JPS61271000A - Pseudo stereo device - Google Patents

Abstract

PURPOSE:To obtain a sound image having a broadening feeling by obtaining a sum and a difference of a signal obtained by delaying a monaural signal and an original signal to input to R(right) system and L(left) system and similarly processing the signal obtained by shifting a phase of the monaural signal by 90 deg. to input to the R system and the L system. CONSTITUTION:A monaural sound signal 1 is directly inputted to a comb line filter F1 and the 90 deg. phase shifted 5 signal is inputted to a comb line filter F2. In the filter F1, a sum signal 3 and a difference signal 4 of a signal delaying 2 an original signal and the original signal are obtained. In the filter F2, a sum signal 7 and a difference signal 8 of a signal delaying 6 a phase shift signal 5 and the phase shift signal 5 are obtained. The sum signal 3 and the difference signal 8 are added 9 to drive a speaker spR of R system. The subtraction 10 between the difference signal 4 and the sum signal 7 is performed to drive a speaker SpL of L system. Thereby, in a whole frequency range, and right left channels having small correlation are formed and a broadening sound image is realized and a stereophomic feeling is increased.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a pseudo-stereo device.

(Prior Art) Generally, a so-called pseudo-stereo device is known that processes a monaural signal to create a left ear signal and a right ear signal, and supplies the signals to left and right speakers to create a stereo sound field. In this case, it has been reported that in broadband noise, the closer the correlation coefficient between the left and right signals is to O, the wider the sound image is perceived (Journal of the Acoustical Society of Japan, Vol. 39, No. 4, 1983.
253).

Conventionally, this type of device, as shown in FIG. 6, delays a main signal, which is a monaural signal, by a delay circuit 21 for a predetermined time, and mixes the main signal and the delayed signal by an adder 22 and a subtracter 23, respectively. It realized left and right channel signals.

(Problems to be Solved by the Invention) In the above device, as shown in FIG. 7, the amplitude levels EL and ER of the left and right signals intersect in a comb shape to reduce the correlation, but EL = At a frequency that is ER, the correlation coefficient is 1, and there are also frequencies where only one of ER or EL is O, and only one channel has an amplitude. That is, in the above device, since the correlation coefficient does not become small at all frequencies, there is a problem that the sound image is insufficiently spread.

SUMMARY OF THE INVENTION In view of the problems of the prior art described above, it is an object of the present invention to provide a pseudo-stereo device that can obtain a sound image with a sense of spaciousness by reducing the correlation coefficient in all frequency bands.

(Means for Solving the Problems) In order to solve the above problems, the present invention includes a first delay circuit that delays a monaural signal, and a second delay circuit that adds the monaural signal and the delayed signal of the first delay circuit. a first subtraction circuit that subtracts a monaural signal and a delayed signal of the first delay circuit; a phase shifter that shifts the phase of the monaural signal by 90°; and a signal of the phase shifter. a second delay circuit that delays the signal of the phase shifting means and a delayed signal of the second delay circuit; a second delay circuit that adds the signal of the phase shifting means and the delayed signal of the second delay circuit; a second subtraction circuit that subtracts the delayed signal of the first subtraction circuit; a third addition circuit that adds the signal of the first addition circuit and the signal of the second subtraction circuit; a third subtraction circuit that subtracts the signal and the second addition circuit, and the signal of the third addition circuit and the signal of the third subtraction circuit are used as left and right channel signals. Features.

(Function) With the above configuration, the present invention reduces the correlation between left and right channel signals in all frequency bands, and realizes a spread sound image.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a pseudo-stereo device according to the present invention, and shows a case where the input signal is a monaural audio signal.

The input terminal 1 is connected to the input terminal of the delay circuit 2 of the comb filter F1, one Φλ input terminal of the adder 3, the e terminal of the subtracter, and the input terminal of the 90° phase shift circuit 5. The output terminal of the delay circuit 2 is connected to the other e input terminal of the adder 3 and the e input terminal of the subtracter 4.

The 90° phase shift circuit 5 operates in the audible frequency band (40Hz to 20KH).
z), and its output terminal is connected to the input terminal of the delay circuit 6 of the comb filter F2, one e input terminal of the adder 7, and the input terminal of the subtracter 8. The output terminal of the delay circuit 6 is the e input terminal of the adder 7 and the e input terminal of the subtracter 8.
connected to the input terminal.

The output terminal of the adder 3 and the output terminal of the subtracter 8 are each connected to the e input terminal of the adder 9, and the output terminal of the subtracter 4 and the output terminal of the adder 7 are respectively connected to the e input terminal of the subtracter 10. terminal and θλ input terminal are connected. Adder 9 and subtracter 10
The output terminals of are connected to a right (R) channel speaker SpR and a left (L) channel speaker SQL, respectively.

