Measurement device for auditory organ

Abstract

To measure characteristics of an auditory organ non-invasively with high resistance to noise.SOLUTION: A measurement device (1) for an auditory organ includes: a signal output unit (52) configured to output a stimulation sound signal for stimulation sound in order to output, into an external auditory canal of a subject, a stimulation sound which includes at least each frequency component of a frequency band to be measured; a signal acquisition unit (54) configured to acquire, as a measurement signal, a signal indicating a pressure fluctuation in the external auditory canal when the stimulation sound is output toward inside of the external auditory canal of the subject; and an analyzing device (93) configured to assume the auditory organ of the subject to be a linear system or a nonlinear system, estimate an impulse response of the auditory organ by system identification based on the stimulation sound signal and the measurement signal, and analyze a frequency characteristic of the auditory organ by Fourier-transforming the estimated impulse response.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to measurements for the hearing organ, and in particular to non-invasive measurements of the frequency characteristics of the hearing organ. [Background technology]

[0002] Various methods for non-invasively examining the condition of the hearing organ are known. Tympanometry and impedance audiometry are methods for non-invasively examining the condition of the middle ear. Tympanometry is known to be particularly effective in examining serous otitis media. In tympanometry and impedance audiometry, a stimulus sound of a predetermined frequency is input into the ear canal. For example, Patent Document 1 discloses technology related to an ear probe that can be used in tympanometry and impedance audiometry. Middle ear diseases include not only serous otitis media but also various other conditions such as fixation and detachment of the ossicular chain. There is a demand for a non-invasive and appropriate understanding of the condition of the hearing organ, including the middle ear, which may be in various states. Furthermore, hearing tests that involve inputting a stimulus sound into the ear canal as described above require high resistance to noise. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-108617 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to measure the characteristics of the hearing organ non-invasively and with high resistance to noise. [Means for solving the problem]

[0005] According to one aspect of the present invention, a measurement device for an auditory organ comprises a signal output unit configured to output a stimulus sound signal for the stimulus sound, in order to output the stimulus sound including at least each frequency component of a frequency band to be measured into the ear canal of a subject; a signal acquisition unit configured to acquire, as a measurement signal, a signal indicating pressure fluctuations in the ear canal when the stimulus sound is output into the ear canal of the subject; and an analysis device configured to estimate the impulse response of the auditory organ by system identification based on the stimulus sound signal and the measurement signal, assuming that the auditory organ of the subject is a linear or nonlinear system, and to analyze the frequency characteristics of the auditory organ by Fourier transforming the estimated impulse response. [Effects of the Invention]

[0006] According to the present invention, characteristics of the hearing organ can be measured non-invasively and with high resistance to noise. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing an outline of a configuration example of a measurement device according to an embodiment. [Figure 2] FIG. 2 is a functional block diagram showing an outline of a configuration example of a measurement device according to an embodiment. [Figure 3A] FIG. 3A is a diagram for explaining the sound pressure in the ear canal. [Figure 3B] FIG. 3B is a diagram for explaining the sound pressure in the ear canal. [Figure 4] FIG. 4 shows an example of the measurement results of the frequency characteristics of sound pressure levels obtained using a microphone when an adult subject was subjected to a frequency sweep sound as a stimulus sound. [Figure 5] FIG. 5 is a flowchart showing an outline of an example of the operation of the computer of the measurement device according to one embodiment. [Figure 6]FIG. 6 is a diagram showing an example of measurement results, in which the dashed line indicates the SPL curve obtained using the analysis method according to the embodiment, and the solid line indicates the SPL curve obtained by a conventional method as a comparative example. [Figure 7] FIG. 7 is a diagram showing an example of a measurement result when the duration of the stimulation sound is different in the measurement according to the embodiment. [Figure 8] FIG. 8 is a diagram showing the characteristics of music played by a music box, which was used as an example of a stimulus sound. [Figure 9] FIG. 9 is a diagram showing an example of a measurement result when music is used as the stimulating sound in the measurement according to the embodiment. [Figure 10] FIG. 10 is a diagram showing an example of a measurement signal acquired in a measurement in which a frequency sweep signal is superimposed with white noise and used as an input signal. [Figure 11] FIG. 11 is a diagram showing an example of a measurement result when white noise is superimposed on a stimulating sound in a measurement according to the embodiment. [Figure 12] FIG. 12 is a diagram showing an example of a measurement result when white noise is superimposed on a stimulating sound in a measurement according to a comparative example. [Figure 13] FIG. 13 shows the Pearson correlation coefficients of the SPL curves obtained with and without noise at each SNR. [Figure 14] FIG. 14 shows an SPL curve (dashed line) obtained using the analysis method of the embodiment, where the results obtained in each measurement when noise is present as shown in FIG. 11 are considered to be the results obtained in a single series of measurements, and an SPL curve (solid line) obtained using the analysis method of the embodiment from the measurement results when there is no noise. [Figure 15] FIG. 15 shows an SPL curve (dashed line) obtained by averaging the results of each measurement when noise is present as shown in FIG. 12, and an SPL curve (solid line) obtained from the measurement results of a comparative example when there is no noise. [Figure 16] FIG. 16 is a diagram showing an example of a measurement signal acquired in a measurement in which noise caused by the movement of the subject is generated during the measurement. [Figure 17] FIG. 17 is a diagram showing an example of a measurement result when noise caused by the movement of a subject is generated in a measurement according to the embodiment. [Figure 18] FIG. 18 is a diagram showing an example of a measurement result when noise caused by the movement of the subject is generated in a measurement according to a comparative example. [Figure 19] FIG. 19 is a diagram showing the Pearson correlation coefficients of the SPL curves obtained when there is noise due to each movement of the subject and when there is no noise. [Figure 20] Figure 20 shows an SPL curve (dashed line) obtained using the analysis method of the embodiment, where the results obtained in each measurement when there is noise as shown in Figure 17 are considered to be the results obtained in a single series of measurements, and an SPL curve (solid line) obtained using the analysis method of the embodiment from the measurement results when there is no noise. [Figure 21] FIG. 21 shows an SPL curve (dashed line) obtained by averaging the results of each measurement when noise is present as shown in FIG. 18, and an SPL curve (solid line) obtained from the measurement results of a comparative example when there is no noise. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment will be described with reference to the drawings. This embodiment relates to a device for measuring characteristics of the auditory organ. The measurement device of this embodiment can perform measurements non-invasively. As an example, this measurement device outputs a stimulus sound into a subject's ear canal and acquires pressure fluctuations within the ear canal at the time. The measurement device is configured to analyze the characteristics of the subject's auditory organ by analyzing the pressure fluctuations. The measurement device can acquire information related to the impedance of the middle ear, in particular. This impedance reflects the dynamic characteristics of the middle ear system, in particular. Based on the acquired information related to the impedance, the condition of the auditory organ, particularly the middle ear, can be evaluated. For example, an evaluation of the sound conduction characteristics of the middle ear can be obtained. Furthermore, for example, the presence or absence of fixation or disruption of the ossicular chain, the presence or absence of otitis media including serous otitis media, the presence or absence of thinning or adhesion of the tympanic membrane, and the presence or absence of a middle ear malformation can be determined. The acquired information can be used to diagnose middle ear diseases and conductive hearing loss. In other words, this measurement device can function as a diagnostic device for the auditory organ.

