Patent Description:
For example, fingerprint authentication, vein authentication, face authentication, iris authentication, and voice authentication are known as personal authentication technologies (referred to as biometric authentication technologies) based on personal characteristics of a living body. Among the personal authentication technologies, in particular, the in-ear acoustic authentication focuses on a personal characteristic of an internal structure of a human ear hole. 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.

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

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

<CIT> describes an in-ear audio authentication method.

Strictly speaking, the echo signal to be measured in the in-ear acoustic authentication depends not only on the acoustic characteristic of the ear hole of the subject but also on the acoustic characteristic of the earphone-type device (referred to as an audio device) used for authentication. Therefore, the accuracy of authenticating the subject may vary depending on which audio device is used.

The disclosure has been made in view of the above problems, and an object thereof is to provide an in-ear acoustic authentication device, an in-ear acoustic authentication method, and a recording medium capable of accurately authenticating a subject regardless of which audio device is used for the in-ear acoustic authentication.

An in-ear acoustic authentication device according to an aspect of the disclosure includes a feature extraction means configured to input an inspection signal to an ear of a subject by using an audio device, and when receiving an echo signal from the subject, extract, from the echo signal, a first feature related to a system including the audio device and an ear of the subject, a correction means configured to correct the first feature to a second feature in a case where the audio device is a predetermined reference device, and an authentication means configured to authenticate the subject by collating the second feature with a feature indicated in a pre-registered authentication information.

An in-ear acoustic authentication method according to an aspect of the disclosure includes inputting an inspection signal to an ear of a subject by using an audio device, and when receiving an echo signal from the subject, extracting, from the echo signal, a first feature related to a system including the audio device and an ear of the subject, correcting the first feature to a second feature in a case where the audio device is a predetermined reference device, and authenticating the subject by collating the second feature with a feature indicated in a pre-registered authentication information.

A recording medium according to an aspect of the disclosure stores a program for causing a computer to execute inputting an inspection signal to an ear of a subject by using an audio device, and when receiving an echo signal from the subject, extracting, from the echo signal, a first feature related to a system including the audio device and an ear of the subject, correcting the first feature to a second feature in a case where the audio device is a predetermined reference device, and authenticating the subject by collating the second feature with a feature indicated in a pre-registered authentication information.

According to an aspect of the disclosure, it is possible to accurately authenticate the subject regardless of which audio device is used for the in-ear acoustic authentication.

The first example embodiment will be described with reference to <FIG>.

An in-ear acoustic authentication device <NUM> according to the first example embodiment will be described with reference to <FIG> is a block diagram illustrating a configuration of the in-ear acoustic authentication device <NUM>. As illustrated in <FIG>, the in-ear acoustic authentication device <NUM> includes a feature extraction unit <NUM>, a correction unit <NUM>, and an authentication unit <NUM>.

The feature extraction unit <NUM> inputs the inspection signal to the ear of the subject using the audio device, and when receiving an echo signal from the subject, extracts, from the echo signal, a first feature related to a system including the audio device and the ear of the subject.

Specifically, the audio device is worn on the ear of the subject in advance. The feature extraction unit <NUM> causes the audio device to output the inspection signal. The inspection signal is, for example, an impulse wave. The inspection signal reverberates in a closed system including the audio device and the subject's ear. The audio device detects an echo signal output from the ear of the subject.

The feature extraction unit <NUM> communicates with the audio device and receives an echo signal from the audio device in a wired or wireless manner. The feature extraction unit <NUM> extracts an impulse response from the echo signal. The impulse response is a response to an inspection signal that is an impulse wave. The feature extraction unit <NUM> performs Fourier transform or Laplace transform on the impulse response. As a result, the feature extraction unit <NUM> calculates a transfer function indicating an acoustic characteristic of the closed system including the audio device and the ear of the subject. The transfer function is an example of an acoustic characteristic, and the acoustic characteristic is an example of a first feature. Alternatively, the feature extraction unit <NUM> may extract, as the first feature, another response function based on the echo signal instead of the transfer function. The feature extraction unit <NUM> transmits the first feature to the correction unit <NUM>.

The correction unit <NUM> corrects the first feature to a second feature in a case where the audio device is a predetermined reference device.

Specifically, the correction unit <NUM> receives the first feature from the feature extraction unit <NUM>. As described above, in an example, the first feature is an acoustic characteristic related to a closed system including an audio device and an ear of a subject. The correction unit <NUM> corrects the first feature to a second feature that will be obtained from a closed system including a predetermined reference device and an ear of the subject. In other words, the correction unit <NUM> calculates, as the second feature, an acoustic characteristic obtained in a case where the condition regarding the subject does not change and the audio device is replaced with the reference device.

The correction of the first feature will be described by adding a little more. The acoustic characteristic that is the first feature can be separately expressed as (acoustic characteristic with an audio device as a factor) and (acoustic characteristic with a subject as a factor) in a mathematical expression. For each audio device, it is possible to extract an acoustic characteristic with the audio device as a factor from the acoustic characteristic that is the first feature.

