MULTI-CHANNEL AUDIO SIGNAL CORRECTION DEVICE

Abstract

 The present invention provides a multi-channel audio signal correction capable of preventing an increase in the number of steps for installing a speaker or/and an amplifier, which is/are connected to a multi-channel audio reproduction apparatus. The multi-channel audio signal correction device 3 transmits a predetermined measurement signal to a speaker module 2 connected through a network 4 to the multi-channel audio signal correction device 3 and receives a sound output from the speaker module 2. The multi-channel audio signal correction device 3 measures a propagation delay time of each of the received sounds and estimates the position of a speaker 21 provided in the target speaker module 2, in accordance with each of the measured propagation delay times. The multi-channel audio signal correction device 3 assigns an output channel to the target speaker module 2 in accordance with the estimated position of the speaker 21. The multi-channel audio signal correction device 3 generates a correction value used to correct an output of the target speaker module 2 and transmits the correction value to the target speaker module 2.

Description

Technical Field of the Invention

[0001] The present invention relates to a multi-channel audio signal correction device, and more specifically to a multi-channel audio signal correction device to be used in a multi-channel audio reproduction apparatus connected to a plurality of speakers through a network so as to output sounds from the speakers.

Background of the Invention

[0002] Up until now, there have been a wide variety of multi-channel audio reproduction apparatuses to provide a high-quality sound field space.

[0003] Fig. 12 is a diagram showing a conventional multi-channel audio reproduction apparatus including a sound field correction unit 101, power amplifiers 102a to 102e, speakers 103a to 103e, and microphones 104a to 104d. Each of the power amplifiers 102a to 102e amplifies a measurement signal generated from measurement signal generator (not shown). Each of the speakers 103a to 103e outputs the amplified measurement signal as sound. The microphones 104a to 104d are arranged in accordance with a closely located four point microphone method. Each of the microphones 104a to 104d collects the sounds from all the speakers 103a to 103e. The sound field correction unit 101 compares characteristics of the sounds collected by the microphones 104a to 104d with a volume of, a delay time of, and a mixing ratio of sounds set in a controller (not shown), thereby obtaining differential signals of the comparison results. Based on the differential signals, a sound volume controller, a delay circuit, and a mixer (not shown) is controlled to automatically generate a optimal sound field space at a listening point of a user (refer to, for example, Patent Document 1).

[0004] Fig. 13 is a diagram showing another conventional multi-channel audio reproduction apparatus including a measurement signal generator 111, a switch 112, power amplifiers 113a to 113e, a speaker microphone switch 114, a front-left speaker 115a, a front-right speaker 115b, a front-center speaker 115c, a rear-left speaker 115d, a rear-right speaker 115e, microphones 116a and 116b, head amplifiers 117a to 117e, a delay measurement unit 118, a processing unit 119, a listening position input unit 120, and an output signal processing unit 121. Each of the switch 112 and the speaker microphone switch 114 selects one of speakers 115a to 115e. The measurement signal generator 111 generates a measurement signal. Each of the power amplifiers 113a to 113e amplifies the measurement signal generated by the measurement signal generator 111. The selected speaker outputs the amplified measurement signal. The speaker microphone switch 114 connects an output terminal of each of the speakers 115a to 115e other than the selected speaker to a corresponding one of the head amplifiers 117a to 117e. Each of the speakers connected to the corresponding head amplifiers operates as a microphone to collect the measurement signal output from the selected speaker. Each of the head amplifiers 117a to 117e amplifies the collected measurement signal to transmit the amplified measurement signal to the delay measurement unit 118. The microphone 116a and 116b are mounted in the rear-left speaker 115d and the rear-right speaker 115e, respectively. Both of the microphones 116a and 116b collect the measurement signal output from the selected speaker. The head amplifiers 117f and 117g receive the measurement signal from the microphones 116a and 116b to amplify the received measurement signal, respectively. Both of the head amplifiers 117f and 117g transmit the amplified signals to the delay measurement unit 118. The processing unit 119 estimates three-dimensional coordinates of the position of each of the speakers 115a to 115e in accordance with a delay time measured by the delay measurement unit 118 to calculate an appropriate listening position of the user. The output signal processing unit 121 controls a delay time of, a volume of, and a mixing ration of a signal reproduced from each of channels to create an optimal sound field space at the appropriate listening point or a listening point input from the listening position input unit 120, (refer to, for example, Patent Document 2).

