JP7160312B2 - sound system - Google Patents

Description

The present invention relates to sound systems, and more particularly to sound systems for multi-channel sound.

Conventionally, an audio system for multi-channel audio is known (see Non-Patent Document 1, for example).

Non-Patent Document 1 above discloses an audio system for multi-channel audio such as 2ch stereo and 5.1ch surround. In addition, this non-patent document 1 discloses controlling the azimuth of the virtual sound source from the listener by amplitude panning. Here, the amplitude panning is to change the sound image localization by giving an amplitude difference to the sound output from the speaker. Also, although not clearly described in this non-patent document 1, it is believed that the acoustic system is composed of a plurality of dynamic speakers. Here, the dynamic speaker is a speaker that is generally used as an audio device, and refers to a speaker of a dynamic drive system that is driven by a magnet, a coil, or the like.

Kazuho Ono, "Chapter 2 Multichannel Audio", Journal of the Institute of Image Information and Television Engineers, 2014, Vol. 68, No. 8, p. 604-607

However, in the acoustic system described in Non-Patent Document 1, although the azimuth of the virtual sound source from the listener can be changed in the horizontal direction, the distance of the virtual sound source from the listener cannot be changed. . The direct-to-direct ratio of the impulse response is a clue (index) for the sense of distance to the virtual sound source. Perceived, loudspeakers with a large direct-to-direct ratio will perceive the virtual source to be close to the listener. A dynamic speaker is a speaker with a small direct-to-direct ratio, and when amplitude panning is performed only with a dynamic speaker, it is possible to recognize that a virtual sound source exists at a position far from the listener and change the distance between the listener and the virtual sound source. It is thought that there is a problem that it is difficult.

The present invention has been made to solve the above problems, and one object of the present invention is to provide an acoustic system capable of changing the distance between the listener and the virtual sound source. be.

A sound system according to one aspect of the present invention is a sound system for multi-channel sound, and includes a dynamic speaker, a super-directional speaker, and a controller, wherein the controller controls sound output from the dynamic speaker, And, by controlling the sound output from the super-directional speaker by amplitude panning, the distance from the listener of the virtual sound source is controlled , and the control unit adjusts the position of the acoustic center of gravity of the two dynamic speakers to L and Let R be the position of the acoustic center of gravity of the super-directional speaker assumed to be the listener's position, O be the position of the virtual sound source, P be the position of the virtual sound source, La be the intersection of the straight line passing through the positions L and P and the line segment OR, Let Ra be the intersection of the straight line passing through the positions R and P and the line segment OL, and let Oa be the intersection of the straight line passing through the positions O and P and the line segment LR. Based on the length ratio of the line segment PLa, the gain coefficient for the input signal of the dynamic speaker at position L is obtained, and based on the length ratio of the line segment PRa to the length of the line segment RRa, the dynamic Obtaining the gain coefficient for the input signal of the speaker, and obtaining the gain coefficient for the input signal of the super-directive speaker at position O based on the ratio of the length of the line segment POa to the length of the line segment OOa. do.

In the acoustic system according to one aspect of the present invention, as described above, a dynamic speaker having a low direct-to-direct ratio of impulse response (small direct sound) and a superdirective speaker having a high direct-to-direct ratio of impulse response (large direct sound) By performing amplitude panning in combination with dynamic speakers, the impulse at the listener's position becomes a clue (index) for the sense of distance of the virtual sound source, unlike when amplitude panning is performed only with dynamic speakers whose direct-to-direct ratio of the impulse response is low. The direct ratio of the response can be controlled precisely. As a result, it is possible to control the distance of the virtual sound source from the listener with high accuracy even in the vicinity of the listener, so that it is possible to provide an acoustic system capable of changing the distance between the listener and the virtual sound source. .

In the acoustic system according to the above one aspect, preferably, the control unit is characterized by controlling the direct ratio of the impulse responses at the listener's position of the dynamic speaker and the super-directional speaker.

In the acoustic system according to the above one aspect, preferably, the control unit controls the gain coefficient for the input signal of the dynamic speaker and the gain coefficient for the input signal of the super-directional speaker so as to obtain an immediate response of the impulse response at the listener's position. It is characterized by controlling the ratio.

In the acoustic system according to the above aspect, the super-directional speaker preferably includes a parametric speaker. With such a configuration, amplitude panning can be performed by combining a dynamic speaker with a low direct-to-direct ratio of impulse responses and a parametric speaker with a high direct-to-direct ratio of impulse responses, which provides a clue for the sense of distance to the virtual sound source. It is possible to control the direct ratio of the impulse response at the listener's position where .

