Ear model, performance evaluation method, and performance evaluation system

[Problem] To evaluate, easily and at low cost, the performance of an earphone device used for ear acoustic certification.[Solution] Holes are provided in a plurality of plate-shaped members (201), an artificial eardrum member (202) corresponds to the eardrum of an individual, and the holes provided in each of the plurality of plate-shaped members (201) are connected, whereby the plurality of plate-shaped members (201) are layered over the artificial eardrum member (202) so as to simulate the external auditory canal of the individual.

This application is a National Stage Entry of PCT/JP2019/048843 filed on Dec. 13, 2019, the contents of all of which are incorporated herein by reference, in their entirety.

TECHNICAL FIELD

The present invention relates to an ear model, a performance evaluation method, and a performance evaluation system, and particularly relates to a personal authentication technology based on an individual characteristic of a shape of a human ear hole.

BACKGROUND ART

For example, fingerprint authentication, vein authentication, face authentication, iris authentication, and voice authentication have been known as personal authentication technologies (referred to as biometric authentication technologies) based on individual characteristics of living bodies. Among the personal authentication technologies, particularly in-ear acoustic authentication pays attention to individual characteristics of internal structures of human ear holes. In the in-ear acoustic authentication, an inspection signal is input to an ear hole of an individual to be authenticated, and personal authentication is performed using an echo signal based on an echo sound from the ear hole.

The individual (person to be authenticated) to be subjected to the personal authentication wears a device (referred to as an earphone device or a hearable device) having an earphone shape incorporating an in speaker and a microphone on the auricle. The speaker of the earphone device transmits the inspection signal (sound wave) toward the inside of the ear hole of the person to be authenticated. The microphone of the earphone device collects echo sound from the ear hole. Then, an echo signal based on the echo sound is transmitted from the earphone device to a personal authentication device. The personal authentication device performs personal authentication by collating the echo signal received from the earphone device with echo signals of one or a plurality of individuals registered in advance.

The in-ear acoustic authentication technology has advantages that personal authentication is completed instantaneously and stably, that personal authentication can be immediately performed in a state where an individual wears the earphone device (hands-free) even when the individual is moving or working, and that confidentiality regarding an internal structure of a human ear hole is high.

CITATION LIST

Patent Literature

Non Patent Literature

SUMMARY OF INVENTION

Technical Problem

In a related in-ear acoustic authentication technology, performance of an earphone device is evaluated. Specifically, a plurality of subjects are caused to wear the same earphone device in order to test in-ear acoustic authentication, and a false rejection rate (FRR) and a false acceptance rate (FAR), which are index values of performance of the earphone device, are calculated. However, it is necessary to restrain the subjects over a long period of time in order to accurately evaluate the performance of the earphone device, and thus, there are problems that time and effort for the performance evaluation are great and that cost is high.

The present invention has been made in view of the above problems, and an object thereof is to provide a technology for evaluating performance of an earphone device to be used for in-ear acoustic authentication easily and inexpensively.

Solution to Problem

An ear model according to one aspect of the present invention includes: a plurality of plate-shaped members provided with holes; and an artificial eardrum member equivalent to an eardrum of an individual, the holes, each of which is provided in each of the plurality of plate-shaped members, being connected, whereby the plurality of plate-shaped members are stacked on the artificial eardrum member in such a way as to simulate an external auditory canal of the individual.

A performance evaluation method according to one aspect of the present invention is a method for evaluating performance of an earphone device to be used for in-ear acoustic authentication using the ear model, and includes: transmitting an inspection signal from the earphone device toward a site of the ear model equivalent to an external auditory canal opening of the individual; collecting echo sound, transmitted from the ear model after the inspection signal propagates in the ear model, using the earphone device; calculating an acoustic characteristic of the ear model from an echo signal based on the collected echo sound; and evaluating performance of the earphone device based on the acoustic characteristic.

A performance evaluation system according to one aspect of the present invention includes: the ear model; an earphone device that transmits an inspection signal from the earphone device toward a site of the ear model equivalent to an external auditory canal opening of the individual and collects an echo sound transmitted from the ear model after the inspection signal propagates in the ear model; and a computing device that calculates an acoustic characteristic of the ear model from an echo signal based on the collected echo sound and calculates an index value indicating performance of the earphone device based on the acoustic characteristic.

Advantageous Effects of Invention

According to one aspect of the present invention, it is possible to easily and inexpensively evaluate the performance of the earphone device to be used for the in-ear acoustic authentication.

EXAMPLE EMBODIMENT

First Example Embodiment

A first example embodiment will be described below with reference toFIGS.1to7.

A configuration of a performance evaluation system1according to the first example embodiment will be described with reference toFIG.1.FIG.1is a schematic diagram illustrating the configuration of the performance evaluation system1. As illustrated inFIG.1, the performance evaluation system1includes a computing device10, an ear model20, and an earphone device30. The performance evaluation system1is used to evaluate performance of the earphone device30.

