Transfer characteristic correction device, transfer characteristic correction method, and program

Abstract

This transmission characteristics correction device includes: a pseudo inverse filter generating unit that generates a pseudo inverse filter by means of a function for smoothing transmission characteristics from a speaker driver of a wearable open ear-type speaker to the ear canal entrance; and an acoustic signal correcting unit that corrects the acoustic signal on the basis of the pseudo inverse filter and sends the acoustic signal to the wearable open ear-type speaker.

Description

[Technical Field]

[0001] The present disclosure relates to a transfer characteristic correction device, a transfer characteristic correction method, and a program that corrects transfer characteristics to reproduce stereophonic sound using a wearable speaker that does not block the ear canal (hereinafter referred to as a wearable open-ear speaker). [Background technology]

[0002] Stereophonic reproduction is a technique for reproducing sound through speakers (e.g., wearable speakers, headphones, earphones) as if the sound is coming from a source outside the speakers.

[0003] The sound transmission characteristics from the wearable speaker to the user's ear have a significant impact on the sense of sound localization, especially in the elevation direction. To accurately perceive sound, it is necessary to cancel out the sound transmission characteristics resulting from the wearable speaker housing being close to the ear and to flatten the frequency characteristics between the sound that is desired to be heard and the sound that is actually heard.

[0004] In order to improve the accuracy of elevation angle perception in conventional closed headphones, several techniques have been proposed to configure an inverse filter that cancels the frequency characteristics of the housing (for example, Non-Patent Document 1). C The formula for (x) is shown below.

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[0005] When writing characters used in mathematical formulas in the main text of the specification, italics and boldface cannot be used due to the functionality of the electronic application software, so they will be written in roman and normal thickness, respectively.

[0006] To improve the accuracy of elevation angle perception, microphones are placed on the outside and inside of headphones, and a microphone is inserted into the pinna, and a transfer characteristic correction function using an adaptive filter is realized (Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Evaluation of Equalization Methods for Binaural Signals, Zora Scharer and Alexander Lindau, the 126th Convention 2009 May 7-10 Munich, Germany [Non-patent document 2] Natural Listening over Headphones in Augmented Reality Using Adaptive Filtering Techniques, Rishabh Ranjan and Woon-Seng Gan, IEEE / ACM TASLP, vol. 23, no. 11, NOVEMBER 2015 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the prior art (Non-Patent Documents 1 and 2) are all premised on wearable speakers that block the ear canal, and are not premised on wearable open-ear speakers.

[0009] Therefore, an object of the present disclosure is to provide a transfer characteristic correction device that corrects transfer characteristics in order to reproduce stereophonic sound using a wearable open-ear speaker. [Means for solving the problem]

[0010] The transfer characteristic correction device of the present disclosure includes a pseudo-inverse filter generation unit and an acoustic signal correction unit.

[0011] The pseudo-inverse filter generator generates a pseudo-inverse filter using a function that smooths the transfer characteristics from the speaker driver of the wearable open-ear speaker to the entrance of the ear canal. The acoustic signal corrector corrects the acoustic signal based on the pseudo-inverse filter and transmits the corrected acoustic signal to the wearable open-ear speaker. [Effects of the Invention]

[0012] According to the transfer characteristic correction device of the present disclosure, it is possible to correct the transfer characteristics in order to reproduce stereophonic sound using a wearable open-ear speaker. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram showing the functional configuration of a transfer characteristic correction device according to a first embodiment. [Figure 2] 4 is a flowchart showing the operation of the transfer characteristic correction device according to the first embodiment. [Figure 3] 10 is a graph showing an example of generating a kernel ridge pseudo-inverse filter. [Figure 4] 10 is a graph showing an example of generating a softener (Gaussian function) pseudo-inverse filter. [Figure 5] 10 is a graph showing an example of generating a softener (sinc function) pseudo-inverse filter. [Figure 6] 10 is a graph showing an example of generating a softener (trapezoidal smoothing function) pseudo-inverse filter. [Figure 7] 10 is a graph showing an example of generating a pseudo-inverse filter guaranteed to pass low; [Figure 8] FIG. 2 is a diagram showing an example of the functional configuration of a computer. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail. Note that components having the same functions are assigned the same numbers, and redundant explanations will be omitted. [Example]

[0015] The functional configuration of the transfer characteristic correction system and transfer characteristic correction device of the first embodiment will be described below with reference to Fig. 1. As shown in the figure, the transfer characteristic correction system 1 includes a wearable open-ear speaker 11 and a transfer characteristic correction device 12. Examples of wearable open-ear speakers include open-ear earphones, open-ear headphones, and neck speakers.

