Audio playback system, audio playback method, and program

Abstract

An audio playback system (1) comprises a first housing (100), a first speaker (160) provided in the first housing (100), a first microphone (130) provided in the first housing (100), a processor (110), and an equalizer (120), wherein: the processor (110) causes the first speaker (160) to output a first test audio, acquires a first sound pickup signal indicating the first test audio picked up by the first microphone (130), calculates a first frequency characteristic of the first sound pickup signal, estimates the placement of the first housing (100) in space on the basis of the first frequency characteristic, and determines a first correction parameter on the basis of the placement of the first housing (100); the equalizer (120) corrects the frequency characteristic of the input audio signal using the first correction parameter to generate a first corrected audio signal; and the first speaker (160) outputs audio based on the first corrected audio signal.

Description

[Technical Field]

[0001] The present disclosure relates to an audio reproduction system and the like. [Background Art]

[0002] Patent Document 1 discloses a technique for correcting the sound pressure level of a speaker for each frequency band such that the sound pressure level from the speaker at a user's listening position has a preset characteristic over the entire frequency band. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 1-130608 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, in order to correct the frequency characteristic of a sound collection signal at the user's listening position as in the technique disclosed in Patent Document 1, it is necessary for the user to place a microphone at the listening position, collect sound reproduced from the speaker with the microphone, and calculate correction parameters for correcting the frequency characteristic of an input audio signal input to the audio reproduction system. That is, the user needs to separately prepare special equipment such as a microphone in addition to what is required for normal reproduction, and skill and specialized knowledge are required to collect sound at the listening position and calculate the correction parameters. For this reason, it is difficult to achieve the performance (sound quality) intended by the designer in the user's space.

[0005] Accordingly, the present disclosure provides an audio reproduction system and the like that can easily achieve performance as intended by a designer. [Means for Solving the Problem]

[0006] The audio playback system according to this disclosure comprises a first housing installed in a space, a first speaker provided in the first housing, a first microphone provided in the first housing, a processor, and an equalizer unit. The processor causes the first speaker to output a first test sound based on a test signal, acquires a first sound pickup signal indicating the first test sound picked up by the first microphone, calculates a first frequency characteristic of the first sound pickup signal, estimates the placement of the first housing in the space based on the first frequency characteristic, determines a first correction parameter based on the placement of the first housing, the equalizer unit generates a first corrected sound signal by correcting the frequency characteristic of an input sound signal input to the audio playback system using the first correction parameter, and the first speaker outputs sound based on the first corrected sound signal.

[0007] The audio playback method according to this disclosure is an audio playback method performed by an audio playback system, the audio playback system comprising: a first housing installed in a space; a first speaker provided in the first housing; and a first microphone provided in the first housing, wherein the audio playback method involves: outputting a first test sound based on a test signal to the first speaker; acquiring a first sound pickup signal indicating the first test sound picked up by the first microphone; calculating a first frequency characteristic of the first sound pickup signal; estimating the arrangement of the first housing in the space based on the first frequency characteristic; determining a first correction parameter based on the arrangement of the first housing; generating a first corrected sound signal by correcting the frequency characteristic of an input sound signal input to the audio playback system using the first correction parameter; and outputting sound based on the first corrected sound signal to the first speaker.

[0008] The program disclosed herein is a program that causes a computer to execute the above-described audio playback method.

[0009] These comprehensive or specific embodiments may be implemented as a system, method, integrated circuit, computer program, or recording medium such as a computer-readable CD-ROM, or as any combination of a system, method, integrated circuit, computer program, and recording medium. [Effects of the Invention]

[0010] The audio playback system and other features described in this disclosure make it easy to achieve the performance intended by the designer. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an example of the configuration of the audio playback system according to Embodiment 1. [Figure 2] This block diagram shows an example of a correction parameter generator according to Embodiment 1. [Figure 3A] This is a diagram to explain the placement of "Free". [Figure 3B] This is a diagram to explain the placement of "Wall". [Figure 3C] This is a diagram illustrating the placement of "Corner". [Figure 3D] This is a diagram illustrating the arrangement of the "Shelf". [Figure 4] This graph shows an example of the difference between the first frequency response and the first reference frequency response for each actual configuration of the first enclosure. [Figure 5] This block diagram shows another example of a correction parameter generator according to Embodiment 1. [Figure 6] This figure shows an example of the configuration of the audio playback system according to Embodiment 2. [Figure 7A] This graph shows an example of the difference between the second frequency response and the second reference frequency response for each actual slave chassis configuration when the master chassis is configured as "Corner". [Figure 7B]It is a graph showing an example of the difference between the second frequency characteristic and the second reference frequency characteristic for each actual arrangement of the slave enclosure when the arrangement of the master enclosure is "Free". [Figure 7C] It is a graph showing an example of the difference between the second frequency characteristic and the second reference frequency characteristic for each actual arrangement of the slave enclosure when the arrangement of the master enclosure is "Shelf". [Figure 7D] It is a graph showing an example of the difference between the second frequency characteristic and the second reference frequency characteristic for each actual arrangement of the slave enclosure when the arrangement of the master enclosure is "Wall". [Figure 8] It is a diagram showing an example of the configuration of an audio reproduction system according to Embodiment 3. [Figure 9] It is a flowchart showing an example of an audio reproduction method according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, overly detailed descriptions may be omitted. For example, detailed descriptions of already well-known matters and repeated descriptions for substantially the same configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art.

[0013] It should be noted that the inventor provides the accompanying drawings and the following description for those skilled in the art to fully understand the present disclosure, and does not intend to limit the subject matter described in the claims thereby.

[0014] (Embodiment 1) Hereinafter, the audio reproduction system according to Embodiment 1 will be described with reference to FIGS. 1 to 5.

[0015] FIG. 1 is a diagram showing an example of the configuration of an audio reproduction system 1 according to Embodiment 1.

[0016] The audio playback system 1 is a system for outputting audio from the first speaker 160 based on an input audio signal input to the audio playback system 1 from a sound source player connected to the input terminal 140. The sound source player may be built into the audio playback system 1. That is, the sound source player may be an external component of the audio playback system 1, or it may be a component of the audio playback system 1 that is built into the audio playback system 1. The audio playback system 1 has a function for optimizing the frequency characteristics of the audio signal obtained by sound collection at the listening position (hereinafter also referred to as the audio signal at the listening position), and this function will be described below.

[0017] The audio playback system 1 comprises a first housing 100, a processor 110, an equalizer 120, a first microphone 130, an input terminal 140, an amplifier 150, and a first speaker 160.

[0018] The audio playback system 1 is a computer including a processor 110 (microprocessor) and memory 180. The audio playback system 1 may also include a communication interface and a user interface. The memory 180 is a ROM (Read Only Memory) and RAM (Random Access Memory), capable of storing data related to programs and processes executed by the processor 110. As shown in Figure 1, the processor 110 includes a test signal generator 111, a signal switcher 112, a sound acquisition meter 113, and a correction parameter generator 114. In other words, these components are realized by the processor 110, which executes programs stored in the memory 180.

[0019] For example, as shown in Figure 2 later, memory 180 stores data related to processing, such as the reference frequency characteristics (specifically, the first reference frequency characteristics), system information, or correction parameter groups. Note that the program executed by processor 110 and the processing data may be stored in different memories.

[0020] For example, in Embodiment 1, the audio playback system 1 is a computer (device) in a single enclosure, has one input channel, and has one output channel. For example, the audio playback system 1 comprises only one set of a first enclosure 100, a processor 110, an equalizer 120, a first microphone 130, an input terminal 140, an amplifier 150, and a first speaker 160, and reproduces monaural sound.

[0021] Furthermore, the input to the audio playback system 1 may be multiple channels, and the output from the audio playback system 1 may also be multiple channels. In this case, the audio playback system 1 can reproduce stereo sound or surround sound. For example, the audio playback system 1 may be equipped with multiple sets of a first chassis 100, processor 110, equalizer 120, first microphone 130, input terminal 140, amplifier 150, and first speaker 160, and these components may be arranged in one chassis, so that the audio playback system 1 is a device in a single chassis. Alternatively, for example, the audio playback system 1 may be equipped with multiple sets of a first chassis 100, processor 110, equalizer 120, first microphone 130, input terminal 140, amplifier 150, and first speaker 160, and the audio playback system 1 may be a system consisting of multiple chassis. Furthermore, when the input to the audio playback system 1 is multiple channels and the output from the audio playback system 1 is multiple channels, the number of input channels and the number of output channels may be different. For example, the number of output channels can be increased or decreased by appropriately combining the inputs.

[0022] The first enclosure 100 is installed in a space such as the user's room. The first speaker 160 is provided in the first enclosure 100. The first microphone 130 is provided in the first enclosure 100. In other words, the first enclosure 100 is equipped with both a speaker and a microphone.

[0023] Since the frequency characteristics of the audio signal at the listening position change from those of the input audio signal depending on the arrangement of the first enclosure 100 in space, the audio playback system 1 has a function to estimate the arrangement of the first enclosure 100 and to determine a first correction parameter for correcting the frequency characteristics of the audio signal at the listening position based on the estimated arrangement of the first enclosure 100.

[0024] The equalizer 120 is an example of an equalizer unit that generates a corrected audio signal by correcting the frequency characteristics of the input audio signal input to the audio playback system 1, and outputs the corrected audio signal to the first speaker 160. For example, the equalizer 120 is a parametric equalizer that can adjust the center frequency of the input audio signal, the width of the frequency band to be adjusted, and the volume. For example, an amplifier 150 is provided between the equalizer 120 and the first speaker 160, and the sound based on the corrected audio signal amplified by the amplifier 150 can be output from the first speaker 160. Note that the equalizer 120 may be implemented by the processor 110. In other words, the equalizer 120 may be a component of the processor 110.

[0025] The test signal generator 111, signal switcher 112, sound acquisition measuring instrument 113, and correction parameter generator 114 are implemented by a processor 110 that executes a program stored in memory 180. The processor 110 has a mode for optimizing the frequency characteristics of the audio signal at the listening position and a mode for playing normal audio (input audio signal from the sound source player). In the mode for optimizing the frequency characteristics of the audio signal at the listening position, the test signal generator 111 generates a test signal, and the signal switcher 112 connects the test signal generator 111 to the equalizer 120 in order to output the test signal to the equalizer 120. The test signal is, for example, a sine wave signal, a TSP (Time Stretched Pulse) signal, or white noise, with frequency components across the audio band (e.g., 20Hz to 20kHz). In normal audio playback mode, the test signal generator 111 does not generate a test signal, and the signal switcher 112 connects the input terminal 140 to the equalizer 120 in order to output the input audio signal to the equalizer 120.

[0026] In the mode for optimizing the frequency characteristics of the audio signal at the listening position, the equalizer 120 does not perform any correction. In other words, the test signal generated by the test signal generator 111 is not corrected by the equalizer 120. The processor 110 causes the first test audio, based on the test signal generated by the test signal generator 111, to be output to the first speaker 160. As a result, the first test audio is output from the first speaker 160 into the space where the first enclosure 100 is installed.

[0027] The first test sound output from the first speaker 160 into the space where the first enclosure 100 is installed is picked up by the first microphone 130 installed in the first enclosure 100. For example, the first microphone 130 picks up the first test sound, which includes the direct sound from the first speaker 160 and the reflected sound of the sound output from the first speaker 160 reflected by walls, ceilings, floors, furniture, and other objects (hereinafter referred to as walls, etc.) in the space where the first enclosure 100 is installed.

[0028] The sound acquisition measuring instrument 113 acquires a first sound acquisition signal that represents the first test sound picked up by the first microphone 130. Note that the sound picked up by the first microphone 130 at the timing when the first test sound is output from the first speaker 160 includes the direct sound that reaches the first microphone 130 directly and the reflected sound that reaches the first microphone 130 after being reflected by walls, etc., and is different from the first test sound output by the first speaker 160, but for convenience this sound is also called the first test sound. Furthermore, the sound acquisition signal from the first microphone 130 based on the sound that is conveniently called the first test sound is called the first sound acquisition signal. The sound acquisition measuring instrument 113 outputs the acquired first sound acquisition signal to the correction parameter generator 114.

[0029] The correction parameter generator 114 determines the first frequency characteristics of the first sound-collected signal, estimates the placement of the first enclosure 100 in space based on the determined first frequency characteristics, and determines the first correction parameters based on the estimated placement of the first enclosure 100. Details of the correction parameter generator 114 will be explained later in Figure 2. The correction parameter generator 114 sets the determined first correction parameters to the equalizer 120.

[0030] Subsequently, in the mode for normal audio playback, the equalizer 120 generates a first corrected audio signal by correcting the frequency characteristics of the input audio signal input to the audio playback system 1 using a first correction parameter, and outputs audio based on the first corrected audio signal to the first speaker 160. In other words, by outputting audio based on the first corrected audio signal, which is generated by correcting the frequency characteristics of the input audio signal using the first correction parameter, from the first speaker 160, the user can hear audio with improved frequency characteristics at the listening position.

[0031] Next, the details of the correction parameter generator 114 will be explained using Figure 2.

[0032] Figure 2 is a block diagram showing an example of a correction parameter generator 114 according to Embodiment 1.

[0033] As shown in Figure 2, the correction parameter generator 114 comprises a frequency response analysis unit 115, a comparative analysis unit 116, and a determination unit 117. The frequency response analysis unit 115, the comparative analysis unit 116, and the determination unit 117 are implemented by a processor 110 or the like that executes a program stored in memory 180.

