JP7808792B2 - Sound field reproduction device, sound field reproduction method, and sound field reproduction system - Google Patents

Description

This disclosure relates to a sound field reproduction device, a sound field reproduction method, and a sound field reproduction system.

Recently, scene-based 3D sound reproduction technology has been attracting attention for its ability to reproduce sound fields in real time. Scene-based 3D sound reproduction technology is a method of reproducing a three-dimensional sound field in real time using speakers arranged to surround the viewing environment (space) by applying signal processing to multi-channel signals recorded (picked up) using Ambisonics microphones, which have multiple directional microphone elements arranged on a rigid or hollow sphere. This makes it appear as if the listener is actually located where the Ambisonics microphones are installed.

Patent Document 1, for example, is known as prior art related to sound field reproduction. Patent Document 1 discloses a signal processing device that acquires multiple collected signals based on sound collected by multiple sound collection units installed together in a target sound collection space, with the multiple sound collection units installed in multiple different orientations depending on the position of the sound source and the position of objects that reflect the sound emitted from the sound source, and generates an acoustic signal corresponding to a specified listening point within the target sound collection space based on the multiple collected signals.

Japanese Patent Application Laid-Open No. 2019-192975

The configuration of Patent Document 1 assumes that the listening point is located within a target sound collection space where multiple sound collection units are located. Therefore, even if a scene-based 3D sound system is constructed using Patent Document 1, the listener must be located within the target sound collection space where the sound collection units are located. In other words, if the listener is located in a different position from the target sound collection space, it is difficult to reproduce the sound field so that the sound signals collected within the target sound collection space can be heard within that target sound collection space.

On the other hand, it is known that an Ambisonics microphone can synthesize higher-order Ambisonics components (sound field components) as the number of microphone elements arranged on a spherical surface increases, thereby improving directional resolution during recording and reproduction. However, synthesizing higher-order sound field components for real-time live streaming of events such as public viewing requires increasing the number of microphone elements arranged in the recording space to synthesize higher-order sound field components. For this reason, depending on the installation space of the microphone elements, there are physical constraints on microphone element placement. Furthermore, an increase in the number of transmission channels associated with an increase in the number of microphone elements increases the processing load for signal processing and synthesis processes, resulting in output delays for sound field reproduction. Therefore, it is necessary to reproduce the sound field using lower-order sound field components without unnecessarily increasing the number of microphone elements. However, in this case, sound source localization errors increase significantly as the microphone element moves away from the center position of the surrounding speakers, making it impossible to achieve the expected sound field reproduction.

The present disclosure was devised in light of the above-mentioned conventional situation, and aims to provide a sound field reproduction device, sound field reproduction method, and sound field reproduction system that utilizes low-order sound field components recorded using an Ambisonics microphone to suppress increases in sound source localization errors within a sound field reproduction space.

The present disclosure provides a sound field reproduction device comprising: a sound source extraction direction control unit that receives a specified sound source extraction direction within a sound field recording space in which a recording device is placed; a re-encoding unit that generates high-order basis acoustic signals by re-encoding acoustic signals that correspond to the sound source extraction direction among low-order basis acoustic signals based on encoding processing using signals recorded by the recording device; and a sound field reproduction unit that outputs signals based on the high-order basis acoustic signals from each of a plurality of speakers provided in a sound field reproduction space different from the sound field recording space.

The present disclosure also provides a sound field reproduction method comprising the steps of: receiving a designation of a sound source extraction direction within a sound field recording space in which a recording device is placed; generating high-order basis acoustic signals by re-encoding acoustic signals corresponding to the sound source extraction direction among low-order basis acoustic signals based on an encoding process using signals recorded by the recording device; and outputting signals based on the high-order basis acoustic signals from each of a plurality of speakers provided in a sound field reproduction space different from the sound field recording space.

The present disclosure also provides a sound field reproduction system comprising: a sound field recording apparatus having a recording device capable of recording a sound source within a sound field recording space; and a sound field reproduction device that reproduces the sound signal recorded by the recording device in a sound field reproduction space different from the sound field recording space, wherein the sound field reproduction device comprises: a sound source extraction direction control unit that receives a designation of a sound source extraction direction within the sound field recording space; a re-encoding unit that re-encodes, from low-order basis sound signals based on an encoding process using the signal recorded by the recording device, sound signals that correspond to the sound source extraction direction to generate high-order basis sound signals; and a sound field reproduction unit that outputs signals based on the high-order basis sound signals from each of a plurality of speakers provided in the sound field reproduction space.