However, in a case where it is assumed that the subject uses a wide variety of audio devices for the in-ear acoustic authentication, it may not be realistic to obtain in advance the acoustic characteristics related to the closed system including the audio device and the ear of the subject for all sets of the audio devices and the subject.

Therefore, in order to correct the acoustic characteristics related to the closed system including the audio device and the ear of the subject to the acoustic characteristics related to the closed system including the reference device and the ear of the subject, a parameter representing a relationship between (the acoustic characteristic with the audio device as a factor) and (the acoustic characteristic with a predetermined reference device as a factor) is calculated in advance. Specifically, this parameter is expressed as (the acoustic characteristic with a predetermined reference device as a factor)/(the acoustic characteristic with an audio device as a factor). This parameter does not include the acoustic characteristic with the subject as a factor. Therefore, this parameter can be used regardless of the subject.

Specifically, the correction unit <NUM> corrects the first feature including (the acoustic characteristic with the audio device as a factor) and (the acoustic characteristic with the subject as a factor) to the second feature including (the acoustic characteristic with the reference device as a factor) and (the acoustic characteristic with the subject as a factor) using the above relational expression. Details of the relational expression described here will be described in more detail in the third example embodiment.

Alternatively, each of the first feature and the second feature may be information (data) useful for authenticating the subject, extracted from the acoustic characteristics, instead of the acoustic characteristics themselves. In this case, the correction unit <NUM> extracts the first feature from the acoustic characteristic obtained from the closed system including the audio device and the ear of the subject. For example, the first feature may be a mel-frequency cepstrum coefficient (MFCC). The correction unit <NUM> corrects the first feature to the second feature. In this case, the second feature is the same kind of feature as the first feature, extracted from the acoustic characteristic obtained from the closed system including the predetermined reference device and the subject's ear.

The authentication unit <NUM> authenticates the subject by collating the second feature with a feature indicated in authentication information registered in advance.

Specifically, the authentication unit <NUM> receives information indicating the second feature from the correction unit <NUM>. The authentication unit <NUM> collates the second feature with a feature (authentication information) of a person registered in advance. The authentication unit <NUM> calculates similarity (for example, a function of the distance in the feature amount space) between the second feature and the feature of the person registered in advance. When the calculated similarity exceeds the threshold value, the authentication unit <NUM> determines that the subject and the person registered in advance are the same person (authentication succeeds). On the other hand, when the similarity is equal to or less than the threshold value, the authentication unit <NUM> determines that the subject and the person registered in advance are not the same person (authentication fails).

The authentication unit <NUM> may present the authentication result on a display or the like by outputting the authentication result.

The operation of the in-ear acoustic authentication device <NUM> according to the first example embodiment will be described with reference to <FIG> is a flowchart illustrating a flow of processing executed by the in-ear acoustic authentication device <NUM>.

As illustrated in <FIG>, the feature extraction unit <NUM> inputs the inspection signal to the ear of the subject using the audio device, and when receiving an echo signal from the subject, extracts, from the echo signal, a first feature related to a system including the audio device and the ear of the subject (S1). The feature extraction unit <NUM> transmits information indicating the first feature to the correction unit <NUM>.

The correction unit <NUM> receives information indicating the first feature from the feature extraction unit <NUM>. The correction unit <NUM> corrects the first feature to the second feature in a case where the audio device is a predetermined reference device (S2). The correction unit <NUM> transmits information indicating the second feature to the authentication unit <NUM>.

The authentication unit <NUM> receives the information indicating the second feature from the correction unit <NUM>. The authentication unit <NUM> authenticates the subject by collating the second feature with a feature indicated in authentication information registered in advance (S3). Thereafter, the authentication unit <NUM> outputs an authentication result.

As described above, the operation of the in-ear acoustic authentication device <NUM> according to the first example embodiment ends.

According to the configuration of the example embodiment, the feature extraction unit <NUM> inputs the inspection signal to the ear of the subject using the audio device, and when receiving an echo signal from the subject, extracts, from the echo signal, a first feature related to a system including the audio device and the ear of the subject. The correction unit <NUM> corrects the first feature to a second feature in a case where the audio device is a predetermined reference device. The authentication unit <NUM> authenticates the subject by collating the second feature with authentication information registered in advance.

In other words, the in-ear acoustic authentication device <NUM> performs the in-ear acoustic authentication based on not the first feature with the audio device as a factor but the second feature in a case where the audio device is the predetermined reference device. Therefore, it is possible to accurately authenticate the subject regardless of which audio device is used for the in-ear acoustic authentication.

In the second example embodiment, the configuration of the in-ear acoustic authentication device <NUM> is as described in the first example embodiment. Hereinafter, only differences between the second example embodiment and the first example embodiment will be described.

For the purpose of authenticating the subject based on the second feature, the acoustic characteristic with the audio device as a factor is noise. That is, in a case where the in-ear acoustic authentication is performed based on the second feature described in the first example embodiment, there is a possibility that the authentication accuracy varies among individual audio devices. In consideration of this, in the second example embodiment, the correction unit <NUM> of the in-ear acoustic authentication device <NUM> corrects the first feature to another first feature. Here, the first feature is the acoustic characteristic itself for the closed system including the audio device and the subject's ear. Alternatively, the first feature is a feature extracted from the acoustic characteristic. "The another first feature" is different from the first feature described in the first example embodiment, but is included in the concept of the first feature of the disclosure. The second feature can also be corrected using the method described below. In this case, in the following description, the "(original) first feature" is replaced with the "(original) second feature".