Patent Document 1: Japanese Patent Laid-Open Publication No. 2000-354300

Patent Document 2: Japanese Patent Laid-Open Publication No. 2003-250200

Disclosure of the Invention

Problems to be solved by the Invention

[0005] Each of the conventional multi-channel audio reproduction apparatuses, however, assigns an output channel of each of the speakers to a front-right (hereinafter, FR) speaker, a front-left (hereinafter, FL) speaker, a front-center (hereinafter, FC) speaker, a rear-right (hereinafter, RR) speaker, a rear-left (hereinafter, RL) speaker, and a subwoofer (hereinafter, SW). Each of the speakers needs to be placed at the assigned position, and to be then connected to an amplifier output corresponding to the assigned output channel.

[0006] Consequently, the more the number of speakers, the more complicated assignments of output channels to the speakers, and connections between the speakers and the amplifier outputs corresponding to the output channels. As a result, the number of steps for installing the speakers increases, and an incorrect connection may be easily occurred. Especially, since a speaker of an in-vehicle multi-channel audio reproduction apparatus is installed at a predetermined position in a vehicle, setting of the apparatus is complicated and an incorrect connection may be easily occurred. This results in the need to fix the incorrect connection.

[0007] It is, therefore, an object of the present invention is to provide a multi-channel audio signal correction device capable of reducing the number of steps for installing a speaker and/or an amplifier, which is/are connected to a multi-channel audio reproduction apparatus.

Means of Solving the Problems

[0008] To accomplish the above object, the first aspect of the present invention is directed to a multi-channel audio signal correction device. The device comprises: a measurement signal generator for generating a measurement signal; a speaker switching section connected to a plurality of speaker modules through a network, operable to select one of the plurality of the speaker modules and to transmit, to the selected speaker module, measurement signal generated by the measurement signal generator; a plurality of sound collection units for each collecting, as a measurement sound, a sound output from the selected speaker module in accordance with the measurement signal; a delay measurement section operable to measure a propagation delay time of each of the measurement sounds collected by the plurality of the sound collection units; a position estimation section operable to estimate the position of a speaker provided in the selected speaker module in accordance with each of the propagation delay times measured by the delay measurement section; a channel assignment section operable to assign an output channel to the selected speaker module in accordance with the position of the speaker, the position being estimated by the position estimation section; and a sound field correction section operable to generate a correction value in accordance with each of the propagation delay times measured by the delay measurement section and with the output channel assigned by the channel assignment section and to transmit the generated correction value to the selected speaker module, the correction value being used to correct an output of the selected speaker module.

[0009] The multi-channel audio signal correction device further comprises a frequency characteristic analysis section operable to analyze a frequency characteristic of the selected speaker module in accordance with each of the measurement sounds collected by the plurality of the sound collection units. The channel assignment section further refers to the frequency characteristic analyzed by the frequency characteristic analysis section to assign an output channel to the selected speaker module. The sound field correction section further refers to the frequency characteristic analyzed by the frequency characteristic analysis section to generate a correction value used to correct an output of the selected speaker module.

[0010] The multi-channel audio signal correction device further comprises a frequency range determination section operable to determine a reproduction frequency range of the selected speaker module in accordance with the frequency characteristic analyzed by the frequency characteristic analysis section.. The sound field correction means further uses the reproduction frequency range determined by the reproduction frequency range determination section to generate a correction value used to correct an output of the selected speaker module.