[0016] The transfer characteristic correction system 1 is characterized by generating a pseudo-inverse filter that smooths the transfer characteristic from the speaker driver of a wearable open-ear speaker to the ear canal, correcting an acoustic signal based on the generated pseudo-inverse filter, and reproducing the corrected acoustic signal from the wearable open-ear speaker.

[0017] Transfer characteristic correction device 12 includes transfer characteristic measurement unit 121, kernel ridge pseudo-inverse filter generation unit 122, softener pseudo-inverse filter generation unit 123, low-pass guaranteed pseudo-inverse filter generation unit 124, and acoustic signal correction unit 125. The operation of each component in transfer characteristic correction device 12 will be described in detail below with reference to FIG.

[0018] <Transfer characteristic measuring unit 121> The transfer characteristic measurement unit 121 uses any impulse response measurement method to measure the transfer characteristic from the speaker driver of the wearable open-ear speaker 11 to the entrance of the ear canal (S121). Note that if the transfer characteristic from the speaker driver of the wearable open-ear speaker 11 to the ear canal is measured and recorded in advance using a separate device, the transfer characteristic measurement unit 121 can be omitted.

[0019] <Pseudo-inverse filter generation units 122, 123, and 124> Pseudo inverse filter generators 122, 123, and 124, which will be described below, are characterized by generating pseudo inverse filters using a function that smooths the transfer characteristics from the speaker driver of the wearable open-ear speaker to the entrance of the ear canal.

[0020] <Kernel Ridge Pseudo Inverse Filter Generator 122> The kernel ridge pseudo-inverse filter generation unit 122 generates a kernel ridge pseudo-inverse filter, which is a pseudo-inverse filter using kernel ridge regression (S122).

[0021] First, the kernel ridge pseudo-inverse filter generator 122 calculates the peak H(x peak ) and notch H(x notch ) to detect.

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[0022] <Softener pseudo-inverse filter generation unit 123> Softener pseudo-inverse filter generation unit 123 generates a softener pseudo-inverse filter, which is a pseudo-inverse filter using a softener (S123).

[0023] First, softener pseudo-inverse filter generation unit 123 applies the following three types of softeners f(x) to the transfer characteristic H(x) from the wearable open-ear speaker earphone to the ear canal. The following equations represent the convolution of the softener f(x) and the transfer characteristic H(x) from the wearable open-ear speaker to the ear canal, and X is used to represent the convolution.

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[0024] <Low-pass guaranteed pseudo-inverse filter generation unit 124> The low-pass guaranteed pseudo-inverse filter generation unit 124 calculates a moving average of the transfer characteristics from the wearable open-ear speaker to the ear canal, and generates a low-pass guaranteed pseudo-inverse filter that is a pseudo-inverse filter that guarantees the passage of low-frequency sounds in an inverse filter whose regularization strength can be specified for each frequency (S124).

[0025] First, the low-pass guaranteed pseudo-inverse filter generating unit 124 calculates a moving average of the transfer characteristic from the wearable open-ear speaker to the ear canal.

[0026] Next, the low-pass guaranteed pseudo-inverse filter generation unit 124 generates a low-pass filtered transfer characteristic obtained by applying a low-pass filter to the transfer characteristic after the moving average, and a band-pass filtered transfer characteristic obtained by applying a band-pass filter to the transfer characteristic after the moving average.

[0027] Next, the low-pass guaranteed pseudo-inverse filter generating unit 124 generates an inverse filter that can specify the strength of regularization for each frequency based on the technique of Non-Patent Document 1 from the band-pass filtered transfer characteristic.

[0028] Next, the low-pass guaranteed pseudo-inverse filter generation unit 124 multiplies the low-pass filtered transfer characteristic by a constant so that the value of the high-frequency end point of the low-pass filtered transfer characteristic matches the value of the low-frequency end point of the band-pass filtered transfer characteristic.

[0029] Next, the low-pass guaranteed pseudo-inverse filter generation unit 124 generates a low-pass guaranteed pseudo-inverse filter by combining an inverse filter generated from the band-pass filtered transfer characteristic with the low-pass filtered transfer characteristic multiplied by a constant.

[0030] <Acoustic signal correction unit 125> The acoustic signal correction unit 125 corrects the acoustic signal using one of the pseudo-inverse filters generated in steps S122, S123, and S124, and transmits the corrected acoustic signal to the wearable open-ear speaker (S125). The pseudo-inverse filter used for correction can be selected by the user.

