JPS5814798B2 - 3D sound field expansion device - Google Patents

Description

Detailed Description of the Invention Normally, when a three-dimensional reproduction sound field (stereo sound field) is formed and listened to by two speakers (reproduction sound sources), the sound image is localized within a plane surrounded by the two speakers. However, the listener cannot be made to feel that the sound image is localized to the outside of the two speakers.

Therefore, if the distance between two speakers arranged to form a stereo sound field cannot be widened for some reason, for example, due to the condition of the listening room,
Alternatively, if speakers are built into a stereo playback device, the range of sound image localization in the stereo sound field formed by the two speakers will be narrow. If it is possible to localize the sound image outside the position of the speakers actually placed in the space, the listener in the playback sound field will be able to experience an expanded three-dimensional sound feeling that is greater than the three-dimensional sound sensation that should be obtained due to the actual speaker arrangement. Because it is convenient to be able to get a sense of pitch, three-dimensional sound can be created by applying the same method used in sound image localization devices to each channel signal of a two-channel stereo system. Attempts have been made to expand the field, and as an application example of a sound image localization device, the applicant's company uses the signals of each channel in a two-channel stereo signal as separate input signals, and , a sound image localization setting circuit portion consisting of two sets of signal converters that convert these signals into signals such that the sound image is localized in the direction that the listener intends to localize; The above-mentioned method is configured such that a signal having a signal form similar to the output signal from the sound image localization setting circuit section is given as a binaural signal to a listener in a reproduction sound field formed by a plurality of speakers arranged in the space. A three-dimensional structure having a configuration in which a circuit section for converting an output signal from a sound image localization setting circuit section into a signal in a signal form in which crosstalk that should occur in the reproduction sound field is canceled in advance is connected in cascade. We proposed a sound field expansion device.

FIG. 1 is a block diagram of an embodiment of the three-dimensional sound field expansion device immediately proposed by the above-mentioned applicant company. In FIG. 1, 1 and 2 are two-channel stereo type An input terminal to which each channel signal is individually applied, SX is a sound image localization setting circuit section SX1, and a circuit section SX2 for eliminating crosstalk occurring in the reproduction sound field in advance, hereinafter referred to as a crosstalk removal circuit section SX2. ), 3 and 4 are output terminals.

The sound image localization setting circuit section SX1 is configured to localize the sound image in the direction in which the listener intends to localize each channel signal individually input to the input terminals 1 and 2. The signal conversion circuit 5 includes two sets of signal conversion circuits 5 and 6 that convert the signal into a signal (pinaural signal), and the signal conversion circuit 5 includes blocks 7 to 9 and 11, and a signal conversion circuit 6. is block 8,10
It is composed of 12 parts.

In each of the blocks described above, blocks 8 and 11 are adders, and blocks 7 and 10 are Sai in FIG.
．． Among the transfer characteristics Ai, Bi between both ears of the listener M and the virtual sound sources Sai, Sbi in the virtual sound field formed by the virtual sound sources denoted by Sbi, the virtual one between each ear of the listener M and the one near it is The circuit has a characteristic Ai corresponding to a transfer characteristic Ai between the blocks 9 and 12, and the blocks 9 and 12 are configured to calculate the interaural difference between both ears of the listener M in the virtual sound field, that is, the interaural difference between the listener M's both ears in the virtual sound field. The circuit has characteristics (Bi/Ai) corresponding to the ratio of transfer characteristics (Bi/Ai) between the ear and the virtual sound sources Sai and Sbi, and the circuits 7, 10, and 10 have the characteristics as described above. 9, 12, etc. are each constructed of a filter having a required frequency response characteristic, a delay circuit (phase shift circuit) having a required time delay characteristic, and the like.

In the above-mentioned FIG. 2, Sa and Sb are two speakers (
(playback sound source), and A and B in the figure are two speakers Sa.
, Sb and the listener's ears in the reproduction sound field.