The computing device10reproduces an inspection signal and causes the inspection signal to be transmitted from the earphone device30to the ear model20. Then, the computing device10observes an echo signal based on echo sound, transmitted from the ear model20after the inspection signal propagates in the ear model20, and calculates an index value indicating the performance of the earphone device30based on the echo signal.

In general, there are two elements in the performance of the earphone device30. That is, there are a false rejection rate (FRR) and a false acceptance rate (FAR). When the performance of the earphone device30is high, both the false rejection rate (FRR) and the false acceptance rate (FAR) are low. In the first example embodiment, the computing device10calculates a J value as one index value indicating the performance of the earphone device30. The J value will be described in detail later.

The ear model20simulates an internal structure of an ear hole of an individual. More specifically, the ear model20is provided with a hole, and this hole simulates at least the internal structure (hereinafter, referred to as an external auditory canal) from an external auditory canal opening to an eardrum in the ear hole of an individual (the hole of the ear model20will be described later). An auricle model is placed on the ear model20. The auricle model is manufactured to match a shape of the earphone device30(FIG.1). For example, the auricle model is manufactured by taking a mold of an auricle of an individual and pouring a material such as silicone rubber of a fluid into the mold. Alternatively, an auricle of an individual may be scanned to generate 3D data of the auricle, and an auricle model may be manufactured by a 3D printer technology based on the generated 3D data of the auricle.

The earphone device30incorporates at least a speaker and a microphone. However, inFIG.1, the speaker and microphone incorporated in the earphone device30are schematically illustrated on the surface of the earphone device30. The earphone device30is attached so as to be embedded in a portion equivalent to an ear hole opening of the auricle model. The earphone device30is connected to the computing device10in a wireless or wired manner.

The earphone device30receives an instruction to transmit the inspection signal from the computing device10. The earphone device30transmits the inspection signal from the speaker incorporated in the earphone device30to the inside of the hole of the ear model20through an ear hole opening provided in the auricle model. The earphone device30collects echo sound, transmitted from the ear model20after the inspection signal propagates in the ear model20, by the microphone. The earphone device30generates the echo signal based on the echo sound collected by the microphone and transmits the echo signal to the computing device10.

FIG.2is a cross-sectional view of an ear model20awhich is an example of the ear model20illustrated inFIG.1. As illustrated inFIG.2, the ear model20aaccording to the first example embodiment includes at least a plurality of plate-shaped members201and one artificial eardrum member202.FIG.2does not illustrate an auricle model (also referred to as an artificial auricle) on the ear model20a. The plate-shaped member201is made of, for example, acrylic. The artificial eardrum member202is, for example, a film made of silicon or Teflon.

An upper surface of the ear model20aillustrated inFIG.2corresponds to a surface on which the auricle model is arranged inFIG.1. A hole of the plate-shaped member201located on the uppermost surface of the ear model20ais equivalent to an external auditory canal opening of an individual. An internal structure (specifically, an external auditory canal) of an ear hole of an individual is simulated by connecting holes provided at centers of the plurality of plate-shaped members201from the upper surface of the ear model20a(the surface in contact with the auricle model) to the artificial eardrum member202. The plurality of plate-shaped members201are stacked and accommodated in a hollow cylinder. In the hollow cylinder, the plate-shaped member201on the upper side is in close contact with the plate-shaped member201on the lower side (or the artificial eardrum member202) by its own weight and the weight of the plate-shaped member201on the upper side thereof.

FIG.3illustrates a shape of the plate-shaped member201forming the ear model20a. As illustrated inFIG.3, the hole penetrating through the plate-shaped member201in the thickness direction is provided at the center of the plate-shaped member201. A thickness of the plate-shaped member201is, for example, 5 mm. A size (R) of a diameter of the hole is variable, for example, between 5 mm and 20 mm. The plate-shaped member201is made of, for example, acrylic.

However, a material of the plate-shaped member201is not particularly limited. In general, acoustic characteristics of the ear hole depend on a length and a thickness, but do not depend on the complexity of the curvature of the ear hole. An acoustic characteristic of the ear hole do not depend on a material or texture (hardness) of an inner wall of the ear hole. Therefore, even if the ear model20ais formed using the plate-shaped member201having a material or texture different from that of a human ear, or even if the plurality of plate-shaped members201are linearly arranged, the acoustic characteristic substantially equivalent to those of an ear hole of an individual having the same length and thickness as those of the hole of the ear model20a.

In the ear model20a, the plurality of plate-shaped members201are stacked in an arrangement order according to the number (n) assigned to each of the plate-shaped members201in advance. The sizes (R) and arrangement orders (n) of the holes of the plurality of plate-shaped members201are determined based on an internal structure of an ear hole of an individual to be simulated by the ear model20a.