Note that these comprehensive or specific aspects may be realized as a system, device, method, integrated circuit, computer program, or recording medium, or as any combination of a system, device, method, integrated circuit, computer program, and recording medium.

This disclosure makes it possible to utilize low-order sound field components recorded using an Ambisonics microphone, thereby suppressing increases in sound source localization errors within the sound field reproduction space.

A schematic diagram showing the concept of scene-based 3D sound reproduction using Ambisonics microphones, from sound field recording to sound field reproduction. FIG. 1 shows an example of a basis of Ambisonics components based on spherical harmonic expansion for degree n and degree m. FIG. 1 is a block diagram showing an example of the system configuration of a sound field reproduction system according to a first embodiment. FIG. 1 is a diagram showing an example of an outline of operations from sound field recording to sound field reproduction according to the first embodiment; 1 is a flowchart showing an example of a procedure for reproducing a sound field by the sound field reproduction device according to the first embodiment in chronological order. A block diagram showing an example of the system configuration of a sound field reproduction system according to a second embodiment. FIG. 10 is a diagram showing an example of an outline of operations from sound field recording to sound field reproduction according to the second embodiment. 10 is a flowchart showing an example of the operation procedure for reproducing a sound field by the sound field reproduction device according to the second embodiment in chronological order.

Hereinafter, with appropriate reference to the drawings, detailed descriptions will be provided of specific embodiments of the sound field reproduction device, sound field reproduction method, and sound field reproduction system disclosed herein. However, more detailed descriptions than necessary may be omitted. For example, detailed descriptions of already well-known matters and redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter of the claims.

In the following embodiments, we will explain an example of a scene-based stereophonic reproduction technology that uses an Ambisonics microphone as a recording device to record sound source signals such as sounds, music, and human voices within a sound field recording space (e.g., a live venue). In scene-based stereophonic reproduction technology using an Ambisonics microphone, signals (recorded signals) or point sound sources recorded by multiple microphone elements that make up the Ambisonics microphone are represented (encoded) as an intermediate representation ITMR1 (see Figure 1) or B-format signal using spherical harmonic functions, thereby handling the sound field arriving from all directions in a unified manner in the Ambisonics signal domain (see below). Furthermore, speaker drive signals are generated by decoding this intermediate representation, thereby achieving the desired sound field reproduction within a sound field reproduction space (e.g., a satellite venue).

(Embodiment 1)
First, the concept of scene-based stereophonic sound reproduction technology will be described with reference to Fig. 1. Fig. 1 is a diagram schematically illustrating the concept from sound field recording to sound field reproduction in scene-based stereophonic sound reproduction technology using Ambisonics microphones 11. The Ambisonics microphones 11 are placed in a sound field recording space such as a live music venue LV1. At the live music venue LV1, a performance is held using multiple sound sources (for example, in the case of a band performance by multiple people, various sound sources such as vocals, bass, guitar, and drums), and the sounds of the performance are recorded by the Ambisonics microphones 11.

The Ambisonics microphone 11, an example of a recording device, has four microphone elements Mc1, Mc2, Mc3, and Mc4. Each of the microphone elements Mc1 to Mc4 is positioned in midair so that it faces one of the four vertices from the center of the cube CB1 in Figure 1, with direction Dr1 being the front direction, and has unidirectionality in the direction of each vertex. Microphone element Mc1 faces the front left and upper left (FLU) of the Ambisonics microphone 11 and records sound in that front left and upper (FLU) direction. Microphone element Mc2 faces the front right and lower (FRD) of the Ambisonics microphone 11 and records sound in that front right and lower (FRD) direction. Microphone element Mc3 faces toward the back left down (BLD: Back Left Down) of the Ambisonics microphone 11 and records sound from the back left down direction. Microphone element Mc4 faces toward the back right up (BRU: Back Right Up) of the Ambisonics microphone 11 and records sound from the back right up direction.