[0034] The correction parameter generator 114 uses the first reference frequency characteristics stored in the memory 180 to estimate the arrangement of the first enclosure 100 and to determine the first correction parameters.

[0035] The frequency response analysis unit 115 calculates the first frequency characteristics of the first sound pickup signal, which represents the first test sound output from the first speaker 160 and picked up by the first microphone 130. For example, the frequency response analysis unit 115 calculates the first frequency characteristics of the first sound pickup signal by performing an FFT (Fast Fourier Transform) on the first sound pickup signal.

[0036] The comparative analysis unit 116 estimates the placement of the first housing 100 by comparing the first reference frequency characteristics stored in the memory 180 with the first frequency characteristics. The comparative analysis unit 116 may also use system information, including information regarding the frequency characteristics of the first microphone 130, when estimating the placement of the first housing 100. The method for estimating the placement of the first housing 100 will now be explained using Figures 3A to 3D and Figure 4.

[0037] Figure 3A is a diagram illustrating the placement of "Free".

[0038] Figure 3B is a diagram illustrating the placement of the "Wall".

[0039] Figure 3C is a diagram illustrating the placement of "Corner".

[0040] Figure 3D is a diagram illustrating the arrangement of the "Shelf".

[0041] In Figures 3A to 3D, "SP" indicates an enclosure in which a speaker is installed, and Figures 3A to 3D show examples of the arrangement of two enclosures, each in which a speaker is installed. Figures 3A to 3C are top views of the space (viewed from the ceiling), and Figure 3D is a front view of the bookshelf.

[0042] Figure 3A shows the "Free" configuration, in which the enclosure containing the speaker is placed away from the walls of the space.

[0043] Figure 3B shows the "Wall" configuration, in which the speaker enclosure is placed in close proximity to one of the walls of the space.

[0044] Figure 3C shows the "Corner" configuration, in which the speaker enclosure is placed in the corner of the space. Specifically, in the "Corner" configuration, the speaker enclosure is placed close to either of the two walls of the space.

[0045] Figure 3D shows the arrangement of the "Shelf," in which the enclosure containing the speaker is placed on a bookshelf in the space.

[0046] For example, in a space such as a room, several predetermined arrangements of speaker enclosures, as shown in Figures 3A to 3D, are assumed. For example, the comparative analysis unit 116 estimates the arrangement of the first enclosure 100 by estimating which of the multiple predetermined arrangements shown in Figures 3A to 3D the arrangement of the first enclosure 100 is closest to.

[0047] Figure 4 is a graph showing an example of the difference between the first frequency response and the first reference frequency response for each actual arrangement of the first enclosure 100.

[0048] The first reference frequency response is a frequency response calculated in advance from the sound pickup signal obtained by capturing the first reference test sound, which is based on a test signal output from a first test speaker installed in a first test enclosure located at a specific position in the test space, using a first test microphone installed in the first test enclosure.

[0049] The first test enclosure, first test speaker, and first test microphone are basically the same as the first enclosure 100, first speaker 160, and first microphone 130, and the first reference test audio is the same as the first test audio. When the first reference test audio is output from the first test speaker, the equalizer does not perform any correction on the test signal representing the reference test audio. The first reference frequency response is the frequency response calculated from the sound picked up by the first test microphone when the first reference test audio is output from the first test speaker while the first test enclosure is in a standard "Free" configuration (specifically, an average configuration within the "Free" configuration).

[0050] For example, the designer of audio playback system 1 designs the entire audio playback system, including speaker characteristics, so that the frequency characteristics of the audio signal are optimized in a standard "Free" configuration. Then, a first reference test audio based on a test signal is captured by a first test microphone installed in the first test enclosure, and the first reference frequency characteristics are calculated from the captured signal. At this time, no equalizer correction is applied, but the first reference audio with optimal frequency characteristics is output from the first test speaker, which is in a standard "Free" configuration.

[0051] In Embodiment 1, the arrangement of the first test enclosure is the "Free" arrangement shown in Figure 3A. In other words, the first reference frequency response is calculated when the first test enclosure is in the "Free" arrangement.

[0052] For example, the comparative analysis unit 116 calculates the difference in a predetermined frequency band (e.g., 50Hz to 6kHz) between a first reference frequency characteristic calculated in advance using a first test enclosure installed at a specific position in the test space, and a first frequency characteristic calculated in the user's space. If the arrangement of the first enclosure 100 in the user's space corresponds to the "Free" arrangement (or an arrangement close to "Free"), the difference between the first reference frequency characteristic and the first frequency characteristic in the predetermined frequency band will be close to 0 over the predetermined frequency band, as shown in the graph in the upper left of Figure 4.

[0053] In the user's space, if the arrangement of the first enclosure 100 corresponds to an arrangement that is close to a "Wall", then the difference between the first reference frequency characteristic and the first frequency characteristic in a predetermined frequency band will occur to some extent over that predetermined frequency band, as shown in the upper right graph of Figure 4.

[0054] In the user's space, if the placement of the first enclosure 100 corresponds to a "Corner" (a placement close to a "Corner"), the difference between the first reference frequency characteristic and the first frequency characteristic in a predetermined frequency band is larger over the predetermined frequency band than when the placement of the first enclosure 100 corresponds to a "Wall," as shown in the graph in the lower left of Figure 4.

[0055] In the user's space, if the arrangement of the first enclosure 100 corresponds to the arrangement "Shelf" (or an arrangement close to "Shelf"), the difference between the first reference frequency characteristic and the first frequency characteristic in a predetermined frequency band is larger over the predetermined frequency band than when the arrangement of the first enclosure 100 corresponds to the arrangement "Corner," as shown in the graph in the lower right of Figure 4.

[0056] In this way, the comparative analysis unit 116 estimates the arrangement according to the size of the difference. Specifically, it determines it as "Free" when the difference is almost zero, and as the difference increases, it determines it as "Wall," "Corner," or "Shelf."

[0057] For example, the comparative analysis unit 116 smooths the first reference frequency response and the first frequency response using an octave band filter such as a 1 / 3 octave filter, then normalizes the amplitude level at a 1 kHz signal level and converts the amplitude level to decibels. By normalizing the amplitude level, it becomes possible to appropriately compare the first reference frequency response and the first frequency response even if there is a difference in the sound pickup levels between them.

[0058] For example, the comparative analysis unit 116 estimates the configuration of the first enclosure 100 by adding the absolute values ​​of the frequency differences between the first reference frequency characteristics and the first frequency characteristics in a predetermined frequency band, and determining which of the numerical ranges set for each of the multiple predetermined configurations (for example, the "Free" configuration, the "Wall" configuration, the "Corner" configuration, and the "Shelf" configuration) the added value falls into. The numerical ranges set for each of the multiple predetermined configurations do not overlap. For example, if the added value falls into the numerical range set for the "Free" configuration, the configuration of the first enclosure 100 can be estimated to be the "Free" configuration. For example, if the added value falls into the numerical range set for the "Wall" configuration, the configuration of the first enclosure 100 can be estimated to be the "Wall" configuration. For example, if the added value falls into the numerical range set for the "Corner" configuration, the configuration of the first enclosure 100 can be estimated to be the "Corner" configuration. For example, if the added value falls within the numerical range set for the "Shelf" arrangement, it can be inferred that the arrangement of the first enclosure 100 is the "Shelf" arrangement.

[0059] The comparison result between the first reference frequency response and the first frequency response changes according to the change in the arrangement of the first enclosure 100. In other words, there is a correlation between the comparison result between the first reference frequency response and the first frequency response and the arrangement of the first enclosure 100. Therefore, by comparing the first reference frequency response and the first frequency response, the arrangement of the first enclosure 100 can be easily estimated.

[0060] Returning to the explanation in Figure 2, the determination unit 117 determines a predetermined correction parameter as the first correction parameter for the predetermined configuration estimated to be the configuration of the first enclosure 100 from among a plurality of predetermined configurations (for example, the "Free" configuration, the "Wall" configuration, the "Corner" configuration, and the "Shelf" configuration). As shown in Figure 2, the memory 180 stores a group of predetermined correction parameters for a plurality of predetermined configurations. For example, the memory 180 stores a predetermined correction parameter for the "Free" configuration, a predetermined correction parameter for the "Wall" configuration, a predetermined correction parameter for the "Corner" configuration, and a predetermined correction parameter for the "Shelf" configuration.

[0061] The designer of the audio playback system 1 can pre-determine the optimal correction parameters for each of the multiple predetermined arrangements by conducting experiments or simulations. Therefore, the first correction parameter can be easily determined by using the pre-determined correction parameters for the pre-determined arrangement estimated as the arrangement of the first housing 100 as the first correction parameter. For example, if the arrangement of the first housing 100 is estimated to be the "Free" arrangement among the multiple predetermined arrangements (specifically, an arrangement close to the "Free" arrangement), then the pre-determined correction parameters for the "Free" arrangement among the set of correction parameters can be used as the first correction parameter.

[0062] Furthermore, the first frequency characteristics used to estimate the arrangement of the first enclosure 100 may be used to determine the first correction parameter. This will be explained with reference to Figure 5.

[0063] Figure 5 is a block diagram showing another example of the correction parameter generator 114 according to Embodiment 1. The correction parameter generator 114 shown in Figure 5 differs from the correction parameter generator 114 shown in Figure 2 in that it includes a determination unit 117a instead of a determination unit 117, and the memory 180 does not store the correction parameter group. Other aspects are the same as the correction parameter generator 114 shown in Figure 2, so a description is omitted.

[0064] Memory 180 does not store the correction parameter group. In other words, the determination unit 117a determines the first correction parameter without using the correction parameter group.

[0065] The determination unit 117a determines a first correction parameter that reduces the difference between the first reference frequency characteristic and the first frequency characteristic in a predetermined frequency range for a predetermined arrangement that has been estimated as the arrangement of the first housing 100 from among a plurality of predetermined arrangements.

[0066] For example, the first reference frequency response is the frequency response of a first reference test audio based on a test signal, calculated with an equalizer designed so that the frequency response of the audio signal is optimized at the listening position of the audio playback system 1. Therefore, by determining a first correction parameter that reduces the difference between the first frequency response and the first reference frequency response in a predetermined frequency band, the frequency response of the audio signal can be improved even at the listening position in the user's space.

[0067] However, the first reference frequency response is the frequency response calculated when the first test enclosure is in a specific position (the "Free" configuration), and the configuration of the first test enclosure may differ from the configuration of the first enclosure 100. Therefore, the frequency range over which the first reference frequency response and the first frequency response should be compared will differ depending on the configuration of the first enclosure 100.

[0068] In contrast, the designer can pre-determine, through experiments or simulations, the frequency range over which the first reference frequency characteristic and the first frequency characteristic should be compared for each of several predetermined arrangements. Therefore, the first correction parameter can be determined according to the arrangement of the first enclosure 100.

[0069] As explained above, the first microphone 130, which is necessary to determine the first correction parameter for the first speaker 160 installed in the first housing 100, is pre-installed in the first housing 100. Therefore, the user does not need to prepare any special equipment such as a microphone in addition to what is necessary for normal playback. Furthermore, the placement of the first housing 100 is automatically estimated from the first frequency characteristics of the first sound pickup signal representing the first test sound picked up by the first microphone 130, and the first correction parameter is automatically determined from the estimated placement of the first housing 100. As a result, the user does not need the skills and expertise to pick up the sound signal at the listening position and determine the correction parameter. Therefore, a user without expertise can automatically improve the frequency characteristics at the listening position with a single touch, making it easy to achieve the performance intended by the designer.

[0070] (Embodiment 2) Next, the audio playback system according to Embodiment 2 will be described using Figures 6 and 7A to 7D.

[0071] Figure 6 shows an example of the configuration of the audio playback system 2 according to Embodiment 2.

[0072] The audio playback system 2 is a system for outputting audio from the first speaker 160 and the second speaker 230 based on an input audio signal input to the audio playback system 2 from a sound source player connected to the input terminal 140. The sound source player may be built into the audio playback system 2. That is, the sound source player may be an external component of the audio playback system 2, or it may be built into the audio playback system 2 as a component of the audio playback system 2. The audio playback system 2 has a function for optimizing the frequency characteristics of the audio signal at the listening position, and this function will be described below.

[0073] The audio playback system 2 comprises a first enclosure 101, a processor 110a, an equalizer 120a, a first microphone 130, an input terminal 140, an amplifier 150, a first speaker 160, and a first communication interface 170, as well as a second enclosure 201, a second communication interface 210, an amplifier 220, and a second speaker 230.

[0074] Regarding the estimation of the arrangement of the first housing 101, the determination of the first correction parameter, and the operation during playback related to the sound output from the first speaker 160, the explanation will be omitted for parts that are the same as in Embodiment 1. Here, the explanation will focus on the estimation of the arrangement of the second housing 201, the determination of the second correction parameter, and the operation during playback related to the sound output from the second speaker 230. In addition, explanations of components with the same reference numerals and terms with the same names as in Embodiment 1 may be omitted.

[0075] The audio playback system 2 is a computer that includes a processor 110a (microprocessor), memory 180, and a communication interface. The audio playback system 2 may also have a user interface. As shown in Figure 6, the processor 110a includes a test signal generator 111a, a signal switcher 112, a sound pickup meter 113a, and a correction parameter generator 114a. In other words, these components are implemented by the processor 110a, which executes a program stored in memory 180.