In the second example embodiment, the correction unit <NUM> corrects the first feature to another first feature. Specifically, in the first example embodiment, the correction unit <NUM> converts (scales) the original first feature into another first feature based on the following mathematical expression. Hereinafter, correction may be described in the sense of conversion (scaling). [Math <NUM>] <MAT>
where µtar is an average of features obtained from a closed system including an audio device and ears of respective persons for a combination of the audio device and a plurality of different persons. σtar is a standard deviation of the features obtained from the closed system including the audio device and the ears of respective persons for a combination of the audio device and a plurality of different persons. The plurality of different persons may or may not include the subject. Another first feature MYtar shown in Expression (<NUM>) schematically indicates that attention is paid to how far the first feature Ytar deviates from the average µtar.

µtar means an average of features extracted from the corrected acoustic characteristics when a plurality of persons is authenticated using an audio device. In Expression (<NUM>), the acoustic characteristic with the audio device as a factor is included in Ytar and µtar in common. Therefore, by the calculation of (Ytar - µtar) in the above Expression, in another first feature MYtar, the acoustic characteristic with the audio device as a factor is eliminated or is at least reduced as compared with the original first feature Ytar.

Alternatively, the correction unit <NUM> may convert the first feature Ytar into another first feature MYtar' based on the following Expression (<NUM>) instead of the above-described Expression (<NUM>). [Math <NUM>] <MAT>
where µref is an average of features obtained from a closed system including an audio device and ears of respective persons for a combination of the reference device and a plurality of different persons. Fref is a feature obtained from a closed system including a reference device and an ear of a specific person. Ftar is a feature obtained from a closed system including an audio device and an ear of a specific person. The specific person is one person different from the subject. The reference device may be one audio device or may be virtually a combination of a plurality of audio devices. In a case where the reference device is a combination of a plurality of (M > <NUM>) audio devices, a value (µvref) obtained by dividing the sum of the averages of the features of the respective audio devices by M is replaced with µref in Expression (<NUM>). In this case, a value (σvref) obtained by dividing the sum of the standard deviations of the features for the respective audio devices by M is replaced with σref in Expression (<NUM>).

Referring to the right side of Expression (<NUM>), the original first feature Ytar has been converted (scaled) based on the average µref of the features of the reference device. That is, another first feature MYtar' indicated by Expression (<NUM>) may be regarded as the scaled first feature Ytar. Still another first feature MYtar may be obtained by substituting the scaled first feature Ytar (= MYtar') into Expression (<NUM>) (modification).

The correction unit <NUM> transmits, to the authentication unit <NUM>, information indicating another second feature obtained from another first feature (MYtar or MYtar') obtained as described above.

In the second example embodiment, the authentication unit <NUM> authenticates the subject by collating another second feature obtained from another first feature with authentication information registered in advance. That is, the authentication unit <NUM> calculates the similarity between another second feature and the feature of the person registered in advance. When the similarity exceeds the threshold value, the authentication unit <NUM> determines that the subject and the person registered in advance are the same person (authentication succeeds). On the other hand, when the similarity is equal to or less than the threshold value, the authentication unit <NUM> determines that the subject and the person registered in advance are not the same person (authentication fails).

According to the configuration of the example embodiment, the feature extraction unit <NUM> inputs the inspection signal to the ear of the subject using the audio device, and when receiving an echo signal from the subject, extracts, from the echo signal, a first feature related to a system including the audio device and the ear of the subject. The correction unit <NUM> corrects the first feature to a second feature in a case where the audio device is a predetermined reference device. The authentication unit <NUM> authenticates the subject by collating another second feature with authentication information registered in advance.

That is, the in-ear acoustic authentication device <NUM> performs the in-ear acoustic authentication based on not the first feature with the audio device as a factor but the another second feature in a case where the audio device is the predetermined reference device. Therefore, it is possible to accurately authenticate the subject regardless of which audio device is used for the in-ear acoustic authentication.

Furthermore, when the acoustic characteristic with the audio device as a factor is regarded as noise, the second feature varies due to noise for each individual audio device. In view of this, in the example embodiment, the in-ear acoustic authentication device <NUM> corrects the first feature to the another first feature described above. Thereby, in another first feature, the acoustic characteristic with the audio device as a factor is eliminated or at least reduced compared to the original first feature.

In a modification, another first feature MYtar' indicated by the foregoing Expression (<NUM>) is regarded as the scaled first feature Ytar. In the modification, MYtar' expressed in Expression (<NUM>) is introduced as Ytar in the right side of Expression (<NUM>). However, in this case, µtar and σtar of Expression (<NUM>) also need to be scaled as in Ytar based on the average µref of the features of the reference devices.