In the above configuration, the output of the adder 3 of the comb filter F1 becomes 0 under the condition of the formula ωT = (2N+1)π, and reaches the maximum value under the condition of the formula ωT = 2Nπ (Realty 8 in Fig. 2 (a>)) .The output of the subtractor 4 is expressed by the formula ωT-(2N+l)π
It reaches its maximum value under the condition of ωT=2Nπ, and becomes O under the condition of the formula ωT=2Nπ (dashed line in FIG. 2(b)). Adder 7 of i-type filter F2. Similarly, the outputs of the subtractor 8 are shown by dotted lines in FIG. 2(b).

It will look like the broken line in FIG. 2(a).

The output of the adder 9 (R channel output) has a comb-shaped frequency distribution due to the 0° and 90' components, as shown in FIG. As shown in Figure (b), the 270° and 180° components form a comb-shaped frequency distribution.

As is clear from FIGS. 3(a) and 3(b), the R channel and L channel co-synthesized outputs have a flat frequency distribution. Also, FIGS. 3(a) and (b).

As shown in (C), each frequency component is either 90° out of phase or has an opposite phase (at a frequency where the amplitudes of 0° and 90' are equal, the phase is 45°, and 1800 and 27
At frequencies where the amplitude at 0° is equal, the phase is 225°, and the R channel and L channel have an opposite phase relationship. ).

As described above, in the above embodiment, the phase difference between the left ear signal and the right eye signal is 90° to 1800° at all frequencies, the correlation is small, and the sound image is expanded.

Incidentally, as shown in FIG. 3, a bipolar switch SW is provided before the above-mentioned subtracter 4, and by switching the bipolar switch SW, the phase of the output of the subtracter 4 becomes 180 and 00. In this case, the phase difference (LR) is -90° in the entire band. Similarly, if a bipolar switch SW is provided before the subtracter 8, the phase of 270° can be set to 90'.

Although the above embodiment has been described using a monaural audio signal as an input signal, when an AM receiver is used as a signal source, it can be combined with the circuit shown in FIG. 4.

The filter 11 in FIG. 4 has the characteristics shown in FIG.
Orthogonal audio signals with phases of 0° and 90' are obtained. The output of low pass filter (LPF) 14.15 is respectively,
The delay circuit 6, the adder 7, the subtracter 8, and the delay circuit 2. It is connected to an adder 3 and a subtracter 4.

The phase difference of the output signal of LPF14.15 is in the audible frequency band C
In the case of AM broadcasting, the phase difference between EL and ER (4011z to 9 KHz) is all 90'', but by combining the circuits shown in FIG. 1, the correlation becomes smaller over a wider frequency band and the sound image is expanded. Similarly, the spread of the sound image can be controlled by switching the switch SW shown in FIG.

(Effects of the Invention) As described above, according to the present invention, it is possible to obtain left and right channel signals with low correlation in all frequency bands, so a spread sound image can be realized, and the stereo effect is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a pseudo-stereo device according to the present invention, FIG. 2(a) is a graph of the right channel signal, FIG. 2(b) is a graph of the left channel signal, and FIG. C) is a graph showing the phase difference between left and right channel signals, FIG. 3 is a block diagram of main parts showing a modification of FIG. 1, FIG. 4 is a block diagram of another embodiment, and FIG. A graph showing the frequency characteristics of the filter, FIG. 6 is a block diagram of a conventional example, and FIG. 7 is a graph of left and right channel signals in FIG. 6. 1... Monaural audio signal input terminal, 2, 6... Delay circuit, 5... 90° phase shift circuit, 3.7.9... Addition circuit, 4.8.10... Subtraction circuit. Patent applicant Clarion Co., Ltd. agent Patent attorney Tetsuji Iwakura (and 1 other person) Figure 1 Figure 2

Claims (1)

[Claims] a first delay circuit that delays a monaural signal; a first addition circuit that adds the monaural signal and the delayed signal of the first delay circuit; and a first addition circuit that subtracts the monaural signal and the delayed signal of the first delay circuit. The first subtraction circuit and the monaural signal at 90°
a phase shifter for shifting the phase; a second delay circuit for delaying the signal of the phase shifter; and a second addition circuit for adding the signal of the phase shifter and the delayed signal of the second delay circuit. , a second subtraction circuit that subtracts the signal of the phase shifting means and the delayed signal of the second delay circuit; and a second subtraction circuit that adds the signal of the first addition circuit and the signal of the second subtraction circuit. and a third subtraction circuit that subtracts the signal of the first subtraction circuit and the second addition circuit, and a third subtraction circuit that subtracts the signal of the third addition circuit and the third subtraction circuit. A pseudo-stereo device characterized in that signals of a subtraction circuit are used as left and right channel signals.