[0076] For example, memory 180 stores data related to processing, such as reference frequency characteristics, system information, or correction parameter groups, similar to Embodiment 1. However, as reference frequency characteristics, a first reference frequency characteristic for the first housing 101 and a second reference frequency characteristic for the second housing 201 are stored.

[0077] For example, in the audio playback system 2, the first chassis 101, which houses the processor 110a, acts as the master chassis, and the second chassis 201 acts as the slave chassis. Alternatively, the master chassis and the slave chassis may be located within a single chassis, so that the audio playback system 2 is a single-chassis device.

[0078] The first housing 101 is a component corresponding to the first housing 100 of Embodiment 1, and any explanation that overlaps with Embodiment 1 will be omitted.

[0079] The second enclosure 201 is installed in the space where the first enclosure 101 is installed. The second speaker 230 is installed in the second enclosure 201.

[0080] Since the frequency characteristics of the audio signal at the listening position change from those of the input audio signal depending on the arrangement of the second enclosure 201 in space, the audio playback system 2 has a function to estimate the arrangement of the second enclosure 201 and to determine a second correction parameter for correcting the frequency characteristics of the audio signal at the listening position based on the estimated arrangement of the second enclosure 201, as will be described later.

[0081] Equalizer 120a is a component corresponding to equalizer 120 in Embodiment 1, and any explanation that overlaps with Embodiment 1 will be omitted.

[0082] Embodiment 2 describes a configuration in which a one-channel audio signal is input and sound based on that audio signal is output from the first speaker 160 of the first housing 101 and the second speaker 230 of the second housing 201, respectively. However, stereo sound may be reproduced by inputting two-channel audio signals, with one output from the first speaker 160 and the other output from the second speaker 230. The same applies when there are three or more input channels and three or more housings (speakers). In this case, surround sound may also be reproduced.

[0083] The first communication interface 170 is provided on the first enclosure 101 and is a communication interface capable of transmitting voice signals. The first communication interface 170 transmits voice signals to the second communication interface 210 on the second enclosure 201. The first communication interface 170 does not necessarily have a receiving function. In other words, the first communication interface 170 may have only a transmitting function.

[0084] The second communication interface 210 is provided in the second housing 201 and is capable of receiving audio signals from the first communication interface 170. The first communication interface 170 and the second communication interface 210 may be connected wirelessly or by wire. The second communication interface 210 does not need to have a transmission function. In other words, the second communication interface 210 may have only a reception function.

[0085] The second speaker 230 outputs audio based on the audio signal received by the second communication interface 210. For example, an amplifier 220 is provided between the second communication interface 210 and the second speaker 230, and audio based on the corrected audio signal amplified by the amplifier 220 can be output from the second speaker 230.

[0086] The test signal generator 111a, signal switcher 112, sound collection measuring instrument 113a, and correction parameter generator 114a are implemented by a processor 110a that executes a program stored in memory 180.

[0087] In the mode for optimizing the frequency characteristics of the audio signal at the listening position, the equalizer 120a does not perform any correction. In other words, the test signal generated by the test signal generator 111a is not corrected by the equalizer 120a. The processor 110a causes the first speaker 160 to output a first test audio based on the test signal generated by the test signal generator 111a. As a result, the first test audio is output from the first speaker 160 into the space where the first enclosure 101 and the second enclosure 201 are installed. The test signal generator 111a also causes the second speaker 230 to output a second test audio based on the test signal by sending a test signal from the first communication I / F 170 to the second communication I / F 210. As a result, the second test audio is output from the second speaker 230 into the space where the first enclosure 101 and the second enclosure 201 are installed.

[0088] The second test sound output from the second speaker 230 into the space where the first enclosure 101 and the second enclosure 201 are installed is picked up by the first microphone 130 installed in the first enclosure 101. For example, the first microphone 130 picks up the reflected sound of the sound output from the second speaker 230 reflected by the walls and other surfaces in the space where the first enclosure 101 and the second enclosure 201 are installed, as the second test sound.

[0089] Furthermore, the period during which the first test sound is output from the first speaker 160 and the period during which the second test sound is output from the second speaker 230 do not overlap. If these periods overlapped, the first microphone 130 would pick up both the first and second test sounds at the same time, making it difficult to distinguish between the first and second test sounds.

[0090] The sound acquisition measuring instrument 113a acquires a first sound acquisition signal indicating the first test sound picked up by the first microphone 130. The sound acquisition measuring instrument 113a also acquires a second sound acquisition signal indicating the second test sound picked up by the first microphone 130.

[0091] The audio picked up by the first microphone 130 at the time the second test audio is output from the second speaker 230 includes both the direct sound that reaches the first microphone 130 directly and the reflected sound that reaches the first microphone 130 after being reflected by walls, etc. Although this audio is different from the second test audio output by the second speaker 230, it is also referred to as the second test audio for convenience. Furthermore, the sound signal picked up by the first microphone 130 based on this audio, which is conveniently referred to as the second test audio, is called the second sound pickup signal.

[0092] The sound acquisition measuring instrument 113a outputs the acquired first sound acquisition signal and second sound acquisition signal to the correction parameter generator 114a.

[0093] The correction parameter generator 114a calculates the first frequency characteristics of the first sound-collected signal, estimates the placement of the first enclosure 101 in space based on the calculated first frequency characteristics, and determines the first correction parameters based on the estimated placement of the first enclosure 101. The correction parameter generator 114a also calculates the second frequency characteristics of the second sound-collected signal, estimates the placement of the second enclosure 201 in space based on the calculated second frequency characteristics, and determines the second correction parameters based on the estimated placement of the second enclosure 201. Details of the correction parameter generator 114a will be described later. The correction parameter generator 114a sets the determined first and second correction parameters to the equalizer 120a.

[0094] Subsequently, in the mode for normal audio playback, the equalizer 120a generates a first corrected audio signal by correcting the frequency characteristics of the input audio signal input to the audio playback system 2 using a first correction parameter, and outputs audio based on the first corrected audio signal to the first speaker 160. Furthermore, the equalizer 120a generates a second corrected audio signal by correcting the frequency characteristics of the input audio signal input to the audio playback system 2 using a second correction parameter, and outputs audio based on the second corrected audio signal to the second speaker 230 via the first communication I / F 170. In other words, audio based on the first corrected audio signal, generated by correcting the frequency characteristics of the input audio signal using the first correction parameter, is output from the first speaker 160, and audio based on the second corrected audio signal, generated by correcting using the second correction parameter, is output from the second speaker 230, so that the user can hear audio with improved frequency characteristics at the listening position.

[0095] Next, the details of the correction parameter generator 114a will be explained using Figure 2. Figure 2 is a block diagram showing an example of the correction parameter generator 114 according to Embodiment 1, but in the description of Embodiment 2, the correction parameter generator 114 shown in Figure 2 is replaced with the correction parameter generator 114a.

[0096] The correction parameter generator 114a comprises a frequency response analysis unit 115, a comparative analysis unit 116, and a determination unit 117. The frequency response analysis unit 115, the comparative analysis unit 116, and the determination unit 117 are implemented by a processor 110a or the like that executes a program stored in memory 180.

[0097] The correction parameter generator 114a uses the first reference frequency characteristics for the first enclosure 101 and the second reference frequency characteristics for the second enclosure 201 stored in the memory 180 to estimate the arrangement of the first enclosure 101 and the second enclosure 201, and to determine the first and second correction parameters.

[0098] The frequency response analysis unit 115 calculates the first frequency characteristics of the first sound pickup signal, which is output from the first speaker 160 and picked up by the first microphone 130, and the second frequency characteristics of the second sound pickup signal, which is output from the second speaker 230 and picked up by the first microphone 130. For example, the frequency response analysis unit 115 calculates the first frequency characteristics of the first sound pickup signal by performing an FFT on the first sound pickup signal, and calculates the second frequency characteristics of the second sound pickup signal by performing an FFT on the second sound pickup signal.

[0099] The comparative analysis unit 116 estimates the arrangement of the first housing 101 and uses the estimation result (i.e., the arrangement of the first housing 101) to estimate the arrangement of the second housing 201. Specifically, the comparative analysis unit 116 estimates the arrangement of the first housing 101 by comparing the first reference frequency characteristics stored in the memory 180 with the first frequency characteristics, and then, taking the estimation result into consideration, estimates the arrangement of the second housing 201 by comparing the second reference frequency characteristics stored in the memory 180 with the second frequency characteristics. The comparative analysis unit 116 may also use system information, including information regarding the frequency characteristics of the first microphone 130, when estimating the arrangement of the first housing 101 and the second housing 201. The method for estimating the arrangement of the first housing 101 is the same as that described in Embodiment 1, so the explanation will be omitted. The method for estimating the arrangement of the second housing 201 will be explained using Figures 7A to 7D.

[0100] Figure 7A is a graph showing an example of the difference between the second frequency response and the second reference frequency response for each actual arrangement of the slave enclosure (second enclosure 201) when the master enclosure (first enclosure 101) is arranged in "Corner".

[0101] Figure 7B is a graph showing an example of the difference between the second frequency response and the second reference frequency response for each actual arrangement of the slave enclosure (second enclosure 201) when the arrangement of the master enclosure (first enclosure 101) is "Free".

[0102] Figure 7C is a graph showing an example of the difference between the second frequency response and the second reference frequency response for each actual configuration of the slave enclosure (second enclosure 201) when the master enclosure (first enclosure 101) is configured as "Shelf".

[0103] Figure 7D is a graph showing an example of the difference between the second frequency response and the second reference frequency response for each actual arrangement of the slave enclosure (second enclosure 201) when the master enclosure (first enclosure 101) is arranged in a "Wall" configuration.

[0104] Figures 7A to 7D show the arrangement of the master enclosure (first enclosure 101) and the slave enclosure (second enclosure 201) in space, labeled "SP". "Shelf" indicates that either the master enclosure (first enclosure 101) or the slave enclosure (second enclosure 201) is placed on a bookshelf.

[0105] For example, in a space such as a room, several predetermined arrangements of speaker enclosures can be assumed, as shown in Figures 3A to 3D. For example, the comparative analysis unit 116 estimates the arrangement of the first enclosure 101 and the second enclosure 201 by estimating which of the several predetermined arrangements shown in Figures 3A to 3D the arrangement of the first enclosure 101 and the arrangement of the second enclosure 201 are closest to.

[0106] The second reference frequency response is a frequency response pre-calculated from the sound pickup signal obtained by capturing the second reference test audio, which is based on a test signal output from a second test speaker installed in a second test enclosure located at a specific position in the test space, using a first test microphone installed in the first test enclosure.

[0107] The second test enclosure and second test speaker are basically the same as the second enclosure 201 and second speaker 230, and the second reference test audio is the same as the second test audio. When the second reference test audio is output from the second test speaker, the equalizer does not correct the test signal representing the second reference test audio. The second reference frequency response is the frequency response calculated from the sound picked up by the first test microphone when the second reference test audio is output from the second test speaker while the second test enclosure is in a standard "Free" configuration (specifically, an average configuration within the "Free" configuration).

[0108] For example, the designer of the audio playback system 2 designs the entire audio playback system, including the speaker characteristics, so that the frequency characteristics of the audio signal are optimized in a standard "Free" configuration. Then, a second reference test audio based on a test signal is captured by a first test microphone installed in the first test enclosure, and the second reference frequency characteristics are calculated from the captured signal. At this time, no equalizer correction is applied, but the second reference audio with optimal frequency characteristics is output from the second test speaker, which is in a standard "Free" configuration. The first reference frequency characteristics are calculated in the same manner as in Embodiment 1.

[0109] In Embodiment 2, the arrangement of the first and second test enclosures is the "Free" arrangement shown in Figure 3A. In other words, the first reference frequency and second reference frequency characteristics were calculated when the first and second test enclosures were in the "Free" arrangement.

[0110] For example, the comparative analysis unit 116 calculates the difference in a predetermined frequency band (e.g., 50Hz to 6kHz) between a second reference frequency characteristic calculated in advance using a second test enclosure installed at a specific location in the test space, and a second frequency characteristic calculated in the user's space. However, since the second sound pickup signal, which represents the second test sound output from the second speaker 230, is picked up by the first microphone 130 installed in the first enclosure 101, the second frequency characteristic of the second sound pickup signal is affected by the placement of the first enclosure 101. Therefore, the difference between the second reference frequency characteristic and the second frequency characteristic will differ depending on the placement of the first enclosure 101. Accordingly, the comparative analysis unit 116 estimates the placement of the second enclosure 201 using the estimation result of the placement of the first enclosure 101 as described above.

[0111] Figure 7A shows the difference in a predetermined frequency band between the second reference frequency characteristics and the second frequency characteristics for the configuration of the second enclosure 201 ("Free", "Wall", "Corner", and "Shelf"), when the configuration of the first enclosure 101 in the user's space corresponds to the "Corner" configuration (a configuration close to the "Corner").

[0112] Figure 7B shows the difference in a predetermined frequency band between the second reference frequency characteristics and the second frequency characteristics for the configuration of the second enclosure 201 ("Free", "Wall", "Corner", and "Shelf") when the configuration of the first enclosure 101 in the user's space corresponds to the "Free" configuration (or a configuration close to "Free").