[0011] Furthermore, the reproduction frequency range determination section determines the reproduction frequency range of the speaker provided in the selected speaker module in accordance with the position of the speaker, the position being estimated by the position estimation section.

[0012] The second aspect of the present invention is directed to a method for correcting a multi-channel audio signal used in a multi-channel audio reproduction apparatus. The method comprising steps of: generating a measurement signal; selecting one of a plurality of speaker modules connected through a network to transmit, to the selected speaker module, the generated measurement signal; collecting, with a plurality of sound collection units different from each other to receive, a sound output from the selected speaker module in accordance with the measurement signal input to the speaker module, as a measurement sound; measuring a propagation delay time of each of the collected sounds; estimating the position of a speaker provided in the selected speaker module in accordance with each of the measured propagation delay times; assigning an output channel to the selected speaker module in accordance with the estimated position of the speaker; and generating a correction value in accordance with each of the measured propagation delay times and with the assigned output channel, the correction value being used to correct an output of the selected speaker module.

Effect of the Invention

[0013] According to the first and second aspects of the present invention, the position of a speaker provided in the speaker module connected through the network is estimated by measuring the propagation delay time of the measurement signal, and the output channel is then automatically assigned to the selected speaker module in accordance with the estimated position. In accordance with the measured propagation delay time and the assigned output channel, a sound is output from an amplifier output corresponding to the output channel automatically assigned under the condition that an audio signal transmitted to the speaker module is corrected. This makes it possible to create a sound environment suitable for the position of a listener. As apparent from the above description, according to the first and second aspects of the present invention, the output channel is automatically assigned to the selected speaker module. It is therefore not necessary for a user to connect the speaker module to the amplifier output corresponding to the output channel. This does not increase the number of steps for installing a speaker or/and an amplifier, regardless of the fact that the number of speakers or/and the number of amplifiers increase(s) with increasing the number of channels.

Brief Description of the Drawings

[0014] 

Fig. 1 is a block diagram showing a multi-channel audio reproduction system according to a first embodiment of the present invention.

Fig. 2 is a flowchart showing steps of a sound correction process performed in the system shown in Fig. 1.

Fig. 3 is a flowchart showing detail steps included in step 13 shown in Fig. 2.

Fig. 4 is a diagram showing the configuration of a sound collection unit 34 shown in Fig. 1.

Fig. 5 is a graph showing a method for obtaining the position of each of speakers 21a to 21e shown in Fig. 1.

Fig. 6 is a diagram showing a positional relationship between the speakers 21a to 21e and the sound collection unit 34 that is fixed to a driver seat in a vehicle.

Fig. 7 is a graph showing frequency characteristics of a speaker 21 functioning as a super woofer shown in Fig. 1.

Figs. 8(a) to 8(d) are graphs each showing a reproduction frequency range assigned by a frequency range determination section 38 shown in Fig. 1.

Fig. 9 is a diagram showing the position of each of the speakers, which is substantially the same as that of a corresponding one of the speakers shown in Fig. 1.

Fig. 10 is a flowchart showing detail steps included in step S19 shown in Fig. 2.

Fig. 11 is a flowchart showing steps of a sound reproduction process performed in the system shown in Fig. 1.

Fig. 12 is a block diagram showing an example of the configuration of a conventional multi-channel audio reproduction apparatus.

Fig. 13 is a block diagram showing another example of the configuration of a conventional multi-channel audio reproduction apparatus.