In the modification, the above-described Expression (<NUM>) is modified as the following Expression (<NUM>)'. [Math <NUM>] <MAT>
where the second feature Ytar' is equal to MYtar' expressed in the above-described Expression (<NUM>). µtar' is obtained by recalculating the above-described µtar in association with the scaling of the second feature Ytar. σtar' is obtained by recalculating the above-described σtar in association with the scaling of the second feature Ytar.

According to the configuration of the modification, the second feature Ytar is scaled based on the average µref of the features of the reference devices according to the calculation formula indicated in the right side of Expression (<NUM>). Another first feature MYtar is calculated from the scaled second feature Ytar' according to Expression (<NUM>)'. In this way, the another first feature MYtar may be obtained from the scaled first feature Ytar'.

The third example embodiment will be described with reference to <FIG>.

<FIG> is a diagram schematically illustrating a configuration of a system <NUM> according to the third example embodiment. In <FIG>, the system <NUM> includes an in-ear acoustic authentication device <NUM>, a storage device <NUM>, and an audio device <NUM>. The in-ear acoustic authentication device <NUM>, the storage device <NUM>, and the audio device <NUM> may be part of the authentication device for the in-ear acoustic authentication.

Alternatively, the in-ear acoustic authentication device <NUM> and the storage device <NUM> may be on a network server. In this case, the audio device <NUM>, the in-ear acoustic authentication device <NUM>, and the storage device <NUM> are communicably connected by radio, for example, a mobile network. Alternatively, only the storage device <NUM> may be on the network server. In this case, the in-ear acoustic authentication device <NUM> and the audio device <NUM> are part of the authentication device, and the in-ear acoustic authentication device <NUM> and the storage device <NUM> are communicably connected by a wireless network.

The audio device <NUM> generates the inspection signal to transmit the inspection signal from the speaker (<FIG>) of the audio device <NUM> toward the ear of the subject. As in the first example embodiment, the inspection signal is, for example, an impulse wave. The audio device <NUM> transmits the transmitted inspection signal to a feature extraction unit <NUM> of the in-ear acoustic authentication device <NUM>.

The audio device <NUM> observes an echo signal from the subject. Specifically, the audio device <NUM> detects an echo signal from the subject using the microphone (<FIG>) of the audio device <NUM> to transmit the detected echo signal to the feature extraction unit <NUM> of the in-ear acoustic authentication device <NUM>.

A configuration of the in-ear acoustic authentication device <NUM> according to the third example embodiment will be described with reference to <FIG> is a block diagram illustrating a configuration of the in-ear acoustic authentication device <NUM>. As illustrated in <FIG>, the in-ear acoustic authentication device <NUM> includes a filter generating unit <NUM> in addition to the feature extraction unit <NUM>, a correction unit <NUM>, and an authentication unit <NUM>. The in-ear acoustic authentication device <NUM> may further include an audio device control unit (not illustrated). In this case, all or some of the operations of the audio device <NUM> described above is controlled by the audio device control unit of the in-ear acoustic authentication device <NUM>.

The feature extraction unit <NUM> inputs the inspection signal to the ear of the subject using the audio device <NUM>, and when receiving an echo signal from the subject, extracts, from the echo signal, a first feature related to a system including the audio device <NUM> and the ear of the subject.

Specifically, the audio device <NUM> is worn on the ear of the subject in advance. The feature extraction unit <NUM> controls the audio device <NUM> to output an inspection signal. The inspection signal is, for example, an impulse wave. The inspection signal reverberates in a closed system including the audio device <NUM> and the subject's ear. The audio device <NUM> detects an echo signal output from the ear of the subject.

The feature extraction unit <NUM> communicates with the audio device <NUM> and receives an echo signal from the audio device <NUM> in a wired or wireless manner. The feature extraction unit <NUM> extracts an impulse response from the echo signal. The feature extraction unit <NUM> calculates a transfer function indicating an acoustic characteristic of a closed system including the audio device <NUM> and the ear of the subject by performing Fourier transform or Laplace transform on the impulse response. The acoustic characteristic and the transfer function are examples of the first feature. Alternatively, the feature extraction unit <NUM> may extract, as the first feature, another response function based on the echo signal instead of the transfer function. The feature extraction unit <NUM> transmits the first feature to the correction unit <NUM>.

The correction unit <NUM> corrects the first feature to a second feature in a case where the audio device <NUM> is a predetermined reference device.

Specifically, the correction unit <NUM> receives the first feature from the feature extraction unit <NUM>. The correction unit <NUM> corrects the first feature to the second feature that will be obtained from a closed system including a predetermined reference device and an ear of the subject. In other words, the correction unit <NUM> calculates, as the second feature, an acoustic characteristic obtained in a case where the condition regarding the subject does not change and the audio device <NUM> is replaced with the reference device. Alternatively, the correction unit <NUM> may correct the second feature to another first feature, as in the correction unit <NUM> according to the second example embodiment. In this case, in the following description, the "second feature" is replaced with "another first feature".