The thicknesses and the number of the plurality of plate-shaped members201constituting the ear model20aare related to a length from the external auditory canal opening to the eardrum of the individual (simulated by the internal structure of the hole of the ear model20a).

The size of the diameter of the hole provided in each of the plurality of plate-shaped members201forming the ear model20aare related to the thickness of the external auditory canal of the individual (simulated by the internal structure of the hole of the ear model20a).

Data on the internal structure of the ear hole of the individual is obtained by, for example, computed tomography (CT) scanning. In this case, parameters (R, n) of the ear model20amay be obtained from a result of executing the CT scan on a subject.

In one example, three-dimensional data of an external auditory canal of the subject may be displayed on a display to request a worker to input the parameters (R, n) of the ear model20a. In another example, the computing device10analyzes the result of executing the CT scan to determine the parameters (R, n).

Note that the performance evaluation system1can also be applied to a speech communication device other than the earphone device30. For example, the performance evaluation system1evaluates performance of a headphone device covering an auricle model, instead of the earphone device30. In this case, a speaker and a microphone may be provided in an ear-contact portion of the headphone device. In another application example, the performance evaluation system1can also evaluate performance of a telephone device in which a speaker and a microphone are provided in a portion equivalent to a receiver, instead of the earphone device30.

A configuration of the computing device10according to the first example embodiment will be described with reference toFIG.4.FIG.4is a block diagram illustrating a configuration of the computing device10. As illustrated inFIG.4, the computing device10includes an inspection signal reproduction unit101, an echo signal observation unit102, an acoustic characteristic calculation unit103, an input unit104, an acoustic characteristic accumulation unit105, and an index value calculation unit106.

The inspection signal reproduction unit101reproduces an inspection signal to be input to the ear model20a. The inspection signal input to the ear model20aechoes inside a hole of the ear model20a, and echo sound is output from the ear model20a. Data obtained by encoding the inspection signal reproduced by the inspection signal reproduction unit101is stored in advance in a recording medium (not illustrated). The inspection signal reproduction unit101acquires the data of the inspection signal stored in the recording medium, and reproduces the inspection signal. How to determine the inspection signal is not particularly limited. For example, the inspection signal is experimentally determined based on general thickness and length of ear holes of a plurality of individuals such that echo sound from the ear hole of any individual is strong (or S/N is large).

The echo sound indicates a characteristic depending on an internal structure of the hole of the ear model20a(referred to as an acoustic characteristic of the ear model20a). The acoustic characteristic of the ear model20ais equivalent to an acoustic characteristic of an ear hole of an individual simulated by the hole of the ear model20a. Since an internal structure of an ear hole of an individual has individuality, it is possible in principle to identify the individual based on the acoustic characteristic of the ear hole of the individual.

The inspection signal reproduction unit101transmits the reproduced inspection signal to the earphone device30in a wireless or wired manner, and causes the inspection signal to be output from the speaker of the earphone device30. Specifically, the inspection signal is an impulse wave.

The echo signal observation unit102observes the echo signal based on the echo sound from the ear model20ausing the microphone of the earphone device30. More specifically, the echo sound is output from the ear model20aafter the inspection signal propagates in the ear model20a. The microphone of the earphone device30collects the echo sound output from the ear model20a. The earphone device30converts the echo sound collected by the microphone into digital data to generate the echo signal.

The echo signal observation unit102requests the echo signal from the earphone device30. The earphone device30transmits the echo signal to the echo signal observation unit102in a wireless or wired manner. The echo signal observation unit102receives the echo signal from the earphone device30in a wireless or wired manner. The echo signal observation unit102transmits the echo signal received from the earphone device30to the acoustic characteristic calculation unit103.

The acoustic characteristic calculation unit103receives the echo signal from the echo signal observation unit102. The acoustic characteristic calculation unit103calculates a transfer function as the acoustic characteristic of the ear model20afrom the received echo signal. That is, the transfer function is an example of the acoustic characteristic. A response function based on a response (echo signal) of the ear model20ato the inspection signal is another example of the acoustic characteristic.

Specifically, the acoustic characteristic calculation unit103first extracts an impulse response from the echo signal. The impulse response is a response (echo signal) of the ear model20with respect to the inspection signal that is the impulse wave. The acoustic characteristic calculation unit103performs Fourier transform or Laplace transform on the impulse response to calculate the transfer function. The acoustic characteristic calculation unit103transmits data of the calculated transfer function to the acoustic characteristic accumulation unit105.

The input unit104acquires information indicating the size (R) of the diameter of the hole provided at the center of each of the plate-shaped members201(FIG.4) and a number of each of the plate-shaped members201, that is, the arrangement order (n) as the parameters of the ear model20a. For example, the input unit104requests a user to input the size (R) of the diameter of the hole provided in each of the plurality of plate-shaped members201and the arrangement orders of the plate-shaped members201by display, sound, or other means.