According to the present invention, as described above, it is possible to provide an acoustic system capable of changing the distance between the listener and the virtual sound source.
Also, if this sound system is used in the field of virtual reality, a virtual sound source can be set at the position where a virtual speaker exists. It sounds as if the speaker is speaking. Unlike the conventional speaker's voice coming out from the place where the speaker is installed, a more realistic feeling can be obtained. Furthermore, it can be used to a great extent in the field of what is commonly called remote presence (Telexistence).

1 illustrates an audio system according to an embodiment of the invention; FIG. FIG. 4 is a diagram for explaining control of the distance from the listener of the virtual sound source of the acoustic system according to one embodiment of the present invention; It is a figure which shows the arrangement|positioning conditions of a microphone, a speaker, and a virtual sound source in an objective evaluation experiment. It is a figure which shows the arrangement|positioning conditions of a microphone and a speaker (real sound source) in an objective evaluation experiment. FIG. 10 is a diagram showing placement conditions of listeners, speakers, and virtual sound sources in a subjective evaluation experiment; FIG. 10 is a diagram showing conditions of arrangement of listeners and speakers (real sound sources) in a subjective evaluation experiment; FIG. 10 is a graph showing the frequency distribution of responses regarding distance in a real sound source obtained in a subjective evaluation experiment; FIG. FIG. 10 is a graph showing the frequency distribution of answers regarding distance in a virtual sound source obtained in a subjective evaluation experiment; FIG.

Embodiments embodying the present invention will be described below with reference to the drawings.

A configuration of an acoustic system 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

(Sound system configuration)
The sound system 100 according to one embodiment is a sound system for multi-channel sound. The acoustic system 100 includes one parametric speaker 10 , multiple (four) dynamic speakers 20 , and a control section 30 . The parametric speaker 10 is an example of a "super-directional speaker" in the claims.

The parametric speaker 10 is a speaker using ultrasonic waves as carrier waves. The parametric speaker 10 is placed in front of the listener O. As shown in FIG. The dynamic speaker 20 is a speaker using a permanent magnet and a moving coil. The four dynamic speakers 20 are positioned on the left front, right front, left rear, and right rear sides with respect to the listener O, respectively.

The control unit 30 is a control circuit including a processor (not shown) such as a CPU and a storage unit (not shown) such as ROM and RAM. The control unit 30 controls the parametric speaker 10 and the four dynamic speakers 20 so as to output sounds corresponding to the input signal S, which is an audio signal.

Here, in the present embodiment, the control unit 30 controls the sound output from the dynamic speaker 20 and the sound output from the parametric speaker 10 by amplitude panning so that the virtual sound source P (see FIG. 2) from the listener O (listener position). By controlling the distance of the virtual sound source P from the listener O, an optimal sound environment for the listener can be realized. Further, in this embodiment, the control unit 30 is configured to control the distance of the virtual sound source P from the listener O by controlling the direct ratio of the impulse response at the listener's position. An example of controlling the distance of the virtual sound source P from the listener O by the parametric speaker 10, the front left dynamic speaker 20, and the front right dynamic speaker 20 will be described below with reference to FIG.

As shown in FIG. 2, vector base amplitude panning (VBAP) divides a reproduction space into triangular regions each composed of three speakers. 2, the acoustic center of gravity of the front left dynamic speaker 20 is L, the acoustic center of gravity of the front right dynamic speaker 20 is R, and the acoustic center of gravity of the parametric speaker 10 is O. In FIG. Note that the acoustic center of gravity O of the parametric speaker 10 is the listener's position. This is because the parametric speaker 10 has a high direct-to-direct ratio of the impulse response, so the listener O perceives the virtual sound source in the immediate vicinity of the listener O. Further, in FIG. 2, the intersection point of the line segment OR of the straight line passing through the acoustic center of gravity L and the virtual sound source P is denoted by La, the intersection point of the line segment OL of the straight line passing through the acoustic center of gravity R and the virtual sound source P is denoted by Ra, An intersection point of a straight line segment LR passing through the acoustic center of gravity O and the virtual sound source P is Oa.