[0009] [Device configuration] Fig. 1 is a schematic diagram showing an outline of an example configuration of a measurement device 1 according to this embodiment. Fig. 2 is a functional block diagram showing an outline of an example configuration of the measurement device 1 according to this embodiment. As shown in Fig. 1, the measurement device 1 includes a computer 10, an AD / DA converter 60, an amplifier system 70, and a probe 80.

[0010] The probe 80 is configured so that its tip is inserted into the ear canal 210 of the subject 200. The probe 80 includes an earphone 82 for outputting a stimulating sound toward the ear canal 210, and a microphone 84 for acquiring pressure fluctuations within the ear canal 210.

[0011] The computer 10 is a general-purpose computer, and may be, for example, a personal computer. The computer 10 includes, for example, a central processing unit (CPU) 11, various integrated circuits such as a memory 12 and a storage 13, and various interfaces 14. The computer 10 may further include a field programmable gate array (FPGA) or the like that is prepared according to the processing of the measuring device 1. The computer 10 performs processing such as controlling the operation of each part of the measuring device 1, generating signals related to the stimulating sound, and analyzing pressure fluctuations in the ear canal. The operation of the computer 10 is performed according to a program that is recorded in the computer 10 as software or hardware, or that is provided from outside the computer 10. The program may be recorded on various recording media.

[0012] The AD / DA converter 60 has a DA converter 62 and an AD converter 64. The amplifier system 70 has an earphone amplifier 72 and a microphone amplifier 74. The DA converter 62 of the AD / DA converter 60 converts the digital signal related to the stimulation sound output from the computer 10 into an analog signal and outputs it to the earphone amplifier 72 of the amplifier system 70. The earphone amplifier 72 amplifies the analog signal related to the stimulation sound input from the DA converter 62 and outputs the stimulation sound from the earphone 82 of the probe 80. The microphone amplifier 74 of the amplifier system 70 amplifies the analog signal related to pressure fluctuations in the ear canal 210 acquired by the microphone 84 of the probe 80 and outputs it to the AD converter 64 of the AD / DA converter 60. The AD converter 64 converts the analog signal acquired from the microphone amplifier 74 into a digital signal and inputs it to the computer 10.

[0013] The computer 10 has functions as a control unit 22, a stimulation sound signal generating unit 32, a signal output unit 52, a signal acquiring unit 54, an analyzing device 93, etc. The control unit 22 controls each operation of the computer 10.

[0014] The stimulation sound signal generating unit 32 generates a stimulation sound signal related to the stimulation sound to be output. The generated stimulation sound signal related to the stimulation sound is output to the DA converter 62 via the signal output unit 52. The stimulation sound signal generating unit 32 may prepare and output a stimulation sound signal based on, for example, audio data recorded in the storage 13, or may synthesize and output a stimulation sound signal based on, for example, a program recorded in the storage 13.

[0015] In this embodiment, the stimulation sound is configured to include each frequency component in the measurement target frequency band. For example, if the measurement target frequency band is from 100 Hz to 2000 Hz, the stimulation sound may include at least frequency components from 100 Hz to 2000 Hz.

[0016] The stimulation sound is preferably, but not limited to, non-mechanical and does not cause discomfort to the subject 200. For example, the stimulation sound preferably includes at least each frequency component in the frequency band to be measured and has a rhythmic frequency that changes over time. The stimulation sound may be, for example, music, i.e., a combination of pitch, intensity, duration, tone, chords, etc., selected and selected in a certain manner. Using music or the like as the stimulation sound reduces discomfort to the subject 200 during measurement or provides the subject 200 with a sense of comfort during measurement. The stimulation sound may particularly be a lullaby. For example, when the subject 200 is an infant, using a lullaby as the stimulation sound can be expected to relax the subject 200 and allow for appropriate measurement. In pediatric disease examinations, multiple measurements may be performed under sedation. In such cases, it is particularly important not to awaken or excite the subject 200. Using lullabies rather than mechanical sounds may reduce the risk of waking or arousing a sleeping or calm child.

[0017] The stimulation sound may not have a constant sound pressure amplitude, and the frequency and sound pressure amplitude of the sound waves may not change monotonically. The sound pressure amplitude and frequency of the stimulation sound may change discontinuously over time. Therefore, the energy of each frequency of the stimulation sound may be non-uniform. The stimulation sound may include, for example, a series of high and low tones that unfold with a certain rhythm. It is preferable that the stimulation sound includes a chord, or a series of multiple chords, so as to include each frequency component in the frequency band to be measured.

[0018] Even when the stimulus sound is music, it may generally contain various frequency components due to harmonics, distorted waves, etc. In order to include each frequency component in the measurement target frequency band, the stimulus sound is preferably a recording of music played by a musical instrument, for example. The musical instrument may include an automatic playing instrument such as a music box, an electric instrument, etc.