The recorded signals of these four directions (i.e., FLU, FRD, BLD, BRU) are called A-format signals. A-format signals cannot be used as is and are converted into B-format signals, which are intermediate representations ITMR1 that have directional characteristics (directivity). B-format signals include, for example, B-format signal W for omnidirectional (omnidirectional) sounds, B-format signal X for front-to-back sounds, B-format signal Y for left-to-right sounds, and B-format signal Z for up-down sounds. A-format signals are converted into B-format signals using the following conversion formula:

W=FLU+FRD+BLD+BRU
X=FLU+FRD-BLD-BRU
Y=FLU-FRD+BLD-BRU
Z=FLU-FRD-BLD+BRU

By combining the B format signals W, X, Y, and Z, sound signals in all directions (front/back, left/right, up/down) can be obtained. Then, by changing the signal levels of the B format signals W, X, Y, and Z and combining them, sound signals with omnidirectional characteristics in any of the directions (front/back, left/right, up/down) can be generated. For example, as shown in Figure 1, consider a three-dimensional coordinate system similar to that of the sound field recording space (e.g., live venue LV1) (i.e., the front/back, left/right, up/down directions are parallel or the same).

The position of each of the speakers SPk1 to SPk8 can be specified by a predetermined distance and angle (azimuth angle _θi and elevation angle _φi ) from a reference position (e.g., center position LSP1) of the sound field reproduction space (e.g., satellite venue STL1). i is a variable indicating the speaker located in the sound field reproduction space (e.g., satellite venue STL1), and takes an integer from 1 to 8 in the example of Figure 1.

Assume that a user, a listener (listener), is present at the center position LSP1 of a sound field reproduction space (for example, a satellite venue STL1) and is facing forward (Front). Under such circumstances, the sound field in the sound field recording space (for example, a live venue LV1) can be freely reproduced in the sound field reproduction space (for example, a satellite venue STL1) based on the data of the B format signals W, X, Y, and Z obtained by encoding based on the A format signal recorded in the sound field recording space (for example, a live venue LV1) and the respective directions of the speakers SPk1 to SPk8 in the sound field reproduction space (for example, a satellite venue STL1). In other words, when a user, a listener (listener), is present in the sound field reproduction space (for example, a satellite venue STL1), the direction in front of the listener is set as the reference direction, and it is possible to reproduce and output sound in any three-dimensional direction (for example, the sound source presentation direction θ _target described later) from that reference direction.

Next, with reference to Figure 2, we will explain the basis of Ambisonics components based on spherical harmonic expansion for order n and frequency m. Figure 2 shows an example of the basis of Ambisonics components based on spherical harmonic expansion for order n and frequency m.

The horizontal axis (m) in FIG. 2 indicates the degree, and the vertical axis (n) in FIG. 2 indicates the order. The degree m ranges from −n to +n. Spherical harmonics up to order n=N include a total of (N+1) ² bases. For example, when n=N=0, one basis (i.e., the omnidirectional B-format signal W) is obtained. For example, when n=N=1, four bases (i.e., the omnidirectional B-format signal W corresponding to (n, m)=(0, 0), the front-to-back B-format signal X corresponding to (n, m)=(1, −1), the up-down B-format signal Z corresponding to (n, m)=(1, 0), and the left-to-right B-format signal Y corresponding to (n, m)=(1, 1)) are obtained. Note that the same applies for n=N=2 and onward, and therefore a description thereof will be omitted.

Spherical harmonics are known to have the property that their spatial periodicity increases as n and m increase. This makes it possible to express B-format signals with different directional patterns (directional characteristics) depending on the combination of n and m. If the dimensions for order n and degree m are defined as K = n(n+1) + m based on Ambisonics Channel Numbering (ACN), spherical harmonics can be expressed in vector form as shown in equation (1). In equation (1), the superscript T indicates transposition.

Next, the system configuration and operation overview of the sound field reproduction system 100 according to embodiment 1 will be described with reference to Figures 3 and 4. Figure 3 is a block diagram showing an example of the system configuration of the sound field reproduction system 100 according to embodiment 1. Figure 4 is a diagram showing an example of the operation overview from sound field recording to sound field reproduction according to embodiment 1.

The sound field reproduction system 100 includes a sound field recording device 1 and a sound field reproduction device 2. The sound field recording device 1 and the sound field reproduction device 2 are connected to each other via a network NW1 so that they can communicate data with each other. The network NW1 may be a wired network or a wireless network. The wired network may be, for example, at least one of a wired local area network (LAN), a wired wide area network (WAN), or power line communication (PLC), or may be any other network configuration capable of wired communication. On the other hand, the wireless network may be at least one of a wireless LAN such as Wi-Fi (registered trademark), a wireless WAN, a short-range wireless communication such as Bluetooth (registered trademark), or a mobile communication network such as 4G or 5G, or may be any other network configuration capable of wireless communication.