The input unit104analyzes an input operation of the user with respect to the computing device10to acquire information indicating the parameters (R, n) of the ear model20a. The input unit104transmits the information indicating the parameters (R, n) of the ear model20ato the acoustic characteristic accumulation unit105.

The acoustic characteristic accumulation unit105receives the data of the transfer function from the acoustic characteristic calculation unit103. The acoustic characteristic accumulation unit105receives the information indicating parameters (R, n) of the ear model20afrom the input unit104. The acoustic characteristic accumulation unit105accumulates the data of the transfer function received from the acoustic characteristic calculation unit103in the recording medium (not illustrated) as acoustic characteristic data in association with information indicating the parameters (R, n) of the ear model20a(here, the first flow ends).

Thereafter, the worker detaches the earphone device30from the ear model20aand attaches the same earphone device30to the same ear model20aagain (the second flow starts from here). The computing device10acquires the acoustic characteristic data again by the above-described procedure. As the acoustic characteristic data is repeatedly acquired this manner, it is possible to evaluate how much reproducibility the earphone device30has with respect to attachment and detachment to and from the single ear model20a, that is, how much the acoustic characteristic data with little variation can be acquired.

Hereinafter, a flow ID: i (i=1, 2, . . . ) is introduced to distinguish the transfer function acquired in the first flow from transfer functions acquired in the second and subsequent flows. The computing device10stores data (xi) of the acoustic characteristic obtained in the i-th flow and the parameters (R, n) in the recording medium in association with each other. The above procedure is repeated a predetermined plurality of times. Thereafter, the acoustic characteristic accumulation unit105transmits the acoustic characteristic data (that is, the transfer function (xi) (i=1, 2, . . . ) and the parameters (R, n)) accumulated in the recording medium to the index value calculation unit106. As above, the data of the transfer function (xi) (i=1, 2, . . . ) has been collected using the single ear model20a(more specifically, the ear model20ahaving the same parameters).

Subsequently, the worker attaches the earphone device30to another ear model (hereinafter, referred to as another ear model20a) having parameters (R, n) different from those of the ear model20adescribed above. Here, the parameters (R, n) of the another ear model20ais different from the parameters (R, n) of the ear model20adescribed above. The computing device10acquires the transfer functions (xi) for a predetermined plurality of times by the above-described procedure, and stores a set of the parameters (R, n) and the transfer functions (xi) for the predetermined plurality of times in the recording medium in association with each other.

Hereinafter, the plurality of ear models20ahaving different parameters (R, n) are distinguished by ear model IDs: g=1 to G (>1). The ear model20aassigned with the ear model ID: g is sometimes described as “ear model20a(ear model ID: g)”.

FIG.5is an example of the acoustic characteristic data stored in the recording medium by the acoustic characteristic accumulation unit105. As illustrated inFIG.5, the acoustic characteristic data includes the parameters (R, n) of the ear model20aand the transfer function (xi) (i=1, 2, . . . ). As described above, the parameters (R, n) are the size (R) of the diameter of the hole of the plate-shaped member201and the number (n) of the plate-shaped member201. The acoustic characteristic accumulation unit105generates the acoustic characteristic data illustrated inFIG.5for each of the plurality of ear models20ahaving the different parameters (R, n).

The index value calculation unit106receives the acoustic characteristic data illustrated inFIG.5from the acoustic characteristic accumulation unit105. The index value calculation unit106calculates an index value indicating performance of the earphone device30using the received acoustic characteristic data. Specifically, the index value calculation unit106calculates VBand the VWaccording to the following formulas.

Here, in Formula (2), bold yi(i=1, 2, . . . ) is a vector (referred to as output vector) representing an output when a predetermined input is received by a system of the ear model20a(ear model ID: g) having the transfer function (xi) (i=1, 2, . . . ) and the earphone device30. The number of measurements related to one ear model20a(ear model ID: g) is represented by ng(g=1 to G). An average value of output vectors regarding one ear model20a(ear model ID: g) is represented by μg. An average value of μg(g=1 to G) regarding all the ear models20a(ear model IDs: 1 to G) is represented by p. T represents transposition of the vector. In addition, “i: =g” of the second sigma in Formula (2) indicates that i is a variable and g is fixed.

In Formula (1), VBis obtained by summing variances of the average values μg(g=1 to G) of the output vectors regarding the system in which one ear model20a(ear model ID: g) and the earphone device30are integrated for all the ear models20a(ear model IDs: 1 to G). VBvaries depending on how the earphone device30is attached to the ear model20a, and VBalso varies depending on characteristics, arrangement, volume, and the like of the speaker and the microphone of the earphone device30. The earphone device30with larger VBis preferable in terms of identification of the ear model20a(and identification of an individual). VBrelates to a false acceptance rate (FAR) indicating first performance of the earphone device30.

