JP2984718B2 - 3D sound generation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a three-dimensional stereophonic sound generation system for generating a synthetic stereo signal from a single sound source.

[0002]

2. Description of the Related Art In recent years, various systems such as three-dimensional stereoscopic images and three-dimensional graphic images have been put into practical use, and there is a feeling that the dawn of the multimedia era has begun. Along with this, as another important element of this media, similar to the three-dimensional image,
There has been a demand for three-dimensional sound.

A conventional method for realizing a three-dimensional sound is a four-channel method in which sound is reproduced by four speakers arranged in front, rear, left and right on the basis of four different channel signals, and a Dolby surround method. ,
2. Description of the Related Art There has been widely used a method of achieving a three-dimensional sound with a five-speaker system (modified four-channel system) including three speakers installed at the left, right, and center of a front position and two speakers installed at a rear position.

By the way, as a method of three-dimensional stereophonic sound by a two-speaker system, a left and right stereo signal (R) (L) is combined with a sum or a difference to create a synthesized sound source signal, and the synthesized sound source signal has a frequency of a sound spreading element. The SRS (Sound Retrieval Syestem) method that expands the stereo point of the sound field by applying filter processing with characteristics is 1).
U.S. Pat. No. 4,786,669, 2) U.S. Pat. No. 48
No. 41572, 3) U.S. Pat. No. 4,866,774.

[0005] The SRS system is based on a method of generating ergonomics in which a physiological function (relative phase, relative intensity, relative time and frequency characteristics of a sound source reaching both ears) by which a human distinguishes sounds is replaced by an electrically similar function. Things. According to the technique presented in the above 1), when the relationship between the frequency dependence of sound and the azimuth is given a frequency characteristic of relative intensity with respect to the sound field signal, the auditory sensation in the human ear and brain can be improved. This makes it possible to realize a three-dimensional sound. Further, according to the technique presented in the above 2), when the same left and right monaural signals are used as sound source signals, a three-dimensional stereoscopic sound field is formed by adding a temporal phase difference between the left and right signals. Can be created. This is what is called a three-dimensional 3D monostereo, and can be practically used together with the SRS3D stereo described in 1) above.

In the three-dimensional 3D mono-stereo means, Hilbert transform is performed to generate left and right signals (R, L) for stereo reproduction from a monaural signal. Thus, two signals (LR) having a phase difference of 90 ° C.
(L + R) is obtained (refer to FIG. 4.) A filter (B) for reinforcing the sound spread in the frequency B (intermediate frequency region) of the two signals (LR) (L + R) having a phase difference in the entire frequency band. Since the influence of the low and high frequency regions is small, the left and right output signals (R ′, L ′) can be obtained as a preferred sound field signal synthesized as shown in the vector diagram of FIG. In a region where the phase difference between the signal (LR) and the signal (L + R) disappears at the frequency A (low frequency region), the output signal (R ', L') is 180 ° C. as shown in FIG.
Since they cancel each other out as a phase difference, it becomes difficult to hear bass sounds. In the other SRS3D stereo means, since the in-phase component is large in the low frequency area, the difference signal in this area is not so large. However, in the 3D monostereo means, the difference signal (LR) 'in this area is as described above. The bass sound was emphasized because it did not decrease in a natural way as in the case of a stereo signal.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to develop a 3D monostereo system having a more realistic effect by eliminating the unnatural emphasis of the reproduced bass in the 3D 3D monostereo as described above.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a three-dimensional 3D mono-stereo system.
Hilbert transformed left and right signal with phase difference
Processing is basically performed as input signal processing for the D stereo system.

[0009]

For this purpose, in the present invention, two signals separated from a monaural signal are used as input signals for stereo reproduction, and an output signal obtained by Hilbert transforming these input signals in the entire frequency domain is used as a difference between left and right signals. And a re-processing through a 3D stereo system reproduced by a combination processing of the sum signal and the sum signal. Left and right signals having a certain phase difference in all frequency domains are Hilbert-transformed to suppress abnormal emphasis in a low frequency domain in the frequency domain. The output of the Hilbert transform circuit is placed before the 3D stereo system circuit.

[0010]

FIG. 1 is a block diagram showing an embodiment of the system of the present invention. An input signal M consisting of a single monaural signal is supplied to a Hilbert transform circuit HC as a sound source signal.
The circuit HC outputs left and right output signals (L ″, R ″) having a phase difference of 90 ° C. from each other. This pre-processing circuit is the same as the configuration of the part in the 3D mono-stereo system presented above. The left and right output signals (L ″,
R ″) is the above-mentioned S including a sum and difference generating circuit SD, a high / low frequency band emphasizing filter FR, a mixer MX, and the like.
By inputting to the RS3D stereo system circuit, left and right 3D monostereo output signals (L ′, R ′) are obtained.

FIG. 2 shows the frequency characteristic of the phase difference between the left and right signals in the above-described embodiment circuit, and FIG.

[0012]

As described above, according to the present invention, in the 3D monostereo system, the Hilbert-transformed left and right signals are reprocessed as input signals of the SRS3D stereo system. By suppressing abnormal bass emphasis in the low frequency range of the case, it is possible to realize a full-fledged 3D mono-stereo sound with less sensation of fatigue in a situation closer to nature with excellent audibility.

[Brief description of the drawings]

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

FIG. 2 is a graph showing a frequency characteristic of a phase difference between left and right signals in the embodiment shown in FIG. 1;

FIG. 3 is a graph showing frequency characteristics of the amplification degree in the difference signal.

FIG. 4 is a graph showing a frequency characteristic of a phase difference in a sum and difference signal in a conventional 3D monostereo system.

FIG. 5 is a composite vector diagram of an intermediate frequency band of left and right signals in a conventional 3D monostereo system.

FIG. 6 is a vector diagram in a low frequency band of left and right signals in a conventional 3D monostereo system.

[Description of Signs] M Monaural input signal HC Hilbert conversion circuit L ", R" Left / right output signal L ', R' 3D monostereo output signal SD Sum and difference generation circuit FR High / low frequency band MX mixer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-295175 (JP, A) JP-A-7-288897 (JP, A) JP-A-2-53700 (JP, A) 21530 (JP, B1) JP 49-42323 (JP, B1) JP-T3-505030 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04S 1/00-7 / 00

Claims (3)

(57) [Claims] A left and right signal composed of a single monaural signal is used as an input signal for stereo reproduction, and an output signal obtained by Hilbert transforming these input signals in the entire frequency domain is combined with a difference signal and a sum signal of sound source signals. Reprocessing through a 3D stereo system reproduced by
3D sound generation system. 2. The system according to claim 1, wherein the left and right signals having a constant phase difference in all frequency domains are Hilbert-transformed to suppress abnormal emphasis in a low frequency domain in the frequency domain. 3D sound generation system. 3. The three-dimensional stereophonic sound generating system according to claim 1, wherein an output of the Hilbert transform circuit is provided before the 3D stereo system circuit.