[0113] Figure 7C shows the difference in a predetermined frequency band between the second reference frequency characteristics and the second frequency characteristics for the configuration of the second enclosure 201 ("Free", "Wall", "Corner", and "Shelf"), when the configuration of the first enclosure 101 in the user's space corresponds to the configuration "Shelf" (configuration close to "Shelf").

[0114] Figure 7D shows the difference in a predetermined frequency band between the second reference frequency characteristics and the second frequency characteristics for the configuration of the second enclosure 201 ("Free", "Wall", "Corner", and "Shelf"), when the configuration of the first enclosure 101 in the user's space corresponds to the configuration "Wall" (configuration close to "Wall").

[0115] For example, the comparative analysis unit 116 smooths the second reference frequency response and the second frequency response using an octave band filter such as a 1 / 3 octave, then normalizes the amplitude level at a 1 kHz signal level and converts the amplitude level to decibels. By normalizing the amplitude level, it becomes possible to appropriately compare the second reference frequency response and the second frequency response even if there is a difference in the sound pickup levels between them.

[0116] For example, the comparative analysis unit 116 estimates the configuration of the second enclosure 201 by adding the absolute values ​​of the frequency differences between the second reference frequency characteristic and the second frequency characteristic in a predetermined frequency band, and determining which of the numerical ranges set for each of the multiple predetermined configurations (e.g., "Free" configuration, "Wall" configuration, "Corner" configuration, and "Shelf" configuration) and according to the configuration of the first enclosure 101. For example, if the configuration of the first enclosure 101 is "Corner", the unit determines which of the numerical ranges set for each of the multiple predetermined configurations when the configuration of the first enclosure 101 is "Corner" falls into. For example, if four predetermined configurations are assumed for both the configuration of the first enclosure 101 and the configuration of the second enclosure 201, four numerical ranges are set for each configuration of the first enclosure 101, resulting in a total of 16 numerical ranges.

[0117] For example, if the configuration of the first enclosure 101 is "Corner", then numerical range A is set to determine that the configuration of the second enclosure 201 is "Free", numerical range B is set to determine that the configuration of the second enclosure 201 is "Wall", numerical range C is set to determine that the configuration of the second enclosure 201 is "Corner", and numerical range D is set to determine that the configuration of the second enclosure 201 is "Shelf".

[0118] For example, if the configuration of the first enclosure 101 is "Free", then a numerical range E is set to determine that the configuration of the second enclosure 201 is "Free", a numerical range F is set to determine that the configuration of the second enclosure 201 is "Wall", a numerical range G is set to determine that the configuration of the second enclosure 201 is "Corner", and a numerical range H is set to determine that the configuration of the second enclosure 201 is "Shelf".

[0119] For example, if the configuration of the first enclosure 101 is "Shelf", a numerical range I is set to determine that the configuration of the second enclosure 201 is "Free", a numerical range J is set to determine that the configuration of the second enclosure 201 is "Wall", a numerical range K is set to determine that the configuration of the second enclosure 201 is "Corner", and a numerical range L is set to determine that the configuration of the second enclosure 201 is "Shelf".

[0120] For example, if the configuration of the first enclosure 101 is "Wall", a numerical range M is set to determine that the configuration of the second enclosure 201 is "Free", a numerical range N is set to determine that the configuration of the second enclosure 201 is "Wall", a numerical range O is set to determine that the configuration of the second enclosure 201 is "Corner", and a numerical range P is set to determine that the configuration of the second enclosure 201 is "Shelf".

[0121] When the configuration of the first enclosure 101 is "Corner", the numerical ranges A to D do not overlap. Similarly, when the configuration of the first enclosure 101 is "Free", the numerical ranges E to H do not overlap, when the configuration of the first enclosure 101 is "Shelf", the numerical ranges I to L do not overlap, and when the configuration of the first enclosure 101 is "Wall", the numerical ranges M to P do not overlap. For example, when the configuration of the first enclosure 101 is "Corner", if the added value falls within the numerical range A, it can be inferred that the configuration of the second enclosure 201 is "Free".

[0122] The comparison result between the second reference frequency response and the second frequency response changes in accordance with the change in the arrangement of the second enclosure 201. In other words, there is a correlation between the comparison result between the second reference frequency response and the second frequency response and the arrangement of the second enclosure 201. Therefore, by comparing the second reference frequency response with the second frequency response, the arrangement of the second enclosure 201 can be easily estimated.

[0123] In this embodiment 2, the arrangement of the first housing 101 is estimated, and the second frequency characteristic of the second sound pickup signal, which is output from the second speaker 230 of the second housing 201 and picked up by the first microphone 130, is calculated. Next, the difference between the second reference frequency characteristic and the second frequency characteristic is calculated, and the calculated difference is quantified. Then, the arrangement of the second housing 201 is estimated according to which of the numerical ranges set for each of the multiple predetermined arrangements the calculated numerical value falls into. As mentioned above, the numerical ranges set for each of the multiple predetermined arrangements are prepared in advance for each arrangement of the first housing 101.

[0124] Returning to the explanation in Figure 2, the determination unit 117 determines a predetermined correction parameter as the first correction parameter for the predetermined configuration estimated to be the configuration of the first enclosure 101 from among a plurality of predetermined configurations (for example, the configuration of "Free", the configuration of "Wall", the configuration of "Corner", and the configuration of "Shelf"). The determination unit 117 also determines a predetermined correction parameter as the second correction parameter for the predetermined configuration estimated to be the configuration of the second enclosure 201 from among the plurality of predetermined configurations. As shown in Figure 2, the memory 180 stores a group of predetermined correction parameters for a plurality of predetermined configurations. For example, the memory 180 stores predetermined correction parameters for the "Free" configuration, predetermined correction parameters for the "Wall" configuration, predetermined correction parameters for the "Corner" configuration, and predetermined correction parameters for the "Shelf" configuration.

[0125] The designer of the audio playback system 2 can pre-determine the optimal correction parameters for each of the multiple predetermined arrangements by conducting experiments or simulations. Therefore, the first correction parameter can be easily determined by simply using the predetermined correction parameters for the predetermined arrangement estimated for the first housing 101 as the first correction parameter. Similarly, the second correction parameter can be easily determined by simply using the predetermined correction parameters for the predetermined arrangement estimated for the second housing 201 as the second correction parameter. For example, if the arrangement of the first enclosure 101 is estimated to be the "Corner" arrangement among several predetermined arrangements (specifically, an arrangement close to the "Corner" arrangement), and the arrangement of the second enclosure 201 is estimated to be the "Free" arrangement among several predetermined arrangements (specifically, an arrangement close to the "Free" arrangement), then the correction parameter predetermined for the "Corner" arrangement from the set of correction parameters can be used as the first correction parameter, and the correction parameter predetermined for the "Free" arrangement from the set of correction parameters can be used as the second correction parameter.

[0126] Furthermore, the first frequency characteristics used to estimate the arrangement of the first housing 101 and the second frequency characteristics used to estimate the arrangement of the second housing 201 may be used to determine the first and second correction parameters. This will be explained with reference to Figure 5. Figure 5 is a block diagram showing another example of the correction parameter generator 114 according to Embodiment 1, but in the description of Embodiment 2, the correction parameter generator 114 shown in Figure 5 is replaced with the correction parameter generator 114a.

[0127] The correction parameter generator 114a differs from the correction parameter generator 114a described with reference to Figure 2 in that it includes a determination unit 117a instead of a determination unit 117, and the memory 180 does not store the correction parameter group. Other aspects are the same as the correction parameter generator 114a described with reference to Figure 2, so further explanation is omitted.

[0128] Memory 180 does not store the correction parameter group. In other words, the determination unit 117a determines the first and second correction parameters without using the correction parameter group.

[0129] The determination unit 117a determines the first correction parameter in the same manner as in Embodiment 1. The determination unit 117a also determines a second correction parameter that reduces the difference between the second reference frequency characteristic and the second frequency characteristic in a predetermined frequency range for a predetermined arrangement that is estimated as the arrangement of the second housing 201 from among a plurality of predetermined arrangements.

[0130] For example, the first reference frequency response is the frequency response of a first reference test audio based on a test signal, calculated under a standard "Free" setup where the entire audio playback system, including speaker characteristics, is designed to optimize the frequency response of the audio signal. Similarly, the second reference frequency response is the frequency response of a second reference test audio based on a test signal, calculated under a standard "Free" setup where the entire audio playback system, including speaker characteristics, is designed to optimize the frequency response of the audio signal.

[0131] Therefore, by determining a first correction parameter that reduces the difference between the first frequency response and the first reference frequency response in a predetermined frequency band, and by determining a second correction parameter that reduces the difference between the second frequency response and the second reference frequency response in a predetermined frequency band, the frequency characteristics of the audio signal can be improved even at the listening position in the user's space.

[0132] However, the first reference frequency response is the frequency response calculated when the first test enclosure is in a specific position ("Free" configuration), and the configuration of the first test enclosure may differ from the configuration of the first enclosure 101. Similarly, the second reference frequency response is the frequency response calculated when the second test enclosure is in a specific position ("Free" configuration), and the configuration of the second test enclosure may differ from the configuration of the second enclosure 201. Therefore, the frequency range over which the first reference frequency response should be compared with the first frequency response, and the frequency range over which the second reference frequency response should be compared with the second frequency response, will differ depending on the configuration of the first enclosure 101 and the second enclosure 201.

[0133] In contrast, the designer can pre-determine, through experiments or simulations, the frequency range in which the first reference frequency characteristics should be compared with the first frequency characteristics, and the frequency range in which the second reference frequency characteristics should be compared with the second frequency characteristics, for each of several predetermined arrangements. Therefore, the first and second correction parameters can be determined according to the arrangement of the first housing 101 and the second housing 201.

[0134] As explained above, the first microphone 130, which is necessary to determine the second correction parameter for the second speaker 230 located in the second housing 201, is pre-installed in the first housing 101. Therefore, the user does not need to prepare any special equipment such as a microphone in addition to what is necessary for normal playback. Furthermore, the placement of the second housing 201 is automatically estimated from the second frequency characteristics of the second sound pickup signal, which represents the second test sound picked up by the first microphone 130, and the second correction parameter is automatically determined from the estimated placement of the second housing. As a result, the user does not need the skills and expertise to pick up the audio signal at the listening position and determine the correction parameter. Therefore, even if the audio playback system 2 has multiple speakers and the microphone is located in only one housing, a user without specialized knowledge can automatically improve the frequency characteristics at the listening position with a single touch, making it easy to achieve the performance intended by the designer.

[0135] (Embodiment 3) Next, the audio playback system according to Embodiment 3 will be described using Figure 8.

[0136] Figure 8 shows an example of the configuration of the audio playback system 3 according to Embodiment 3.

[0137] The audio playback system 3 is a system for outputting audio from the first speaker 160 and the second speaker 230 based on an input audio signal input to the audio playback system 3 from a sound source player connected to the input terminal 140. The sound source player may be built into the audio playback system 3. In other words, the sound source player may be an external component of the audio playback system 3, or it may be built into the audio playback system 3 as a component of the audio playback system 3. The audio playback system 3 has a function for optimizing the frequency characteristics of the audio signal at the listening position, and this function will be described below.

[0138] The audio playback system 3 comprises a first enclosure 102, a processor 110b, an equalizer 120a, a first microphone 130, an input terminal 140, an amplifier 150, a first speaker 160, and a first communication interface 170a, as well as a second enclosure 202, a second communication interface 210a, an amplifier 220, a second speaker 230, and a second microphone 240.

[0139] In the following, explanations of components with the same reference numerals and terms with the same names as those in Embodiment 1 or 2 may be omitted.

[0140] The audio playback system 3 is a computer that includes a processor 110b (microprocessor), memory 180, and a communication interface. The audio playback system 3 may also have a user interface. As shown in Figure 8, the processor 110b includes a test signal generator 111a, a signal switcher 112, a sound pickup meter 113b, and a correction parameter generator 114b. In other words, these components are implemented by the processor 110b, which executes a program stored in memory 180.

[0141] For example, memory 180 stores data related to processing, such as reference frequency characteristics, system information, or correction parameter groups, similar to Embodiment 1. However, as reference frequency characteristics, it stores the first and fourth reference frequency characteristics for the first housing 102, and the second and third reference frequency characteristics for the second housing 202.

[0142] For example, the audio playback system 3 can reproduce stereo sound by operating with a first chassis 102, which houses the processor 110b, as the master chassis, and a second chassis 202 as the slave chassis. The audio playback system 3 may also have another slave chassis to reproduce surround sound. Furthermore, the audio playback system 3 may be a single-chassis device by arranging the master chassis and slave chassis within a single chassis.

[0143] The first housing 102 is a component corresponding to the first housing 100 of Embodiment 1 and the first housing 101 of Embodiment 2, and any explanation that overlaps with Embodiments 1 and 2 will be omitted.

[0144] The second enclosure 202 is installed in the space where the first enclosure 102 is installed. The second speaker 230 is installed in the second enclosure 202. The second microphone 240 is installed in the second enclosure 202. In other words, the second enclosure 202 is equipped with both a speaker and a microphone.

[0145] The first communication interface 170a is provided on the first enclosure 102 and is a communication interface capable of transmitting voice signals. The first communication interface 170a transmits voice signals to the second communication interface 210a on the second enclosure 202.