Description of Reference Numerals

[0015] 

1:

Reproduction apparatus

11:

Reproduction section

12:

Network driver

2a to

2e: Speaker module

21a to

21e: Speaker

22a to

22e: Power amplifier

23a to

23e: Signal processor

24a to

24e: Storage

25a to

25e: Network driver

3:

Correction device

31:

Speaker detection section

32:

Measurement signal generator

33:

Speaker switching section

34:

Sound collection unit

35:

Delay measurement section

36:

Position estimation section

37:

Frequency characteristic analysis section

38:

Frequency range determination section

39:

Channel assignment section

40:

Target value input section

41:

Sound field correction section

42:

Network driver

4:

Network

Best Mode for Carrying Out the Invention

[0016] Fig. 1 is a block diagram showing the configuration of a multi-channel audio reproduction system (hereinafter merely referred to as a system) according to an embodiment of the present invention. The system as shown in Fig. 1 is installed, for example, in a vehicle and outputs a sound in accordance with a multi-channel audio signal. The system includes a reproduction apparatus 1, a plurality of speaker modules 2, a multi-channel audio signal correction device 3, and a network 4 connecting the reproduction apparatus 1, the speaker modules 2 and the multi-channel audio signal correction device 3, in order to output a sound. In Fig. 1, five speaker modules 2a to 2e are provided. The number of the speaker modules may be changed. Hereinafter, the description will be made the case of the system including the speaker modules 2a to 2e.

[0017] The reproduction apparatus 1 has a reproduction section 11 and a network driver 12 to output a multi-channel audio signal to a network 4. The reproduction section 11 generates a multi-channel audio signal and outputs the signal to the network driver 12. The network driver 12 transmits the multi-channel audio signal output from the reproduction section 11 to the network 4. The multi-channel audio signal is transmitted through the network 4 to a target one of the speaker modules 2a to 2e.

[0018] The speaker modules 2a to 2e include speakers 21a to 21e, power amplifiers 22a to 22e, signal processors 23a to 23e, storages 24a to 24e, and network drivers 25a to 25e, respectively.

[0019] Each of the network drivers 25a to 25e receives a multi-channel audio signal transmitted through the network 4 from the reproduction apparatus 1 and a correction value transmitted from the multi-channel audio signal correction device 3. The signal processors 23a to 23e are connected to the storages 24a to 24e, respectively. Each of the signal processors 23a to 23e corrects the received multi-channel audio signal in accordance with a correction value (described in detail later) stored in a corresponding one of the storages 24a to 24e. The signal processors 23a to 23e then transmit the corrected signal to the following power amplifiers 22a to 22e, respectively. The power amplifiers 22a to 22e amplify the received multi-channel audio signal to transmit the amplified signal to corresponding speakers 21a to 21e, respectively. Each of the speakers 21a to 21e reproduces a sound in accordance with the received multi-channel audio signal and outputs the sound.

[0020] The multi-channel audio signal correction device 3 includes a speaker detection section 31, a measurement signal generator 32, a speaker switching section 33, a sound collection unit 34, a delay measurement section 35, a position estimation section 36, a frequency characteristic analysis section 37, a frequency range determination section 38, a channel assignment section 39, a target value input section 40, a sound field correction section 41, and a network driver 42.

[0021] The speaker detection section 31 detects the number of the speaker modules 2 connected to the network 4. The measurement signal generator 32 generates a measurement signal. The speaker switching section 33 switches a destination of a measurement signal to a speaker module to be measured. The sound collection unit 34 exemplary includes microphones 34a to 34d, each of which is placed in a vehicle at a tip of a virtually formed equilateral tetrahedron (refer to Fig. 4), to collect the measurement signal output from the speaker to be measured. The delay measurement section 35 measures a propagation delay time of the measurement signal. The position estimation section 36 estimates the position of the speaker in accordance with the measured propagation delay time. The frequency characteristic analysis section 37 analyzes a frequency characteristic of the speaker in accordance with the collected measurement signal. The frequency range determination section 38 determines an assignment of a reproduction frequency range to the speaker module 2 to be measured in accordance with the result of the analysis performed by the frequency characteristic analysis section 37. The channel assignment section 39 assigns an output channel to the speaker module 2 in accordance with the result of the estimation performed by the position estimation section 36 and with the result of the analysis performed by the frequency characteristic analysis section 37. The target value input section 40 responds to an operation performed by a user and sets, to the sound field correction section 41, a target characteristic value for the listening position of the user. The sound field correction section 41 generates and sets a correction value for each of the speaker modules 2 to create a sound environment optimal for the listening position of the user. The network driver 42 is connected to the network 4 and sends out to the network 4 the correction value generated by the sound field correction section 41. After sent out from the network driver 42, the correction value is transmitted through the network 4 to the target speaker module 2.