ここで、
α_Ｌ：前方左側のダイナミックスピーカのゲイン係数
α_Ｒ：前方左側のダイナミックスピーカのゲイン係数
α_Ｏ：パラメトリックスピーカのゲイン係数
ＰＬａ：線分ＰＬａの長さ
ＬＬａ：線分ＬＬａの長さ
ＰＲａ：線分ＰＲａの長さ
ＲＲａ：線分ＲＲａの長さ
ＰＯａ：線分ＰＯａの長さ
ＯＯａ：線分ＯＯａの長さ
である。 In this case, in amplitude panning, the gain coefficients for the input signal S of the three speakers are represented by the following equations (1) to (3), respectively.

here,
α _L : Gain coefficient of front left dynamic speaker α _R : Gain coefficient of front left dynamic speaker α _O : Gain coefficient of parametric speaker PLa: Length of line segment PLa LLa: Length of line segment LLa PRa: Line segment Length of PRa RRa: Length of line segment RRa POa: Length of line segment POa OOa: Length of line segment OOa.

Also, when there are a plurality of input signals S (virtual sound sources P), a gain coefficient is calculated individually for each input signal S (virtual sound source P). Gain coefficients for the i-th input signal S of the three speakers are expressed by the following equations (4) to (6), respectively.

Note that γ in Equation (6) is a correction coefficient for correcting the direct ratio of the impulse response. γ is obtained based on the direct ratio of the impulse responses at the listener positions measured in advance. Also, α _Li , α _Ri and α _Oi are α _L , α _R and α _O for the i-th input signal S, respectively. Also, P _i , L _i , R _i , La _i , Ra _i and Oa _i are the positions of P, L, R, La, Ra and Oa with respect to the i-th input signal S, respectively.

ここで、
ｘ_Ｌ（ｔ）：前方左側のダイナミックスピーカの出力信号
ｘ_Ｒ（ｔ）：前方右側のダイナミックスピーカの出力信号
ｘ_Ｏ（ｔ）：パラメトリックスピーカの出力信号
Ｓ_ｉ（ｔ）：ｉ番目の入力信号
β：パラメトリックスピーカとダイナミックスピーカとの音圧レベルを正規化するための係数
ｃ（ｔ）：パラメトリックスピーカのキャリア波の信号
である。 In amplitude panning, the output signals X of the three speakers are respectively represented by the following equations (7) to (9).

here,
x _L (t): output signal of front left dynamic speaker x _R (t): output signal of front right dynamic speaker x _O (t): output signal of parametric speaker S _i (t): i-th input signal β: a coefficient for normalizing the sound pressure levels of the parametric speaker and the dynamic speaker c(t): the carrier wave signal of the parametric speaker.

As described above, first, the control unit 30 sets the acoustic center of gravity of the dynamic speaker 20 to the actual position, and sets the acoustic center of gravity of the parametric speaker 10 assuming that it is located at the listener's position. , the gain coefficient for the input signal S of the parametric speaker 10 and the gain coefficient for the input signal S of the dynamic speaker 20 are obtained. When there are a plurality of input signals S, the control unit 30 acquires the gain coefficient for the input signal S of the parametric speaker 10 and the gain coefficient for the input signal S of the dynamic speaker 20 for each input signal S individually. At this time, the control unit 30 acquires the gain coefficient of the parametric speaker 10 by correcting it with a correction coefficient γ for correcting the direct ratio of the impulse response.

Then, the control unit 30 distributes the input signal S to the parametric speaker 10 and the dynamic speaker 20 according to the acquired gain coefficient, and acquires the output signal X of the parametric speaker 10 and the output signal X of the dynamic speaker 20 . At this time, the control unit 30 acquires the output signal X of the parametric speaker 10 after correcting it with a coefficient β for normalizing the sound pressure level. Then, the control unit 30 controls the parametric speaker 10 and the dynamic speaker 20 so as to output sounds corresponding to the input signals S based on each output signal X acquired. Thereby, amplitude panning is performed and the distance of the virtual sound source P from the listener O is controlled. In this way, the control unit 30 sets the position of the virtual sound source P by controlling the gain coefficient for the input signal S of the dynamic speaker 20 and the gain coefficient for the input signal S of the parametric speaker 10 . from the listener O. At this time, the control unit 30 controls the direct ratio by changing the synthesis ratio of the impulse responses of the dynamic speaker 20 and the parametric speaker 10 at the listener's position. Specifically, the control unit 30 controls the gain coefficient for the input signal of the dynamic speaker 20 and the gain coefficient for the input signal of the parametric speaker 10 to change the synthesis ratio of impulse responses at the listener's position. Control the ratio.

