JP2000037000A - Surround circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To configure a circuit that uses a front speaker by which a sound is obtained from behind a listener in a pseudo way with an analog circuit. SOLUTION: A pseudo stereo circuit 12 generates a reflection sound from behind a listener and a reverberation tone based on left and right audio input signals L, R and a pseudo arithmetic circuit 13 generate surround signals LS3, RS3 so as to reproduce the reflected sound and the reverberation sound from behind the listener only with front speakers 5, 6. The stereo pseudo signal to generate sounds from behind the listener is generated from the input audio signal and then one stereo pseudo signal whose phase, level or frequency characteristic is changed is added to the other stereo pseudo signal to obtain the surround effect using the two speakers, then the circuit configuration is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surround circuit for generating a surround effect using only two speakers.

[0002]

2. Description of the Related Art Heretofore, when watching a movie at home, two speakers are arranged before and after a listener,
Furthermore, by arranging the center speaker between the front left and right speakers, it was possible to enjoy the surround effect of being in a movie theater while staying at home. In recent years, DSP
(Digital signal processor),
The surround effect can be obtained only with the front left and right speakers without using five speakers as described above. Fig. 4 shows a surround circuit using a conventional DSP.
Shown in

In FIG. 4, left and right stereo signals L and R
And the surround signal S are input. The surround signal S is a signal for generating reflected sound and reverberant sound when the left and right stereo signals L and R are reflected or reverberated in a room such as a movie theater. From the surround signal S, a stereo circuit 1 outputs stereo signals L1 and R1.
Is generated by digital signal processing and applied to the adders 2 and 3 respectively. The stereo signals L1 and R1 are signals for generating reflected sound and reverberant sound. Also, the stereo signals L1 and R1 are input to the DSP 4,
After being converted into a digital signal in P4, signal processing for forming a sound field is performed so that sound can be heard from a speaker in front of the viewer from behind, and further converted back to an analog audio signal, and output signals LS1 and RS1 are added to an adder circuit. 2 and 3 respectively.

In the adder circuit 2, the left stereo signal L,
The stereo signal L1 and the signal RS1 are added, the added signal is applied to the left speaker 5, and the addition circuit 3 outputs the right stereo signal R, the stereo signal R1, and the signal LS.
Are added, and the added signal is applied to the right speaker 6. Therefore, a surround effect is formed by the left and right speakers 5 and 6 in addition to the left and right stereo sounds, the reverberation sound, the reflected sound, and the sound heard from behind the listener.

[0005]

However, the conventional circuit has a disadvantage that the reverberation sound, reverberation sound, and sound from the rear are all generated by digital signal processing, so that the circuit becomes complicated and expensive. is there. In addition, since the above-described reverberation sound and the like are generated based on the surround signal S, there is a disadvantage that a surround effect cannot be obtained in an acoustic system having no surround signal.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a surround circuit for generating a surround effect by two speakers installed in front of a listener, and to a listener based on left and right audio input signals. A pseudo-stereo circuit that generates left and right stereo pseudo signals to form reverberation and reflection from behind, and a sound field that is pseudo-emitted from behind the listener from the front speaker. A pseudo-arithmetic circuit for calculating the left and right stereo pseudo-signals to generate a left-right audio pseudo-signal, and a first and a second adder for respectively adding the left and right audio pseudo-signals and the left and right audio input signals from the pseudo-arithmetic circuit; It is characterized by having.

In particular, the pseudo operation circuit adds first and second signal processing circuits for respectively processing the characteristics of the left and right stereo pseudo signals, an output signal of the second signal processing circuit, and the left stereo pseudo signal. A third addition circuit for generating the left audio pseudo signal, and a fourth addition circuit for adding the output signal of the first signal processing circuit and the right stereo pseudo signal to generate the right audio pseudo signal. It is characterized by.

Further, the signal processing circuit performs a process of changing a frequency characteristic and a level while delaying.

The pseudo-stereo circuit includes a delay circuit for delaying a sum signal or a difference signal of the left and right audio signals, an attenuation circuit for attenuating the sum signal or the difference signal, an output signal of the delay circuit, and an output signal of the delay circuit. It is characterized by comprising a first addition circuit for adding an inverted signal of the output, and a second addition circuit for adding the output signal of the delay circuit and the output signal of the attenuation circuit.

According to the present invention, a left and right stereo pseudo signal for forming a reflected sound or a reverberant sound is generated from a left and right audio input signal, and a left and right audio pseudo signal is generated by calculating the left and right stereo pseudo signal. It is possible to form a sound field as if the sound is sounding from behind the listener.

