A broadband short-time signal masking method for bone-conducted auditory evoked potential testing

Abstract

The present invention discloses a method for measuring the masking level of a wide-spectrum, short-duration signal used in a bone-conduction auditory evoked potential (BAP) test. The method comprises: measuring the stimulation force level of a subject's bone vibrator; placing the BAP vibrator of the evoked potential instrument at the mastoid process on one side of the subject, outputting a short-duration signal at a set intensity as a stimulus; and simultaneously applying white noise of varying intensities to both sides of the subject; and calculating, based on the stimulation force level and the subject's response, the contralateral noise masking level sufficient to mask the BAP signal. This invention, for the first time, derives the contralateral masking level of a BAP wide-spectrum, short-duration signal, providing a reference value for the practical application of BAP.

Description

Technical Field

[0001] The present invention relates to the technical field of signal measurement, in particular to a wide-spectrum short-time signal masking method for bone-conduction auditory evoked potential testing. Background Art

[0002] Auditory Brainstem Responses (ABRs) are short-latency auditory evoked potentials (ABRs) that originate in the inner ear, auditory nerve, and auditory brainstem and are recorded on the surface of the skull via air- or bone-conducted sound stimulation. They are capable of assessing the integrity of the auditory pathway from the inner ear to the auditory brainstem. Bone-conducted sound stimulation uses a bone vibrator to transmit the stimulus directly to the inner ear through the skull, bypassing the outer and middle ears, causing discharges in the auditory nerve.

[0003] The interaural attenuation (IA) of a bone vibrator is very small, which can easily cause cross-hearing. Therefore, masking is often considered a key issue in bone conduction ABR testing, and the masking method directly affects the test results. Short-duration signals, which are signals with a duration of less than 200ms, are commonly used as stimulation signals for brainstem auditory evoked potentials. Currently, the most commonly used broadband short-duration signals in this field are clicks. In recent years, CE-chirps have also been gradually applied. White noise, which also has a broadband spectrum, is often used to mask broadband stimulation sounds. For ABRs induced by bone conduction clicks and CE-chirps, there is currently no recognized standard for the interaural attenuation and efficient masking level (EML) of commonly used bone vibrators, and the masking methods used in bone conduction ABR testing vary.

[0004] Bone conduction ABR was first described by Yoshie in 1937. Although the output range of bone conduction ABR is limited compared to air conduction, studies have shown that under certain stimulation intensities, bone conduction can elicit clear, stable, reproducible, and well-differentiated waveforms similar to those of air conduction ABR. Because bone conduction ABR not only reflects the auditory function of the cochlea but also helps diagnose the type of hearing loss, it is of great significance for the detection of newborns with sensorineural and conductive hearing loss, the assessment of cochlear function, and the differential diagnosis of various hearing losses. Therefore, it has gradually gained widespread clinical application.

[0005] Among the short-term signals output by bone vibrators, only the click signal currently has a standardized benchmark equivalent threshold vibration force level (0dB nHL corresponds to 51.5dB peFL, GB / T 4854.6-2014). Other signals, such as chirps and tone bursts, lack standards. Furthermore, only the Radioear B-71 bone vibrator has a standardized benchmark equivalent threshold vibration force level; other bone vibrator models (such as the Radioear B-81) have not yet been included in the standard. This study found that the peak-to-peak equivalent threshold vibration force level of the subjective hearing threshold of CE-Chirp sounds was significantly lower than that of click sounds in young adults with normal hearing (P < 0.01), consistent with the design of CE-Chirp sounds that can overcome some of the traveling wave delay in the cochlea. According to the traveling wave theory of the cochlea, due to the cochlea's unique anatomical structure and morphological characteristics, high-frequency sounds primarily stimulate the base of the cochlear basilar membrane, while low-frequency sounds primarily stimulate the top of the membrane. Mid- and high-frequency stimuli continue to propagate toward the cochlear apex before completely attenuating, thereby affecting the vibration of the low-frequency basilar membrane and, consequently, the low-frequency hearing threshold. Clicks are broadband signals with a very short duration. CE-Chirps are a new type of linear frequency-modulated pulse tone that releases low-frequency signals first and high-frequency signals last. Figures 1(a) and 1(b) show the time domain waveforms of clicks and CE-Chirps, respectively, measured using a B&K3052 sound analyzer and a B&K4930 force coupler (IEC 60318-6). The characteristic of CE-Chirp that preferentially releases low-frequency sound signals can excite more nerve fibers within a certain period of time and improve the synchronization of nerve fiber discharge. That is, CE-Chirp sound can synchronize the vibration of the basilar membrane of the cochlea, overcome the partial traveling wave delay of the cochlea, and thus obtain a lower bone conduction hearing threshold of CE-Chirp sound.