[0019] When a stimulus sound is output from earphones 82 inserted into the ear canal 210 of the subject 200, pressure fluctuations occur in the ear canal 210 as a result of the stimulus sound acting on the subject 200. The microphone 84 acquires this pressure fluctuation in the ear canal 210. The analysis device 93 acquires a measurement signal related to the pressure fluctuations in the ear canal acquired by the microphone 84 from the AD converter 64 via the signal acquisition unit 54. The analysis device 93 analyzes the acquired signal. The analysis device 93 analyzes the frequency characteristics of the auditory organ of the subject 200 based on the stimulus sound signal and the measurement signal. More specifically, the analysis device 93 analyzes the frequency characteristics of the auditory organ of the subject 200, particularly the middle ear, based on the stimulus sound input to the ear canal 210 and the acquired pressure fluctuations in the ear canal 210.

[0020] As described above, the signal output unit 52, DA converter 62, earphone amplifier 72, earphone 82, etc. collectively function as a stimulation sound output unit 91 configured to output a stimulation sound based on a stimulation sound signal toward the ear canal 210 of the subject 200. Furthermore, the signal acquisition unit 54, AD converter 64, microphone amplifier 74, microphone 84, etc. collectively function as a sound receiving unit 92 configured to acquire a signal indicating pressure fluctuations in the ear canal 210 when the stimulation sound output unit 91 is outputting the stimulation sound.

[0021] The configuration of the measuring device 1 shown here is an example, and can be modified as appropriate as long as it performs the same functions. Here, an example has been shown in which the computer 10 performs all of the various controls related to the operation of the measuring device 1 and all of the data analysis, but this is not limiting. The functions of the computer 10 may be realized by any number of devices. Furthermore, some of the functions of the computer 10 may be performed by other devices located in remote locations and connected to the computer 10 via a network. For example, the operation of each component of the measuring device 1 may be controlled from a remote location, or the acquired data may be analyzed by a server located in a remote location. While various physical configurations are possible, the measuring device 1 performs functions such as a stimulation sound output unit 91, a sound receiving unit 92, and an analysis unit 93.

[0022] [Measurement principle] The principles of measurement and analysis of auditory organ characteristics using the measuring device 1 will now be described. As shown in FIG. 1 , in the human auditory organ, the eardrum 222 at the end of the external auditory canal 210 and the cochlea 232 of the inner ear are connected via ossicles 224, including the malleus 225, incus 226, and stapes 227. The middle ear consists of the eardrum 222, the ossicles 224, and the tympanic cavity, a small, air-filled space in which the ossicles 224 are located. Vibrations from the eardrum 222 are transmitted via the chain of ossicles 224 to the cochlea 232, where sensory cells reside. Middle ear diseases, such as those caused by lesions, can cause conductive hearing loss. For example, there are known middle ear diseases in which vibrations from the eardrum 222 cannot be properly transmitted to the cochlea 232 due to a partial rupture of the chain of ossicles 224 or partial fixation of the ossicles 224. Other known middle ear diseases include various types of otitis media, including serous otitis media, thinning and adhesion of the tympanic membrane, and middle ear malformations.

[0023] The sound pressure inside the ear canal 210 will now be described. During measurement using the measurement device 1, the diaphragm 83 of the earphone 82 vibrates at one end of the ear canal 210, and the eardrum 222 vibrates at the other end of the ear canal 210. Figures 3A and 3B are diagrams that schematically show this state.

[0024] When the frequency of the stimulation sound output from earphone 82 is lower than the resonance frequency of the middle ear, as shown in FIG. 3A, vibrating membrane 83 of earphone 82 and eardrum 222 are displaced in the same phase. Therefore, pressure P in ear canal 210 is expressed as follows: P=K(ΔV-ΔV TM ) / V Here, K is the bulk modulus of air, ΔV is the volume change caused by the diaphragm 83 of the earphone 82, and ΔV TM is the volume change caused by the eardrum 222, and V is the volume of the ear canal 210. At this time, the more the eardrum 222 vibrates, the smaller the volume change becomes, and the smaller the sound pressure becomes.

[0025] When the frequency of the stimulation sound output from the earphone 82 reaches the resonant frequency of the middle ear, the phase of the eardrum 222 is inverted, as shown in FIG. 3B. Therefore, the pressure P in the ear canal 210 is P=K(ΔV+ΔVTM ) / V At this time, the more the eardrum 222 vibrates, the greater the volume change and the greater the sound pressure.

[0026] FIG. 4 shows an example of measurement results using an adult subject 200 and a device having the same hardware configuration as the measurement device 1. The measurement results shown in FIG. 4 were performed using a conventionally known method, different from the method according to this embodiment. That is, measurement was performed by outputting a frequency sweep sound, the frequency of which varied from 100 Hz to 2000 Hz, from earphone 82 over 10 seconds. When this frequency sweep sound was output, the sound pressure in ear canal 210 was measured using microphone 84. The solid line in FIG. 4 shows the sound pressure level (SPL) acquired using microphone 84 versus the frequency of the stimulus sound. Here, SPL is defined as: SPL = 20 log | P / P REF | where P is the sound pressure measured by microphone 84 and P REF is the reference sound pressure, 2.0×10 -5 The sound pressure level is expressed as a frequency characteristic of the eardrum 222. ...

[0027] The SPL curve indicates the characteristics of the auditory organs of subject 200, including the outer ear, middle ear, and inner ear. In particular, the SPL curve is known to primarily indicate the characteristics of the middle ear of subject 200. It is known that large changes in SPL observed in the SPL curve indicate resonance in the middle ear. In FIG. 4, the intermediate value between the frequency showing the minimum value and the frequency showing the maximum value of the SPL curve is indicated by a dashed-dotted arrow as the resonance frequency (RF) of the middle ear. It is also known that ΔSPL, which is the difference between the minimum value and the maximum value of the SPL curve, indicates the mobility of the eardrum 222.