The sound field recording device 1 is placed, for example, in a sound field recording space (e.g., a live performance venue LV1) and includes an Ambisonics microphone 11, an A/D converter 12, an encoder 13, and a microphone element direction designator 14. Note that the sound field recording device 1 only needs to have at least the Ambisonics microphone 11; the A/D converter 12, encoder 13, and microphone element direction designator 14 may be provided in the sound field reproduction device 2. In other words, the Ambisonics microphone 11 may be provided outside the sound field reproduction device 2.

The Ambisonics microphone 11 includes four microphone elements Mc1, Mc2, Mc3, and Mc4. The microphone element Mc1 records sound from the upper left front direction (see FIG. 1), the microphone element Mc2 records sound from the lower right front direction (see FIG. 1), and the microphone element Mc3 records sound from the lower left rear direction (see FIG. 1) and the upper right rear direction (see FIG. 1). The Ambisonics microphone 11 may include more unidirectional microphone elements than the four microphone elements Mc1, Mc2, Mc3, and Mc4 arranged in midair, or may include omnidirectional microphone elements arranged on a rigid sphere. Using an Ambisonics microphone with multiple microphone elements enables the encoding unit 13 to synthesize second- or higher-order Ambisonics signals. The signals (recorded signals) recorded by each microphone element constituting the Ambisonics microphone 11 are input to the A/D conversion unit 12.

The A/D conversion unit 12, encoding unit 13, and microphone element direction designation unit 14 are configured by a semiconductor chip or dedicated hardware that implements at least one of the following electronic devices: a CPU (Central Processing Unit), a DSP (Digital Signal Processor), a GPU (Graphical Processing Unit), an FPGA (Field Programmable Gate Array), etc.

The A/D conversion unit 12 converts the analog recording signals from each microphone element that makes up the Ambisonics microphone 11 into digital recording signals and sends them to the encoding unit 13.

The encoding unit 13 generates a low-order basis acoustic signal (for example, a first-order Ambisonics signal) by encoding the recorded signal converted by the A/D conversion unit 12 using the recorded signal converted by the A/D conversion unit 12 and the direction vector θ _m from the microphone element direction designation unit 14. Details of the encoding process by the encoding unit 13 will be described later.

Here, we will explain the details of the encoding process performed by the encoding unit 13.

It is generally known that the sound pressure p observed (recorded) at a position of radius r for any angle (θ, φ) on a sphere can be expanded as equation (4) using the spherical harmonic functions of equation (2) as a basis for wave number k as a solution to an internal problem in the spherical harmonic domain of the wave equation. In equation (4), A ^m _n are expansion coefficients, and R _n (kr) is a radial function term. Furthermore, an infinite sum with respect to order n is approximated by truncation at a finite order N, and the accuracy of sound field reproduction changes depending on this truncation order N. Hereinafter, the truncation order will be expressed as N.

In equation (6), i is the imaginary unit, j _n (kr) is the nth-order spherical Bessel function, and j ^' _n (kr) is its derivative. In this disclosure, the expansion coefficient vector γ ^m _n for this plane wave is treated as a B-format signal (intermediate representation) that is the output of the encoding process by the encoding unit 13. Hereinafter, this expansion coefficient vector may be referred to as an Ambisonics domain signal or simply as an Ambisonics signal.

More specifically, in the encoding process by the encoding unit 13, the recorded signal, which is a time-domain signal after conversion by the A/D conversion unit 12, is converted into an Ambisonics signal (e.g., a first-order Ambisonics signal), and this Ambisonics signal (e.g., a first-order Ambisonics signal) is decoded by each of the first decoding unit 25 and second decoding unit 26 of the sound field reproduction device 2 and converted into a speaker drive signal.

The sound field reproduction device 2 is placed, for example, in a sound field reproduction space (for example, satellite venue STL1) and includes a sound source extraction direction control unit 21, a sound source presentation direction control unit 22, a re-encoding unit 23, a speaker direction designation unit 24, a first decoding unit 25, a second decoding unit 26, a signal mixing unit 27, a sound field reproduction unit 28, and speakers SPk1, SPk2, ..., SPk8. In the following description, the number of speakers arranged is 8 as an example, but it goes without saying that it is not limited to 8 as long as it is an integer greater than or equal to 2.