In Formula (2), VWrelates to the system in which one ear model20a(ear model ID: g) and the earphone device30are integrated. In Formula (2), the variance of the output vectors (bold yi) (i=1, 2, . . . , ng) obtained by ngflows is obtained, and the sum of the variance is obtained for all the ear models20a(ear model IDs: g=1 to G). VWvaries depending on how the earphone device30is attached to the ear model20a, and this variance also varies depending on characteristics, arrangement, volume, and the like of the speaker and the microphone of the earphone device30. The earphone device30with smaller VWis preferable in that a success rate (or non-authentication rate) of personal authentication can be made constant. VWrelates to a false rejection rate (FRR) indicating second performance of the earphone device30. Hereinafter, VBis sometimes referred to as (the sum of) inter-model variance, and VWis sometimes referred to as (the sum of) intra-model variance.

The index value calculation unit106calculates the following J value using the inter-model variance VBand the intra-model variance VW. The J value indicates a characteristic of a system in which the earphone device30and the ear model20aare regarded as the integrated system. The larger the J value is, the higher the accuracy with which the computing device10correctly identifies the ear model20a.

Strictly speaking, when a combination of the earphone device30and the ear model20a(or an individual) is different, the inter-model variance VBand the intra-model variance VWare different. However, as long as the inter-model variance VBand the intra-model variance VWare obtained for the ear models20aof a sufficient number of samples G and the ear models20aare equivalent to ear holes of individuals with various attributes (for example, age, sex, race, height, and the like), it is considered that such a large difference is not generated in the inter-model variance VBand the intra-model variance VWeven if some ear models20aare replaced with other ear models. In that case, as long as the accuracy with which the computing device10identifies a certain ear model20a(or certain individual) is high, it can be expected that the identification accuracy for another ear model20a(or another individual) is also high.

Therefore, it is possible to measure the inter-model variance VBand the intra-model variance VWfor combinations of the earphone device30and several ear models20a(or several individuals), and evaluate whether the earphone device30is suitable for the purpose of identifying a large number of ear models20a(or a large number of individuals) based on the magnitude of the following J value.

The J value is a function of a frequency ω. The J value is called an evaluation function in Fisher's linear discriminative analysis (LDA) (for example, PTL 3 and NPL 1). According to Formula (3), the larger the inter-model variance VB, the larger the J value. The smaller the intra-model variance VW, the larger the J value. The large inter-model variance VBmeans that accuracy of an identification function of the ear model20aby the earphone device30is high. The small intra-model variance VWmeans that the variation in accuracy with which in-ear acoustic authentication succeeds is small even if the same earphone device30is repeatedly attached to and detached from the same ear model20a. Therefore, it can be said that the earphone device30having a high J value has high performance.

A performance evaluation method executed by the computing device10of the performance evaluation system1according to the first example embodiment will be described with reference toFIG.6.FIG.6is a flowchart illustrating a flow of the performance evaluation method.

As illustrated inFIG.6, first, a first variable g and a second variable i are set in the performance evaluation method (S1, S10). The first variable g indicates the above-described ear model ID. The second variable i is a flow ID for identifying a plurality of measurements.

The inspection signal reproduction unit101reproduces an inspection signal to be input to a hole of the ear model20a(S102).

The inspection signal reproduction unit101transmits the reproduced inspection signal to the earphone device30(FIG.1) in a wireless or wired manner. The inspection signal reproduction unit101causes the reproduced signal to be transmitted from a speaker of the earphone device30. The speaker incorporated in the earphone device30transmits the inspection signal toward the hole of the ear model20a.

A microphone of the earphone device30collects echo sound from the ear model20a. The earphone device30converts the collected echo sound into digital data to generate an echo signal. Then, the earphone device30transmits the echo signal to the computing device10in a wireless or wired manner.

Returning toFIG.6, the echo signal observation unit102of the computing device10observes the echo signal based on the echo sound from the ear model20a(S103). Specifically, the echo signal observation unit102receives the echo signal generated from the echo sound in a wireless or wired manner from the earphone device30.

The acoustic characteristic calculation unit103calculates an acoustic characteristic of the ear model20abased on the received echo signal (S104). Specifically, the acoustic characteristic calculation unit103calculates a transfer function, obtained by performing Fourier transform or Laplace transform on an impulse response, as the acoustic characteristic of the ear model20a. The acoustic characteristic calculation unit103transmits data of the calculated transfer function (xi) to the acoustic characteristic accumulation unit105.

The acoustic characteristic accumulation unit105receives the data of the transfer function (xi) from the acoustic characteristic calculation unit103. The acoustic characteristic accumulation unit105receives the parameters (R, n) of the ear model20afrom the input unit104. The acoustic characteristic accumulation unit105accumulates the acoustic characteristic data (xi) received from the acoustic characteristic calculation unit103in a recording medium (not illustrated) as acoustic characteristic data (FIG.5) in association with the information indicating the parameters (R, n) (S105).