[0031] Figure 3 shows an example of a generated kernel ridge pseudo-inverse filter. Figure 4 shows an example of a generated softener (Gaussian function) pseudo-inverse filter. Figure 5 shows an example of a generated softener (sinc function) pseudo-inverse filter. Figure 6 shows an example of a generated softener (trapezoid-smoothing function) pseudo-inverse filter. Figure 7 shows an example of a generated low-pass guaranteed pseudo-inverse filter. In all of the graphs in Figures 3 to 7, the vertical axis represents sound pressure [dB] and the horizontal axis represents frequency [Hz]. The solid line graph represents the transfer characteristics from the wearable open-ear speaker to the ear canal, the dashed line graph shows the results of applying a pseudo-inverse filter to the transfer characteristics, and the dotted line graph shows the characteristics of the pseudo-inverse filter.

[0032] The transfer characteristic correction system 1 and transfer characteristic correction device 12 of the present disclosure have realized stereophonic sound reproduction with high elevation angle perception accuracy using wearable open-ear speakers.

[0033] Furthermore, according to the transfer characteristic correction system 1 and the transfer characteristic correction device 12 of the present disclosure, a pseudo-inverse filter can be generated without inserting a microphone into the ear, thereby improving user convenience.

[0034] The generation of a pseudo-inverse filter using kernel ridge regression (step S122) has the advantage that a pseudo-inverse filter can be generated if only the positions of the peaks and notches in the frequency characteristics and the sound pressure values ​​are known.

[0035] In Non-Patent Document 1, the frequency characteristics are averaged by measuring as many as 10 times for one user, which places an excessive burden on the user. However, the pseudo-inverse filter generation using a softener (S123) solves this problem by smoothing the signal after one measurement using a softener while retaining the information on the positions of peaks and notches.

[0036] Regarding the pseudo-inverse filter generation (S124) that guarantees the low-pass of the inverse filter in Non-Patent Document 1, the problem of excessive burden on the user in Non-Patent Document 1 was solved by smoothing it by taking a moving average. Furthermore, another problem in Non-Patent Document 1, the characteristic of reducing the sound pressure in the low range, was solved by combining it with a low-pass filter.

[0037] <Additional Notes> The device disclosed herein may, for example, be a single hardware entity having an input unit to which a keyboard or the like can be connected, an output unit to which an LCD display or the like can be connected, a communication unit to which a communication device (e.g., a communication cable) capable of communicating with an external device can be connected, a CPU (which may also include a central processing unit, cache memory, registers, etc.), memories such as RAM and ROM, an external storage device such as a hard disk, and buses connecting these input unit, output unit, communication unit, CPU, RAM, ROM, and external storage device so that data can be exchanged between them. If necessary, the hardware entity may also be provided with a device (drive) capable of reading and writing to a recording medium such as a CD-ROM. A physical entity equipped with such hardware resources includes a general-purpose computer.

[0038] The external storage device of the hardware entity stores the programs required to realize the above-mentioned functions and the data required for processing these programs (the programs may be stored in a ROM, which is a read-only storage device, for example, instead of an external storage device). Data obtained by processing these programs is stored in RAM, the external storage device, etc. as appropriate.

[0039] In a hardware entity, each program stored in an external storage device (or ROM, etc.) and the data required to process each program are loaded into memory as needed, and interpreted, executed, and processed by the CPU as appropriate, resulting in the CPU realizing a predetermined function (each component represented as a unit, means, etc., above).

[0040] The present disclosure is not limited to the above-described embodiments, and modifications can be made as appropriate without departing from the spirit of the present disclosure. Furthermore, the processes described in the above embodiments may not only be executed in chronological order according to the order described, but may also be executed in parallel or individually depending on the processing capabilities of the devices that execute the processes or as needed.

[0041] As described above, when the processing functions of the hardware entities (apparatuses of the present disclosure) described in the above embodiments are realized by a computer, the processing contents of the functions that the hardware entities should have are described by a program. Then, by executing this program on a computer, the processing functions of the hardware entities are realized on the computer.

[0042] The various processes described above can be implemented by loading a program that executes each step of the above method into the recording unit 10020 of the computer 10000 shown in Figure 8, and operating the control unit 10010, input unit 10030, output unit 10040, etc.

[0043] The program describing the processing contents can be recorded on a computer-readable recording medium. Examples of computer-readable recording media include magnetic recording devices, optical disks, magneto-optical recording media, and semiconductor memories. Specifically, examples of magnetic recording devices include hard disk drives, flexible disks, and magnetic tapes; optical disks include DVDs (Digital Versatile Discs), DVD-RAMs (Random Access Memory), CD-ROMs (Compact Disc Read Only Memory), and CD-Rs (Recordable) / RWs (Rewritable); magneto-optical recording media include MOs (Magneto-Optical discs), and semiconductor memories include EEP-ROMs (Electrically Erasable and Programmable-Read Only Memory).