The signal mixer 27 mixes the speaker drive signals corresponding to the high-order base acoustic signals from the first decoding unit 25 and the speaker drive signals corresponding to the low-order base acoustic signals from the second decoding unit 26 so as to correspond to each speaker, and sends the mixed signals to the sound field reproduction unit 28. Note that the signal mixer 27 may be omitted from the sound field reproduction device 2; in this case, only the high-order base acoustic signals from the first decoding unit 25 are output from each of the speakers SPk1 to SPk8 via the sound field reproduction unit 28.

The sound field reproduction unit 28 converts the digital speaker drive signals for each speaker after mixing by the signal mixing unit 27 into analog speaker drive signals, amplifies the signals, and outputs (plays) them from the corresponding speakers.

Speakers SPk1, SPk2, ..., SPk8 are each placed at the vertices of a sound field reproduction space (e.g., satellite venue STL1) modeled as a cube, and reproduce (reproduce) the sound field based on the speaker drive signal from the sound field reproduction unit 28. The number of speakers installed may vary depending on the sound field to be reproduced. In cases where reproduction is not performed in a specific direction, or by combining commonly known virtual sound image generation methods such as a transaural system or the VBAP (Vector Based Amplitude Panning) method, sound field reproduction may be performed using fewer than eight speakers. Conversely, sound field reproduction may be performed using more than eight speakers. Furthermore, the speakers may be installed at locations other than the vertices of the sound field reproduction space (e.g., satellite venue STL1) as long as they are installed to surround the reference position of satellite venue STL1 (e.g., center position LSP1). The sound field reproduction unit 28 may output signals to a binaural reproduction device such as headphones or earphones worn by a listener (user) instead of speakers. When supplying signals to a binaural reproduction device (for example, the above-mentioned headphones or earphones) of the listener (user), the sound field reproduction unit 28 may generate reproduction signals corresponding to azimuth angles of +-90° by a decoding process described later, or may generate virtual sound images for a plurality of directions surrounding the head and generate reproduction signals by multiplying in the frequency domain or convolving in the time domain the virtual sound images for the corresponding directions with transfer characteristics such as HRTFs (Head Related Transfer Functions) corresponding to the plurality of angles that allow the user to perceive a three-dimensional sound image. This means that sound field reproduction is not limited to the speakers SPk1, SPk2, ..., SPk8 located in satellite venue STL1, but also makes it possible to reproduce the sound field on playback devices (for example, the headphones or earphones mentioned above) worn by listeners (users) located in satellite venue STL1.

Here, we will explain in detail the re-encoding process by the re-encoding unit 23 and the processing by the first decoding unit 25 and second decoding unit 26.

Next, the operational procedure for sound field reproduction by the sound field reproduction device 2 will be described with reference to Figure 5. Figure 5 is a flowchart showing an example of the operational procedure for sound field reproduction by the sound field reproduction device 2 according to embodiment 1 in chronological order. Note that in the following explanation, the processes of steps St1 and St2 are described as being executed within the sound field recording device 1, but the process of step St2 may be executed by the sound field reproduction device 2 if components other than the Ambisonics microphone 11 of the sound field recording device 1 are provided within the sound field reproduction device 2.

After the processing of step St2, the sound field reproduction device 2 executes a series of processes from step St3 to step St6 (i.e., re-encoding processes to generate higher-order basis acoustic signals) and the processing of step St7 (i.e., decoding processes to generate lower-order basis acoustic signals) in parallel.

The signal mixing unit 27 of the sound field reproduction device 2 mixes the speaker drive signals (an example of the output of the first decoding process) corresponding to the high-order basis acoustic signals from the first decoding unit 25 in step St6 with the speaker drive signals (an example of the output of the second decoding process) corresponding to the low-order basis acoustic signals from the second decoding unit 26 in step St7 so as to correspond to each speaker (step St8). The sound field reproduction unit 28 of the sound field reproduction device 2 converts the digital speaker drive signals for each speaker after mixing by the signal mixing unit 27 in step St8 into analog speaker drive signals, amplifies the signals, and outputs (plays) them from the corresponding speakers SPk1 to SPk8 (step St9).

The recording device is also composed of an Ambisonics microphone 11, with multiple microphone elements Mc1 to Mc4 arranged three-dimensionally so that each faces a different direction. This allows the sound field recording device 1 to three-dimensionally record the atmospheric sounds of a performance or other event produced by multiple sound sources within the sound field recording space (live venue LV1).