The first feature and the second feature described above will be additionally described. Here, the acoustic characteristic as the first feature is assumed to be a transfer function of a system including an audio device and an ear of a subject. When the subject wears the audio device, the audio device and the ear hole of the subject can be regarded as one sound system. In this case, as is well known, the acoustic characteristic of the entire acoustic system, that is, the acoustic characteristic that is the first feature, is represented by a product of the acoustic characteristic with the audio device as a factor and the acoustic characteristic with the subject as a factor. The transfer function is an example of acoustic characteristics. Alternatively, the feature extraction unit <NUM> may extract, as the first feature, another response function based on the echo signal instead of the transfer function. Hereinafter, a case where the acoustic characteristic as an example of the first feature is a transfer function will be described. Specifically, the acoustic characteristic (an example of the first feature) as the first feature is expressed by the following mathematical expression. In Expression (<NUM>), ω is the acoustic frequency. [Math <NUM>] <MAT>.

In Expression (<NUM>), Gtar is defined as an acoustic characteristic that is a first feature of a system including the audio device <NUM> and the ear of a specific person. Dtar(ω) is defined as an acoustic characteristic with the audio device <NUM> as a factor. p(ω) is defined as an acoustic characteristic with the subject as a factor.

The feature extraction unit <NUM> calculates an acoustic characteristic of a system including the audio device <NUM> and the ear of the subject. That is, the first feature is Gtar of Expression (<NUM>).

Here, the acoustic characteristic as the second feature is assumed to be a transfer function of a system including the reference device and the ear of the subject. In this case, the acoustic characteristic that is the second feature is represented by a product of an acoustic characteristic with the reference device as a factor and an acoustic characteristic with the subject as a factor. Specifically, the acoustic characteristic (an example of the second feature) calculated by the correction unit <NUM> is expressed by the following mathematical expression. In Expression (<NUM>), ω is the acoustic frequency. [Math <NUM>] <MAT>.

In Expression (<NUM>), Gref is defined as an acoustic characteristic that is a second feature of a system including a reference device and an ear of a specific person. Dref is defined as an acoustic characteristic with the reference device as a factor. As described above, p is an acoustic characteristic with the subject as a factor. The first feature and the second feature are not limited to transfer functions. The first feature may be an acoustic characteristic different from the transfer function as long as the first feature is expressed in the form of Expression (<NUM>) described above. The second feature may be an acoustic characteristic different from the transfer function as long as the second characteristic is expressed in the form of the above-described expression (<NUM>).

The filter generating unit <NUM> generates a correction filter that is a ratio between the acoustic characteristic with the audio device <NUM> as a factor and the acoustic characteristic with the reference device as a factor. Then, the filter generating unit <NUM> stores the calculated correction filter as device information in the storage device <NUM> of the system <NUM>.

A procedure in which the filter generating unit <NUM> according to the third example embodiment generates the above-described correction filter will be described. For example, a correction filter for the audio device <NUM> is generated by the filter generating unit <NUM> for each type, each production lot, or each manufacturer of the audio device <NUM>.

<FIG> is a flowchart illustrating a flow of processing executed by the filter generating unit <NUM>. Here, it is assumed that device information indicating the acoustic characteristic (G'ref) related to a system including a reference device and a specific person is registered in advance in the storage device <NUM> of the system <NUM>. The specific person may be or may not be the subject.

As illustrated in <FIG>, the filter generating unit <NUM> first acquires device information related to the audio device <NUM> from the storage device <NUM> of the system <NUM> (S201). The filter generating unit <NUM> includes the acoustic characteristic (G'tar) related to a system including the audio device <NUM> and a specific person from the device information. The filter generating unit <NUM> acquires the acoustic characteristic (G'ref) related to a system including a reference device and a specific person (S202).

The following parameter Ftar indicating the relationship between the acoustic characteristic G'tar and the acoustic characteristic G'ref is defined. G'tar is obtained by replacing the acoustic characteristic p(ω) with the subject as a factor with the acoustic characteristic p'(ω) with the specific person as a factor in Expression (<NUM>). G'ref is obtained by replacing the acoustic characteristic p(ω) with the subject as a factor with the acoustic characteristic p'(ω) with the specific person as a factor in Expression (<NUM>). [Math <NUM>] <MAT>.

G'tar, with p(ω) replaced with p'(ω) in Expression (<NUM>), and G'ref, with p(ω) replaced with p'(ω) in Expression (<NUM>) are substituted into Expression (<NUM>). [Math <NUM>] <MAT>.

In Expression (<NUM>), Dtar(ω) is an acoustic characteristic with the audio device <NUM> as a factor. p'(ω) is an acoustic characteristic with the specific person as a factor. As described above, the specific person may be determined independently of the subject.

That is, the parameter Ftar represents a relationship between the acoustic characteristic Dref with the reference device as a factor and the acoustic characteristic Dtar with the audio device <NUM> as a factor. In a case where the parameter Ftar is applied to Gtar, the acoustic characteristic Dtar with the audio device <NUM> as a factor is removed (filtered out). In this sense, hereinafter, the parameter Ftar is referred to as a correction filter. The correction filter Ftar is a ratio between the acoustic characteristic Dtar with the audio device <NUM> as a factor and the acoustic characteristic Dref with the reference device as a factor.