[0028] For example, it is known that evaluating the resonant frequency (RF) and ΔSPL can provide information such as whether the middle ear is normal or whether there is a middle ear disease due to a lesion or the like. For example, when the ossicles 224 are fixed and difficult to move, it is known that the ΔSPL is smaller and the RF is slightly higher compared to a normal ear. It is also known that when the ossicles 224 are detached and unable to transmit sound to the inner ear, it is known that the ΔSPL is larger and the RF is slightly lower compared to a normal ear. In this way, feature quantities such as RF and ΔSPL are identified from the SPL curve, and the characteristics of the auditory organ, particularly the characteristics of the middle ear, can be identified based on these feature quantities. The feature quantities used to identify the characteristics of the auditory organ are not limited to the RF and ΔSPL of the SPL curve. Various feature quantities, such as the maximum and minimum values ​​of the SPL curve, can also be used. Based on the characteristics of the auditory organ, for example, the condition of the auditory organ of the subject 200 can be evaluated. Based on the evaluated condition of the auditory organ, for example, the sound conduction characteristics of the middle ear of the subject 200 can be evaluated, which can be used for diagnosis, etc.

[0029] The effectiveness of conventional measurement methods using the above-described frequency sweep sound as the stimulus sound has been confirmed. However, this measurement method is susceptible to adverse effects of noise and the like. Furthermore, when a frequency sweep sound is used as the stimulus sound, the measurement takes a relatively long time, such as 10 seconds in the above example. For the subject 200, a shorter measurement time is preferable. Furthermore, mechanical sounds such as frequency sweep sounds tend to cause discomfort to the subject 200. Similarly, mechanical sounds such as clicking sounds tend to cause discomfort to the subject 200. In particular, if the subject 200 is an infant or young child and finds the stimulus sound uncomfortable, the sleeping subject 200 may wake up or move, making stable measurement impossible. Therefore, unlike the above-described conventional method, the measurement device 1 of this embodiment performs measurements to obtain an SPL curve as follows.

[0030] It is assumed that the auditory organ of the subject 200 is a linear system. In this case, the relationship between the stimulus sound, i.e., the sound x(t) input to the ear canal 210 using the earphone 82, and the acquired sound, i.e., the sound y(t) acquired from the ear canal using the microphone 84, can be expressed by the following equation using the impulse response h(t) of the auditory organ system.

number

[0031] Here, we consider the audio x(t) related to the stimulating sound as the stimulating sound signal x(t) output from the signal output unit 52, and the audio y(t) related to the acquired sound as the measurement signal y(t) acquired by the signal acquisition unit 54, and estimate the impulse response h(t) from these.

[0032] The least squares method is used to obtain the optimum impulse response h(t) of the system in the above equation, i.e.,

number

[0033] From the above equation, it can be seen that the auditory system can be identified regardless of the type and length of the stimulus sound signal x(t).

[0034] In this embodiment, the stimulation sound may include at least each frequency component in the frequency band to be measured. Accordingly, the stimulation sound signal x(t) may be any signal as long as it includes at least each frequency component in the frequency band to be measured. The duration of the stimulation sound signal x(t) may be any length based on the measurement principle described above. By increasing the measurement time and acquiring more information, improved measurement accuracy can be expected. On the other hand, when a shorter measurement time is required, the duration of the stimulation sound signal x(t) can be shortened, for example, to less than 3 seconds or less than 2 seconds. Furthermore, the duration of such a stimulation sound signal x(t) can be further shortened, for example, to approximately 1 second, 0.2 seconds, 0.1 seconds, or 0.01 seconds. The duration of the stimulation sound signal x(t) may be an extremely short time, as long as it is longer than 0 seconds, depending on the hardware performance and measurement accuracy. Reducing the measurement time reduces the burden on the subject. Furthermore, reducing the time required for a single measurement allows multiple measurements, such as repeated measurements or measurements under multiple conditions, to be performed in a short period of time. The duration of the stimulation sound signal x(t) can be set appropriately depending on various conditions. Furthermore, the stimulation sound may be one in which the sound pressure amplitude and frequency change discontinuously over time. Accordingly, the amplitude and frequency of the stimulation sound signal x(t) may also change discontinuously over time. Therefore, the sound represented by the stimulation sound signal x(t) may be a sound that is pleasant to the subject 200, rather than a mechanical sound. For example, the stimulation sound signal x(t) may be music such as a lullaby. Therefore, as long as conditions for stable measurement are met, the duration of the stimulation sound signal x(t) may be a relatively long time, such as a complete phrase of a song.

[0035] The measuring device 1 inputs a stimulus sound using such a stimulus sound signal x(t) into the ear canal 210 of the subject 200 as described above, and acquires the response of the middle ear system, which is the object of observation, as a measurement signal y(t) using the microphone 84.

[0036] The analysis device 93 has functions such as a system identification unit 41, a Fourier transform unit 42, a feature identification unit 43, and an auditory organ characteristic analysis unit 44. The system identification unit 41 performs the above-mentioned calculation based on the stimulus sound signal x(t) and the measurement signal y(t) to perform system identification processing, estimating the impulse response h(t) of the auditory organ system. The Fourier transform unit 42 uses an algorithm such as a fast Fourier transform (FFT) to Fourier transform a function related to the impulse response h(t) obtained by the system identification unit 41, thereby obtaining the frequency response of the auditory organ including the middle ear system being observed, i.e., the above-mentioned SPL curve.

[0037] The feature identifying unit 43 identifies feature quantities, such as the above-mentioned resonant frequency (RF) and ΔSPL, based on the obtained SPL curve. The auditory organ property analyzing unit 44 analyzes the properties of the auditory organs of the subject 200 based on these feature quantities.

[0038] [Device Operation] The operation of the measurement device 1 will now be described. During measurement, the probe 80 is inserted into the ear canal 210 of the subject 200. Figure 5 is a flowchart showing an outline of an example of the operation of the computer 10. The operation will be described with reference to this flowchart.

[0039] In step S1, the computer 10 generates a stimulation sound signal x(t) based on, for example, audio data recorded on a recording device. In step S2, the computer 10 outputs the generated stimulation sound signal x(t) to the DA converter 62. Based on this stimulation sound signal x(t), the stimulation sound is output from the earphone 82 to the ear canal 210 of the subject 200 via the DA converter 62 and the earphone amplifier 72.

[0040] At this time, as a result of the stimulus sound acting on the subject 200, a pressure fluctuation occurs in the ear canal 210. A signal indicating the sound pressure in the ear canal 210 is generated by the microphone 84. The signal generated by the microphone 84 is input to the computer 10 via the microphone amplifier 74 and the AD converter 64. In step S3, the computer 10 acquires the sound pressure signal from the microphone 84 as a measurement signal y(t).