[0011]

FIG. 1 is a diagram showing an embodiment of the present invention. Reference numeral 10 denotes a pseudo-stereo circuit for generating stereo pseudo signals LS2 and RS2 based on left and right audio input signals L and R, and reference numeral 11 denotes a stereo pseudo circuit. A pseudo operation circuit that generates the surround signals LS3 and RS3 by calculating the signals LS and RS, 12 is an adder that adds the left audio input signal L and the surround signal LS3, and 13 is a adder that generates the left audio input signal R and the surround signal RS3. It is an adding circuit for adding.

In FIG. 1, the left and right audio input signals L
And R generate pseudo left and right stereo signals LS2 and LS3 in the pseudo stereo circuit 10 so that the listener can hear the sound spread like a stereo. Further, the left and right stereo pseudo signals LS2 and LS3 are further operated by the pseudo operation circuit 11. Then, the calculation is performed so that the listener can hear the sound spread to the rear from the speakers 5 and 6 disposed in front of the listener. The surround signals LS3 and RS3 from the pseudo operation circuit 11 are applied to addition circuits 12 and 13, respectively, and added to the left and right audio input signals, respectively. Adder circuits 12 and 1
The speakers 5 and 6 are driven by the output signal of 3, and a sound having a surround effect is generated for the listener.

FIG. 2 is a diagram showing a specific circuit of the pseudo operation circuit of FIG. 1. Reference numeral 20 denotes a first delay circuit for delaying the left stereo pseudo signal LS2, and reference numeral 21 denotes a second delay circuit for delaying the right stereo pseudo signal RS2. , 22 are a first LPF that passes only the low-frequency component of the output signal of the first delay circuit 20, 23 is a second LPF that passes only the low-frequency component of the output signal of the second delay circuit 21, and 24 is an output signal of the first LPF 22. A damping circuit for attenuating the output signal of the second LPF; 26, an adding circuit for adding the left stereo pseudo signal LS2 and the output signal RS4 of the second attenuating circuit 25; Stereo pseudo signal RS2 and first attenuation circuit 2
4 is an addition circuit for adding the output signal LS4.

In FIG. 2, the left stereo pseudo signal LS2
Is delayed, allowing only the low-frequency components to pass through,
After attenuating, the right stereo pseudo signal RS2
Is added. Therefore, in the surround signal RS3,
A left stereo pseudo signal LS2 delayed by using the right stereo pseudo signal RS2 as a main signal is included. Further, the right stereo pseudo signal RS2 is delayed, a low-frequency component thereof is passed therethrough, attenuated, and then added to the left stereo pseudo signal LS2 by the adding circuit 27. Therefore, the surround signal LS3 includes the right stereo pseudo signal RS2 delayed by using the left stereo pseudo signal LS2 as a main signal. Due to the delay, the left and right stereo pseudo signals are
It is applied to both the left and right speakers 5 and 6 with a time difference.

When the same signal is generated by the same signal from the speakers 5 and 6, the sound is localized in the middle of the speakers 5 and 6. Here, by adding each of the stereo pseudo signals, the surround signal LS of FIG.
Since the signals 4 and RS4 are not the same signal, the sound is not localized between the speakers 5 and 6 by the surround signal. In addition, when looking at the left stereo pseudo signal LS2, a sound related to the stereo pseudo signal LS is generated from the speaker 6 after a predetermined time delay after the sound is generated from the speaker 5. Also, the right stereo pseudo signal RS2 is emitted from the speaker 5 with a delay after being emitted from the speaker 6. Therefore, by the circuit of FIG. 2, the left and right stereo pseudo signals have different times to reach the listener from the left and right speakers 5 and 6, respectively, and the delayed left and right stereo pseudo signals are output from the left and right opposite speakers. Therefore, it is possible to form a sound field such that sound is generated from the front by the front speaker.

The surround signals LS3 and RS3
Is output from the left and right speakers 5 and 6 together with the left and right audio input signals, and a surround effect is obtained.

FIG. 3 is a diagram showing a specific circuit of the pseudo stereo circuit 12, and reference numeral 30 denotes a left and right audio input signal L.
And a subtraction circuit 31 for subtracting the left and right audio input signals L and R, and 32 and 33 a first circuit for selecting an output signal of the addition circuit 30 or the subtraction circuit 31.
A second selection circuit; 34, a delay circuit for delaying the output signal of the first selection circuit 32; 35, an attenuation circuit for attenuating the output signal level of the second selection circuit 33; 36, an output signal of the attenuation circuit 35; An inverter 37 is an addition circuit that adds the output signal of the delay circuit 34 and the output signal of the inverter 36, and 38 is an addition circuit that adds the output signal of the delay circuit 24 and the output signal of the attenuation circuit 35.