[0044] The program may be distributed, for example, by selling, transferring, lending, etc. a portable recording medium such as a DVD or CD-ROM on which the program is recorded. Furthermore, the program may be stored in a storage device of a server computer, and then transferred from the server computer to another computer via a network, thereby distributing the program.

[0045] A computer that executes such a program may first temporarily store the program recorded on a portable recording medium or transferred from a server computer in its own storage device. Then, when executing a process, the computer reads the program stored on its own recording medium and executes the process in accordance with the read program. Alternatively, the computer may read the program directly from a portable recording medium and execute the process in accordance with the program. Furthermore, the computer may execute the process in accordance with the received program each time a program is transferred from a server computer to the computer. Alternatively, the server computer may not transfer the program to the computer, but may execute the process through a so-called ASP (Application Service Provider) service, which realizes the processing function by issuing an execution instruction and obtaining the results. In this embodiment, the program includes information used for processing by a computer that is equivalent to a program (such as data that is not a direct instruction to the computer but has properties that define computer processing).

[0046] In addition, in this embodiment, a hardware entity is configured by executing a predetermined program on a computer, but at least a part of the processing contents may be realized by hardware.

Claims

1. A pseudo-inverse filter generator that generates a kernel ridge pseudo-inverse filter, which is a pseudo-inverse filter using kernel ridge regression that smooths the transfer characteristics from a speaker driver of a wearable open-ear speaker to the entrance of the ear canal; and an acoustic signal correction unit that corrects an acoustic signal based on the kernel ridge pseudo-inverse filter and transmits the corrected acoustic signal to the wearable open-ear speaker. Transfer characteristic correction device.

2. A pseudo-inverse filter generation unit that uses a moving average of the transfer characteristic as a function for smoothing the transfer characteristic from the speaker driver of a wearable open-ear speaker to the entrance of the ear canal, generates a low-pass filtered transfer characteristic by applying a low-pass filter to the transfer characteristic after the moving average, and a band-pass filtered transfer characteristic by applying a band-pass filter to the transfer characteristic, generates an inverse filter from the band-pass filtered transfer characteristic that can specify the strength of regularization for each frequency, multiplies the low-pass filtered transfer characteristic by a constant so that the value of the high-frequency end point of the low-pass filtered transfer characteristic matches the value of the low-frequency end point of the band-pass filtered transfer characteristic, and combines the inverse filter generated from the band-pass filtered transfer characteristic with the low-pass filtered transfer characteristic multiplied by the constant to generate a low-pass guaranteed pseudo-inverse filter that is a pseudo-inverse filter that guarantees the passage of low-frequency sounds through the inverse filter. and an acoustic signal correction unit that corrects an acoustic signal based on the low-pass guaranteed pseudo-inverse filter and transmits the corrected acoustic signal to the wearable open-ear speaker. Transfer characteristic correction device.

3. A transfer characteristic correction method executed by a transfer characteristic correction device, generating a kernel ridge pseudo-inverse filter, which is a pseudo-inverse filter using kernel ridge regression that smooths the transfer characteristics from a speaker driver of a wearable open-ear speaker to the entrance of the ear canal; and correcting the acoustic signal based on the kernel ridge pseudoinverse filter and transmitting the corrected acoustic signal to the wearable open-ear speaker. Transfer characteristic correction method.

4. A transfer characteristic correction method executed by a transfer characteristic correction device, comprising: a moving average of the transfer characteristic from the speaker driver of the wearable open-ear speaker to the entrance of the ear canal is used as a function for smoothing the transfer characteristic, and a low-pass filtered transfer characteristic is generated by applying a low-pass filter to the moving averaged transfer characteristic, and a band-pass filtered transfer characteristic is generated by applying a band-pass filter to the moving averaged transfer characteristic; an inverse filter is generated from the band-pass filtered transfer characteristic, and the strength of regularization can be specified for each frequency; the low-pass filtered transfer characteristic is multiplied by a constant so that the value of the high-frequency end point of the low-pass filtered transfer characteristic matches the value of the low-frequency end point of the band-pass filtered transfer characteristic; and a low-pass guaranteed pseudo-inverse filter is generated by combining the inverse filter generated from the band-pass filtered transfer characteristic and the multiplied low-pass filtered transfer characteristic. and correcting the acoustic signal based on the low-pass guaranteed pseudo-inverse filter and transmitting the corrected acoustic signal to the wearable open-ear speaker. Transfer characteristic correction method.

5. A program for causing a computer to function as the transfer characteristic correction device according to claim 1 or 2.

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