Filter information generation device, method, and program

Abstract

This filter information generation device comprises: an impulse response input unit 11 to which is inputted an impulse response measured in a free sound field, or in a sound field approximating the free sound field, of a wearable device that reproduces sound without completely shielding an external auditory foramen; and a filter information generation unit 12 for generating, from the impulse response, filter information pertaining to a filter for weakening the acoustic characteristics of the wearable device determined from the impulse response and performing a filter process on a signal to be reproduced by the wearable device.

Description

Filter information generation device, method, and program

[0001] The disclosed technology relates to a technology for generating information about a filter.

[0002] For example, it is known that sound reproduced from a wearable device whose sound wave radiation hole is located above the ear canal is localized slightly above the head due to the influence of the headphone transfer function (HpTF) from the speaker of the wearable device to the entrance of the ear canal.

[0003] To reduce this effect, a technique has been proposed in which an inverse filter of the HpTF is applied to the reproduced sound source.In addition, a technique has been proposed in which statistics such as the mean value, median value, and upper variance limit value of the HpTF measured on a dummy head or a human body are used as the HpTF used to generate the inverse filter (see, for example, Non-Patent Document 1).

[0004] Bruno Masiero, Janina Fels, "Perceptually Robust Headphone Equalization for Binaural Reproduction", AES Conv. 2011

[0005] However, when statistical quantities such as the mean, median, and upper variance limit of HpTF measured on a dummy head or human body are used as the HpTF used to generate the inverse filter, the correction of sound quality and localization may be insufficient.

[0006] To achieve sufficient correction of sound quality and localization, it is necessary to measure the HpTF of the wearer of a wearable device that reproduces sound without completely blocking the ear canal, but measuring the HpTF for each wearer is time-consuming.

[0007] The disclosed technology aims to provide a filter information generation device, method, and program that do not require measuring the HpTF of a wearer of a wearable device that reproduces sound without completely blocking the external auditory canal.

[0008] A filter information generating device, which is one aspect of the disclosed technology, includes an impulse response input unit to which an impulse response measured in a free sound field or a sound field approximating a free sound field of a wearable device that reproduces sound without completely blocking the external auditory canal is input, and a filter information generating unit that generates, from the impulse response, filter information that is information about a filter for performing filtering on a signal that the wearable device is to reproduce, which filter is for weakening the acoustic characteristics of the wearable device determined from the impulse response.

[0009] According to the disclosed technology, filter information can be generated without measuring the HpTF of a wearer of a wearable device that reproduces sound without completely blocking the external ear canal.

[0010] Fig. 1 is a diagram showing an example of the functional configuration of a filter information generating device. Fig. 2 is a diagram showing an example of a processing procedure of a filter information generating method. Fig. 3 is a diagram for explaining an example of changing an impulse response. Fig. 4 is a diagram for explaining an example of changing an impulse response. Fig. 5 is a diagram for explaining a plurality of different positions for measuring an impulse response. Fig. 6 is a diagram showing an example of the functional configuration of a computer. Fig. 7 is a diagram showing an example of an experimental result.

[0011] Hereinafter, embodiments of the disclosed technology will be described with reference to the drawings. Note that components having the same functions in the drawings are given the same reference numerals, and redundant description will be omitted.

[0012] [Filter Information Generating Device and Method] As shown in Fig. 1, the filter information generating device includes, for example, an impulse response input unit 11 and a filter information generating unit 12. The filter information generating device may further include a filter processing unit 13 indicated by a dashed line in Fig. 1.

[0013] The filter information generating method is realized, for example, by each unit of the filter information generating device performing the processes of steps S11 and S12 shown in FIG.

[0014] Each part of the filter information generating device will be described below.

[0015] <Impulse response input unit 11> The impulse response input unit 11 receives an impulse response measured in a free sound field or a sound field approximating a free sound field of a wearable device that reproduces sound without completely blocking the external auditory canal (step S11).