The acoustic characteristic G'tar of the system including the audio device <NUM> and the ear of the specific person is calculated under the same condition as when the acoustic characteristic Gref of the system including the reference device and the ear of the specific person is calculated. Specifically, the same person as the specific person for which the acoustic characteristic Gref is calculated wears the audio device <NUM>. The audio device <NUM> transmits from the speaker the same inspection signal as that when the acoustic characteristic Gref is calculated. The audio device <NUM> observes the echo signal from the ear of the specific person using the microphone of the audio device <NUM>. The audio device <NUM> transmits the observed echo signal to the filter generating unit <NUM>.

The filter generating unit <NUM> acquires the acoustic characteristic G'tar of the system including the audio device <NUM> and the ear of the specific person based on the known inspection signal and the echo signal received from the audio device <NUM> (S203).

The filter generating unit <NUM> generates the correction filter Ftar related to the combination of the reference device and the audio device <NUM> based on the above-described Expression (<NUM>) (S204). Then, the filter generating unit <NUM> stores the calculated correction filter Ftar as the device information in the storage device <NUM> of the system <NUM> (S205).

Thus, the generation of the correction filter ends.

The correction unit <NUM> illustrated in <FIG> acquires the device information stored in the storage device <NUM> of the system <NUM>, and corrects the first feature (Gtar) to the second feature (Gref) using the correction filter Ftar illustrated in Expression (<NUM>). That is, the correction unit <NUM> performs the following calculation.

The correction unit <NUM> transmits information indicating the second feature (Gref) calculated in this manner to the authentication unit <NUM>.

Specifically, the authentication unit <NUM> receives information indicating the second feature from the correction unit <NUM>. The authentication unit <NUM> collates the second feature with a feature (authentication information) of a person registered in advance. The authentication unit <NUM> calculates the similarity (for example, the mel-frequency cepstrum coefficient (MFCC)) between the second feature and the feature of the person registered in advance. When the similarity exceeds the threshold value, the authentication unit <NUM> determines that the subject and the person registered in advance are the same person (authentication succeeds). On the other hand, when the similarity is equal to or less than the threshold value, the authentication unit <NUM> determines that the subject and the person registered in advance are not the same person (authentication failure).

The authentication unit <NUM> outputs an authentication result. For example, the authentication unit <NUM> may cause a display device (not illustrated) to display information indicating whether the authentication succeeds or fails.

A modification related to the generation of the correction filter by the filter generating unit <NUM> will be described.

In the modification, p'(ω) in Expression (<NUM>) relates to a plurality of persons. In other words, the specific person described above is virtually a combination of a plurality of persons. Specifically, in a plurality of systems including the reference device and ears of a plurality of persons, the acoustic characteristic with each person as a factor is assumed as pi (i = <NUM>, <NUM>,. In this case, the correction filter Ftar is obtained as follows. [Math <NUM>] <MAT>.

According to Expression (<NUM>)', the acoustic characteristics Gref of the system including the reference device and the ears of specific persons (related to a plurality of persons in the modification) can be separated into the acoustic characteristic Dref with the reference device as a factor and the sum of the acoustic characteristics pi (i = <NUM>, <NUM>,. ) with a plurality of persons as factors. The acoustic characteristics G'tar of the system including the audio device <NUM> and the ears of specific persons (related to a plurality of persons in the modification) can be separated into the acoustic characteristic Dtar with the audio device <NUM> as a factor and the sum of the acoustic characteristics pi (i = <NUM>, <NUM>,. ) with a plurality of persons as factors. The reference device may be virtually a combination of a plurality of (N > <NUM>) audio devices <NUM>. In this case, a value (Dvref) obtained by dividing the sum of the acoustic characteristics Dref with respective audio devices <NUM> as factors by N is replaced with Dref of Expression (<NUM>)'.

The right side of Expression (<NUM>)' according to the modification is the same as the right side of Expression (<NUM>) described above. This is because the sum of the acoustic characteristics pi (i = <NUM>, <NUM>,. ) with a plurality of persons as factors is canceled out between the denominator and the numerator at the second from the right in Expression (<NUM>)'. That is, in the modification, the process of calculating the correction filter Ftar is different, but the correction filter Ftar obtained by Expression (<NUM>)' is the same as the correction filter Ftar obtained by Expression (<NUM>).

In the modification, the sum (or the average) of the acoustic characteristics pi (i = <NUM>, <NUM>,. ) with a plurality of persons as factors can be related to the acoustic characteristic with a virtual specific person as a factor. Therefore, it can be expected that fluctuation (noise) of the measurement value of the acoustic characteristic with each person as a factor is offset.

The operation of the in-ear acoustic authentication device <NUM> according to the second example embodiment will be described with reference to <FIG> is a flowchart illustrating a flow of processing executed by the in-ear acoustic authentication device <NUM>.

As illustrated in <FIG>, the audio device <NUM> generates the inspection signal to transmit the inspection signal from the speaker (<FIG>) of the audio device <NUM> toward the ear of the subject (S101). The audio device <NUM> transmits the transmitted inspection signal to the feature extraction unit <NUM>.

The audio device <NUM> observes an echo signal from the subject (S102). The audio device <NUM> transmits the observed echo signal to the feature extraction unit <NUM>.