The signal conversion circuit 5 shown in block 5 in FIG. Convert it into a signal (pinaural signal) in which the sound image is localized in the intended direction, for example in the direction of the pseudophase sound source Sai in Figure 2, and remove crosstalk. Circuit part SX2
In addition, a signal conversion circuit 6 shown as a block 6 converts the input signal (the other channel signal of the 2-channel stereo signal) supplied to the input terminal 2 into a signal that the listener wants to localize within the reproduction sound field. The signal is converted into a signal (pinaural signal) in which the sound image is localized in the intended direction, and is applied to the crosstalk removal circuit section SX2.

The crosstalk removal circuit portion SX2 includes subtracters 14 and 18
, blocks 13, 16, 15, 17, etc. each having characteristics as shown in the figure.

Note that A and B in FIG. 1 correspond to A and B in FIG. 2, which indicate the transfer characteristics between both ears of the listener M in the reproduction sound field and the reproduction sound sources Sa and sb, and T indicates a delay.

The previously proposed three-dimensional sound field expansion device SX having the configuration shown in the first diagram described above has output signals Lsp and R to two speakers Sa and Sb that form a reproduced sound field from the output terminals 3 and 4.
sp, it is possible to give the listener M a three-dimensional sound sensation that makes him feel a sound image localized outside the speakers Sa and Sb.Next, the three-dimensional sound field expansion device shown in the first figure , the fact that the above operations can be performed will be explained in more detail.

The three-dimensional sound field enlarging device SX shown in FIG. Since it is determined based on the transmission characteristics between the listener's ears, the human input signals supplied to input terminals 1 and 2 are now Lspi and Rspi, and the output signals appearing at output terminals 3 and 4 are Lsp and Rsp. Assuming that, the relationship between the input and output signals of the three-dimensional sound field expansion device shown in FIG. 1 is determined by the following equation (1).

By the way, the listener M's binaural signals Re, Le in the reproduction sound field
Since the relationship of equation (2) above holds between the signals Rsp and Lsp of speakers Sb and Sa, the above (1),
From equation (2), equation (3) is obtained.

Transforming equation (3) using the relationship in equation (4), we get the following (
5) Equation is obtained.

The above equation (5) is calculated when the binaural signals obtained by both ears of the listener M in the virtual sound field and the output signals Rsp, Lsp of the circuit arrangement shown in Figure 1 are applied to the narrowly arranged speakers Sb, Sa. This shows that the binaural signals obtained by both ears of the listener M are equal, and therefore it can be seen that the circuit arrangement having the configuration shown in the first figure operates as a three-dimensional sound field enlarging device.

However, the sound image localization means in a sound image localization device originally converts an independent signal that does not have localization information (for example, even an individual channel signal in a monaural signal or a stereo signal) into other channel signals. The transmission characteristics between the intended sound source position and the listener's ears, as well as the relationship between the speakers and the listener's ears in the playback sound field. By deforming according to the transfer characteristics between Therefore, regarding the above-described three-dimensional sound field enlarging device, if it operates according to the original operating mode of the above-mentioned sound image localization device, that is, the input signal to the three-dimensional sound field enlarging device is input to one of the input terminals 1 and 2. What happens when only one of the two channel signals is input (a state where only one channel signal of the two channel stereo signals is supplied as an input signal to the 3D sound field expansion device)? Although good stereo sound field expansion can be performed without any problems, stereo signals that include localization information in relation to the mutual signal contents are input to the input terminals 1 and 2 of the 3D sound field expansion device. When each channel signal is inputted, the sound quality of the reproduced sound changes depending on the localization direction of the sound image, giving rise to an undesirable result that an unnatural sound sensation is given to the listener.

This is because, as mentioned above, the sound image localization means in a sound image localization device is based on the assumption that an independent signal without localization information is used as the original signal, but in a three-dimensional sound field expansion device, This is because the sound image localization means is applied to two signals that each contain localization information in relation to the signal contents as the original signals.