[0041] In step S4, the computer 10 performs a process to identify the auditory system based on the stimulus sound signal x(t) and the measurement signal y(t) as described above. That is, the computer 10 estimates a function corresponding to the impulse response h(t) of the auditory system. In step S5, the computer 10 performs a Fourier transform on the estimated impulse response h(t) to obtain an SPL curve that indicates the frequency characteristics of the auditory system.

[0042] Based on the SPL curve, computer 10 analyzes the characteristics of the hearing organs of subject 200. For example, in step S6, computer 10 identifies, based on the SPL curve, feature quantities such as the resonant frequency of the middle ear and / or the ΔSPL value indicating the mobility of eardrum 222. In step S7, based on the identified feature quantities, computer 10 evaluates the characteristics of the hearing organs, such as the sound conduction characteristics of the middle ear, for example, whether subject 200's hearing organs are normal or whether they have a middle ear disease, and if so, what type of disease it is.

[0043] Note that the measurement need not be performed only once, but may be performed repeatedly. For example, the measurement may be performed repeatedly while adjusting the insertion of the probe 80 into the ear canal 210, and may be terminated when an appropriate measurement is obtained. The analysis device 93 may also perform system identification by processing a group of results from multiple measurements in the same way as results obtained from a single series of measurements. This processing also obtains a function corresponding to the impulse response h(t) of the auditory organ system, and an SPL curve is obtained based on this function. For example, multiple measurements may be performed, and measurement results that satisfy predetermined conditions may be used as a group of results for system identification. The output time of the stimulus sound corresponding to one measurement included in the multiple measurements may be less than 2 seconds, for example. In this case, the time required for the entire multiple measurements may be, for example, several seconds to several tens of seconds.

[0044] [Measurement example] <First measurement example> A measurement example using the measurement device 1 of this embodiment will be described. An adult male was used as the subject (subject 1), and measurements were performed using the method according to this embodiment and a conventional method as a comparative example. In both measurements, the stimulus sound signal used as the stimulus sound was a frequency sweep signal whose frequency changed from 100 Hz to 2000 Hz over 10 seconds.

[0045] In the analysis method according to this embodiment, system identification was performed based on a measurement signal acquired using the microphone 84, and an impulse response was estimated. An FFT process was performed on a function corresponding to the acquired impulse response to obtain an SPL curve. On the other hand, in the method of the comparative example, the sound pressure acquired using the microphone 84 was directly converted to a sound pressure level, and the SPL curve was obtained by plotting it in correspondence with the frequency of the input stimulus sound at the time of sound pressure acquisition.

[0046] An example of the measurement results is shown in Figure 6. The dashed line indicates the SPL curve obtained using the analysis method according to this embodiment. The solid line indicates the SPL curve obtained by a conventional method as a comparative example. As shown in Figure 6, the dashed line and the solid line match well. This demonstrates that the analysis method according to this embodiment can obtain an SPL curve similar to that obtained by the conventional method, the effectiveness of which has been confirmed.

[0047] <Second measurement example> The effect of the duration of the stimulus sound on the resulting SPL curve was investigated. The subject was the same adult male (subject 1) as in the first measurement example. The stimulus sound signal used for the stimulus sound was a frequency sweep signal whose frequency changed from 100 Hz to 2000 Hz, and the frequency sweep speed was varied to set the duration of the stimulus sound to 10 seconds, 1 second, 0.5 seconds, 0.4 seconds, 0.3 seconds, 0.2 seconds, and 0.1 seconds. In each case, the system identification and FFT analysis method of this embodiment was used.

[0048] The obtained SPL curves are shown in Figure 7. As shown in this figure, when the stimulus sound duration was 10 seconds, 1 second, 0.5 seconds, 0.4 seconds, 0.3 seconds, and 0.2 seconds, the obtained SPL curves were in good agreement. When the stimulus sound duration was 0.1 seconds, the measurement results were different from the measurement results for other cases. Therefore, it was revealed that, using the measurement device and the analysis method of this embodiment, good measurements can be obtained even when the stimulus sound duration is shortened to approximately 0.2 seconds. The reason for the different measurement results when the stimulus sound duration was 0.1 seconds was thought to be due to hardware performance, such as the slow startup time of the microphone 84. By improving hardware performance, it is possible to shorten the stimulus sound duration to less than 0.2 seconds, for example, to approximately 0.1 seconds or 0.01 seconds.

[0049] <Third measurement example> The same adult male (subject 1) as in the first measurement example was used as the subject, and the stimulus sound was a recording of music played on a music box. Measurements were conducted using the analysis method of this embodiment. The characteristics of the stimulus sound used are shown in Figure 8. In this figure, (a) shows the relationship between normalized sound pressure amplitude and elapsed time, (b) shows the relationship between sound pressure level and frequency, and (c) shows the relationship between frequency, elapsed time, and sound pressure amplitude. While the music used as the stimulus sound has a limited number of fundamental waves, due to being played on a music box, the stimulus sound contains many harmonics and other components, including each frequency component in the frequency band being measured. It can also be seen that the music used as the stimulus sound changes discontinuously over time, and the energy at each frequency is non-uniform.

[0050] In the analysis method according to this embodiment, a measurement signal was obtained using a microphone 84 while a stimulus sound, which was music played by a music box, was input into the ear canal 210 via earphones 82. System identification was performed based on the stimulus sound signal and the measurement signal, and an impulse response was estimated. An FFT process was performed on a function corresponding to the obtained impulse response to obtain an SPL curve. On the other hand, in the conventional measurement according to the comparative example, the stimulus sound signal used for the stimulus sound was a frequency sweep signal whose frequency changed from 100 Hz to 2000 Hz over 10 seconds. In the method of the comparative example, the sound pressure obtained using the microphone 84 was directly converted to a sound pressure level, and the SPL curve was obtained by plotting it in correspondence with the frequency of the input stimulus sound at the time of sound pressure acquisition.