[0022] The network drivers 12, 25a to 25e and 42 assign a unique network ID to each device connected to the network 4. Each of the devices connected through the network 4 can obtain the type of the other device connected through the network 4 and the network ID of the other device if necessary.

[0023] Fig. 2 is a flowchart showing steps of a sound field correction process performed in the system shown in Fig. 1. First, the target value input section 40 provided in the multi-channel audio signal correction device 3 sets a target characteristic value for the listening position of a user. Next, the speaker detection section 31 obtains the types of all devices connected to the network 4 and detects an N number of the speaker modules 2 (N = 5 in the example shown in Fig. 1) in accordance with the acquired types of the devices. Then, the speaker detection section 31 transmits data on the N number of the speaker modules 2 to the sound field correction section 41 (Step S11).

[0024] Next, the sound field correction section 41 sets a loop variable "i" to "1"(Step S12), and then obtains information on the speaker modules 2 (Step S13). Detailed process in the step S13 will be described later with reference to Fig. 3. Then, the sound field correction section 41 adds one to the loop variable "i"(Step S14), and then determines whether or not the variable "i" is equal to or less than the N number of the speaker modules 2. The step S13 described above is repeated while the variable "i" is equal to or less than the N number of the speaker modules 2.

[0025] Fig. 3 is a flowchart showing detail steps included in step S13 shown in Fig. 2. As shown in Fig. 3, in the multi-channel audio signal correction device 3, the measurement signal generator 32 generates an impulse response between the speaker modules and the sound collection unit 34, more specifically an impulse signal as an example of a measurement signal used to obtain a propagation delay time of and a frequency characteristic of a sound output from any one of the speakers 21(Step S31). In the present embodiment, the impulse signal will be described as an example of the measurement signal. An M-sequence noise and a sweep signal may be used as the measurement signal. The impulse signal generated by the measurement signal generator 32 is transmitted through the network driver 42 and the network 4 to a target one of the speaker modules 2 which is selected by the speaker switching section 33(Step S32).

[0026] In the target speaker module 2, the network driver 25 in the target speaker module 2 receives the impulse signal through the network 4(Step S33), the speaker 21 receives the impulse signal through the signal processor 23 and the power amplifier 22. Then, the speaker 21 outputs a measurement sound in accordance with the received impulse signal(Step S34).

[0027] The measurement sound output from the speaker 21 to be measured is collected by the sound collection unit 34 including the microphones 34a to 34d as shown in Fig. 4(Step S35).

[0028] The delay measurement section 35 measures a propagation delay time of the measurement sound in accordance with the impulse response to the measurement sound received by the sound collection unit 34. The propagation delay time measured by the delay measurement section 35 is stored in the storage 24 provided in the speaker module 2 to be measured(Step S36).

[0029] Next, the position estimation section 36 estimates the position of the speaker 2 to be measured in accordance with the measured propagation delay time. The estimated position of the speaker 2 is stored in the storage 24 provided in the speaker module 2 to be measured(Step S37).

[0030] As shown in Fig. 5, the three-dimensional coordinates of the position of the speaker 2 to be measured are estimated in accordance with the arrival times t1 to t4 of the measurement sounds and the positions of the microphones 34a to 34d, the measurement sounds being collected by the microphones 34a to 34d provided in the sound collection unit 34.