Thereafter, one is added to the above-described second variable (flow ID) i (S20). When the second variable i is equal to or less than ng(No in S30), the flow returns to step S101. At this time, a worker detaches the earphone device30from the ear model20aand attaches the same earphone device30to the same ear model20aagain. Here, the same ear model20ameans the ear models20ahaving the same parameters (R, n), and thus, is not necessarily one specific ear model20a.

When the second variable i exceeds ng(Yes in S30), one is added to the first variable g (ear model ID) (S2). In this case, the flow proceeds to step S3. InFIG.6, “ng” is written as “n_g”. At this time, the worker detaches the earphone device30from the ear model20a, and attaches the earphone device30to another ear models20ahaving different parameters (R, n).

When the first variable g does not exceed G (No in S3), the flow returns to step S10. When the first variable g exceeds G (Yes in S3), the acoustic characteristic accumulation unit105transmits the acoustic characteristic data accumulated in the recording medium to the index value calculation unit106.

The index value calculation unit106receives the acoustic characteristic data from the acoustic characteristic accumulation unit105. The index value calculation unit106calculates a J value, which is one index value indicating performance of the earphone device30, according to the above-described Formula (3) using the received acoustic characteristic data (S106). The flow of the performance evaluation method ends as above.

(Evaluation Result of Performance of Earphone Device30)

FIG.7illustrates an evaluation result of performance of the earphone device30by the computing device10.FIG.7illustrates an example of a J value which is an index value calculated by the index value calculation unit106.FIG.7illustrates graphs of the J values regarding two earphone devices30(A and B). According toFIG.7, the earphone device (B) has the larger J value in a frequency band of 10 kHz and its vicinity than that of the earphone device (A). That is, it can be said that the earphone device (B) has higher performance than the earphone device (A) at least in this frequency band. A reason why a difference between the J value of the earphone device (A) and the J value of the earphone device (B) is large in an extremely low frequency band (near 0 kHz) is that a normal speaker has a small output in the extremely low frequency band that is inaudible to humans, so that an echo sound is weak, and the influence of noise on the weak echo sound is relatively large.

Effects of Present Example Embodiment

According to the configuration of the present example embodiment, the plurality of plate-shaped members201are provided with holes, the artificial eardrum member202is equivalent to an eardrum of an individual, and the holes, each of which is provided in each of the plurality of plate-shaped members201, are connected, whereby the plurality of plate-shaped members201are stacked on the artificial eardrum member202so as to simulate an external auditory canal of the individual. The earphone device30is attached to the ear model20a, and the in-ear acoustic authentication is tried to evaluate the performance of the earphone device30. The ear models20ahaving various parameters (R, n) can be easily obtained by changing sizes of diameters of the holes provided in the plurality of plate-shaped members201and arrangement orders of the plurality of plate-shaped members201. As a result, it is possible to easily and inexpensively evaluate the performance of the earphone device30to be used for the in-ear acoustic authentication.

Second Example Embodiment

A second example embodiment will be described with reference toFIG.8.

FIG.8is a cross-sectional view of an ear model20bwhich is an example of the ear model20illustrated inFIG.1. As illustrated inFIG.8, the ear model20baccording to the second example embodiment further includes two air pressure control units203in addition to the plurality of plate-shaped members201and one artificial eardrum member202.FIG.8does not illustrate an auricle model on the ear model20b.

As illustrated inFIG.8, the plurality of plate-shaped members201are arranged on both upper and lower sides of the artificial eardrum member202with the artificial eardrum member202interposed therebetween in the ear model20b. Holes of the plurality of plate-shaped members201on the upper side of the artificial eardrum member202simulate an external auditory canal of an individual. On the other hand, holes of the plurality of plate-shaped members201on the lower side of the artificial eardrum member202simulate a middle ear cavity of an individual.

The air pressure control units203control the air pressure in a cavity formed in the ear model20b. The air pressure control unit203is an example of an air pressure control means. For example, the air pressure control unit203includes a valve inserted into the plate-shaped member201, a compressor that sends air into a cavity formed in the ear model20b, a pressure gauge that measures the air pressure in the cavity formed in the ear model20b, and a pipe configured to send air.

One of the air pressure control units203controls the air pressure in a space formed by the holes of the plurality of plate-shaped members201on the upper side of the artificial eardrum member202, that is, the space simulating the external auditory canal of the individual. The other air pressure control unit203controls the air pressure in a space formed by the holes of the plurality of plate-shaped members201on the lower side of the artificial eardrum member202, that is, the space simulating the middle ear cavity of the individual. For example, the two air pressure control units203perform control such that the air pressure in the space simulating the external auditory canal of the individual is high (low) and the air pressure in the space simulating the middle ear cavity of the individual is low (high). As a result, for example, a low pressure in the high ground or the sky or a high pressure in the water can be reproduced in the ear model20b.