(Objective evaluation experiment)
Next, with reference to FIGS. 3, 4, and Tables 1 to 4, an objective evaluation experiment conducted for distance control of the virtual sound source P of this embodiment will be described.

As shown in FIG. 3, in the objective evaluation experiment, the position of the virtual sound source P was changed to R0.3, R1.0, R2.0, C0.3, C1.0 by the distance control of the virtual sound source P of this embodiment. , C1.7, L0.3, L1.0, and L2.0, and the impulse response was measured with a microphone placed at the listener's position. γ is set to 1, and β is experimentally adjusted using measured sound pressure levels.

The letters "R", "L" and "C" indicate directions relative to the listener's position. Specifically, "R" indicates the right direction (direction of 30 degrees) with respect to the listener's position, "C" indicates the front direction of the listener's position, and "L" indicates the direction in front of the listener's position. indicates the left direction (direction of -30 degrees) with respect to the listener position. Also, the numbers "0.3", "1.0", "1.7" and "2.0" indicate the distance to the listener position.

Also, in order to compare with the measurement results of the impulse response of the virtual sound source P, real sound sources (dynamic speakers) were set to R0.3, R1.0, R2.0, C0.3, C1. 0, C1.7, L0.3, L1.0, and L2.0, and impulse responses were measured with microphones placed at the listener's position.

ここで、
ＤＲＲ：インパルス応答の直間比
Ｏ_ｅ（ｎ）：計測したインパルス応答
Ｔｄ：直接波の信号長
Ｔ’：インパルス応答の信号長
である。 Also, based on the measured impulse responses, the direct ratio of the impulse responses was obtained by the following equation (10).

here,
DRR: direct ratio of impulse response O _e (n): measured impulse response Td: signal length of direct wave T′: signal length of impulse response.

Note that Td was set to 7 ms. Impulse responses were measured using the TSP (Time-stretched pulse) method. A TSP signal (signal length: 2 ¹⁹ , frequency width: 0 to 8 kHz) was used as the sound source. In addition, Table 1 below shows the experimental equipment in the objectivity evaluation experiment, Table 2 below shows the experimental conditions in the objectivity evaluation experiment, and Table 3 below shows the experimental conditions of the parametric speaker 10 in the objectivity evaluation experiment. there is Table 4 below shows the direct ratio of the impulse response obtained in the objectivity evaluation experiment.

As shown in Table 4, there is a very high correlation between the direct ratio of the impulse response by the distance control of the virtual sound source P in this embodiment and the direct ratio of the impulse response by the real sound source, and the error is large. It can be seen that it is about 2 to 3 dB at most. From this, it was found that the direct ratio of the impulse response, which is an important physical index for the sense of distance, can be controlled with high accuracy by the distance control of the virtual sound source P of the present embodiment.

(Subjective evaluation experiment)
Next, with reference to FIGS. 5 to 8 and Table 5, a subjective evaluation experiment conducted on the distance control of the virtual sound source P of this embodiment will be described.

As shown in FIG. 5, in the subjective evaluation experiment, the position of the virtual sound source P was changed to R0.3, R1.0, R2.0, C0.3, C1.0 by the distance control of the virtual sound source P of this embodiment. , C1.7, L0.3, L1.0, and L2.0, and the subject positioned at the listener's position listened.

Also, in order to compare with the results of listening to the virtual sound source P by the subject, real sound sources (dynamic speakers) were set to R0.3, R1.0, R2. , C1.7, L0.3, L1.0, and L2.0, and the subject positioned at the listener's position listened.

There were seven subjects, and they were asked to listen to the sound twice at each position and answer the distance. In addition, the sounds to be listened to were presented at random. As the sound source, white noise (frequency range: 0-8 kHz) was used.

As shown in FIGS. 7 and 8, it can be seen that the distance presentation performance by the distance control of the virtual sound source P of this embodiment and the distance presentation performance by the real sound source are substantially the same. In addition, as shown in Table 5 below, this tendency can also be seen from the rate of correct answers for the distance. From the above, it was found that the distance control of the virtual sound source P of the present embodiment achieves high distance presentation performance.

(Effect of this embodiment)
The following effects can be obtained in this embodiment.