[0006] Sound stimulation can be diffracted from the test ear or transmitted through the skull to the non-test ear and thus heard by the non-test ear, which is called cross-hearing. Bone conduction signals are sent through a bone vibrator, which can usually directly vibrate the skull and cause responses in both ears. Therefore, in order to avoid the participation of the non-test ear during the test, masking is usually required in the non-test ear during bone conduction testing. The attenuation that occurs when the sound stimulus is transmitted from one ear to the other is called interaural attenuation (IA) or transcranial transmission loss (TTL). Due to the small interaural attenuation value of bone conduction, bone conduction attenuation is generally considered to be 0dB in clinical applications. However, when it comes to masking of short-term bone conduction signals, there is no clear evidence as to whether the interaural attenuation of the signal needs to be taken into account. Summary of the Invention

[0007] This invention aims to overcome the shortcomings of the prior art by proposing a method for measuring the effective masking level of bone-conducted, wide-spectrum, short-duration signals. The method measures the effective noise masking level and interaural attenuation reference values for click and CE-Chirp stimuli delivered by a Radioear B-81 bone vibrator in normal hearing individuals, providing reference data for bone-conducted ABR masking methods.

[0008] To achieve the above object, the present invention proposes a method for measuring the masking level of a wide-spectrum, short-duration signal in a bone-conduction auditory evoked potential test, the method comprising:

[0009] Step 1) measuring the stimulation force level of the subject's bone vibrator;

[0010] Step 2) placing the bone vibrator of the evoked potential instrument on the mastoid process of one side of the subject and outputting a short-duration signal at a set intensity as a stimulus sound; and simultaneously applying white noise of varying intensities to both sides of the subject;

[0011] Step 3) Calculate the contralateral noise masking level that can just mask the bone conduction signal based on the stimulation force level and the subject's response.

[0012] As an improvement to the above method, step 1) specifically involves using an acoustic analyzer and a force coupler to measure the stimulation force level of the subject's bone vibrator.

[0013] As an improvement to the above method, the short-term signal in step 2) is a click sound or a CE-Chirp sound.

[0014] As an improvement to the above method, the step 2) provides white noise of different intensities to both sides of the subject; specifically includes: providing white noise of different intensities to both sides of the subject through insert earphones of a pure tone audiometer.

[0015] As an improvement to the above method, step 3) specifically includes:

[0016] When the short-term signal is a click sound, the contralateral noise masking level L EML-Contra for:

[0017] L EML-Contra = stimulation level + first range value Where, L EML-Contra The unit is dB SPL, the unit of stimulus level is dB peFL. The first range value is related to the contralateral hearing of the test ear. When the contralateral hearing of the test ear is normal or there is no difference between air conduction and bone conduction, the first range value is -16 to -12dB; when there is a difference between the contralateral hearing threshold of the test ear between air conduction and bone conduction, the first range value is -16 to -12dB + the difference between the contralateral hearing threshold between air conduction and bone conduction.