[0051] An example of an SPL curve obtained by measurement is shown in FIG. 9. In this figure, the solid line indicates the SPL curve obtained using the analysis method according to this embodiment for the above-mentioned subject (subject 1). The dashed line indicates the SPL curve obtained using a conventional method as a comparative example for the same subject (subject 1). As shown in FIG. 9, the solid and dashed lines closely match. This demonstrates that the analysis method according to this embodiment can obtain an SPL curve similar to that obtained using conventional methods whose effectiveness has been confirmed. It has been demonstrated that the analysis method according to this embodiment can obtain an appropriate SPL curve even when using a stimulus sound such as music, in which the energy at each frequency is non-uniform and both the sound pressure amplitude and frequency change discontinuously over time.

[0052] Furthermore, a different adult male was used as the subject (subject 2) and measurements were similarly conducted using the measurement device 1 of this embodiment, with music played on a music box as the stimulus sound. The results are shown by the dashed-dotted line in Figure 9. In this case as well, an appropriate SPL curve was obtained. It was also revealed that differences in SPL curves due to individual differences could be obtained.

[0053] In this way, it has become clear that the analysis method according to this embodiment allows for extremely high degree of freedom in setting the stimulus sound.

[0054] <Fourth measurement example> The robustness of measurements related to this embodiment to noise was evaluated. The subject was the same adult male (subject 1) as in the first measurement example. As in the first measurement example, the stimulus sound signal used for the stimulus sound was a frequency sweep signal whose frequency changed from 100 Hz to 2000 Hz over 10 seconds. In this measurement, white noise was superimposed on this frequency sweep signal to create the stimulus sound signal. Measurements were performed under conditions of the signal-to-noise ratio (SNR) expressed by the following formula: -20 dB, -15 dB, -10 dB, -5 dB, 0 dB, 5 dB, 10 dB, 15 dB, and 20 dB.

number

[0055] The measurement signal y(t) obtained using microphone 84 for each measurement is shown in Figure 10. In this figure, (a) Clean indicates the measurement signal y(t) obtained when the stimulus sound signal x(t) does not contain noise. (b) to (j) indicate the measurement signals y(t) obtained when white noise was superimposed on the stimulus sound signal x(t) so that the SNRs were -20 dB, -15 dB, -10 dB, -5 dB, 0 dB, 5 dB, 10 dB, 15 dB, and 20 dB, respectively.

[0056] Fig. 11 shows SPL curves obtained using the analysis method according to this embodiment for each measurement. As described above, the analysis method according to this embodiment estimates an impulse response by performing system identification based on the measurement signal acquired by microphone 84, and then performs FFT processing on a function corresponding to the obtained impulse response to obtain an SPL curve. Fig. 12 shows SPL curves obtained using a method of the comparative example for each measurement. As described above, the method of the comparative example converts the sound pressure acquired using microphone 84 directly into a sound pressure level, and plots this in correspondence with the frequency of the input stimulus sound at the time the sound pressure was acquired to obtain an SPL curve.

[0057] When the analysis method according to this embodiment was used, the absolute value of the sound pressure level shifted when the noise level was high, but in all cases the shape of the SPL curve remained the same as when there was no noise. It was revealed that the analysis method according to this embodiment could appropriately derive values ​​such as ΔSPL and RF obtained from the SPL curve regardless of the presence of noise. In other words, it was revealed that the analysis method according to this embodiment is robust against external noise.

[0058] On the other hand, when using the method of the comparative example, when noise levels increased, the SPL curve obtained was also strongly affected by the noise, and the shape of the SPL curve differed from that obtained when there was no noise. As a result, in the case of the comparative example, values ​​such as ΔSPL and RF could not be obtained appropriately.

[0059] Thus, when the analysis method according to this embodiment was used, in contrast to the case where the analysis method according to the comparative example was used, an SPL curve showing the characteristics of the object to be measured, as shown in FIG. 11, was obtained with almost no influence of noise.

[0060] FIG. 13 shows the Pearson correlation coefficients of SPL curves obtained with and without noise at each SNR. After 1,000 permutations, a Pearson correlation coefficient greater than 0.25 was confirmed to be statistically significant (p<0.01). From a practical perspective of obtaining an SPL curve similar to that obtained without noise, it was determined that a Pearson correlation coefficient greater than 0.8 was necessary. It was believed that a Pearson correlation coefficient of 0.8 or greater would provide results similar to those obtained without noise, even in the presence of noise. According to the analysis method of this embodiment, the Pearson correlation coefficient was 0.8 or greater in all measurements. That is, results obtained with noise were considered to be similar to those obtained without noise. In contrast, in the comparative example, the Pearson correlation coefficient was less than 0.8 for SNRs ranging from -20 dB to -5 dB, and in these cases, adequate results were not obtained due to the noise.

[0061] The results obtained from measurements with S / N ratios ranging from -20 dB to 20 dB shown in FIG. 11 were considered as a group of results obtained from a series of measurements, and SPL curves were obtained using the analysis method of this embodiment. The results are shown by the dashed line (Group-level) in FIG. 14. The solid line (clean) in FIG. 14 shows the SPL curve obtained using the analysis method of this embodiment based on measurement results in the absence of noise. The Pearson correlation coefficient between the results shown by the dashed line (Group-level) and the solid line (clean) in FIG. 14 was 0.95. This demonstrates that even in situations where the environment is changing, SPL curves can be obtained with high accuracy by processing results obtained from multiple measurements in the same way as results obtained from a series of measurements and obtaining SPL curves using the analysis method of this embodiment.

[0062] As a comparative example, an SPL curve was obtained by averaging the results obtained using the analysis method of the comparative example from measurements with S / N ratios of -20 dB to 20 dB, as shown in FIG. 12. The results are shown by the dashed line (Response averaging) in FIG. 15. The solid line (clean) in FIG. 15 shows the SPL curve obtained using the analysis method of the comparative example based on measurement results in the absence of noise. The Pearson correlation coefficient between the results shown by the dashed line (Response averaging) and the solid line (clean) in FIG. 15 was -0.06. As such, in situations where the environment changes, an appropriate SPL curve could not be obtained by averaging multiple measurement results using the method of the comparative example.