When the above-described conventional device shown in the first figure is used as a three-dimensional sound field expansion device, and two signals containing localization information in relation to the signal contents are used as input signals, the original signals are as follows. A change in sound quality occurs in the reproduced sound depending on the direction of sound image localization, but the change in sound quality that occurs at this time occurs when signals of the same phase and level are input to input terminals 1 and 2, that is, when the signal is in front of the listener. This is most noticeable when a signal that localizes a sound image is input, but in general, a sound image that is localized in front of the listener, such as the voice of a singer,
In other words, since the sound image localized at the center is considered most important when playing music, the sound quality of the sound image localized at the center of the reproduction sound field is as if it were a sound image, as in the conventional three-dimensional sound field expansion device described above. It is undesirable for the sound quality to change as if it were localized at a position offset from the center because it would give an unnatural feeling to the listener.

A more specific explanation of this point is as follows.

Now, if the input signals Rspi and Lspi respectively supplied to the input terminals 2 and 1 of the three-dimensional sound field enlarging device SX having the configuration shown in the first diagram are signals S of the same phase and the same level, that is, , When Rspi=Lspi=S, the three-dimensional sound field expansion device S
Output signal Rsp output to output terminals 4 and 3 of X
, Lsp are expressed as in the following equation (6).

Considering the sound quality (frequency amplitude characteristics) of the reproduced sound from equation (6) above, in equation A(6), T is a time delay, so T has a flat frequency response characteristic, but (6 ), (A+B) and (Ai+Bi), etc., represent transfer characteristics A, B, Ai, etc. with time differences from each other, respectively.
Since it shows the sum of Bi, these (A+B
), (Ai+Bi), etc. each indicate different characteristics of the comb filter.

Therefore, when input signals S of the same phase and level are simultaneously supplied to the input terminals 2 and 1 of the conventional stereoscopic sound field enlarging device SX, the output signal is a ratio of the input signal S to two different comb filter characteristics. Therefore, the output from the 3D sound field expansion device SX when the signals S of the same phase and the same level are simultaneously supplied to the input terminals 2 and 1 of the 3D sound field expansion device SX. Signal Rsp=Ls
It is clear that p has a significantly degraded sound quality.

The present invention takes a two-channel stereo signal as input, and allows a listener in a reproduction sound field formed by a plurality of speakers to experience a three-dimensional sound sensation that is more expanded than the three-dimensional sound sensation that should be obtained due to the actual arrangement of the speakers. Three-dimensional sound field expansion configured by cascadingly connecting a circuit section for setting sound image localization and a circuit section for eliminating crosstalk occurring in the reproduction sound field in advance so as to output the signal that can be obtained. When the device is in a state where only one channel of a two-channel stereo signal is supplied as an input signal, if a sound source exists in the direction that the listener intends to localize, In order to output an output signal that has an interaural difference that is approximately equal to the interaural difference obtained at both ears of the listener in the playback sound field, the in-phase and the same level In order to output an output signal equal to the input signal when two channel signals are simultaneously supplied as input signals, a sound image localization setting circuit section and a circuit for eliminating crosstalk occurring within the reproduction sound field are provided. Including parts and
The present invention provides a three-dimensional sound field expansion device in which the problems of the conventional example described above are satisfactorily resolved by determining the overall transfer characteristics between the output terminals, the contents of which will be explained in detail below. .

FIG. 3 is a block diagram of an embodiment of the three-dimensional sound field enlarging device SXx of the present invention, and in FIG.
, 2 are input terminals, 3a and 4a are output terminals, and SX is a circuit portion having the same configuration as the circuit layout indicated by the symbol SX in FIG. This is a compensation circuit having frequency and amplitude characteristics equal to the frequency and amplitude characteristics.