[0018] As an improvement to the above method, step 3) specifically includes:

[0019] When the short-term signal is CE-Chirp sound, the opposite side noise masking level L EML-Contra for:

[0020] L EML-Contra =stimulation force level + second range value, where the second range value is related to the contralateral hearing of the test ear. When the contralateral hearing of the test ear is normal or there is no difference between air conduction and bone conduction, the second range value is -10 to -6dB. When there is a difference between the air conduction and bone conduction hearing thresholds of the contralateral ear, the second range value is -10 to -6dB + the difference between the air conduction and bone conduction hearing thresholds of the contralateral ear.

[0021] As an improvement to the above method, the method further includes: before step 2), using an acoustic analyzer to calibrate the short-time signal.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] 1. This invention proposes for the first time a method for measuring the contralateral noise masking level, which uses the stimulus force level and combines different short-term signals to derive the corresponding contralateral noise masking level.

[0024] 2. This invention is the first to provide the corresponding contralateral noise masking level for CE-Chirp sound;

[0025] 3. This invention is the first to provide the corresponding contralateral noise masking level for the output signal of the Radioear B-81 bone vibrator;

[0026] 4. The present invention obtains the contralateral masking level of the bone-conducted wide-spectrum short-term signal for the first time, providing a reference value for the practical application of bone-conducted auditory evoked potentials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a time domain waveform diagram of a wide-spectrum, short-duration signal produced by the B-81 bone conduction earphone, wherein Figure 1(a) is a time domain waveform diagram of a click bone conduction signal; Figure 1(b) is a time domain waveform diagram of a CE-Chirp bone conduction signal;

[0028] Figure 2 This is the rear view of the headset being worn during testing. DETAILED DESCRIPTION

[0029] The method of the present invention comprises the following steps:

[0030] Step 1) measuring the stimulation force level of the subject's bone vibrator;

[0031] Step 2) placing the bone vibrator of the evoked potential instrument on the subject's mastoid process and outputting a short-duration signal at a set intensity as a stimulus sound; and simultaneously applying white noise of varying intensities to both sides of the subject;

[0032] Step 3) Calculate the contralateral noise masking level that can just mask the bone conduction signal based on the stimulation force level and the subject's response.

[0033] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0034] Example

[0035] The embodiments of the present invention provide a method for measuring the interaural attenuation value and effective masking level of a bone-conducted wide-spectrum, short-duration signal. The specific steps are as follows:

[0036] Before testing, the instrument's bone-conduction click or CE-chirp stimulus was calibrated using a sound analyzer (referring to the peak-to-peak equivalent reference threshold vibration force level (peRETVFL) specified in GB / T4854.6-2014 / ISO 389-6:2007). The headphones used were Radioear B-71 or Radioear B-81 bone-conduction headphones and ER-3A insert air-conduction headphones. The output sound pressure level of white noise was measured using a sound analyzer. The data were statistically analyzed. The short-term signal consisted of a click or CE-chirp.

[0037] The recommended masking method for the click signal is:

[0038] L EML-Contra (dB SPL) = stimulus force level (dB peFL) + first range value;

[0039] L EML-Contra The unit is dB SPL, the unit of stimulus level is dB peFL. The first range value is related to the contralateral hearing of the test ear. When the contralateral hearing of the test ear is normal or there is no difference between air conduction and bone conduction, the first range value is: -16 to -12dB; when there is a difference between the contralateral hearing threshold of the test ear between air conduction and bone conduction, the first range value is: -16 to -12dB + the difference between the contralateral hearing threshold between air conduction and bone conduction.

[0040] The recommended masking method for CE-Chirp signals is:

[0041] L EML-Contra (dB SPL) = stimulus force level (dB peFL) + second range value.

[0042] Among them, the second range value is related to the contralateral hearing condition of the test ear. When the contralateral hearing of the test ear is normal or there is no difference between air conduction and bone conduction, the second range value is: -10 to -6dB; when there is a difference between the air conduction and bone conduction hearing thresholds of the contralateral ear, the second range value is: -10 to -6dB + the difference between the air conduction and bone conduction hearing thresholds of the contralateral ear.