Effects of Present Example Embodiment

According to the configuration of the present example embodiment, the plurality of plate-shaped members201are provided with holes, the artificial eardrum member202is equivalent to an eardrum of an individual, and the holes, each of which is provided in each of the plurality of plate-shaped members201, are connected, whereby the plurality of plate-shaped members201are stacked on the artificial eardrum member202so as to simulate an external auditory canal of the individual. The earphone device30is attached to the ear model20b, and in-ear acoustic authentication is tried to evaluate performance of the earphone device30. The ear models20bhaving various parameters (R, n) can be easily obtained by changing sizes of diameters of the holes provided in the plurality of plate-shaped members201and arrangement orders of the plurality of plate-shaped members201. As a result, it is possible to easily and inexpensively evaluate the performance of the earphone device30to be used for the in-ear acoustic authentication.

Furthermore, the air pressure in the cavity formed in the ear model20bis controlled by the air pressure control unit203according to the configuration of the present example embodiment. As a result, it is possible to evaluate the performance of the earphone device30under various environments.

Third Example Embodiment

A third example embodiment will be described with reference toFIG.9.

FIG.9is a cross-sectional view of an ear model20cwhich is an example of the ear model20illustrated inFIG.1. As illustrated inFIG.9, the ear model20caccording to the third example embodiment further includes an artificial muscle member204in addition to the plurality of plate-shaped members201and one artificial eardrum member202.FIG.9does not illustrate an auricle model on the ear model20c.

The artificial muscle member204is equivalent to a muscle in a vocal tract of an individual. The artificial muscle member204is a type of actuator that simulates a structure and properties of the muscle in the vocal tract of the individual. The artificial muscle member204is made of, for example, a polymer such as a synthetic resin. Alternatively, the artificial muscle member204may be made of a shape memory alloy, a hydrogel, or the like.

The artificial muscle member204responds to vibration of air generated in a cavity in the ear model20c. In other words, the artificial muscle member204converts the vibration of air into elastic energy. As a result, it is possible to reproduce tremor of the vocal tract when sound is generated in an ear hole. Furthermore, the interaction between the sound and the tremor of the vocal tract can be reproduced.

In the ear model20caccording to the third example embodiment, the plurality of plate-shaped members201are arranged vertically with the artificial eardrum member202interposed therebetween, which is similar to the ear model20baccording to the second example embodiment. Holes of the plurality of plate-shaped members201on the upper side of the artificial eardrum member202simulate an external auditory canal of an individual. Holes of the plurality of plate-shaped members201on the lower side of the artificial eardrum member202and on the upper side of the artificial muscle member204simulate a middle ear cavity of an individual.

The holes of the plurality of plate-shaped members201on the lower side of the artificial muscle member204simulate the vocal tract of the individual. That is, the ear model20csimulates an internal structure from an external auditory canal opening (portion connected to an auricle) to the vocal tract in the ear hole of the individual.

Effects of Present Example Embodiment

According to the configuration of the present example embodiment, the plurality of plate-shaped members201are provided with holes, the artificial eardrum member202is equivalent to an eardrum of an individual, and the holes, each of which is provided in each of the plurality of plate-shaped members201, are connected, whereby the plurality of plate-shaped members201are stacked on the artificial eardrum member202so as to simulate an external auditory canal of the individual. The earphone device30is attached to the ear model20c, and in-ear acoustic authentication is tried to evaluate performance of the earphone device30. The ear models20chaving various parameters (R, n) can be easily obtained by changing sizes of diameters of the holes provided in the plurality of plate-shaped members201and arrangement orders of the plurality of plate-shaped members201. As a result, it is possible to easily and inexpensively evaluate the performance of the earphone device30to be used for the in-ear acoustic authentication.

Furthermore, the artificial muscle member204is equivalent to the muscle in the vocal tract of the individual according to the configuration of the present example embodiment. The vibration of the artificial muscle member204reproduces the tremor of the vocal tract of the individual when the sound is generated in the ear hole. As a result, it is possible to more precisely evaluate the performance of the earphone device30.

Each of components of the computing device10described in the first to third example embodiments indicates a block of a functional unit. Some or all of these components are implemented by an information processing device900as illustrated inFIG.10, for example.FIG.10is a block diagram illustrating an example of a hardware configuration of the information processing device900.