The above-mentioned compensation circuits 19 and 20 may be, for example, resonant sound quality adjustment circuits (so-called SE announced by the applicant's company) each configured to correspond to a large number of different frequency ranges.
(Circuit A) may be configured so that at least only the frequency amplitude characteristics of the characteristics of can be compensated for, or the characteristics included in the time domain of the characteristics of can also be compensated for.
The compensating circuits 19 and 20 may be configured with a "convolution integrating circuit" such as a transversal filter that provides the impulse response that should be provided when performing the original compensation operation.

In the three-dimensional sound field enlarging device SXx according to the embodiment of the present invention shown in the third diagram described above, the input/output characteristics when in-phase and same-level signals S are applied to the input terminals 2 and 1 are as follows (6) The formula is multiplied by the characteristics of the compensation circuits 19 and 20 described above, that is, Rsp=Lsp=T・S...
・(7) Since it is expressed by the above equation (7), it can be concluded that the problems of the conventional one described above are well solved by the structure shown in the third diagram. I understand.

It should be noted that the three-dimensional sound field expansion device shown in FIG. 3 also has the same binaural difference characteristics as the conventional example.

FIG. 4 is a block diagram of another embodiment of the three-dimensional sound field enlarging device SXx of the present invention.

The 3D sound field enlarging device SXx shown in the fourth diagram is configured to include a sound image localization setting circuit portion SX1x and a crosstalk removal circuit portion SX2x which are connected in series to constitute the 3D sound field enlarging device SXx. , each part SX1,
Transfer characteristics Ai, Bi, A, which were originally provided to SX2,
A sound field expansion device in which the overall circuit configuration is simplified by sharing the transfer characteristics Ai, Bi, A, and B necessary for obtaining the compensation characteristics described above, and which also has the required characteristics. It is designed so that it can be obtained.

That is, the three-dimensional sound field expansion device SXx of the present invention shown in FIG.
Now, blocks 9 and 12 of the sound image localization setting circuit portion SX1 in the conventional three-dimensional sound field expansion device SX shown in FIG.
Using the characteristics (Bi/Ai) of 1, create the characteristics in the sound image localization setting circuit section SX1x to perform compensation, and also create the characteristics (B/Ai) of blocks 15 and 17 of the crosstalk removal circuit section SX2.
By using A) and performing compensation by creating the (A+B) characteristic in the crosstalk removal circuit part SX2x, the stereophonic sound field expansion device SX can be compensated by the compensation characteristic comprehensively between the input and output terminals. The three-dimensional sound field enlarging device SXx of the present invention is configured as given in FIG.

In FIG. 4, 21, 22, 29, 30 are bathopher amplifiers, 25, 26, 33, 34 are subtracters, 27, 28,
35 and 36 are adders, and 23 and 24 are (Bi
/Ai), 31 and 32 are (B/A)
This is a circuit equipped with an am-t.

The relationship between the input signals Lspi, Rspi and the output signals Lsp, Rsp of the three-dimensional sound field enlarging device having the configuration shown in FIG. 4 is expressed by the following equation (8).

Therefore, when the in-phase and same-level signals S=Lspi=Rspi are simultaneously supplied to the input terminals 1 and 2, the output signals appearing at the output terminals 3a and 4a are equal to the input signal S as shown in the following equation (9). Become something.

Therefore, in the stereoscopic sound field expansion device SXx shown in FIG. 4 in a state where signals of the same phase and the same level are supplied to the input terminals 1 and 2, the input signal and the output signal are equal, that is, the transfer function between the input and output terminals is is 1, the frequency amplitude characteristic is flat, and the quality of the reproduced sound is not impaired at all.