[0146] The second communication interface 210a is located in the second enclosure 202 and is capable of receiving audio signals from the first communication interface 170a. The second communication interface 210a also transmits the sound signal picked up by the second microphone 240 to the first communication interface 170a in the first enclosure 102. The first communication interface 170 and the second communication interface 210 may be connected wirelessly or by a wired connection.

[0147] The test signal generator 111a, signal switcher 112, sound collection measuring instrument 113b, and correction parameter generator 114b are implemented by a processor 110b that executes a program stored in memory 180.

[0148] In the mode for optimizing the frequency characteristics of the audio signal at the listening position, the equalizer 120a does not perform any correction. In other words, the test signal generated by the test signal generator 111a is not corrected by the equalizer 120a. The processor 110b causes the first test audio, based on the test signal generated by the test signal generator 111a, to be output to the first speaker 160. As a result, the first test audio is output from the first speaker 160 into the space where the first enclosure 102 and the second enclosure 202 are installed. The test signal generator 111a also causes the first communication I / F 170a to transmit a test signal to the second communication I / F 210a, thereby causing the second test audio, based on the test signal, to be output to the second speaker 230. As a result, the second test audio is output from the second speaker 230 into the space where the first enclosure 102 and the second enclosure 202 are installed.

[0149] The first test sound output from the first speaker 160 into the space where the first enclosure 102 and the second enclosure 202 are installed is picked up by the first microphone 130 installed in the first enclosure 102 and the second microphone 240 installed in the second enclosure 202. For example, the first microphone 130 picks up the direct sound from the first speaker 160 as the first test sound, as well as the reflected sound of the sound output from the first speaker 160 reflected by the walls and other surfaces in the space where the first enclosure 102 and the second enclosure 202 are installed. Also, for example, the second microphone 240 picks up the reflected sound of the sound output from the first speaker 160 reflected by the walls and other surfaces in the space where the first enclosure 102 and the second enclosure 202 are installed as the first test sound.

[0150] The second test sound output from the second speaker 230 into the space where the first enclosure 102 and the second enclosure 202 are installed is picked up by the first microphone 130 installed in the first enclosure 102 and the second microphone 240 installed in the second enclosure 202. For example, the first microphone 130 picks up the reflected sound of the sound output from the second speaker 230 reflected off the walls and other surfaces in the space where the first enclosure 102 and the second enclosure 202 are installed, as the second test sound. Also, for example, the second microphone 240 picks up the direct sound from the second speaker 230, as well as the reflected sound of the sound output from the second speaker 230 reflected off the walls and other surfaces in the space where the first enclosure 102 and the second enclosure 202 are installed, as the second test sound.

[0151] Furthermore, the period during which the first test sound is output from the first speaker 160 does not overlap with the period during which the second test sound is output from the second speaker 230. If these periods overlapped, the first microphone 130 would pick up both the first and second test sounds at the same time, and the second microphone 240 would also pick up both the first and second test sounds at the same time, making it difficult to distinguish between the first and second test sounds.

[0152] The sound pickup measuring instrument 113b acquires a first sound pickup signal indicating the first test sound picked up by the first microphone 130. The sound pickup measuring instrument 113b also acquires a second sound pickup signal indicating the second test sound picked up by the first microphone 130. Furthermore, the third sound pickup signal indicating the second test sound picked up by the second microphone 240 is transmitted from the second communication I / F 210a to the first communication I / F 170a, thereby allowing the sound pickup measuring instrument 113b to acquire a third sound pickup signal indicating the second test sound picked up by the second microphone 240. Furthermore, the fourth sound pickup signal indicating the first test sound picked up by the second microphone 240 is transmitted from the second communication I / F 210a to the first communication I / F 170a, thereby allowing the sound pickup measuring instrument 113b to acquire a fourth sound pickup signal indicating the first test sound picked up by the second microphone 240. In other words, the sound acquisition measuring instrument 113b acquires the audio from the first microphone 130 and the audio from the second microphone 240 transmitted via the second communication interface 210a and the first communication interface 170a.

[0153] The audio picked up by the second microphone 240 at the time the second test audio is output from the second speaker 230 includes both the direct sound that reaches the second microphone 240 directly and the reflected sound that reaches the second microphone 240 after being reflected by walls, etc. Although this audio is different from the second test audio output by the second speaker 230, it is also referred to as the second test audio for convenience. Furthermore, the sound signal picked up by the second microphone 240 based on this audio, which is conveniently referred to as the second test audio, is called the third sound pickup signal.

[0154] Furthermore, the sound picked up by the second microphone 240 at the time the first test sound is output from the first speaker 160 includes both the direct sound that reaches the second microphone 240 directly and the reflected sound that reaches the second microphone 240 after being reflected by walls, etc. This sound is different from the first test sound output by the first speaker 160, but for convenience, this sound is also referred to as the first test sound. In addition, the sound picked up by the second microphone 240 based on this sound, which is conveniently referred to as the first test sound, is called the fourth sound picked up signal.

[0155] The sound acquisition measuring instrument 113b outputs the acquired first sound acquisition signal, second sound acquisition signal, third sound acquisition signal, and fourth sound acquisition signal to the correction parameter generator 114b.

[0156] The correction parameter generator 114b calculates the first frequency characteristics of the first sound-collected signal, estimates the placement of the first enclosure 102 in space based on the calculated first frequency characteristics, and determines the first correction parameter based on the estimated placement of the first enclosure 102. The correction parameter generator 114b also calculates the third frequency characteristics of the third sound-collected signal, estimates the placement of the second enclosure 202 in space based on the calculated third frequency characteristics, and determines the second correction parameter based on the estimated placement of the second enclosure 202. Details of the correction parameter generator 114b will be described later. The correction parameter generator 114b sets the determined first and second correction parameters to the equalizer 120a.

[0157] Subsequently, in the mode for normal audio playback, the equalizer 120a generates a first corrected audio signal by correcting the frequency characteristics of the input audio signal input to the audio playback system 3 using a first correction parameter, and outputs audio based on the first corrected audio signal to the first speaker 160. Furthermore, the equalizer 120a generates a second corrected audio signal by correcting the frequency characteristics of the input audio signal input to the audio playback system 3 using a second correction parameter, and outputs audio based on the second corrected audio signal to the second speaker 230 via the first communication I / F 170a. In other words, audio based on the first corrected audio signal generated by correcting the frequency characteristics of the input audio signal using the first correction parameter is output from the first speaker 160, and audio based on the second corrected audio signal generated by correcting using the second correction parameter is output from the second speaker 230, so that the user can hear audio with improved frequency characteristics at the listening position.

[0158] Next, the details of the correction parameter generator 114b will be explained using Figure 2. Figure 2 is a block diagram showing an example of the correction parameter generator 114 according to Embodiment 1, but in the description of Embodiment 3, the correction parameter generator 114 shown in Figure 2 is replaced with the correction parameter generator 114b.

[0159] The correction parameter generator 114b comprises a frequency response analysis unit 115, a comparative analysis unit 116, and a determination unit 117. The frequency response analysis unit 115, the comparative analysis unit 116, and the determination unit 117 are implemented by a processor 110b or the like that executes a program stored in memory 180.

[0160] The correction parameter generator 114b uses the first reference frequency characteristics for the first enclosure 102 and the second enclosure 202, stored in the memory 180, as well as the first reference frequency characteristics for the second enclosure 202 and the second reference frequency characteristics, to estimate the arrangement of the first enclosure 102 and the second enclosure 202, and to determine the first and second correction parameters.

[0161] The third reference frequency response is a frequency response pre-calculated from the sound captured signal obtained by capturing the second reference test audio, which is based on a test signal output from a second test speaker installed in a second test enclosure located at a specific position in the test space, using a second test microphone installed in the second test enclosure.

[0162] The second test microphone is essentially the same as the second microphone 240. The third reference frequency response is the frequency response calculated from the sound signal captured by the second test microphone when the second reference test sound is output from the second test speaker while the second test enclosure is in a standard "Free" configuration (specifically, an average configuration within the "Free" configuration).

[0163] The fourth reference frequency response is a frequency response pre-calculated from the sound-collected signal obtained by capturing the first reference test audio, which is based on a test signal output from a first test speaker installed in a first test enclosure located at a specific position in the test space, using a second test microphone installed in a second test enclosure.

[0164] The fourth reference frequency response is the frequency response calculated from the sound signal captured by the second test microphone when the first reference test sound is output from the first test speaker while the first test enclosure is in a standard "Free" configuration (specifically, an average configuration within the "Free" configuration).

[0165] For example, the designer of the audio playback system 3 has designed the entire audio playback system, including speaker characteristics, to optimize the frequency characteristics of the audio signal in a standard "Free" configuration. The designer then calculates the third reference frequency characteristics from the acquired signal, which is obtained by capturing a second reference test audio based on a test signal using a second test microphone located in the second test enclosure. In this case, no equalizer correction is applied, but the second reference audio with optimal frequency characteristics is output from the second test speaker in a standard "Free" configuration. Furthermore, the designer of the audio playback system 3, with the entire audio playback system designed as described above, calculates the fourth reference frequency characteristics from the acquired signal, which is obtained by capturing a first reference test audio based on a test signal using a second test microphone located in the second test enclosure. In this case, no equalizer correction is applied, but the first reference audio with optimal frequency characteristics is output from the first test speaker in a standard "Free" configuration. The first and second reference frequency characteristics are calculated in the same manner as in Embodiments 1 and 2.

[0166] In Embodiment 3, the arrangement of the first and second test enclosures is the "Free" arrangement shown in Figure 3A. In other words, the first reference frequency, second reference frequency characteristics, third reference frequency characteristics, and fourth reference frequency characteristics were calculated when the first and second test enclosures were in the "Free" arrangement.

[0167] The frequency response analysis unit 115 calculates the first frequency response of the first sound pickup signal output from the first speaker 160 and picked up by the first microphone 130, the second frequency response of the second sound pickup signal output from the second speaker 230 and picked up by the first microphone 130, the third frequency response of the third sound pickup signal output from the second speaker 230 and picked up by the second microphone 240 and the fourth frequency response of the fourth sound pickup signal output from the first speaker 160 and picked up by the second microphone 240. For example, the frequency response analysis unit 115 calculates the first frequency characteristics of the first sound-collected signal by performing an FFT on the first sound-collected signal, calculates the second frequency characteristics of the second sound-collected signal by performing an FFT on the second sound-collected signal, calculates the third frequency characteristics of the third sound-collected signal by performing an FFT on the third sound-collected signal, and calculates the fourth frequency characteristics of the fourth sound-collected signal by performing an FFT on the fourth sound-collected signal.

[0168] The comparative analysis unit 116 estimates the placement of the first housing 102 by comparing the first reference frequency characteristics stored in the memory 180 with the first frequency characteristics, and estimates the placement of the second housing 202 by comparing the third reference frequency characteristics stored in the memory 180 with the third frequency characteristics. The comparative analysis unit 116 may also use system information, including information regarding the frequency characteristics of the first microphone 130 and the second microphone 240, when estimating the placement of the first housing 102 and the second housing 202. The method for estimating the placement of the first housing 102 is the same as that described in Embodiment 1, so the explanation is omitted. Similarly, the method for estimating the placement of the second housing 202 is basically the same as that for estimating the placement of the first housing 102, so the explanation is omitted. In Embodiment 2, the second housing 201 is not equipped with a microphone, and the arrangement of the first housing 101 is estimated using the first microphone 130 provided in the first housing 101. Thus, the method for estimating the arrangement of the first housing 101 and the method for estimating the arrangement of the second housing 201 were different. However, in Embodiment 3, the second housing 202 is equipped with a second microphone 240, just like the first housing 102. Thus, the arrangement of the second housing 202 can be estimated using the second speaker 230 and second microphone 240 provided in the second housing 202, in the same way that the arrangement of the first housing 102 is estimated using the first speaker 160 and first microphone 130 provided in the first housing 102.

[0169] The determination unit 117 determines a predetermined correction parameter as the first correction parameter for the predetermined configuration estimated to be the configuration of the first enclosure 102 from among a plurality of predetermined configurations (for example, the configuration of "Free", the configuration of "Wall", the configuration of "Corner", and the configuration of "Shelf"). The determination unit 117 also determines a predetermined correction parameter as the second correction parameter for the predetermined configuration estimated to be the configuration of the second enclosure 202 from among the plurality of predetermined configurations. As shown in Figure 2, the memory 180 stores a group of predetermined correction parameters for a plurality of predetermined configurations. For example, the memory 180 stores predetermined correction parameters for the "Free" configuration, predetermined correction parameters for the "Wall" configuration, predetermined correction parameters for the "Corner" configuration, and predetermined correction parameters for the "Shelf" configuration.

[0170] The designer of the audio playback system 3 can pre-determine the optimal correction parameters for each of the multiple predetermined arrangements by conducting experiments or simulations. Therefore, the first correction parameter can be easily determined by simply using the predetermined correction parameters for the predetermined arrangement estimated for the first housing 102 as the first correction parameter. Similarly, the second correction parameter can be easily determined by simply using the predetermined correction parameters for the predetermined arrangement estimated for the second housing 202 as the second correction parameter. For example, if the arrangement of the first enclosure 102 is estimated to be the "Corner" arrangement among several predetermined arrangements (specifically, an arrangement close to the "Corner" arrangement), and the arrangement of the second enclosure 202 is estimated to be the "Free" arrangement among several predetermined arrangements (specifically, an arrangement close to the "Free" arrangement), then the correction parameter predetermined for the "Corner" arrangement from the set of correction parameters can be used as the first correction parameter, and the correction parameter predetermined for the "Free" arrangement from the set of correction parameters can be used as the second correction parameter.