[0016] To perform measurements in a free sound field or a sound field approximating a free sound field, the measurements are performed, for example, in an anechoic chamber or semi-anechoic chamber. After the measurements are performed in an anechoic chamber or semi-anechoic chamber, processing to remove reflected waves may be performed. Furthermore, measurements in a free sound field or a sound field approximating a free sound field may be performed using software processing.

[0017] The input impulse response is output to the filter information generating unit 12 .

[0018] When generating filter information by <<Method (2)>> described later, a plurality of impulse responses at a plurality of different positions measured in a free sound field or a sound field approximating a free sound field of a wearable device that reproduces sound without completely blocking the external ear canal may be input to the impulse response input unit 11. In this case, the input plurality of impulse responses are output to the filter information generation unit 12. The processing in this case will be described in detail later.

[0019] Examples of wearable devices that reproduce sound without completely blocking the ear canal include open-ear earphones, shoulder speakers, audio glasses, smart glasses, audio glasses, and open headphones. Hereinafter, wearable devices that reproduce sound without completely blocking the ear canal may be abbreviated as "wearable devices."

[0020] For example, the impulse response is measured in an anechoic or semi-anechoic chamber with a microphone placed 1 cm away from the front of a wearable device that reproduces sound without completely blocking the ear canal.

[0021] Because the housing of a wearable device that reproduces sound without completely blocking the ear canal is smaller than that of a headphone, the influence of reflections between the ear and the housing is reduced. Therefore, the transfer function (Headphone Transfer Function - Free Sound Field (HpTF-FSF)) calculated from the impulse response measured in a free sound field or a sound field that approximates a free sound field for a wearable device that reproduces sound without completely blocking the ear canal is relatively close to the spectral shape of the true HpTF. Therefore, there is no problem in generating a filter based on the HpTF-FSF.

[0022] Furthermore, for a wearable device that reproduces sound without completely blocking the external auditory canal, the frequency characteristics of the transfer function calculated from the impulse response measured in a free sound field or a sound field that approximates a free sound field are less likely to have sharp high-frequency peaks or notches. Therefore, by using the impulse response measured in a free sound field or a sound field that approximates a free sound field, the filter can be stably determined.

[0023] <Filter Information Generator 12 > The filter information generator 12 receives the impulse response from the impulse response input unit 11 .

[0024] The filter information generation unit 12 generates filter information from the input impulse response, which is information about a filter for weakening the acoustic characteristics of a wearable device that reproduces sound without completely blocking the external ear canal, and which is information about a filter for performing filtering on a signal that the wearable device that reproduces sound without completely blocking the external ear canal is trying to reproduce (step S12).

[0025] The generated filter information is output from the filter information generation unit 12. For example, the filter information is output to the filter processing unit 13 shown by the dashed line in FIG. 1 . The filter processing unit 13 performs filter processing determined by the input filter information on a playback signal, which is a signal to be played back by a wearable device that plays back sound without completely blocking the external ear canal, and outputs a filter-processed playback signal. Examples of filter processing include FIR filter processing using a simple convolution, overlap-add method, or overlap-save method. After that, sound corresponding to the filter-processed playback signal is output from the wearable device that plays back sound without completely blocking the external ear canal.

[0026] Examples of filters for attenuating the acoustic characteristics of a wearable device that reproduces sound without completely blocking the ear canal include an inverse filter of HpTF-FSF and an approximation filter of the inverse filter of HpTF-FSF.A filter for attenuating the acoustic characteristics of a wearable device that reproduces sound without completely blocking the ear canal may also be a filter that is obtained by appropriately changing the impulse response, as in <<Method (1)>> and <<Method (2)>> described below.

[0027] The filter information is information for identifying a filter. The filter information is, for example, a filter coefficient and a parameter for determining the filter coefficient. Examples of the parameters for determining the filter coefficient are a frequency, a gain, and a Q value. The filter information may be an impulse response obtained by performing an inverse Fourier transform on the generated filter, or an FIR filter obtained from the impulse response obtained by performing an inverse Fourier transform on the generated filter.