Note that the signal processing between input and output in the stereophonic sound field enlarging device shown in the fourth diagram is performed according to the above-mentioned formula (8), and the signal processing in the stereophonic sound field enlarging device shown in the first diagram is performed according to the formula (1) described above. Signal processing between input and output is performed by combining the same matrix as shown in the following equation with other coefficients, so even if we look at the input signal of only one channel in both of the above devices, , it is clear that both give signals of the same relationship to both ears of the listener, and it is clear that the three-dimensional sound field enlarging device of the present invention does not impair the localization of the sound image.

When the three-dimensional sound field enlarging device of the present invention is constructed as in the embodiment shown in FIG. 4, the circuits shown by blocks 7, 10, 13, 16, etc. in the conventional example shown in FIG. , the circuit configuration is simplified and the device can be manufactured at low cost.

In other words, the circuits such as blocks 7, 10, 13, and 16 that Maeyoshi introduced are constructed by a combination of filters with required characteristics and/or delay circuits with required delay times. The fact that the circuit part is unnecessary is a very big advantage in terms of manufacturing configuration.

In the case of the circuit arrangement shown in the fourth figure, the number of circuits such as adders and subtracters is increased compared to the circuit arrangement shown in the first figure, but this point may be due to configuration, cost, or other reasons. From this point of view, it does not cause any problems.

As is clear from the above detailed explanation, the three-dimensional sound field expansion device of the present invention has an extremely simple configuration and can be localized to the central part of the reproduced sound field, which has been a problem with the conventional device described above. Deterioration of the sound quality in the sound image is completely prevented, and an enlarged three-dimensional sound feeling can be given to the listener without impairing the natural feeling.

In other words, in the device of the present invention, as in a program source in which a singer sings in the center, the most important voice of the singer in the center is made natural, and the sound quality of sound images localized outside the center becomes unnatural. Since the listener feels that the sound quality of the sound image localized in the center is the same as when the singer is actually singing in the center, changes in the sound quality of the sound image localized outside the center are not as noticeable as on the left. It is possible to provide the listener with an expanded sense of three-dimensional sound without impairing the sense of naturalness.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the three-dimensional sound field expansion device proposed previously.
FIG. 2 is an explanatory diagram of the transfer characteristics between a sound source and both ears of a listener in a virtual sound field and a reproduced sound field, and FIGS. 3 and 4 show different embodiments of the three-dimensional sound field expansion device according to the present invention. FIG. SX, SXx...Stereoscopic sound field expansion device, SX1,
SX1x...Sound image localization setting circuit part, SX2
, SX2x...Crosstalk removal circuit part, 1
, 2... Input terminal, 3, 4, 3a, 4a...
...Output terminal, 5, 6...Signal conversion circuit, 8
, 11, 27, 28, 35, 36...adder,
14, 18, 25, 26, 33, 34... Subtractor, 7, 9, 10, 13, 16, 19, 20, 23, 2
4, 31, 32...Circuit with required characteristics,
21, 22, 29, 30... buffer amplifier,
M...listener, Sa, Sb...speaker, Sai, Sbi...virtual sound source.

Claims (1)

[Claims] 1. With a two-channel stereo signal as input, the listener in the reproduction sound field formed by multiple speakers can obtain a three-dimensional sound sensation that is more expanded than the one that should be obtained due to the actual speaker arrangement. In a three-dimensional sound field expansion device configured by cascadingly connecting a circuit section for setting sound image localization and a circuit section for preliminarily removing crosstalk occurring within a reproduction sound field, so as to output a signal that allows When only one channel of a two-channel stereo signal is supplied as an input signal, if a sound source exists in the direction that the listener intends to localize, the listener's In order to output an output signal with a binaural difference that is approximately equal to the binaural difference obtained in both ears of the listener in the playback sound field, two-channel signals of the same phase and level are used. is simultaneously supplied as an input signal, so that an output signal equal to the input signal is output.
A three-dimensional sound field expansion device characterized in that a comprehensive transfer characteristic between input and output terminals is determined, including a circuit section for setting sound image localization and a circuit section for preliminarily removing crosstalk occurring within a reproduction sound field.