First, with reference to Figures 6 and 7, the system configuration and operation overview of sound field reproduction system 100A according to embodiment 2 will be described. Figure 6 is a block diagram showing an example system configuration of sound field reproduction system 100A according to embodiment 2. Figure 7 is a diagram showing an example of the operation overview from sound field recording to sound field reproduction according to embodiment 2. In the explanation of Figures 6 and 7, the same reference numerals will be used to simplify or omit explanations of content that overlaps with the configuration and operation of the corresponding Figures 3 and 4, and different content will be explained.

Sound field reproduction system 100A includes sound field recording device 1 and sound field reproduction device 2A. The configuration of sound field recording device 1 is the same as in embodiment 1, so a description thereof will be omitted.

The sound field reproduction device 2A is placed, for example, in a sound field reproduction space (for example, satellite venue STL1) and includes a sound source extraction direction control unit 21, a sound source presentation direction control unit 22, a re-encoding unit 23, a speaker direction designation unit 24, a first decoding unit 25, a sound source acquisition unit 29, a second encoding unit 30, a second signal mixing unit 31, a second decoding unit 32, a signal mixing unit 27, a sound field reproduction unit 28, and speakers SPk1, SPk2, ..., SPk8.

The sound source acquisition unit 29 acquires acoustic signals s1[n], ..., sb[n] of multiple sound sources (e.g., various sound sources such as vocals, bass, guitar, drums, etc.) to be presented in a sound field reproduction space (e.g., satellite venue STL1) and sends them to the second encoding unit 30. Each acoustic signal s1[n], ..., sb[n] can be expressed as a point sound source. n indicates a discrete time, and b indicates the number of sound sources. These sound sources may be recorded individually in the sound field recording space (live venue Lv1), or may be sound sources unrelated to the sound field recording space.

The second signal mixer 31 mixes the higher-order basis acoustic signals (e.g., Nth-order Ambisonics signals) for each sound source obtained by the encoding process by the second encoder 30, and sends the mixed signals to the second decoder 32.

Next, the operational procedure for sound field reproduction by the sound field reproduction device 2A will be described with reference to Figure 8. Figure 8 is a flowchart showing an example of the operational procedure for sound field reproduction by the sound field reproduction device 2A according to embodiment 2 in chronological order. In the description of Figure 8, processes that overlap with the description of Figure 5 will be assigned the same step numbers, and the description will be simplified or omitted, and only differences will be described.

8 , the sound source acquisition unit 29 of the sound field reproduction device 2A acquires acoustic signals s1[n], ..., sb[n] (examples of point sound source signals) of multiple sound sources (e.g., various sound sources such as vocals, bass, guitar, drums, etc.) to be presented in a sound field reproduction space (e.g., satellite venue STL1) (step St11). The second encoding unit 30 of the sound field reproduction device 2A reads out direction vectors θ _b of b point sound sources from a memory (not shown) or acquires them based on specifications from a user interface (not shown) (step St12).

As described above, the sound field reproduction device 2A according to embodiment 2 further includes a second encoding unit 30 that encodes each of multiple sound source signals (e.g., sound signals from various sound sources such as vocals, bass, guitar, and drums) to be presented in the sound field reproduction space (satellite venue STL1) to generate second higher-order basis sound signals (Nth-order Ambisonics signals), and a second signal mixing unit 31 that mixes the second higher-order basis sound signals for each sound source signal. As a result, the sound field reproduction device 2A according to embodiment 2 can output atmospheric sounds from sound sources that are to be uniquely presented in the sound field reproduction space (satellite venue STL1), while maintaining high directional resolution through the use of high-order basis signals, unlike the sound field recording space (live venue LV1).

Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It will be clear to those skilled in the art that various modifications, alterations, substitutions, additions, deletions, and equivalents may be conceived within the scope of the claims, and it is understood that these also fall within the technical scope of the present disclosure. Furthermore, the components of the above-described embodiments may be combined in any manner as long as they do not deviate from the spirit of the invention.

This disclosure is useful as a sound field reproduction device, sound field reproduction method, and sound field reproduction system that utilizes low-order sound field components recorded using an Ambisonics microphone to suppress increases in sound source localization errors within a sound field reproduction space.