[0028] Below, <<Method (1)>> and <<Method (2)>>, which are examples of the processing methods of the filter information generating unit 12, will be described.

[0029] <<Method (1)>> Method (1) is method (1-1) or method (1-2) described below.

[0030] First, the method (1-1) will be explained.

[0031] In the method (1-1), the impulse response input from the impulse response input unit 11 is changed, and filter information is generated from the changed impulse response.

[0032] For example, the filter information generating unit 12 modifies the impulse response by changing the values ​​of samples other than those included in a predetermined range including the sample corresponding to the maximum value of the impulse response so that they do not exceed the maximum value, and generates filter information from the modified impulse response.

[0033] An example of the samples included in the predetermined range including the sample corresponding to the maximum value of the impulse response is a plurality of consecutive samples including the sample corresponding to the maximum value of the impulse response. The samples included in the predetermined range including the sample corresponding to the maximum value of the impulse response may be only the sample corresponding to the maximum value of the impulse response.

[0034] The filter information generator 12 modifies the impulse response by, for example, multiplying the values ​​of samples other than those included in a predetermined range that includes the sample corresponding to the maximum value of the impulse response by a predetermined real number. The predetermined real number is, for example, a value greater than or equal to 0 and less than 1. The predetermined real number may also be a value greater than 1. However, the predetermined real number is set so that the value of the sample multiplied by the predetermined real number does not exceed the maximum value of the impulse response before modification.

[0035] In the example of Fig. 3, the impulse response is changed by multiplying the values ​​of samples other than sample S1 corresponding to the maximum value of the impulse response by a predetermined real number f(c). In this example, the only sample included in the predetermined range that includes sample S1 corresponding to the maximum value of the impulse response is sample S1 corresponding to the maximum value of the impulse response. Furthermore, c is a predetermined real number, and f(c) is a predetermined function, and in this example, f(c) is a value that is greater than or equal to 0 and less than 1. Examples of f(c) are f(c)=c, f(c)=c k where k is a predetermined real number. The predetermined real number f(c) is sometimes called the IR coefficient ratio.

[0036] In the examples of Figures 3 and 4, samples that fall within a predetermined range including sample S1 corresponding to the maximum value of the impulse response are shown with solid lines, and samples other than those that fall within the predetermined range including sample S1 corresponding to the maximum value of the impulse response are shown with double lines.

[0037] In the example of Figure 4, the impulse response is modified by multiplying the values ​​of samples other than consecutive samples S2, S1, and S3 including sample S1 corresponding to the maximum value of the impulse response by a predetermined real number f(c). In this example, the samples included in the predetermined range including sample S1 corresponding to the maximum value of the impulse response are the three consecutive samples S2, S1, and S3 including sample S1 corresponding to the maximum value of the impulse response, more specifically, sample S1 corresponding to the maximum value of the impulse response and the samples S2 and S3 before and after it. f(c) is the same as in the example of Figure 3.

[0038] The filter information generation unit 12 generates a filter from the modified impulse response to weaken the acoustic characteristics of a wearable device that reproduces sound without completely blocking the external auditory canal, for example, using the method described in Reference 1.

[0039] [Reference 1] Scharer, Zora, and Alexander Lindau, "Evaluation of equalization methods for binaural signals", Audio Engineering Society Convention 126, Audio Engineering Society, 2009. In this method, for example, a filter H is calculated based on the following equation: c (x) is generated. x is the frequency. H c (x) is a filter generated by the filter information generating unit 12. D * (x) is a specific bandpass filter. * means a complex conjugate number. A bandpass filter is a filter that passes signals with frequencies between 100 Hz and 20,000 Hz. D *(x) is determined appropriately to obtain a desired result. H(x) is the frequency characteristic of a transfer function that can be obtained by Fourier transforming the modified impulse response. B(x) is a predetermined high-pass filter for regularization. B(x) is determined appropriately to obtain a desired result. β is a predetermined weight for regularization. β is determined appropriately to obtain a desired result.