[0171] Furthermore, in order to determine the first and second correction parameters, the first frequency characteristics used to estimate the arrangement of the first housing 102, the third frequency characteristics used to estimate the arrangement of the second housing 202, the second frequency characteristics of the second sound pickup signal representing the second test sound output from the second speaker 230 and picked up by the first microphone 130, and the fourth frequency characteristics of the fourth sound pickup signal representing the first test sound output from the first speaker 160 and picked up by the second microphone 240 may be used. This will be explained with reference to Figure 5. Figure 5 is a block diagram showing another example of the correction parameter generator 114 according to Embodiment 1, but in the description of Embodiment 3, the correction parameter generator 114 shown in Figure 5 is replaced with the correction parameter generator 114b.

[0172] The correction parameter generator 114b differs from the correction parameter generator 114b described with reference to Figure 2 in that it includes a determination unit 117a instead of a determination unit 117, and the memory 180 does not store the correction parameter group. Other aspects are the same as the correction parameter generator 114b described with reference to Figure 2, so further explanation is omitted.

[0173] Memory 180 does not store the correction parameter group. In other words, the determination unit 117a determines the first and second correction parameters without using the correction parameter group.

[0174] The determination unit 117a determines a first correction parameter for each predetermined frequency range for a predetermined arrangement that has been estimated as the arrangement of the first housing 102 from among a plurality of predetermined arrangements, which reduces the difference between the first reference frequency characteristic and the first frequency characteristic, or the difference between the fourth reference frequency characteristic and the fourth frequency characteristic.

[0175] Furthermore, the determination unit 117a determines a second correction parameter for each predetermined frequency range for a predetermined arrangement that has been estimated as the arrangement of the second housing 202 from among a plurality of predetermined arrangements, which reduces the difference between the second reference frequency characteristic and the second frequency characteristic, or the difference between the third reference frequency characteristic and the third frequency characteristic.

[0176] For example, the first reference frequency response is the frequency response of a first reference test audio based on a test signal, calculated under the assumption that the entire audio playback system, including speaker characteristics, is designed to optimize the frequency response of the audio signal in a standard "Free" setup. Similarly, the third reference frequency response is the frequency response of a second reference test audio based on a test signal, calculated under the assumption that the entire audio playback system, including speaker characteristics, is designed to optimize the frequency response of the audio signal in a standard "Free" setup.

[0177] Therefore, by determining a first correction parameter that reduces the difference between the first frequency response and the first reference frequency response in a predetermined frequency band, and by determining a second correction parameter that reduces the difference between the third frequency response and the third reference frequency response in a predetermined frequency band, the frequency characteristics of the audio signal can be improved even at the listening position in the user's space.

[0178] However, the first reference frequency response is the frequency response calculated when the first test enclosure is in a specific position (the "Free" configuration), and the configuration of the first test enclosure may differ from the configuration of the first enclosure 102. Similarly, the third reference frequency response is the frequency response calculated when the second test enclosure is in a specific position (the "Free" configuration), and the configuration of the second test enclosure may differ from the configuration of the second enclosure 201. Therefore, the frequency range over which the first reference frequency response should be compared with the first frequency response will differ depending on the configuration of the first enclosure 102, and the frequency range over which the third reference frequency response should be compared with the third frequency response will differ depending on the configuration of the second enclosure 202. Furthermore, since the second frequency characteristics of the second sound pickup signal representing the second test sound of the second speaker 230 picked up by the first microphone 130, and the fourth frequency characteristics of the fourth sound pickup signal representing the first test sound of the first speaker 160 picked up by the second microphone 240 can also be calculated, depending on the arrangement of the first housing 102, there may be a frequency range in which it is better to compare the fourth reference frequency characteristics with the fourth frequency characteristics. Also, depending on the arrangement of the second housing 202, there may be a frequency range in which it is better to compare the second reference frequency characteristics with the second frequency characteristics.

[0179] In contrast, the designer can predetermine, through experiments or simulations, the frequency range over which the first, second, third, or fourth reference frequency characteristics should be compared with the first, second, third, or fourth frequency characteristics for each of several predetermined configurations. For example, the designer can predetermine, through experiments or simulations, that when the configuration of the first enclosure 102 is "Corner," it is better to compare the first reference frequency characteristics with the first frequency characteristics from aHz to bHz, and the fourth reference frequency characteristics with the fourth frequency characteristics from bHz to cHz in a predetermined frequency band. Similarly, the designer can predetermine, through experiments or simulations, that when the configuration of the second enclosure 202 is "Shelf," it is better to compare the third reference frequency characteristics with the third frequency characteristics from dHz to eHz, and the second reference frequency characteristics with the second frequency characteristics from eHz to fHz in a predetermined frequency band. Therefore, the first and second correction parameters can be determined according to the arrangement of the first housing 102 and the second housing 202.

[0180] As explained above, the second microphone 240, which is necessary to determine the second correction parameter for the second speaker 230 located in the second housing 202, is pre-installed in the second housing 202. Therefore, the user does not need to prepare any special equipment such as microphones in addition to what is necessary for normal playback. Furthermore, the placement of the second housing 202 is automatically estimated from the third frequency characteristics of the third sound pickup signal representing the second test sound picked up by the second microphone 240, and the second correction parameter is automatically determined from the estimated placement of the second housing 202. As a result, the user does not need the skills and expertise to pick up the audio signal at the listening position and determine the correction parameter. Therefore, even if the audio playback system 3 is equipped with multiple speakers and multiple microphones, a user without specialized knowledge can automatically improve the frequency characteristics at the listening position with a single touch, making it easy to achieve the performance intended by the designer.

[0181] (Other embodiments) As described above, embodiments have been explained as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited thereto and can be applied to embodiments that are modified, replaced, added, or omitted as appropriate. Furthermore, it is possible to create new embodiments by combining the components described in the above embodiments.

[0182] For example, the equalizer described in the above embodiment may be a graphic equalizer.

[0183] For example, the equalizer described in the above embodiment is an equalizer that performs corrections caused by the speaker placement, but the audio playback system may also have an equalizer separate from that equalizer that performs corrections at the design stage (for example, before the user purchases it) to make the speaker characteristics as intended by the designer.

[0184] For example, the arrangement of the first and second test enclosures described in the above embodiment is the "Free" arrangement shown in Figure 3A, but the arrangement of the first and second test enclosures may also be the "Wall" arrangement shown in Figure 3B, the "Corner" arrangement shown in Figure 3C, or the "Shelf" arrangement shown in Figure 3D. Furthermore, the reference frequency characteristics may be calculated when the test enclosures are arranged in a configuration other than the "Free" configuration (for example, the "Wall" configuration, the "Corner" configuration, or the "Shelf" configuration).

[0185] For example, in the above embodiment, an example was described in which the reference frequency characteristics are pre-calculated when the test enclosure is installed in a specific location, but this is not limited to this. For example, the reference frequency characteristics may be pre-calculated for each of the multiple predetermined configurations (e.g., "Free" configuration, "Wall" configuration, "Corner" configuration, and "Shelf" configuration). In other words, the reference frequency characteristics for the "Free" configuration, the reference frequency characteristics for the "Wall" configuration, the reference frequency characteristics for the "Corner" configuration, and the reference frequency characteristics for the "Shelf" configuration may be pre-calculated.

[0186] This allows us to estimate the configuration of the first or second enclosure based on a predetermined arrangement that corresponds to the reference frequency characteristic with the smallest difference between it and the frequency characteristic of the recorded signal representing the test audio, among the multiple reference frequency characteristics calculated. For example, if the difference between the first frequency characteristic and the reference frequency characteristic for the "Wall" configuration is smallest, then the configuration of the first enclosure can be estimated to be "Wall". Furthermore, by determining the first or second correction parameter using the reference frequency characteristic corresponding to the estimated configuration of the first or second enclosure, the first or second correction parameter can be determined with greater accuracy.

[0187] For example, this disclosure can be implemented not only as an audio playback system, but also as an audio playback method that includes steps (processing) performed by the components constituting the audio playback system.

[0188] Figure 9 is a flowchart showing an example of an audio playback method according to another embodiment.

[0189] The audio playback method is an audio playback method performed by an audio playback system, the audio playback system comprising a first enclosure installed in space, a first speaker provided in the first enclosure, and a first microphone provided in the first enclosure, and in the audio playback method, as shown in Figure 9, a first test sound based on a test signal is output to the first speaker (step S11), a first sound pickup signal indicating the first test sound picked up by the first microphone is acquired (step S12), a first frequency characteristic of the first sound pickup signal is calculated (step S13), the arrangement of the first enclosure in space is estimated based on the first frequency characteristic (step S14), a first correction parameter is determined based on the arrangement of the first enclosure (step S15), a first corrected sound signal is generated by correcting the frequency characteristic of the input sound signal input to the audio playback system using the first correction parameter (step S16), and audio based on the first corrected sound signal is output to the first speaker (step S17).

[0190] For example, this disclosure can be implemented as a program that causes a computer (processor) to execute the steps included in the audio playback method. Furthermore, this disclosure can be implemented as a non-temporary computer-readable recording medium, such as a CD-ROM, on which the program is recorded.

[0191] For example, if this disclosure is implemented in a program (software), each step is executed by the program using hardware resources such as the computer's CPU, memory, and input / output circuits. In other words, each step is executed by the CPU obtaining data from memory or input / output circuits, performing calculations, and outputting the calculation results to memory or input / output circuits.

[0192] In the above embodiment, each component included in the audio playback system may be implemented by dedicated hardware or by executing a software program suitable for each component. Each component may also be implemented by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0193] Some or all of the functions of the audio playback system according to the above embodiment are typically implemented as an LSI (Large-Scale Integrated Circuit). These may be individually integrated onto a single chip, or some or all of them may be integrated onto a single chip. Furthermore, the integration is not limited to an LSI; it may also be implemented using a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array), which can be programmed after the LSI is manufactured, or a reconfigurable processor that allows for the reconfiguration of the connections and settings of the circuit cells inside the LSI may also be used.

[0194] Furthermore, if advances in semiconductor technology or other derived technologies lead to the emergence of integrated circuit technologies that replace LSIs, then naturally, these technologies may be used to integrate each component included in the audio playback system.

[0195] Furthermore, this disclosure also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of each embodiment without departing from the spirit of this disclosure.

[0196] (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0197] (Technical 1) A sound playback system comprising: a first housing installed in a space; a first speaker provided in the first housing; a first microphone provided in the first housing; a processor; and an equalizer unit, wherein the processor causes the first speaker to output a first test sound based on a test signal, acquires a first sound pickup signal indicating the first test sound picked up by the first microphone, calculates a first frequency characteristic of the first sound pickup signal, estimates the arrangement of the first housing in the space based on the first frequency characteristic, determines a first correction parameter based on the arrangement of the first housing, the equalizer unit generates a first corrected sound signal by correcting the frequency characteristic of an input sound signal input to the sound playback system using the first correction parameter, and the first speaker outputs sound based on the first corrected sound signal.

[0198] According to this, the first microphone necessary for determining the first correction parameter for the first speaker installed in the first housing is pre-installed in the first housing, so the user does not need to prepare any special equipment such as a microphone other than what is necessary for normal playback. Furthermore, the placement of the first housing is automatically estimated from the first frequency characteristics of the first sound pickup signal representing the first test sound picked up by the first microphone, and the first correction parameter is automatically determined from the estimated placement of the first housing, so the user does not need the skills and expertise to pick up the sound signal at the listening position and determine the correction parameter.Therefore, a user without expertise can automatically improve the frequency characteristics at the listening position with a single touch, making it easy to achieve the performance intended by the designer.

[0199] (Technology 2) The audio playback system according to Technology 1, wherein the processor estimates the arrangement of the first enclosure by comparing the first reference frequency characteristics for the first enclosure with the first frequency characteristics.

[0200] According to this, the comparison result between the first reference frequency response and the first frequency response changes in accordance with the change in the arrangement of the first enclosure. In other words, there is a correlation between the comparison result between the first reference frequency response and the first frequency response and the arrangement of the first enclosure. Therefore, by comparing the first reference frequency response and the first frequency response, the arrangement of the first enclosure can be easily estimated.

[0201] (Technology 3) The audio playback system according to Technology 1 or 2, wherein the processor determines a predetermined correction parameter as the first correction parameter for a predetermined arrangement that is estimated to be the arrangement of the first enclosure from among a plurality of predetermined arrangements.

[0202] According to this, the designer can pre-determine the optimal correction parameters for each of the multiple predetermined arrangements by conducting experiments or simulations. Therefore, the first correction parameter can be easily determined by simply using the predetermined correction parameters for the predetermined arrangement estimated as the arrangement of the first enclosure as the first correction parameter.

[0203] (Technical 4) The audio playback system according to Technical 2, wherein the processor uses the first reference frequency characteristics to estimate the arrangement of the first housing and determine the first correction parameters.

[0204] According to this, by using a first reference frequency characteristic calculated in advance by the designer, the placement of the first enclosure and the determination of the first correction parameters can be easily performed.