The feature extraction unit <NUM> inputs the inspection signal to the ear of the subject using the audio device <NUM>, and when receiving an echo signal from the subject, extracts, from the echo signal, a first feature related to a system including the audio device <NUM> and the ear of the subject. Specifically, the feature extraction unit <NUM> calculates the acoustic characteristic Gtar, which is the first feature, based on the inspection signal and the echo signal (S103). The feature extraction unit <NUM> transmits information indicating the first feature to the correction unit <NUM>.

The correction unit <NUM> receives information indicating the first feature from the feature extraction unit <NUM>. The correction unit <NUM> corrects the first feature to a second feature in a case where the audio device <NUM> is a predetermined reference device.

Specifically, the correction unit <NUM> acquires the correction filter Ftar stored as the device information in the storage device <NUM> (S104).

Then, the correction unit <NUM> corrects the acoustic characteristic Gtar (first feature) to the acoustic characteristic Gref (second feature) using the correction filter Ftar (S105). The correction unit <NUM> transmits information indicating the second feature to the authentication unit <NUM>.

The authentication unit <NUM> receives the information indicating the second feature from the correction unit <NUM>. The authentication unit <NUM> authenticates the subject by collating the second feature with a feature indicated in authentication information registered in advance (S106). Thereafter, the authentication unit <NUM> outputs an authentication result (S107).

As described above, the operation of the in-ear acoustic authentication device <NUM> according to the second example embodiment ends.

According to the configuration of the example embodiment, the feature extraction unit <NUM> inputs the inspection signal to the ear of the subject using the audio device <NUM>, and when receiving an echo signal from the subject, extracts, from the echo signal, a first feature related to a system including the audio device <NUM> and the ear of the subject. The correction unit <NUM> corrects the first feature to a second feature in a case where the audio device <NUM> is a predetermined reference device. The authentication unit <NUM> authenticates the subject by collating the second feature with a feature indicated in authentication information registered in advance.

That is, the in-ear acoustic authentication device <NUM> performs the in-ear acoustic authentication based on not the first feature with the audio device <NUM> as a factor but the second feature in a case where the audio device <NUM> is a predetermined reference device. Therefore, it is possible to accurately authenticate the subject regardless of which audio device <NUM> is used for the in-ear acoustic authentication.

Furthermore, the filter generating unit <NUM> generates the correction filter Ftar that is a ratio between the acoustic characteristic G'tar of the system including the audio device <NUM> and the ear of the specific person and the acoustic characteristic Gref of the system including the reference device and the ear of the specific person. As a result, the correction unit <NUM> can correct the acoustic characteristic G'tar as the first feature to the second feature Gref in a case where the audio device <NUM> is the predetermined reference device, using the correction filter Ftar.

The fourth example embodiment will be described with reference to <FIG>.

A configuration of an in-ear acoustic authentication device 100a according to the fourth example embodiment will be described with reference to <FIG> is a block diagram illustrating a configuration of the in-ear acoustic authentication device 100a. As illustrated in <FIG>, the in-ear acoustic authentication device 100a includes a registration unit <NUM> in addition to the feature extraction unit <NUM>, the correction unit <NUM>, and the authentication unit <NUM>. The in-ear acoustic authentication device 100a may further include an audio device control unit (not illustrated). In this case, all or some of the operations of the audio device <NUM> (<FIG>) to be described later is controlled by the audio device control unit of the in-ear acoustic authentication device 100a.

In a case where the subject is a registered subject, the registration unit <NUM> registers the second feature corrected by the correction unit <NUM> as authentication information in association with the subject.

Processes executed by the feature extraction unit <NUM>, the correction unit <NUM>, and the authentication unit <NUM> of the in-ear acoustic authentication device 100a according to the fourth example embodiment are similar to those of the in-ear acoustic authentication device <NUM> according to the third example embodiment unless otherwise described below.

The operation of the in-ear acoustic authentication device 100a according to the fourth example embodiment will be described with reference to <FIG> is a flowchart illustrating a flow of processing executed by the in-ear acoustic authentication device 100a.

As illustrated in <FIG>, the audio device <NUM> generates the inspection signal to transmit the inspection signal from the speaker (<FIG>) of the reference device toward the ear of the subject (S301). The reference device transmits the transmitted inspection signal to the feature extraction unit <NUM>. The reference device is a specific audio device <NUM> selected in advance.

The reference device observes the echo signal from the subject (S302). The audio device <NUM> transmits the observed echo signal to the feature extraction unit <NUM>.

The feature extraction unit <NUM> inputs the inspection signal to the ear of the subject using the audio device <NUM>, and calculates the acoustic characteristic Gtar related to the system including the audio device <NUM> and the ear of the subject when receiving the echo signal from the subject (S303). The feature extraction unit <NUM> transmits information indicating the acoustic characteristic Gtar to the registration unit <NUM>.

The registration unit <NUM> receives information indicating the acoustic characteristic Gtar from the feature extraction unit <NUM>. The registration unit <NUM> calculates the acoustic characteristic Gref to be stored as the authentication information in the storage device <NUM> using the acoustic characteristic Gtar and the correction filter Ftar (S304). The acoustic characteristic Gref is obtained as follows. [Math <NUM>] <MAT>.