[0040] Of course, the filter information generating unit 12 may generate a filter from the modified impulse response to weaken the acoustic characteristics of a wearable device that reproduces sound without completely blocking the external auditory canal using a method other than the method described in Reference 1.

[0041] The filter information generating unit 12 outputs filter information, which is information about the generated filter.

[0042] Next, the method (1-2) will be explained.

[0043] In method (1-2), a filter is generated from the impulse response input to the filter information generation unit 12, the impulse response obtained by performing an inverse Fourier transform on the generated filter is changed, and information about the changed impulse response is used as filter information.

[0044] First, the filter information generating unit 12 generates a filter corresponding to the impulse response input to the filter information generating unit 12, for example, by the method described in Reference 1. In other words, the filter information generating unit 12 generates a filter H(x) defined by the above formula (A) using the frequency characteristic of a transfer function that can be obtained by Fourier transforming the impulse response input to the filter information generating unit 12 as H(x). c (x). The explanations of the symbols other than H(x) are the same as above.

[0045] Of course, the filter information generating unit 12 may generate a filter corresponding to the impulse response input to the filter information generating unit 12 using a method other than the method described in Reference 1.

[0046] The filter information generating unit 12 changes the values ​​of samples other than those included in a predetermined range including the sample corresponding to the maximum value of the impulse response obtained by performing an inverse Fourier transform on the generated filter so that the values ​​do not exceed the maximum value, and sets information about the changed impulse response as filter information.

[0047] The information about the impulse response after modification is information for specifying the impulse response after modification.

[0048] An example of the samples included in the predetermined range including the sample corresponding to the maximum value of the impulse response is a plurality of consecutive samples including the sample corresponding to the maximum value of the impulse response. The samples included in the predetermined range including the sample corresponding to the maximum value of the impulse response may be only the sample corresponding to the maximum value of the impulse response.

[0049] The filter information generator 12 modifies the impulse response by, for example, multiplying the values ​​of samples other than those included in a predetermined range that includes the sample corresponding to the maximum value of the impulse response by a predetermined real number. The predetermined real number is, for example, a value greater than or equal to 0 and less than 1. The predetermined real number may also be a value greater than 1. However, the predetermined real number is set so that the value of the sample multiplied by the predetermined real number does not exceed the maximum value of the impulse response before modification.

[0050] In the example of Figure 3, the impulse response is modified by multiplying the values ​​of samples other than sample S1 corresponding to the maximum value of the impulse response by a predetermined real number f(c). In this example, sample S1 corresponding to the maximum value of the impulse response is the only sample included in the predetermined range that includes sample S1 corresponding to the maximum value of the impulse response. Furthermore, c is a predetermined real number, and f(c) is a predetermined function, and in this example, f(c) is a value that is greater than or equal to 0 and less than 1.

[0051] In the examples of Figures 3 and 4, samples that fall within a predetermined range including sample S1 corresponding to the maximum value of the impulse response are shown with solid lines, and samples other than those that fall within the predetermined range including sample S1 corresponding to the maximum value of the impulse response are shown with double lines.

[0052] In the example of Figure 4, the impulse response is modified by multiplying the values ​​of samples other than consecutive samples S2, S1, and S3 including sample S1 corresponding to the maximum value of the impulse response by a predetermined real number f(c). In this example, the samples included in the predetermined range including sample S1 corresponding to the maximum value of the impulse response are the three consecutive samples S2, S1, and S3 including sample S1 corresponding to the maximum value of the impulse response, more specifically, sample S1 corresponding to the maximum value of the impulse response and the samples S2 and S3 before and after it. f(c) is the same as in the example of Figure 3.

[0053] Note that c may be input to the filter information generation unit 12. In this case, the filter information generation unit 12 may calculate the value of f(c) based on the input c, and change the impulse response based on the calculated value of f(c).