In the adding circuit 30 of FIG. 3, the left and right audio signals L and R are added to generate a signal (L + R). Further, in the subtraction circuit 31, the left and right audio signals L and R are subtracted to generate a signal (LR). One of the signal (L + R) or the signal (LR) is the first
After being selected by the second selection circuits 32 and 33, the output signal of the first selection circuit 32 is delayed by a predetermined time by the delay circuit 34, and the output signal of the second selection circuit 33 is attenuated by the attenuation circuit 35. You.

Then, in the adders 37 and 38,
Using the output signal of the delay circuit 34 as a main signal, the attenuated signal (L + R) or (LR) and its inverted signal are added to the main signal. As a result of the addition, left and right stereo pseudo signals LS2 and RS2 are obtained.

Here, in order to understand the operation, it is assumed that a rear speaker that is not originally arranged is arranged, and the left and right stereo pseudo signals LS2 and RS2 are applied to the rear speaker. Since the main signal is a signal obtained by delaying the left and right audio input signals, the same sound is emitted from the rear speaker after the sound is emitted from the front speaker. Therefore, the reflected sound from behind the listener can be reproduced from the left and right audio input signals. Also, the delay circuit 3
4 is added to the output signal of the attenuation circuit 35 and the inverted signal thereof, so that the same sound is not generated from the rear left and right speakers, and the addition circuit 3
The levels and phases of the output signals of 7 and 38 vary differently. As a result, sound from the rear speakers can be prevented from being localized between the rear speakers. Thus, the circuit of FIG. 3 can reproduce the reverberation sound from behind the listener, and can form the sound field behind the listener by reproducing the reflected sound and the reverberation sound.

Therefore, with the circuit of FIG. 3, it is possible to generate a stereo pseudo signal capable of reproducing the sound from behind the listener in a pseudo manner from the left and right audio input signals.

As described above, the stereo pseudo signal capable of forming the sound field behind the listener is further subjected to surround arithmetic processing by the pseudo arithmetic circuit 11, so that only the front speakers 5 and 6 can be used. Can be reproduced.

[0023]

According to the present invention, a stereo pseudo signal for generating a sound from the rear of a listener is generated from an input audio signal, and a phase of one of the stereo pseudo signals is added to the phase of another stereo pseudo signal. , Or the level or frequency characteristics are changed to obtain the surround effect of the two speakers, so that the circuit configuration can be simplified. Therefore, even if a DSP is not used, an analog circuit or Bi-
A CMOS circuit can also be used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a circuit example showing a specific circuit of a pseudo operation circuit 13 of FIG.

FIG. 3 is a circuit example showing a specific circuit of the pseudo stereo circuit 12 of FIG. 1;

FIG. 4 is a block diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 10 pseudo stereo circuit 11 pseudo operation circuit 20, 21, 34 delay circuit 22, 23 LPF 32, 33 selection circuit 35 attenuation circuit 36 inverter

Claims (4)

[Claims] 1. A surround circuit for generating a surround effect by two speakers installed in front of a listener, wherein a reverberation sound or reflection from a rear side to a listener based on left and right audio input signals. A pseudo-stereo circuit for generating left and right stereo pseudo signals to form a sound, and the left and right stereo pseudo signals so as to form a sound field that is pseudo-emitted from the rear of the listener from the front speaker. A surround circuit, comprising: a pseudo operation circuit for calculating and generating a left and right audio pseudo signal; and first and second addition circuits for respectively adding the left and right audio pseudo signals and the left and right audio input signals from the pseudo operation circuit. . 2. The pseudo arithmetic circuit according to claim 1, further comprising: first and second signal processing circuits for processing characteristics of the left and right stereo pseudo signals, and an output signal of the second signal processing circuit and the left stereo pseudo signal. A third addition circuit for generating the left audio pseudo signal, and a fourth addition circuit for adding the output signal of the first signal processing circuit and the right stereo pseudo signal to generate the right audio pseudo signal. The surround circuit according to claim 1, wherein: 3. The signal processing circuit delays,
3. The surround circuit according to claim 2, wherein a process for changing a frequency characteristic and a level is performed. 4. A pseudo-stereo circuit comprising: a delay circuit for delaying a sum signal or a difference signal between left and right audio signals; an attenuation circuit for attenuating the sum signal or the difference signal; 3. The circuit according to claim 1, further comprising: a first adding circuit for adding an inverted output signal; and a second adding circuit for adding an output signal of the delay circuit and an output signal of the attenuation circuit. Surround circuit.