[0031] Specifically, as shown in Fig. 4, if the three-dimensional coordinates of the microphones 34a to 34d are expressed as (Xa, Ya, Za), (Xb, Yb, Zb), (Xc, Yc, Zc), and (Xd, Yd, Zd), and a sonic velocity is expressed as v, the coordinates of the position of the speaker 21 to be measured can be expressed as the following.

[0032] As shown in Fig. 6, since the sound collection unit 34 is exemplary fixed to the driver seat of the vehicle, the position of the speaker 21 to be measured can be estimated in accordance with the three-dimensional coordinates of the sound collection unit 34 and the three-dimensional coordinates of the speaker 21 with respect to the driver seat.

[0033] The frequency characteristic analysis section 37 analyzes a frequency characteristic of the speaker 21 to be measured in accordance with the impulse response to the measurement sound received by the sound collection unit 34. As a result, data on the frequency characteristic is transmitted through the network 4 and stored in the storage 24 provided in the speaker module 2 to be measured(Step S38).

[0034] The abovementioned steps are performed on all the speakers 21a to 21e connected to the network 4 to obtain information on each of the speakers 21a to 21e.

[0035] Referring to Fig. 2 again, the channel assignment section 39 assigns output channels such as an FR channel, FL channel, FC channel, RR channel and RL channel to the speakers 21a to 21e in accordance with the estimated positions of the speakers 21a to 21e. Each of the assigned output channels is transmitted through the network 4 and stored in the storage 24 corresponding to each of the speaker modules 2 (step S16).

[0036] In a 5.1 channel system or the like, the channel assignment section 39 assigns an output channel for a super woofer to any one of the speakers 21a to 21e in accordance with frequency characteristics of the speakers 21a to 21e, the frequency characteristics being analyzed by the frequency characteristic analysis section 37. For example, if the frequency characteristics includes a low frequency output as shown in Fig. 7, the super woofer (SW) is assigned to a speaker providing the low frequency output as an output channel.

[0037]  Next, the frequency range determination section 38 assigns a reproduction frequency range such as a high frequency range, a middle frequency range, and a low frequency range to each of the speakers 21a to 21e in accordance with the frequency characteristic of and the position of each of the speakers 21a to 21e. The frequency range determination section 38 then transmits data on the assigned reproduction frequency range is transmitted through the network 4, and the transmitted data is stored in a corresponding one of the storages 24a to 24e.

[0038] The reproduction frequency range is determined in accordance with the frequency characteristic of the speaker 21 as illustrated in a graph of Fig. 8(a) showing frequencies divided into three ranges, i.e., a low frequency range, a middle frequency range and a high frequency range.

[0039] As shown in Fig. 8(b), the low frequency range is assigned as the reproduction frequency range if frequencies of an output of the speaker 21 cover the low frequency range. As shown in Fig. 8(c), the middle frequency range is assigned as the reproduction frequency range if frequencies of the output of the speaker 21 cover the middle frequency range. As shown in Fig. 8(d), the high frequency range is assigned as the reproduction frequency range if frequencies of the output of the speaker 21 cover the high frequency range.

[0040] The frequency range determination section 38 determines a reproduction frequency range based also on the vertical position of the speaker 21. As shown in Fig. 9, if three speakers 21 are arranged adjacently to each other and at substantially the same position, the frequency range determination section 38 assigns the high, middle, low frequency ranges to the speakers 21 placed at the highest, middle, lowest position, respectively.

[0041] Next, the sound field correction section 41 performs a parameter correction process on each of the speakers 21a to 21e in accordance with the target characteristic value for the listening position of a user. More specifically, the sound field correction section 41 sets the loop variable "i" to "1"(Step S18), and then corrects the parameter described later with reference to Fig. 10(Step S19). Then, the sound field correction section 41 adds one to the variable "i" (Step S20), and then determines whether or not the variable "i" is equal to or less than the N number of the speakers(Step S21). The step S19 is repeated while the variable "i" is equal to or less than the N number of the speakers.