[0063] <Fifth measurement example> The robustness of the measurement of this embodiment against noise was evaluated under different noise generation conditions in the same manner as in the fourth measurement example. The subject was the same adult male (subject 1) as in the first measurement example. As in the first measurement example, the stimulus sound signal used for the stimulus sound was a frequency sweep signal whose frequency changed from 100 Hz to 2000 Hz over 10 seconds. In this measurement, subject 200 either spoke, pressed probe 80, swallowed saliva, moved his head, or shook his hand holding the cable connected to probe 80 during the measurement, generating noise due to the movements of subject 200.

[0064] The measurement signal y(t) obtained using the microphone 84 in each measurement is shown in Figure 16. In this figure, (a) Clean indicates the measurement signal y(t) obtained when no noise was generated. (b) to (f) indicate the measurement signal y(t) obtained when vocalization, holding the probe 80 (cover earphones), swallowing saliva, moving the head, or shaking the hand holding the cable connected to the probe 80 (tremors) were performed during the measurement.

[0065] FIG. 17 shows SPL curves obtained using the analysis method according to this embodiment for each measurement. FIG. 18 shows SPL curves obtained using the comparative method for each measurement. When the analysis method according to this embodiment was used, the shape of the SPL curve was the same as when there was no noise in either case. That is, it was revealed that the analysis method according to this embodiment is robust against noise caused by the movement of the subject 200. This is in contrast to when the comparative method was used. In the comparative example, the shape of the SPL curve was significantly different from when there was no noise, particularly when the subject pressed the probe 80, swallowed saliva, or shook their hand while holding the cable connected to the probe 80.

[0066] 19 shows the Pearson correlation coefficients of the SPL curves obtained with and without noise due to each movement of the subject 200. According to the analysis method of this embodiment, the Pearson correlation coefficient was 0.8 or higher in all measurements. That is, even with noise, results considered to be similar to those obtained without noise were obtained. In contrast, in the comparative example, when the subjects held down the probe 80 (cover earphones), swallowed saliva (swallow), and trembled their hands while gripping the cable connected to the probe 80 (tremors), the Pearson correlation coefficient was less than 0.8, and in these cases, appropriate results were not obtained due to the noise.

[0067] The results obtained from measurements for each noise source shown in FIG. 17 were considered to be the results obtained from a single series of measurements, and an SPL curve was obtained using the analysis method of this embodiment. The results are shown by the dashed line (Group-level) in FIG. 20. The solid line (clean) in FIG. 20 shows the SPL curve obtained using the analysis method of this embodiment based on the measurement results in the absence of noise. The Pearson correlation coefficient between the results shown by the dashed line (Group-level) and the solid line (clean) in FIG. 20 was 0.92. This demonstrates that even in situations where the environment is changing, an SPL curve can be obtained with high accuracy by processing multiple measurements in the same way as the results obtained from a single series of measurements and obtaining an SPL curve using the analysis method of this embodiment.

[0068] As a comparative example, an SPL curve was obtained by averaging the results obtained using the analysis method of the comparative example from measurements for each case of noise generation causes shown in FIG. 18 . The results are shown by the dashed line (Response averaging) in FIG. 21 . The solid line (clean) in FIG. 21 shows the SPL curve obtained using the analysis method of the comparative example based on measurement results in the absence of noise. The Pearson correlation coefficient between the results shown by the dashed line (Response averaging) and the solid line (clean) in FIG. 21 was −0.44. As such, in situations where the environment was changing, an appropriate SPL curve could not be obtained by averaging the results of multiple measurements using the method of the comparative example.

[0069] [About the measuring device] The measurement device 1 according to this embodiment can perform highly accurate measurements while shortening the measurement time compared to conventional methods. Furthermore, the measurement device 1 according to this embodiment obtains an SPL curve by first obtaining a function equivalent to the impulse response and then performing a Fourier transform. This allows for a good SPL curve to be obtained despite noise. Therefore, appropriate measurements can be performed even with a relatively low energy input, for example, by shortening the duration of the stimulus sound while keeping the sound pressure of the stimulus sound at 80 dB SPL or less.

[0070] The measurement device 1 according to this embodiment performs measurements on a living body, namely the auditory organ. A living body generates various noises, such as those caused by the movement of the subject 200 and blood flow. The method and device according to this embodiment, which can detect a slight signal with high sensitivity even in the presence of noise, are particularly effective in measurements on a living body.

[0071] Measurement requires inputting a stimulus sound into the ear canal 210 of the subject 200. Considering the need to avoid damaging the auditory organ, inputting a high volume, such as 90 dB SPL or more, is undesirable. Furthermore, inputting a high volume may trigger the stapedius reflex, which could prevent accurate measurement from being performed to obtain the characteristics of the auditory organ. Therefore, it is important to be able to perform measurements at relatively low sound pressures. For example, in this embodiment, the maximum sound pressure of the stimulus sound can be set to less than 90 dB SPL, such as 80 dB SPL or 70 dB SPL.

[0072] Furthermore, the longer the measurement time, the more susceptible the measurement is to noise, such as the movement of the subject 200. In particular, when measuring small children, such as infants, babies, and newborns, the movement of the subject 200 becomes a major problem. Therefore, it is important to input a stimulus sound at a relatively low sound pressure while keeping the measurement time relatively short.

[0073] Furthermore, since the measurement time can be relatively short, the total measurement time can be shortened even when measurements are performed under various conditions while changing various conditions. For example, in the above-described embodiment, an example is shown in which the pressure in the ear canal 210 is measured as atmospheric pressure, but even if measurements are performed while changing the pressure in the ear canal 210 in various ways, the measurement can be completed in a short time.

[0074] According to the measurement device 1 of this embodiment, the stimulus sound may vary discontinuously over time in both sound pressure amplitude and frequency, or the energy at each frequency may be non-uniform. It is sufficient for the stimulus sound to provide some energy input for each frequency component in the measurement frequency range. Therefore, the stimulus sound may be a sound whose frequency varies over time with rhythm, such as music. In non-invasive measurement of auditory organ characteristics, mechanical stimulus sounds are not pleasant for the subject 200. Using music or other such stimulus sounds can reduce the subject 200's discomfort during measurement, thereby improving the medical quality of the measurement. In particular, when the subject 200 is an infant, the stimulus sound can be music such as a lullaby. Using lullabies or other such music can keep the infant subject 200 calm and relaxed during measurement, which is expected to result in accurate measurements. For example, in pediatric disease examinations, where multiple measurements may be performed under sedation, it may be necessary to avoid waking or arousing the subject during measurement. By using lullabies or other sounds as stimuli, measurements can be performed while maintaining a calm state, enabling accurate measurements to be achieved. These factors contribute to improving the medical quality and accuracy of this measurement.