As illustrated inFIG.10, the information processing device900includes the following configuration as an example.A central processing unit (CPU)901A read only memory (ROM)902A random access memory (RAM)903A program904to be loaded into the RAM903A storage device905storing the program904A drive device907performing read and write with respect to a recording medium906A communication interface908connected to a communication network909An input/output interface910performing input/output of dataA bus911connecting components

Each of the components of the computing device10described in the first to third example embodiments is implemented as the CPU901reads and executes the program904for implementing these functions. The program904for implementing the functions of the components is stored in the storage device905or the ROM902in advance, for example, and is loaded into the RAM903and executed by the CPU901. Note that the program904may be supplied to the CPU901through the communication network909, or may be stored in advance in the recording medium906, and the drive device907may read the program and supply the program to the CPU901.

Effects of Present Example Embodiment

According to the configuration of the present example embodiment, the computing device10described in the above example embodiments is implemented as hardware. Therefore, effects similar to the effects described in the first to third example embodiments can be obtained.

Some or all of the above example embodiments may be described as the following supplementary notes, but are not limited to the following.

An ear model including:a plurality of plate-shaped members provided with holes; andan artificial eardrum member equivalent to an eardrum of an individual,wherein the holes, each of which is provided in each of the plurality of plate-shaped members, are connected, whereby the plurality of plate-shaped members are stacked on the artificial eardrum member in such a way as to simulate an external auditory canal of the individual.
(Supplementary Note 2)

The ear model according to Supplementary Note 1, whereina thickness and a number of the plurality of plate-shaped members are related to a length from an external auditory canal opening to the eardrum of the individual.
(Supplementary Note 3)

The ear model according to Supplementary Note 1 or 2, whereina diameter of the hole provided in each of the plurality of plate-shaped members is related to a thickness of the external auditory canal of the individual.
(Supplementary Note 4)

The ear model according to any one of Supplementary Notes 1 to 3, further includingan air pressure control means configured to control air pressure in a cavity formed in the ear model as the holes, each of which is provided in each of the plurality of plate-shaped members, are connected.
(Supplementary Note 5)

The ear model according to any one of Supplementary Notes 1 to 4, whereinthe holes, each of which is provided in each of the plurality of plate-shaped members, are connected, whereby the plurality of plate-shaped members are stacked on both sides of the artificial eardrum member with the artificial eardrum member interposed between the plate-shaped members in such a way as to simulate the external auditory canal and a middle ear cavity of the individual.
(Supplementary Note 6)

The ear model according to any one of Supplementary Notes 1 to 5, further includingan artificial muscle member equivalent to a muscle in a vocal tract of the individual,wherein the holes, each of which is provided in each of the plurality of plate-shaped members, are connected, whereby the plurality of plate-shaped members are stacked between the artificial muscle member and the artificial eardrum member in such a way as to simulate the vocal tract of the individual.
(Supplementary Note 7)

A performance evaluation method being a method for evaluating performance of an earphone device to be used for in-ear acoustic authentication using the ear model according to any one of Supplementary Notes 1 to 6, the performance evaluation method including:transmitting an inspection signal from the earphone device toward a site of the ear model equivalent to an external auditory canal opening of the individual;collecting echo sound, transmitted from the ear model after the inspection signal propagates in the ear model, using the earphone device;calculating an acoustic characteristic of the ear model from an echo signal based on the collected echo sound; andevaluating performance of the earphone device based on the acoustic characteristic.
(Supplementary Note 8)

The performance evaluation method according to Supplementary Note 7, whereinthe earphone device that is identical is repeatedly attached to and detached from the ear model, andthe acoustic characteristic is calculated every time the identical earphone device is attached to and detached from the ear model, andfirst performance of the identical earphone device is evaluated based on a variance of the repeatedly calculated acoustic characteristics.
(Supplementary Note 9)

The performance evaluation method according to Supplementary Note 7 or 8, whereinthe acoustic characteristic is calculated for each of a plurality of the ear models having different shapes,pieces of acoustic characteristic data in which parameters, each of which represents the shapes of the plurality of ear models, are associated with the acoustic characteristics of the plurality of ear models are accumulated; andsecond performance of the earphone device is evaluated based on a variance of the acoustic characteristics among the plurality of ear models.
(Supplementary Note 10)

The performance evaluation method according to Supplementary Note 9, whereinthe parameter is at least one of a number of the plurality of plate-shaped members related to a length from the external auditory canal opening to the eardrum of the individual and a size of a diameter of the hole related to a thickness of the external auditory canal of the individual.
(Supplementary Note 11)

A performance evaluation system including:the ear model according to any one of Supplementary Notes 1 to 6;an earphone device that transmits an inspection signal toward a site of the ear model equivalent to an external auditory canal opening of the individual and observes an echo signal based on an echo sound transmitted from the ear model after the inspection signal propagates in the ear model; anda computing device that calculates an acoustic characteristic of the ear model from the echo signal based on the echo sound that has been collected and calculates an index value indicating performance of the earphone device based on the acoustic characteristic.

REFERENCE SIGNS LIST