[0205] (Technical 5) The audio playback system according to Technical 4, wherein the processor determines a first correction parameter that reduces the difference between the first reference frequency characteristic and the first frequency characteristic in a predetermined frequency range with respect to a predetermined arrangement estimated as the arrangement of the first enclosure from among a plurality of predetermined arrangements.

[0206] For example, the first reference frequency response is the frequency response of a first reference test audio based on a test signal, calculated under the assumption that the entire audio playback system, including speaker characteristics, is designed to optimize the frequency response of the audio signal in a predetermined configuration (e.g., a standard "Free" configuration). Therefore, by determining a first correction parameter that minimizes the difference between the first frequency response and the first reference frequency response in a given frequency band, the frequency response of the audio signal can be improved even at the listening position in the user's space.

[0207] However, the first reference frequency response is a frequency response calculated when the first test enclosure is in a specific position. The arrangement of the first test enclosure may differ from the arrangement of the first enclosure, and the frequency range over which the first reference frequency response and the first frequency response should be compared will differ depending on the arrangement of the first enclosure. In response to this, the designer can pre-determine the frequency range over which the first reference frequency response and the first frequency response should be compared for each of several predetermined arrangements by conducting experiments or simulations. Therefore, the first correction parameter can be determined according to the arrangement of the first enclosure.

[0208] (Technical 6) The audio playback system according to any one of Technical 2, 4, or 5, wherein the first reference frequency characteristics are frequency characteristics calculated in advance from an acquired signal obtained by picking up a first reference test sound based on the test signal output from a first test speaker provided in a first test enclosure installed at a specific position in the test space using a first test microphone provided in the first test enclosure.

[0209] In this way, the first reference frequency response can be calculated.

[0210] (Technical 7) The audio playback system according to Technical 1, further comprising: a first communication interface provided in the first housing and capable of transmitting an audio signal; a second housing installed in the space; a second communication interface provided in the second housing and capable of receiving the audio signal from the first communication interface; and a second speaker provided in the second housing and outputting audio based on the audio signal received by the second communication interface, wherein the processor further causes the first communication interface to transmit the test signal to the second communication interface, thereby causing the second speaker to output a second test audio based on the test signal; acquires a second sound pickup signal indicating the second test audio picked up by the first microphone; calculates a second frequency characteristic of the second sound pickup signal; estimates the arrangement of the second housing in the space based on the second frequency characteristic; determines a second correction parameter based on the arrangement of the second housing; the equalizer unit further generates a second corrected audio signal by correcting the frequency characteristic of the input audio signal using the second correction parameter; and the second speaker outputs audio based on the second corrected audio signal.

[0211] According to this, the first microphone necessary for determining the second correction parameter for the second speaker located in the second housing is pre-installed in the first housing, so the user does not need to prepare any special equipment such as microphones other than what is necessary for normal playback. Furthermore, the placement of the second housing is automatically estimated from the second frequency characteristics of the second sound pickup signal, which represents the second test sound picked up by the first microphone, and the second correction parameter is automatically determined from the estimated placement of the second housing. Therefore, the user does not need the skills and expertise to pick up the audio signal at the listening position and determine the correction parameter. Consequently, even if the audio playback system has multiple speakers and the microphone is only in one housing, a user without specialized knowledge can automatically improve the frequency characteristics at the listening position with a single touch, making it easy to achieve the performance intended by the designer.

[0212] (Technical 8) The audio playback system according to Technical 6, wherein the processor estimates the arrangement of the first housing by comparing the first reference frequency characteristics for the first housing with the first frequency characteristics, and estimates the arrangement of the second housing by comparing the second reference frequency characteristics for the second housing with the second frequency characteristics.

[0213] According to this, the comparison result between the first reference frequency response and the first frequency response changes in accordance with the change in the arrangement of the first enclosure. In other words, there is a correlation between the comparison result between the first reference frequency response and the first frequency response and the arrangement of the first enclosure. Therefore, by comparing the first reference frequency response and the first frequency response, the arrangement of the first enclosure can be easily estimated. Furthermore, the comparison result between the second reference frequency response and the second frequency response changes in accordance with the change in the arrangement of the second enclosure. In other words, there is a correlation between the comparison result between the second reference frequency response and the second frequency response and the arrangement of the second enclosure. Therefore, by comparing the second reference frequency response and the second frequency response, the arrangement of the second enclosure can be easily estimated.

[0214] (Technical 9) The audio playback system according to Technical 7 or 8, wherein the processor determines a predetermined correction parameter as the first correction parameter for a predetermined arrangement estimated to be the arrangement of the first enclosure from among a plurality of predetermined arrangements, and determines a predetermined correction parameter as the second correction parameter for a predetermined arrangement estimated to be the arrangement of the second enclosure from among the plurality of predetermined arrangements.

[0215] According to this, the designer can pre-determine the optimal correction parameters for each of the multiple predetermined arrangements by conducting experiments or simulations. Therefore, the first correction parameter can be easily determined by simply using the predetermined correction parameters for the predetermined arrangement estimated as the arrangement of the first enclosure as the first correction parameter. Similarly, the second correction parameter can be easily determined by simply using the predetermined correction parameters for the predetermined arrangement estimated as the arrangement of the second enclosure as the second correction parameter.

[0216] (Technical 10) The audio playback system according to Technical 8, wherein the processor uses the first reference frequency characteristics and the second reference frequency characteristics to estimate the arrangement of the first housing and the arrangement of the second housing, and to determine the first correction parameter and the second correction parameter.

[0217] According to this, by using the first and second reference frequency characteristics calculated in advance by the designer, it is possible to easily estimate the arrangement of the first and second enclosures, as well as determine the first and second correction parameters.

[0218] (Technical 11) The audio playback system according to Technical 10, wherein the processor determines a first correction parameter that reduces the difference between the first reference frequency characteristic and the first frequency characteristic in a predetermined frequency range for a predetermined arrangement estimated as the arrangement of the first housing from among a plurality of predetermined arrangements, and determines a second correction parameter that reduces the difference between the second reference frequency characteristic and the second frequency characteristic in a predetermined frequency range for a predetermined arrangement estimated as the arrangement of the second housing from among the plurality of predetermined arrangements.

[0219] For example, the first reference frequency response is the frequency response of a first reference test audio based on a test signal, calculated under the assumption that the entire audio playback system, including speaker characteristics, is designed to optimize the frequency response of the audio signal in a standard, predetermined configuration (e.g., a standard "Free" configuration). Similarly, the second reference frequency response is the frequency response of a second reference test audio based on a test signal, calculated under the assumption that the entire audio playback system, including speaker characteristics, is designed to optimize the frequency response of the audio signal in a standard, predetermined configuration. Therefore, by determining a first correction parameter that minimizes the difference between the first frequency response and the first reference frequency response in a predetermined frequency band, and by determining a second correction parameter that minimizes the difference between the second frequency response and the second reference frequency response in a predetermined frequency band, the frequency response of the audio signal can be improved even at the listening position in the user's space.

[0220] However, the first reference frequency response is the frequency response calculated when the first test enclosure is in a specific position, and the arrangement of the first test enclosure may differ from that of the first enclosure. Depending on the arrangement of the first enclosure, the frequency range over which the first reference frequency response should be compared with the first frequency response will differ. Similarly, the second reference frequency response is the frequency response calculated when the second test enclosure is in a specific position, and the arrangement of the second test enclosure may differ from that of the second enclosure. Depending on the arrangement of the second enclosure, the frequency range over which the second reference frequency response should be compared with the second frequency response will differ.

[0221] In contrast, the designer can pre-determine, through experiments or simulations, the frequency ranges in which the first reference frequency characteristics should be compared with the first frequency characteristics, and the frequency ranges in which the second reference frequency characteristics should be compared with the second frequency characteristics, for each of several predetermined configurations. Therefore, the first and second correction parameters can be determined according to the configuration of the first and second enclosures.

[0222] (Technical 12) The audio playback system according to any one of Technical 8, 10, or 11, wherein the first reference frequency characteristic is a frequency characteristic calculated in advance from an acquired signal obtained by picking up a first reference test sound based on the test signal output from a first test speaker provided in a first test enclosure installed at a specific position in the test space using a first test microphone provided in the first test enclosure, and the second reference frequency characteristic is a frequency characteristic calculated in advance from an acquired signal obtained by picking up a second reference test sound based on the test signal output from a second test speaker provided in a second test enclosure installed at a specific position in the test space using a first test microphone provided in the first test enclosure.

[0223] In this way, the first reference frequency response and the second reference frequency response can be calculated.

[0224] (Technical 13) Furthermore, the first housing is provided with a first communication interface capable of transmitting an audio signal, a second housing installed in the space, a second communication interface provided in the second housing capable of receiving the audio signal from the first communication interface, a second speaker provided in the second housing that outputs audio based on the audio signal received by the second communication interface, and a second microphone provided in the second housing, and the processor further causes the first communication interface to transmit the test signal to the second communication interface, thereby enabling the test signal The audio playback system according to Technical 1, comprising: outputting a second test sound based on the above to the second speaker; acquiring a third sound pickup signal indicating the second test sound picked up by the second microphone; calculating the third frequency characteristics of the third sound pickup signal; estimating the arrangement of the second housing in the space based on the third frequency characteristics; determining a second correction parameter based on the arrangement of the second housing; the equalizer unit further generating a second corrected sound signal by correcting the frequency characteristics of the input sound signal using the second correction parameter; and the second speaker outputting sound based on the second corrected sound signal.

[0225] According to this, the second microphone necessary to determine the second correction parameter for the second speaker located in the second housing is pre-installed in the second housing, so the user does not need to prepare any special equipment such as microphones other than what is necessary for normal playback. Furthermore, the placement of the second housing is automatically estimated from the third frequency characteristics of the third sound pickup signal representing the second test sound picked up by the second microphone, and the second correction parameter is automatically determined from the estimated placement of the second housing. Therefore, the user does not need the skills and expertise to pick up the audio signal at the listening position and determine the correction parameter. Consequently, even if the audio playback system is equipped with multiple speakers and multiple microphones, a user without specialized knowledge can automatically improve the frequency characteristics at the listening position with a single touch, making it easy to achieve the performance intended by the designer.

[0226] (Technical 14) The audio playback system according to Technical 13, wherein the processor estimates the arrangement of the first enclosure by comparing the first reference frequency characteristics for the first enclosure with the first frequency characteristics, and estimates the arrangement of the second enclosure by comparing the third reference frequency characteristics for the second enclosure with the third frequency characteristics.

[0227] According to this, the comparison result between the first reference frequency response and the first frequency response changes in accordance with the change in the arrangement of the first enclosure. In other words, there is a correlation between the comparison result between the first reference frequency response and the first frequency response and the arrangement of the first enclosure. Therefore, by comparing the first reference frequency response and the first frequency response, the arrangement of the first enclosure can be easily estimated. Furthermore, the comparison result between the third reference frequency response and the third frequency response changes in accordance with the change in the arrangement of the second enclosure. In other words, there is a correlation between the comparison result between the third reference frequency response and the third frequency response and the arrangement of the second enclosure. Therefore, by comparing the third reference frequency response and the third frequency response, the arrangement of the second enclosure can be easily estimated.

[0228] (Technical 15) The audio playback system according to Technical 13 or 14, wherein the processor determines a predetermined correction parameter as the first correction parameter for a predetermined arrangement estimated to be the arrangement of the first enclosure from among a plurality of predetermined arrangements, and determines a predetermined correction parameter as the second correction parameter for a predetermined arrangement estimated to be the arrangement of the second enclosure from among the plurality of predetermined arrangements.

[0229] According to this, the designer can pre-determine the optimal correction parameters for each of the multiple predetermined arrangements by conducting experiments or simulations. Therefore, the first correction parameter can be easily determined by simply using the predetermined correction parameters for the predetermined arrangement estimated as the arrangement of the first enclosure as the first correction parameter. Similarly, the second correction parameter can be easily determined by simply using the predetermined correction parameters for the predetermined arrangement estimated as the arrangement of the second enclosure as the second correction parameter.

[0230] (Technical 16) The audio playback system according to Technical 14, wherein the processor uses the first reference frequency characteristics, the second reference frequency characteristics for the second enclosure, the third reference frequency characteristics, and the fourth reference frequency characteristics for the first enclosure to estimate the arrangement of the first enclosure and the arrangement of the second enclosure, and to determine the first correction parameter and the second correction parameter.

[0231] According to this, by using the first, second, third, and fourth reference frequency characteristics calculated in advance by the designer, it is possible to easily estimate the arrangement of the first and second enclosures, as well as determine the first and second correction parameters.

[0232] (Technical 17) The processor further acquires a second sound pickup signal indicating the second test sound picked up by the first microphone, acquires a fourth sound pickup signal indicating the first test sound picked up by the second microphone, calculates the second frequency characteristic of the second sound pickup signal, calculates the fourth frequency characteristic of the fourth sound pickup signal, and for each predetermined frequency range for a predetermined arrangement estimated to be the arrangement of the first housing from among a plurality of predetermined arrangements, calculates the difference between the first reference frequency characteristic and the first frequency characteristic for the predetermined arrangement estimated to be the arrangement of the first housing. The audio playback system according to Technical Reference 16, comprising: determining a first correction parameter that reduces the difference between the fourth reference frequency characteristic and the fourth frequency characteristic by a certain number of minutes; and determining a second correction parameter that reduces the difference between the second reference frequency characteristic and the second frequency characteristic, or the difference between the third reference frequency characteristic and the third frequency characteristic, for each predetermined frequency range for a predetermined arrangement estimated to be the arrangement of the second housing from among the plurality of predetermined arrangements.

