speakers, or a handphone, the % binaural correlation coefficient γ will be 0 or 0. The values are close to each other, and a stereo effect that gives a sense of spaciousness to the sound (II) can be obtained.

Here, to explain the interaural correlation coefficient γ', it is an index that shows the similar and anonymous correlation between sounds and signals that enter both ears of the listener, and is in the range of 10/~-/. is the coefficient of That is, r=+/: Exactly the same at both ears 1...- r=o: Completely unrelated between both ears γ--l:
The mathematical definition of the correlation coefficient γ is that the left ear and the right ear r (the added phonological key signs are L(t) and R, respectively).
(t), it can be expressed by the following formula.

1 knife Part Lh)・)L(t)dt O Next, the present invention will be explained with reference to the drawings.

FIG. 2 shows a basic configuration according to the method of the present invention, which is also an embodiment of a system stereo signal generator, in which a phase shifter 10/)X is used, for example, as shown in FIG. In this example, the phase shifter has a phase frequency characteristic that increases and decreases (decreases in this example) with the frequency at a rate of π/3 radians (ra, d). A pseudo stereo signal is obtained by using the output acoustic signal of /θ as the output.

As mentioned above, as a phase shifter that exhibits a phase shifter that increases and decreases continuously with one frequency without giving a time delay to the signal, for example, "Linear XC Practical Circuit Manual" (
Radio Gijutsusha, published on June 10, 1920), pages 1 to 12 can be used; however, in the present invention, as shown in FIG. The container 10 can be configured. Here, the output signals of l pairs of operational amplifiers /-/~t-S and calls l~λ-j that operate complementary to each other are divided by a series connection of a capacitor C/~Cj and a resistor R/~R5. Then, the phase shifter 10 is constructed by connecting, for example, five stages of unit phase shift circuits which are extracted from the intermediate connection point.

Furthermore, although FIG. 5 shows the phase shifter reduction characteristic of radians (rad) per octave suitable for use in the method of the present invention, the phase shift circuit IO shown in FIG. It can be realized.

Furthermore, the configuration of the pseudo stereo signal generating apparatus according to the present invention is not limited to the second example, but may be configured as shown in FIG. 6. In the configuration shown in FIG. 6, for example, as shown in FIG. 3, a pair of phase shifters exhibiting a phase shift l11 reduction characteristic of /3 radian (rad) per octave complementary to each other and the original sound input to 3θ! # The double signal is supplied in parallel, and the output signal of the l pair of phase shifters and 3θ is used as the pseudo stereo No. 16, and the output /
and the output. These output l and output! between them/pairs of phase shifters and one phase reduction characteristic equal to the sum of the phase shifters by 3θ, i.e. λπ per octave.
Provides a phase shift m reduction characteristic of /3 rad.

Note that in each of the above-described configurations of the present invention, the phase shifter IO
It is assumed that the phase shifter to be given by d decreases the phase shifter monotonically across the entire band of the original sound signal, but it also increases monotonically. There may be. Furthermore, the phase shift ratio of this phase shifter versus frequency is 1, for example.

As shown in Fig. 7, the whole circumference mantissa band is covered.

The monotonous increase and monotonous decrease of the phase shift amount may be alternately repeated at least once.

In addition, pseudo stereo (II generator f
In It, for example, when using the #f configuration shown in the second diagram, the phase shift-reduction characteristic given to the phase shifter /θ, the interaural correlation coefficient between the output l and the output γ is O or a value close to OVC (output l and output 2 are speaker VC
As soon as the connection is made, the phase shift coefficient will not be completely zero, but the approximate VC can be considered to be O) and the spread of the stereo sound image will be enormous. It is also possible to continuously change the degree of spread of the obtained stereo sound image by continuously changing the phase shift change m of the spatial reduction characteristic over time.

As is clear from the above description, according to the invention, the difference between two acoustic signals constituting a pseudo-stereo signal formed from a single channel By setting the interaural cross-correlation coefficient γ to 0 or m close to 0, the spread of the sound image is not biased and the number of flat circumferences is custom-made (amplitude -
frequency characteristics), it is possible to obtain an extremely good sense of spaciousness without unnecessary residual m1ll feeling, and by customizing the phase shift pair frequency of the VL-phase shifter in an appropriate OJ VC setting, the sound image can be improved. It is also possible to arbitrarily change the degree of spread.

By utilizing the excellent features of the present invention, for example, when producing a drama program at a broadcasting station VC, it is possible to
By performing a stereo portrait using the present invention from a monaural effect tape as a scene, and recording this in stereo along with the voices of the characters, it is possible to create a stereo drama program with a rich sense of reality.

[Brief explanation of the drawing]

FIG. 1 is a Bote-Bronck diagram showing the configuration of a conventional pseudo-stereo signal generation device, FIG. 2 is a broken-Bronck diagram of an example of the configuration of an M-simulation stereo signal generation device according to the present invention, and FIG. 3 is a seven-phase shift diagram. 7 is a block diagram illustrating an example of the phase shifter having a decreasing sign, FIG. 7 is a block diagram showing an example of the phase shifter of 7, and FIG. 5 is a pseudo stereo signal generator according to the present invention. A custom-made piece showing another example of the phase shift reduction characteristic of a phase shifter suitable for use in the present invention is shown in Figures 1 and 6. The block diagram in FIG. 7 shows a pseudo stereo signal generating device 11 according to the present invention. FIG. 4 is a characteristic curve diagram showing still another example of the amount of phase shift change vs. custom frequency of a phase shifter used in the present invention. 10/...-microphone (sound source), 10λ-/5-10 λN...Band pass filter,
103-/S10! -2N...phase shifter, 10 da...
Handphone, /θ,〃,3θ...phase shifter, /-/-/-5,2-1~λ-5...filtering amplifier, C
/~Cj...capacitor, R/~FLI...resistance. Figure 1 Figure 3 Figure 4 Nmf[,,m) Figure 5

Claims (1)

[Claims] 1) From a single acoustic signal, the phase difference between them can be determined. Continuously increases or decreases with increasing frequency,
In addition, one type of V# flaw signal is formed by repeating alternating increases and decreases in at least some frequency bands, and these two types of acoustic signals constitute a stereo sound source. Stereo method. 2. The pseudo-stereo system according to claim 1, characterized in that the ratio of increase/decrease in the phase difference to the increase in frequency can be changed.