[0042]  Fig. 10 is a flowchart showing detail steps included in step S19 shown in Fig. 2. The sound field correction section 41 calculates a correction value for correcting the propagation delay time of an output from the speaker 21 to match the propagation delay time with the set target characteristic value in accordance with the propagation delay time of an output from the speaker 21 to be corrected. The correction value for correcting the propagation delay time is transmitted through the network 4 and stored in the storage 24 provided in the speaker module 2 to be corrected (Step S41).

[0043] The sound field correction section 41 calculates a correction value for adjusting an equalizer to match the set target characteristic value in accordance with a frequency characteristic of, a reproduction frequency range of, and a channel assigned to the speaker to be corrected. The correction value for adjusting the equalizer is transmitted through the network 4 and stored in the storage 24 provided in the speaker module 2 to be corrected(Step S42).

[0044] In addition, the sound field correction section 41 calculates a correction value for adjusting a phase characteristic of the speaker 21 to be corrected to match the phase characteristic with the set target characteristic value, the phase characteristic being obtained at the listening position of a user. The correction value for adjusting the phase characteristic is transmitted through the network 4 and stored in the storage 24 provided in the speaker module to be corrected(Step S43).

[0045] If the correction values used for all the speakers 21 are set in the abovementioned steps, and the system reproduces a sound, the reproduction section 11 of the reproduction apparatus 1 transmits a multi-channel audio signal to each of the speaker modules 2a to 2e through the network driver 12 and the network 4 (Step S51).

[0046] Each of the network drivers 25a to 25e receives the multi-channel audio signal through the network 4. The signal processors 23a to 23e process the multi-channel audio signal in accordance with the data on the output channel and the correction value that are stored in the storages 24a to 24e, respectively(Step S52). The signal processors 23a to 23e then transmit the processed multi-channel audio signal to the speakers 21a to 21e through the power amplifiers 22a to 22e, respectively(Step S53). Each of the speakers 21a to 21e then reproduces a sound in accordance with the processed multi-channel audio signal to output the sound to a user.

[0047] In the system according to the present embodiment as described above, the multi-channel audio signal correction device 3 uses the measurement signal to estimate the position of each of the speakers 21a to 21e which are arbitrarily arranged and automatically assigns an output channel to each of the speakers 21a to 21e in accordance with the estimated position. Each of the storages 24a to 24e then stores the output channel. Each of the signal processors 23a to 23e processes the multi-channel audio signal transmitted through the network 4 in accordance with the output channel stored in the storages 24a to 24e to output the processed signal, respectively. Accordingly, the output channel is automatically assigned to each of the speakers 21a to 21e on the basis of the position of each of the speakers 21a to 21e. Each of the speakers 21a to 21e outputs a sound in accordance with the assigned output channel. It is therefore not necessary that the user connect a speaker to an amplifier output corresponding to the output channel assigned in accordance with the position of the speaker. This does not increase the number of steps for installing a speaker and/or an amplifier, although the number of speakers and/or the number of amplifiers increase(s) with increasing the number of channels.

[0048] The multi-channel audio signal correction device 3 analyses the frequency characteristic of the target speaker module by using the measurement signal. The multi-channel audio signal correction device 3 then assigns a reproduction frequency range suitable for each of the speakers 21a to 21e in accordance with the analyzed frequency characteristic, resulting in an improvement of a sound environment.

[0049] In addition, the multi-channel audio signal correction device 3 performs the parameter correction process to match with the target characteristic value for the listening position of a user, the target characteristic value being set by the target value input section 40. This makes it possible to form a sound environment suitable for the position of the listener.

[0050] The network 4 is described above as a ring type in the present embodiment. The network 4, however, may be of a star type and a bus type. Also, the network 4 may be wireless.

[0051] The system with the five speakers 21 and the five speaker modules 2 is described above in the present embodiment. The number of the speakers 21 and the number of the speaker modules 2 may be four or six, or more.