[0233] For example, the first, second, third, and fourth reference frequency characteristics are the frequency characteristics of a reference test audio based on a test signal, calculated under the assumption that the entire audio playback system, including speaker characteristics, is designed to optimize the frequency characteristics of the audio signal in a predetermined configuration (e.g., a standard "Free" configuration). Therefore, by determining a first correction parameter that reduces the difference between the first frequency characteristic and the first reference frequency characteristic in a predetermined frequency band, and by determining a second correction parameter that reduces the difference between the third frequency characteristic and the third reference frequency characteristic in a predetermined frequency band, the frequency characteristics of the audio signal can be improved even at the listening position in the user's space.

[0234] However, the first reference frequency response is the frequency response calculated when the first test enclosure is in a specific position, and the placement of the first test enclosure may differ from that of the first enclosure. Depending on the placement of the first enclosure, the frequency range over which the first reference frequency response should be compared with the first frequency response will differ. Similarly, the third reference frequency response is the frequency response calculated when the second test enclosure is in a specific position, and the placement of the second test enclosure may differ from that of the second enclosure. Depending on the placement of the second enclosure, the frequency range over which the third reference frequency response should be compared with the third frequency response will differ. Furthermore, since the second frequency response of the second sound signal representing the second test sound of the second speaker picked up by the first microphone, and the fourth frequency response of the fourth sound signal representing the first test sound of the first speaker picked up by the second microphone can also be calculated, depending on the placement of the first enclosure, there may be frequency ranges over which it is better to compare the fourth reference frequency response with the fourth frequency response. Furthermore, depending on the placement of the second enclosure, there may be frequency ranges where it is better to compare the second reference frequency response with the second frequency response.

[0235] In contrast, the designer can pre-determine, through experiments or simulations, the frequency range over which the first, second, third, or fourth reference frequency characteristics should be compared with the first, second, third, or fourth frequency characteristics for each of the multiple predetermined configurations. Therefore, the first and second correction parameters can be determined according to the configuration of the first and second enclosures.

[0236] (Technical 18) The audio playback system according to Technical 16 or 17, wherein the first reference frequency characteristic is a frequency characteristic calculated in advance from an acquired signal obtained by picking up a first reference test sound based on the test signal output from a first test speaker provided in a first test enclosure installed at a specific position in the test space using a first test microphone provided in the first test enclosure; the second reference frequency characteristic is a frequency characteristic calculated in advance from an acquired signal obtained by picking up a second reference test sound based on the test signal output from a second test speaker provided in a second test enclosure installed at a specific position in the test space using a first test microphone provided in the first test enclosure; the third reference frequency characteristic is a frequency characteristic calculated in advance from an acquired signal obtained by picking up the second reference test sound using a second test microphone provided in the second test enclosure; and the fourth reference frequency characteristic is a frequency characteristic calculated in advance from an acquired signal obtained by picking up the first reference test sound using a second test microphone.

[0237] In this way, the first reference frequency response, the second reference frequency response, the third reference frequency response, and the fourth reference frequency response can be calculated.

[0238] (Technical 19) A method for reproducing sound performed by a sound reproduction system, wherein the sound reproduction system comprises a first housing installed in a space, a first speaker provided in the first housing, and a first microphone provided in the first housing, and the method for reproducing sound includes: outputting a first test sound based on a test signal to the first speaker, acquiring a first sound pickup signal indicating the first test sound picked up by the first microphone, calculating a first frequency characteristic of the first sound pickup signal, estimating the arrangement of the first housing in the space based on the first frequency characteristic, determining a first correction parameter based on the arrangement of the first housing, generating a first corrected sound signal by correcting the frequency characteristic of an input sound signal input to the sound reproduction system using the first correction parameter, and outputting sound based on the first corrected sound signal to the first speaker.

[0239] This method provides an audio playback method that can easily achieve the performance intended by the designer.

[0240] (Technical 20) A program for causing a computer to execute the audio playback method described in Technical 19.

[0241] This allows us to provide a program that can easily achieve the performance intended by the designer. [Industrial applicability]

[0242] This disclosure can be applied to audio playback systems and the like for playing back audio. [Explanation of Symbols]

[0243] 1, 2, 3 Audio playback system 100, 101, 102 First cabinet 110, 110a, 110b processors 111, 111a Test signal generator 112 Signal Switcher 113, 113a, 113b Sound pickup measuring device 114, 114a, 114b Correction parameter generator 115 Frequency Response Analysis Unit 116 Comparative Analysis Department 117, 117a decision section 120, 120a Equalizer 130 Microphone No. 1 140 input terminals 150, 220 amplifier 160 First speaker 170, 170a 1st communication I / F 180 memory 201, 202 Second cabinet 210, 210a 2nd communication I / F 230 Second speaker 240 Second microphone

Claims

1. It is an audio playback system, The first enclosure is installed in space, The first speaker provided in the first housing, The first microphone provided in the first housing, Processor and It includes an equalizer section, The aforementioned processor, A first test sound based on a test signal is output to the first speaker. A first sound pickup signal is acquired, which represents the first test sound picked up by the first microphone. The first frequency characteristics of the first sound-collected signal are calculated, By comparing the first reference frequency characteristics for the first housing with the first frequency characteristics, the arrangement of the first housing in the space is estimated. Based on the arrangement of the first housing, the first correction parameter is determined, The equalizer unit generates a first corrected audio signal by correcting the frequency characteristics of the input audio signal input to the audio playback system using the first correction parameter. The first speaker outputs sound based on the first corrected sound signal. The first reference frequency characteristics are frequency characteristics calculated in advance from the sound-collected signal obtained by capturing the first reference test sound, which is based on the test signal output from a first test speaker installed in a first test enclosure located at a specific position in the test space, using a first test microphone installed in the first test enclosure. Audio playback system.

2. The processor determines a predetermined correction parameter as the first correction parameter for a predetermined arrangement that is estimated to be the arrangement of the first enclosure from among a plurality of predetermined arrangements. The audio playback system according to claim 1.

3. The processor uses the first reference frequency characteristics to estimate the arrangement of the first enclosure and to determine the first correction parameters. The audio playback system according to claim 1.

4. The processor determines a first correction parameter that reduces the difference between the first reference frequency characteristic and the first frequency characteristic in a predetermined frequency range for a predetermined arrangement that is estimated as the arrangement of the first enclosure from among a plurality of predetermined arrangements. The audio playback system according to claim 3.

5. moreover, The first housing is provided with a first communication interface capable of transmitting audio signals, A second housing is installed in the aforementioned space, A second communication interface is provided in the second housing and capable of receiving the voice signal from the first communication interface, The second housing includes a second speaker that outputs audio based on the audio signal received by the second communication interface, The aforementioned processor further, By transmitting the test signal from the first communication interface to the second communication interface, a second test audio based on the test signal is output to the second speaker. A second sound signal representing the second test sound captured by the first microphone is acquired. The second frequency characteristics of the second sound-collected signal are calculated, By comparing the second reference frequency characteristics for the second housing with the second frequency characteristics, the arrangement of the second housing in the space is estimated. Based on the arrangement of the second housing, the second correction parameter is determined, The equalizer unit further generates a second corrected audio signal by correcting the frequency characteristics of the input audio signal using the second correction parameter. The second speaker outputs sound based on the second corrected sound signal. The second reference frequency characteristic is a frequency characteristic pre-calculated from an acquired signal obtained by capturing the second reference test sound, which is based on the test signal output from a second test speaker installed in a second test enclosure located at a specific position in the test space, by the first test microphone installed in the first test enclosure. The audio playback system according to claim 1.

6. The aforementioned processor, A predetermined correction parameter is determined as the first correction parameter for the predetermined arrangement that is estimated to be the arrangement of the first enclosure from among a plurality of predetermined arrangements. A predetermined correction parameter is determined as the second correction parameter for the predetermined arrangement that is estimated to be the arrangement of the second housing from among the plurality of predetermined arrangements. The audio playback system according to claim 5.

7. The processor uses the first reference frequency characteristics and the second reference frequency characteristics to estimate the arrangement of the first enclosure and the arrangement of the second enclosure, and to determine the first correction parameter and the second correction parameter. The audio playback system according to claim 5.

8. The aforementioned processor, A first correction parameter is determined that reduces the difference between the first reference frequency characteristic and the first frequency characteristic in a predetermined frequency range for a predetermined arrangement that is estimated to be the arrangement of the first housing from among a plurality of predetermined arrangements. The second correction parameter is determined such that the difference between the second reference frequency characteristic and the second frequency characteristic in a predetermined frequency range is small for a predetermined arrangement that is estimated to be the arrangement of the second housing from among the plurality of predetermined arrangements. The audio playback system according to claim 7.

9. moreover, The first housing is provided with a first communication interface capable of transmitting audio signals, A second housing is installed in the aforementioned space, A second communication interface is provided in the second housing and capable of receiving the voice signal from the first communication interface, A second speaker provided in the second housing outputs sound based on the audio signal received by the second communication interface, The second housing includes a second microphone, The aforementioned processor further, By transmitting the test signal from the first communication interface to the second communication interface, a second test audio based on the test signal is output to the second speaker. A third sound signal indicating the second test sound picked up by the second microphone is acquired, The third frequency characteristic of the third sound-collected signal is calculated, By comparing the third reference frequency characteristics for the second housing with the third frequency characteristics, the arrangement of the second housing in the space is estimated. Based on the arrangement of the second housing, the second correction parameter is determined, The equalizer unit further generates a second corrected audio signal by correcting the frequency characteristics of the input audio signal using the second correction parameter. The second speaker outputs sound based on the second corrected sound signal. The third reference frequency characteristic is a frequency characteristic pre-calculated from an acquired signal obtained by capturing a second reference test sound, which is based on the test signal output from a second test speaker installed in a second test enclosure located at a specific position in the test space, using a second test microphone installed in the second test enclosure. The audio playback system according to claim 1.

10. The aforementioned processor, A predetermined correction parameter is determined as the first correction parameter for the predetermined arrangement that is estimated to be the arrangement of the first enclosure from among a plurality of predetermined arrangements. A predetermined correction parameter is determined as the second correction parameter for the predetermined arrangement that is estimated to be the arrangement of the second housing from among the plurality of predetermined arrangements. The audio playback system according to claim 9.

11. The processor uses the first reference frequency characteristics, the second reference frequency characteristics for the second enclosure, the third reference frequency characteristics, and the fourth reference frequency characteristics for the first enclosure to estimate the arrangement of the first enclosure and the arrangement of the second enclosure, and to determine the first correction parameter and the second correction parameter. The audio playback system according to claim 9.

12. The aforementioned processor further, A second sound signal representing the second test sound captured by the first microphone is acquired. A fourth sound pickup signal is acquired, which represents the first test sound picked up by the second microphone. The second frequency characteristics of the second sound-collected signal are calculated, The fourth frequency characteristic of the fourth sound-collected signal is calculated, For each predetermined frequency range of a predetermined arrangement estimated to be the arrangement of the first housing from among a plurality of predetermined arrangements, a first correction parameter is determined that reduces the difference between the first reference frequency characteristic and the first frequency characteristic, or the difference between the fourth reference frequency characteristic and the fourth frequency characteristic, for the predetermined arrangement estimated to be the arrangement of the first housing. For each predetermined frequency range of a predetermined arrangement estimated to be the arrangement of the second housing from among the plurality of predetermined arrangements, a second correction parameter is determined that reduces the difference between the second reference frequency characteristic and the second frequency characteristic, or the difference between the third reference frequency characteristic and the third frequency characteristic, which is predetermined for the predetermined arrangement estimated to be the arrangement of the second housing. The audio playback system according to claim 11.

13. The second reference frequency characteristic is a frequency characteristic calculated in advance from the sound-collected signal obtained by the second reference test sound being picked up by the first test microphone, The fourth reference frequency response is a frequency response calculated in advance from the sound signal obtained when the first reference test sound is picked up by the second test microphone. The audio playback system according to claim 11 or 12.

14. A method for playing back audio that is performed by an audio playback system, The aforementioned audio playback system is The first enclosure is installed in space, The first speaker provided in the first housing, The first housing includes a first microphone, In the aforementioned audio playback method, A first test sound based on a test signal is output to the first speaker. A first sound pickup signal is acquired, which represents the first test sound picked up by the first microphone. The first frequency characteristics of the first sound-collected signal are calculated, By comparing the first reference frequency characteristics for the first housing with the first frequency characteristics, the arrangement of the first housing in the space is estimated. Based on the arrangement of the first housing, the first correction parameter is determined, A first corrected audio signal is generated by correcting the frequency characteristics of the input audio signal input to the audio playback system using the first correction parameter. The audio based on the first corrected audio signal is output to the first speaker. The first reference frequency characteristics are frequency characteristics calculated in advance from the sound-collected signal obtained by capturing the first reference test sound, which is based on the test signal output from a first test speaker installed in a first test enclosure located at a specific position in the test space, using a first test microphone installed in the first test enclosure. How to play audio.

15. A program for causing a computer to execute the audio playback method described in claim 14.

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