[0054] For example, a wearer of a wearable device that reproduces sound without completely blocking the external ear canal may be able to input c to the filter information generating unit 12. This allows a wearer of a wearable device that reproduces sound without completely blocking the external ear canal to select their preferred c, in other words, their preferred sound image localization.

[0055] Furthermore, a third party other than the wearer of the wearable device that reproduces sound without completely blocking the external ear canal, such as an acoustic engineer, or a device other than the filter information generating device may be able to input c to the filter information generating unit 12.

[0056] <<Method (2)>> When generating filter information by <<Method (2)>>, the filter information generation unit 12 receives as input a plurality of impulse responses at a plurality of different positions measured in a free sound field or a sound field approximating a free sound field.

[0057] The position of the wearable device that reproduces sound without completely blocking the external ear canal and the impulse response is specified, for example, by a pair (φ, d) of φ and d shown in FIG. 5. SP in FIG. 5 is a symbol indicating a speaker of the wearable device that reproduces sound without completely blocking the external ear canal, and M in FIG. 5 is a symbol indicating a microphone for measuring the impulse response. φ is the elevation angle indicating the direction of the microphone M when the position of the speaker SP is the origin. d is the horizontal distance between the speaker SP and the microphone M. d is, for example, 2.5 mm, 5.0 mm, 10.0 mm, 15.0 mm, or 20.0 mm. φ is, for example, between -90 degrees and 90 degrees.

[0058] The impulse response of a wearable device that reproduces sound without completely blocking the external ear canal, measured when a microphone M is placed at a position determined by a certain pair of (φ, d) in a free sound field or a sound field approximating a free sound field, is referred to as the impulse response corresponding to (φ, d). In this case, multiple impulse responses corresponding to multiple different pairs of (φ, d) are measured and input to the impulse response input unit 11. The multiple impulse responses input to the impulse response input unit 11 are also input to the filter information generation unit 12.

[0059] The filter information generating unit 12 generates filter information from each of the input impulse responses.

[0060] The filter information generating unit 12 generates a filter corresponding to each impulse response input to the filter information generating unit 12, for example, by the method described in Reference 1. In other words, the filter information generating unit 12 generates a filter H defined by the above formula (A) using the frequency characteristic of a transfer function H(x) that can be obtained by Fourier transforming the impulse response input to the filter information generating unit 12. c (x). The explanations of the symbols other than H(x) are the same as above.

[0061] The filter information generating unit 12 generates filter information, which is information about each generated filter.

[0062] The filter information generating unit 12 selects one of the generated filter information pieces, and outputs the selected filter information piece as the filter generated by the filter information generating unit 12.

[0063] When information specifying filter information is input to the filter information generating unit 12, the filter information generating unit 12 selects filter information specified by the input information specifying filter information.

[0064] For example, a wearer of a wearable device that reproduces sound without completely blocking the external ear canal may be able to input information specifying filter information to the filter information generation unit 12. This allows a wearer of a wearable device that reproduces sound without completely blocking the external ear canal to select filter information that they like, in other words, sound image localization that they like.

[0065] In addition, a third party other than the wearer of a wearable device that reproduces sound without completely blocking the external auditory canal, such as an acoustic engineer, or a device other than the filter information generating device may be able to input information that identifies the filter information into the filter information generating unit 12.

[0066] The above processing makes it possible to generate filter information without measuring the HpTF of a wearer of a wearable device that reproduces sound without completely blocking the external ear canal.

[0067] [Other Modifications] The specific configurations of the embodiments of the disclosed technology are not limited to the configurations described above. The specific configurations of the embodiments of the disclosed technology can be appropriately modified in design, etc., within the scope of the spirit of the embodiments of the disclosed technology.

[0068] The various processes described in the embodiments of the disclosed technology may not only be performed chronologically in the order described, but may also be performed in parallel or individually depending on the processing capacity of the device performing the processes or as needed.