[0052] The sound collection unit 34 includes the four microphones 34a to 34d, and the position estimation section 36 estimates the three-dimensional coordinates of the position of each of the speakers 21 in the present embodiment. The sound collection unit 34 may include three microphones, and the position estimation section 36 may estimate the two-dimensional coordinates of the position of each of the speakers 21. In addition, the sound collection unit 34 may include five or more microphones, and the position estimation section 36 may estimate the two or three-dimensional coordinates of the position of each of the speakers.

[0053] The system according to the present embodiment is installed in a vehicle, but may be installed in a house or an office.

Industrial Applicability

[0054] The multi-channel audio signal correction device according to the present invention makes it possible to prevent an increase in the number of steps for installing a speaker and/or an amplifier which are/is adapted to reproduce and output a sound obtained based on the multi-channel audio signal. The multi-channel audio signal correction device according to the present invention is suitable for a multi-channel audio reproduction apparatus installed in a vehicle.

Claims

1. A multi-channel audio signal correction device comprising:

a measurement signal generator for generating a measurement signal;

a speaker switching section connected to a plurality of speaker modules through a network, operable to select one of said plurality of the speaker modules and to transmit, to said selected speaker module, said measurement signal generated by said measurement signal generator;

a plurality of sound collection units for each collecting, as a measurement sound, a sound output from said selected speaker module in accordance with said measurement signal;

a delay measurement section operable to measure a propagation delay time of each of said measurement sounds collected by said plurality of the sound collection units;

a position estimation section operable to estimate the position of a speaker provided in said selected speaker module in accordance with each of said propagation delay times measured by said delay measurement section;

a channel assignment section operable to assign an output channel to said selected speaker module in accordance with the position of said speaker, the position being estimated by said position estimation section; and

a sound field correction section operable to generate a correction value in accordance with each of said propagation delay times measured by said delay measurement section and with said output channel assigned by said channel assignment section and to transmit said generated correction value to said selected speaker module, said correction value being used to correct an output of said selected speaker module.

2. The multi-channel audio signal correction device according to claim 1, further comprising:

a frequency characteristic analysis section operable to analyze a frequency characteristic of said selected speaker module in accordance with each of said measurement sounds collected by said plurality of the sound collection units, wherein

said channel assignment section further refers to said frequency characteristic analyzed by said frequency characteristic analysis section to assign an output channel to said selected speaker module, and

said sound field correction section further refers to said frequency characteristic analyzed by said frequency characteristic analysis section to generate a correction value used to correct an output of said selected speaker module.

3. The multi-channel audio signal correction device according to claim 2, further comprising:

a frequency range determination section operable to determine a reproduction frequency range of said selected speaker module in accordance with said frequency characteristic analyzed by said frequency characteristic analysis section, wherein

said sound field correction means further uses said reproduction frequency range determined by said reproduction frequency range determination section to generate a correction value used to correct an output of said selected speaker module.

4. The multi-channel audio signal correction device according to claim 3, wherein
said reproduction frequency range determination section determines said reproduction frequency range of said speaker provided in said selected speaker module in accordance with the position of said speaker, the position being estimated by said position estimation section.

5. A method for correcting a multi-channel audio signal used in a multi-channel audio reproduction apparatus, said method comprising steps of:

generating a measurement signal;

selecting one of a plurality of speaker modules connected through a network to transmit, to said selected speaker module, said generated measurement signal;

collecting, with a plurality of sound collection units different from each other to receive, a sound output from said selected speaker module in accordance with said measurement signal input to said speaker module, as a measurement sound;

measuring a propagation delay time of each of said collected sounds;

estimating the position of a speaker provided in said selected speaker module in accordance with each of said measured propagation delay times;

assigning an output channel to said selected speaker module in accordance with the estimated position of said speaker; and

generating a correction value in accordance with each of said measured propagation delay times and with said assigned output channel, said correction value being used to correct an output of said selected speaker module.

Drawing