That is, the registration unit <NUM> obtains the acoustic characteristic Gref by multiplying the acoustic characteristic Gtar by the correction filter Ftar. The registration unit <NUM> stores information indicating the acoustic characteristic Gref as authentication information in the storage device <NUM>.

As described above, the operation of the in-ear acoustic authentication device 100a according to the example embodiment ends.

According to the configuration of the example embodiment, the feature extraction unit <NUM> inputs the inspection signal to the ear of the subject using the audio device <NUM>, and when receiving an echo signal from the subject, extracts, from the echo signal, a first feature related to a system including the audio device <NUM> and the ear of the subject. The correction unit <NUM> corrects the first feature to a second feature in a case where the audio device <NUM> is a predetermined reference device. The authentication unit <NUM> authenticates the subject by collating another first feature with authentication information registered in advance.

That is, the in-ear acoustic authentication device <NUM>, 100a performs the in-ear acoustic authentication based on not the first feature with the audio device <NUM> as a factor but another first feature in a case where the audio device <NUM> is a predetermined reference device. Therefore, it is possible to accurately authenticate the subject regardless of which audio device <NUM> is used for the in-ear acoustic authentication.

In a modification, a combination of the plurality of audio devices <NUM> is a virtual reference device. Specifically, in step S303 of the flow illustrated in <FIG>, the feature extraction unit <NUM> calculates acoustic characteristic related to a system including each audio device <NUM> and the ear of the subject using N (><NUM>) audio devices <NUM>. The feature extraction unit <NUM> transmits information indicating the calculated acoustic characteristics to the registration unit <NUM>. Hereinafter, the acoustic characteristic related to a system including each of the first to N-th audio devices <NUM> and the ear of the subject is Gi (i = <NUM> to N).

The registration unit <NUM> calculates the acoustic characteristic Gref related to a system including the virtual reference device and the ear of the subject based on the acoustic characteristic Gi (i = <NUM> to N). In the modification, the second feature is an average of the acoustic characteristics Gi (second acoustic characteristics) (i = <NUM> to N) of a plurality of systems including a plurality of audio devices <NUM> different from each other and the ear of the subject. Specifically, the acoustic characteristic Gref according to the modification is expressed as follows. [Math <NUM>] <MAT>
where Di(ω) is an acoustic characteristic with the i-th audio device <NUM> combined with the virtual reference device as a factor. p(ω) is an acoustic characteristic with the subject as a factor. Di(ω) with an overline on the right side of Expression (<NUM>) represents an average of (some of) acoustic characteristics with the first to N-th audio devices <NUM> as factors.

According to Expression (<NUM>), in the modification, the average of (some of) the acoustic characteristics with the N audio devices <NUM> as factors relates to the acoustic characteristic with the virtual reference device as a factor. Therefore, it can be expected that fluctuation (noise) of the measurement value of the acoustic characteristic with each audio device <NUM> as a factor is offset.

Each component of the in-ear acoustic authentication device <NUM>, 100a described in the first to fourth example embodiments indicates a block of functional units. Some or all of these components are implemented by an information processing apparatus <NUM> as illustrated in <FIG>, for example. <FIG> is a block diagram illustrating an example of a hardware configuration of the information processing apparatus <NUM>.

As illustrated in <FIG>, the information processing apparatus <NUM> includes the following configuration as an example.

Each component of the in-ear acoustic authentication device <NUM>, 100a described in the first to fourth example embodiments is achieved by the CPU <NUM> reading and executing the program <NUM> for achieving these functions. The program <NUM> for achieving the function of each component is stored in the storage device <NUM> or the ROM <NUM> in advance, for example, and the CPU <NUM> loads the program into the RAM <NUM> and executes the program as necessary. The program <NUM> may be supplied to the CPU <NUM> via the communication network <NUM>, or may be stored in advance in the recording medium <NUM>, and the drive device <NUM> may read the program and supply the program to the CPU <NUM>.

According to the above configuration, the in-ear acoustic authentication device <NUM>, 100a described in the first to fourth example embodiments is achieved as hardware. Therefore, effects similar to the effects described in the first to fourth example embodiments can be obtained.

While the disclosure has been particularly shown and described with reference to exemplary embodiments thereof, the disclosure is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details of the exemplary embodiments may be made therein without departing from the scope of the disclosure as defined by the claims.

Claim 1:
An in-ear acoustic authentication device (<NUM>) comprising:
a feature extraction means (<NUM>) configured to input an inspection signal to an ear of a subject by using an audio device (<NUM>), and when receiving an echo signal from the subject, extract, from the echo signal, a first feature related to a system including the audio device (<NUM>) and an ear of the subject;
a correction means (<NUM>) configured to correct the first feature to a second feature related to a system including a reference device and the ear of the subject using a parameter representing a relationship between the audio device (<NUM>) and the reference device; and
an authentication means (<NUM>) configured to authenticate the subject by collating the second feature with a feature indicated in a pre-registered authentication information.