[0069] For example, in addition to φ and d, an impulse response may be measured for each pair (φ, d, a) determined by the horizontal angle a formed by the speaker SP and microphone M.

[0070] For example, if it is possible to acquire pinna shape information, which is information about the pinna shape of a wearer of a wearable device that reproduces sound without completely blocking the external auditory canal, and if c corresponding to each pinna shape information is predetermined, the filter information generating unit 12 may generate filter information by method (1) using c corresponding to the acquired pinna shape information.

[0071] Furthermore, when it is possible to acquire pinna shape information, which is information about the pinna shape of a wearer of a wearable device that reproduces sound without completely blocking the external ear canal, and filter information corresponding to each pinna shape information is predetermined, the filter information generating unit 12 may select filter information corresponding to the acquired pinna shape information from the filter information generated by method (2). In this way, the information specifying the filter information may be pinna shape information, which is information about the pinna shape of a wearer of a wearable device that reproduces sound without completely blocking the external ear canal.

[0072] The pinna shape information can be acquired by, for example, capturing an image using a camera provided on an information processing device such as a smartphone, tablet terminal, or PC held by the wearer. The pinna shape information may be pinna shape information when a wearable device that reproduces sound without completely blocking the external ear canal is worn, or may be pinna shape information when a wearable device that reproduces sound without completely blocking the external ear canal is not worn.

[0073] Furthermore, data exchange between the components of the filter information generating device may be performed directly or via a storage unit (not shown).

[0074] [Program, Recording Medium] The processing of each unit of the above-described filter information generation device may be realized by a computer. In this case, the processing contents of the functions that the filter information generation device should have are described by a program. Then, by loading this program into storage unit 1020 of computer 1000 shown in Fig. 6 and causing arithmetic processing unit 1010, input unit 1030, output unit 1040, display unit 1060, etc. to operate, various processing functions of the above-described filter information generation device are realized on the computer.

[0075] The program describing the processing contents can be recorded on a computer-readable recording medium, such as a non-transitory recording medium, specifically a magnetic recording device, an optical disk, or the like.

[0076] The program may be distributed, for example, by selling, transferring, lending, etc. a portable recording medium such as a DVD or CD-ROM on which the program is recorded. Furthermore, the program may be stored in a storage device of a server computer, and then transferred from the server computer to another computer via a network, thereby distributing the program.

[0077] A computer executing such a program, for example, first stores the program recorded on a portable recording medium or transferred from a server computer in its own non-transitory storage device, auxiliary storage unit 1050. Then, when executing a process, the computer loads the program stored in auxiliary storage unit 1050, its own non-transitory storage device, into storage unit 1020 and executes processing in accordance with the loaded program. Alternatively, as another form of execution of this program, the computer may load the program directly from a portable recording medium into storage unit 1020 and execute processing in accordance with the program. Furthermore, the computer may execute processing in accordance with the received program each time a program is transferred from a server computer to the computer. Alternatively, the server computer may not transfer the program to the computer, but may instead execute the processing function by issuing an execution instruction and obtaining the results, thereby executing the above-described processing through a so-called ASP (Application Service Provider) type service. Note that, in this embodiment, the program includes information used for processing by a computer that is equivalent to a program (e.g., data that is not a direct instruction to the computer but has properties that define computer processing).

[0078] In this embodiment, the device is configured by executing a predetermined program on a computer, but at least a part of the processing may be realized by hardware. For example, the impulse response input unit 11 and the filter information generation unit 12 may be configured by a processing circuit.

[0079] It goes without saying that other modifications are possible without departing from the spirit of the present invention.

[0080] All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

[0081] [Experimental Results] The following are the results of an experiment conducted on 25 subjects to investigate the effect of the correction filter on the perception of elevation angle.