1 Sound field recording device 2, 2A Sound field reproduction device 11 Ambisonics microphone 12 A/D conversion unit 13 Encoding unit 14 Microphone element direction designation unit 21 Sound source extraction direction control unit 22 Sound source presentation direction control unit 23 Re-encoding unit 24 Speaker direction designation unit 25 First decoding unit 26, 32 Second decoding unit 27 Signal mixing unit 28 Sound field reproduction unit 29 Sound source acquisition unit 30 Second encoding unit 31 Second signal mixing unit 100, 100A Sound field reproduction system SPk1, SPk2, SPk3, SPk4, SPk5, SPk6, SPk7, SPk8 Speaker

Claims (13)

a sound source extraction direction control unit that receives a designation of a sound source extraction direction within a sound field recording space in which a recording device is placed;
a re-encoding unit that re-encodes an acoustic signal corresponding to the sound source extraction direction among low-order basis acoustic signals based on an encoding process using a signal recorded by the recording device to generate a high-order basis acoustic signal;
a sound field reproduction unit that outputs a signal based on the high-order base acoustic signal from each of a plurality of speakers provided in a sound field reproduction space different from the sound field recording space,
Sound field reproduction device. a sound source presentation direction control unit that receives a designation of a sound source presentation direction that is the same as or different from the sound source extraction direction and is a direction of emphasizing sound field reproduction in a sound field reproduction space that is different from the sound field recording space;
the re-encoding unit performs the re-encoding using the acoustic signal and the sound source presentation direction to generate the high-order basis acoustic signal.
The sound field reproduction device according to claim 1 . a first decoding unit that generates a first sound field drive signal having a high-order basis component for each of the speakers by using the high-order basis acoustic signal and arrangement information of each of the plurality of speakers;
The sound field reproduction device according to claim 1 . a second decoding unit that generates a second sound field drive signal having a low-order basis component for each of the speakers by using the low-order basis acoustic signal and arrangement information of each of the plurality of speakers,
The sound field reproduction device according to claim 3. a signal mixer that mixes the first sound field drive signal and the second sound field drive signal for each speaker;
the sound field reproduction unit outputs the mixed signal by the signal mixer to each of the speakers as a signal based on the high-order basis acoustic signal.
The sound field reproduction device according to claim 4. The sound source extraction direction is specified as a three-dimensional direction from a reference position in the sound field recording space.
The sound field reproduction device according to claim 1 . The sound source presentation direction is specified as a three-dimensional direction from a reference position in the sound field recording space.
The sound field reproduction device according to claim 2. a second encoding unit that encodes each of a plurality of sound source signals to be presented in the sound field reproduction space to generate second higher-order basis acoustic signals;
a second signal mixer that mixes the second higher-order basis acoustic signals for each of the sound source signals,
The sound field reproduction device according to claim 3. a second decoding unit that generates a third sound field drive signal having a high-order basis component for each speaker by using the second high-order basis acoustic signal for each sound source signal after mixing by the second signal mixer and arrangement information of each of the plurality of speakers,
The sound field reproduction device according to claim 8. a signal mixing unit that mixes the first sound field drive signal and the third sound field drive signal for each speaker,
the sound field reproduction unit outputs the mixed signal by the signal mixer to each of the speakers as a signal based on the high-order basis acoustic signal.
The sound field reproduction device according to claim 9. receiving a designation of a sound source extraction direction within a sound field recording space in which a recording device is placed;
generating high-order basis acoustic signals by re-encoding acoustic signals corresponding to the sound source extraction direction among low-order basis acoustic signals based on an encoding process using the signals recorded by the recording device;
outputting a signal based on the high-order base acoustic signal from each of a plurality of speakers provided in a sound field reproduction space different from the sound field recording space,
Sound field reproduction method. a sound field recording device having a recording device capable of recording a sound source in a sound field recording space;
a sound field reproduction device that reproduces the acoustic signal recorded by the recording device in a sound field reproduction space that is different from the sound field recording space,
The sound field reproduction device comprises:
a sound source extraction direction control unit that receives a designation of a sound source extraction direction within the sound field recording space;
a re-encoding unit that re-encodes an acoustic signal corresponding to the sound source extraction direction among low-order basis acoustic signals based on an encoding process using a signal recorded by the recording device to generate a high-order basis acoustic signal;
a sound field reproduction unit that outputs a signal based on the high-order base acoustic signal from each of a plurality of speakers provided in the sound field reproduction space,
Sound field reproduction system. The recording device is configured by an Ambisonics microphone in which a plurality of microphone elements are arranged three-dimensionally so that each of the microphone elements faces in a different direction.
A sound field reproduction system according to claim 12.