In the present embodiment, as described above, the dynamic speaker 20 having a low impulse response direct ratio (small direct sound) and the parametric speaker 10 having a high impulse response direct ratio (large direct sound) are combined. By performing amplitude panning, unlike the case of performing amplitude panning only with the dynamic speaker 20 having a low direct-to-direct ratio of the impulse response, the composite ratio of the impulse response at the listener's position, which is a clue (index) for the sense of distance of the virtual sound source P. can be changed to control the indirect ratio with high accuracy. As a result, it is possible to control the distance of the virtual sound source P from the listener O with high precision even in the vicinity of the listener O, so that the distance between the listener O and the virtual sound source P can be freely controlled. A system 100 can be provided.

Further, in the present embodiment, as described above, the control unit 30 controls the direct ratio by changing the synthesis ratio of the impulse responses at the listener's position of the dynamic speaker 20 and the parametric speaker 10, so that the virtual sound source P from the listener O.

Further, in the present embodiment, as described above, the control unit 30 controls the gain coefficient for the input signal of the dynamic speaker 20 and the gain coefficient for the input signal of the parametric speaker 10 to synthesize impulse responses at the listener's position. It is configured to control the direct ratio by changing the ratio.

Moreover, in this embodiment, the super-directional speaker is configured to include the parametric speaker 10 as described above. As a result, amplitude panning can be performed by combining the dynamic speaker 20 with a low direct-to-direct ratio of the impulse response and the parametric speaker 10 with a high direct-to-direct ratio of the impulse response. The direct ratio of impulse responses at different listener positions can be controlled more accurately.

[Variation]
It should be noted that the embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of the claims rather than the above description of the embodiments, and includes all modifications (modifications) within the meaning and scope equivalent to the scope of the claims.

For example, in the above embodiments, the acoustic system is configured to include one parametric speaker (super-directional speaker), but the present invention is not limited to this. In accordance with the present invention, the sound system may be configured with a plurality of super-directional loudspeakers.

Also, in the above embodiment, an example in which the acoustic system is configured to include four dynamic speakers has been shown, but the present invention is not limited to this. In accordance with the present invention, the sound system may be configured with a plurality of dynamic speakers other than one or four.

Also, in the above embodiment, an example in which the super-directional speaker of the present invention is configured by a parametric speaker has been shown, but the present invention is not limited to this. For example, the super-directional speaker may be configured by an array speaker or a curved reflector type speaker.

Further, in the above embodiment, an example in which the parametric speaker (super-directional speaker) is arranged in front of the listener has been shown, but the present invention is not limited to this. In the present invention, super-directional speakers may be placed other than in front of the listener. For example, the super-directional speaker may be placed on the right side, left side, or rear side of the listener.

10 Parametric speaker (super-directional speaker)
20 dynamic speaker 30 control unit 100 sound system

Claims (4)

A sound system for multi-channel sound, comprising:
dynamic speakers and
a super-directional speaker,
and a control unit,
The control unit controls the distance from the listener of the virtual sound source by controlling the sound output from the dynamic speaker and the sound output from the super-directional speaker by amplitude panning ,
The control unit
Let the positions of the acoustic centers of gravity of the two dynamic speakers be L and R, respectively, let the position of the acoustic center of gravity of the super-directional speaker assumed to be the listener's position be O, and let the position of the virtual sound source be P, position L and position Let La be the point of intersection of a straight line passing through P and the line segment OR, let Ra be the point of intersection of the straight line passing through the position R and the position P and the line segment OL, and let Ra be the point of intersection of the straight line and the line segment passing through the position O and the position P. When the intersection with LR is Oa,
Obtaining a gain coefficient for the input signal of the dynamic speaker at the position L based on the ratio of the length of the line segment PLa to the length of the line segment LLa;
obtaining a gain coefficient for the input signal of the dynamic speaker at the position R based on the ratio of the length of the line segment PRa to the length of the line segment RRa;
An acoustic system , wherein a gain factor for an input signal of said super-directive speaker at said position O is obtained based on the ratio of the length of line segment POa to the length of line segment OOa . 2. The sound system according to claim 1, wherein said control unit controls direct-to -direct ratios of impulse responses at a listener's position of said dynamic speaker and said super-directional speaker. The control unit controls a gain coefficient for the input signal of the dynamic speaker and a gain coefficient for the input signal of the super-directional speaker to control the direct ratio of the impulse response at the listener's position. 3. An acoustic system according to claim 1 or 2. An acoustic system according to any one of claims 1 to 3, wherein said super-directional loudspeaker comprises a parametric loudspeaker.

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