[0075] The ability to measure hearing loss in young children, including infants, newborns, and adults is of great significance. Early detection and treatment of hearing disorders, especially in newborns and other young children, can contribute greatly to the subsequent development of language and other abilities.

[0076] [Variations] In the above-described embodiment, an analysis related to system identification assuming that the auditory organs of the subject 200 are a linear system has been described as an example. However, this is not limiting. For example, system identification assuming a nonlinear system may also be performed. Furthermore, in the above-described embodiment, a signal related to pressure fluctuations in the ear canal is used as a measurement signal obtained as a result of a stimulus sound acting on the subject. However, this is not limiting. The measurement signal may be, for example, a signal related to an electroencephalogram obtained as a result of a stimulus sound acting on the subject.

[0077] Therefore, the technology according to the above-described embodiments can also be applied to measurements related to, for example, auditory steady-state evoked responses (ASSR) and distortion product otoacoustic emissions (DPOAE). Generally, in ASSR measurements, sinusoidal amplitude modulated sounds (SAM sounds) at frequencies between 250 Hz and 8 kHz are used as stimulus sounds, and electroencephalograms (EEG) are used as measurement signals. By applying the technology according to the present embodiment, for example, music is used as stimulus sounds, and measurement signals of EEG are used to identify a nonlinear system, thereby obtaining results similar to those obtained by ASSR measurements. Generally, in DPOAE measurements, two pure tones with f2 between 1 and 10 kHz, satisfying the relationship f2 = 1.2f1, are used as stimulus sounds, and the 2f1-f2 component of the sound measured by a microphone is used as the measurement signal. By applying the technology according to the present embodiment, for example, music is used as stimulus sounds, and measurement signals obtained by a microphone are used to identify a nonlinear system, thereby obtaining results similar to those obtained by DPOAE measurements.

[0078] The present invention has been described above by showing preferred embodiments, etc., but it goes without saying that the present invention is not limited to the above-described embodiments, etc., and various modifications can be made within the scope of the present invention. [Explanation of symbols]

[0079] 1: Measuring equipment 10: Computer, 11: CPU, 12: Memory, 13: Storage, 14: Interface 22: Control unit, 32: Stimulus sound signal generation unit, 41: System identification unit, 42: Fourier transform unit, 43: Feature identification unit, 44: Auditory organ characteristic analysis unit, 52: Signal output unit, 54: Signal acquisition unit 60: AD / DA converter, 62: DA converter, 64: AD converter 70: Amplifier system, 72: Earphone amplifier, 74: Microphone amplifier 80: Probe, 82: Earphone, 83: Vibration membrane, 84: Microphone 91: Stimulus sound output section, 92: Sound receiving section, 93: Analysis device 200: subject, 210: ear canal, 222: eardrum, 224: ossicles, 225: malleus, 226: incus, 227: stapes, 232: cochlea

Claims

1. a signal output unit configured to output a stimulus sound signal for the stimulus sound, the stimulus sound including at least each frequency component of the measurement target frequency band, into the ear canal of the subject; a signal acquiring unit configured to acquire, as a measurement signal, a signal indicating a pressure fluctuation in the ear canal when the stimulation sound is output toward the ear canal of the subject; an analysis device configured to estimate an impulse response of the auditory organ of the subject by system identification based on the stimulus sound signal and the measurement signal, assuming that the auditory organ of the subject is a linear system or a nonlinear system, and to analyze the frequency characteristics of the auditory organ by Fourier transforming the estimated impulse response; A measuring device for the hearing organ comprising:

2. 2. The measurement device according to claim 1, wherein the analysis device is configured to derive a function indicating the sound pressure level in the ear canal versus frequency as the frequency characteristic of the subject's hearing organ, identify a feature of the function, and evaluate the characteristics of the subject's hearing organ based on the feature.

3. the feature quantity includes a value related to at least one of a minimum value and a maximum value of an SPL curve indicating the frequency characteristic of the sound pressure level, RF being a frequency related to a resonance of a middle ear calculated from the frequency indicating the minimum value and the frequency indicating the maximum value, and ΔSPL calculated from the difference between the minimum value and the maximum value, the analysis device is configured to evaluate the sound conduction characteristics of the subject's middle ear as the characteristics of the subject's auditory organ. The measuring device according to claim 2 .

4. The analysis device assumes that the auditory organ of the subject is a linear system, defines the stimulus sound signal as x(t) and the measurement signal as y(t), [Equation 1] configured to estimate an impulse response h(t) based on 4. The measuring device according to claim 1.

5. 4. The measurement device according to claim 1, wherein the analysis device is configured to process results of multiple measurements in the same way as results obtained from a single series of measurements to perform the system identification.

6. 4. The measurement device according to claim 1, wherein the sound pressure of the stimulus sound is less than 90 dB SPL.

7. 4. The measuring device according to claim 1, wherein the output time of the stimulus sound for one measurement is less than 2 seconds.

8. 4. The measuring device according to claim 1, wherein the stimulus sound is music or a sound whose sound pressure amplitude and frequency change discontinuously over time.

9. a stimulation sound output unit including an earphone configured to output the stimulation sound toward the ear canal of the subject based on the stimulation sound signal; a sound receiving unit including a microphone configured to acquire a signal indicating a pressure fluctuation in the ear canal when the stimulation sound is output; The measuring device according to claim 1 , further comprising:

10. outputting a stimulus sound into the ear canal of the subject based on a stimulus sound signal including at least each frequency component of the measurement target frequency band; acquiring, as a measurement signal, a signal indicating a pressure fluctuation in the ear canal when the stimulation sound is outputted toward the ear canal of the subject; estimating an impulse response of the auditory organ of the subject by system identification based on the stimulus sound signal and the measurement signal, assuming that the auditory organ of the subject is a linear system or a nonlinear system; Analyzing the frequency characteristics of the auditory organ by Fourier transforming the estimated impulse response. A method for measuring characteristics of the hearing organ, including:

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