[0082] The correction filters were compared using four filters: (1) no correction filter (None), (2) a correction filter calculated using the subject's own HpTF (Indiv.), (3) a correction filter calculated using the HpTF of a dummy head (General), and (4) a correction filter calculated using the earphone's free-field or near-free-field characteristics as the HpTF (FSF). For the FSF, impulse responses were measured in an anechoic chamber using an omnidirectional ECM with a 6 mm acoustic measurement diameter placed 1 cm from the earphone's radiation hole. A SAMAR Type 4700M dummy head was used. The correction filters were calculated using the least-squares method in the frequency domain. The evaluation sound sources used were a female voice (labeled "female voice" in Figure 7) and pink noise (labeled "pink noise" in Figure 7). Because it was difficult to determine the elevation angle, the elevation angle perception was evaluated using Scheffe's paired comparison method (Ura's modified method). In the evaluation, subjects listened to two sound sources with different correction filter conditions in turn, and were asked to choose from three options regarding the height of the localization of the preceding and following sounds. The options were "The following sound is higher," "Both are about the same," and "The following sound is lower." The results were tabulated and subjected to analysis of variance.

[0083] Analysis of variance confirmed significant differences in the main effect, main effect × individual, and order effect × individual for female voices and pink noise. Furthermore, a yardstick test revealed significant differences between the None and other conditions for female voices and pink noise, as shown in the scale diagram in Figure 7. Furthermore, significant differences were confirmed between General and FSF, and General and Individual for pink noise. These results show that the perceived elevation angle was lower than without a correction filter, regardless of which correction filter was applied. Furthermore, it can be seen that correction filters using individual HpTFs, free field characteristics, or sound field characteristics approximating a free field tend to result in lower perceived elevation angle than those using the HpTF of a dummy head.

Claims

1. A filter information generating device including: an impulse response input unit to which an impulse response measured in a free sound field or a sound field approximating a free sound field of a wearable device that reproduces sound without completely blocking the external ear canal is input; and a filter information generating unit that generates, from the impulse response, filter information for weakening the acoustic characteristics of the wearable device determined from the impulse response, the filter information being information about a filter for performing filtering on a signal that the wearable device is to reproduce.

2. A filter information generating device according to claim 1, wherein said filter information generating unit (1) modifies the impulse response by modifying values ​​of samples other than samples included in a predetermined range including a sample corresponding to a maximum value of the impulse response so that they do not exceed the maximum value, and generates said filter information from the modified impulse response, or (2) modifies values ​​of samples other than samples included in a predetermined range including a sample corresponding to a maximum value of an impulse response obtained by performing an inverse Fourier transform on the filter so that they do not exceed the maximum value, and generates information on the modified impulse response as the filter information.

3. A filter information generating device according to claim 2, wherein the filter information generating unit (1) modifies the impulse response by multiplying by a predetermined real number the values ​​of samples other than those included in a predetermined range including the sample corresponding to the maximum value of the impulse response, and generates the filter information from the modified impulse response, or (2) modifies the impulse response by multiplying by a predetermined real number the values ​​of samples other than those included in a predetermined range including the sample corresponding to the maximum value of the impulse response corresponding to the filter, and generates information on the modified impulse response as the filter information.

4. A filter information generating device according to claim 1, wherein the impulse response input unit receives a plurality of impulse responses at different positions measured in a free sound field or a sound field approximating a free sound field of a wearable device that reproduces sound without completely blocking the external ear canal, the filter information generating unit generates the filter information from each of the plurality of impulse responses, and the filter information generating unit selects one of the plurality of pieces of generated filter information.

5. A filter information generation method including: an impulse response input step in which an impulse response measured in a free sound field or a sound field approximating a free sound field of a wearable device that reproduces sound without completely blocking the external ear canal is input; and a filter information generation step in which filter information is generated from the impulse response, the filter information being information about a filter for weakening the acoustic characteristics of the wearable device determined from the impulse response, the filter being used to perform filtering on a signal that the wearable device is to reproduce.

6. A program for causing a computer to function as each part of the filter information generating device according to any one of claims 1 to 4.

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