[0043] Verification experiment

[0044] 1. Methods and Steps

[0045] 1.1 Subjects: Twenty-six young adults (52 ears) aged 18 to 25 years with normal hearing were enrolled. The mean age was 22.5 ± 1.9 years. Thirteen subjects were male (26 ears) and 13 were female (26 ears). All 26 subjects had normal external ears, normal tympanograms, and bilateral acoustic reflexes. They had no history of ototoxic medications, high noise exposure, otologic disorders, or psychiatric disorders. Pure-tone audiometry thresholds at 250, 500, 1000, 2000, 4000, 6000, and 8000 Hz were ≤15 dB HL, and subjective audiometry thresholds for bone-conduction clicks and CE-chirps were ≤10 dB nHL.

[0046] 1.2 Test Instruments and Calibration Methods: All tests were conducted in a soundproof room with a noise floor of less than 30 dB(A) and in compliance with the national standard GB / T16296.2-2016. Short-term signals were provided using an Interacoustics Eclipse evoked potential meter and Radioear B-81 bone conduction headphones, while white noise signals were provided using a MEDSEN Astera pure-tone audiometer and ER-3A insert earphones. Bone conduction stimulation used alternating click and CE-Chirp signals. Before testing, a B&K3052 acoustic analyzer and a B&K4930 force coupler were used to calibrate the instrument for bone-conducted click and CE-Chirp stimuli at different stimulation rates (7.1 times / s, 11.1 times / s, 19.3 times / s, and 45.1 times / s). The calibration was based on the peak-to-peak equivalent reference equivalent threshold vibration force level (peRETVFL) specified in GB / T 4854.6-2014 / ISO389-6:2007, that is, 0 dB nHL corresponds to 51.5 dB peFL.

[0047] Test method: The bone vibrator of the evoked potential instrument was placed on the subject's mastoid process, and sounds were given at the intensity of 30dB nHL (81.5dBpeFL) and 40dB nHL (91.5dBpeFL), respectively. At the same time, white noise of different intensities was given to both sides through the insert earphones of the pure tone audiometer (see Figure 2 ), with the left ear as the test ear, the stimulus sound was delivered through the Radioear B-81 bone conduction earphones, and the white noise masking was delivered through the ER-3A insert earphones. The white noise intensity of both ears was increased or decreased simultaneously in 2dB steps, and the noise level that just masked the corresponding bone conduction signal was found, which was recorded as the bilateral effective masking level L EML-Bi Then gradually reduce the masking noise level of the ear opposite to the bone vibrator, and find the noise level that can just mask the bone conduction signal, which is recorded as the contralateral effective masking level L EML-Contra Calculate the interaural attenuation (IA), that is, the bilateral effective masking level L EML-Bi and the opposite effective masking level L EML-Contra The difference (IA=L EML-Bi -L EML-Contra After the test, the white noise sound pressure level of the insert earphone output was measured using a B&K3092 sound analyzer and a B&K4157 artificial ear.

[0048] 1.3 Statistical Analysis: SPSS 18.0 software was used to statistically analyze the peak-to-peak equivalent threshold vibration force levels of the B-81 bone vibrator click and CE-Chirp signals, the effective masking noise levels of different signal types and intensities, the interaural attenuation values for different genders, and the output force levels of bone conduction short-term signals at different stimulation rates. This analysis determined the effective masking levels (EMLs) of the bone conduction click and CE-Chirp signals for young adults with normal hearing in this laboratory.

[0049] 2 Results

[0050] 2.1 Subjective audiometric peak-to-peak equivalent threshold vibration level of bone conduction short-term signals in young people with normal hearing

[0051] Table 1 shows the subjective peak-to-peak equivalent threshold vibration force levels (PETVFL) for click and CE-Chirp sounds in young adults with normal hearing, measured by gender. Compared to the peak-to-peak equivalent threshold vibration force level (peRETVFL) for clicks specified in GB / T 4854.6-2014 / ISO 389-6:2007 (i.e., 0 dB nHL corresponds to 51.5 dB peFL), the results of this study are higher. The results showed that the PETVFL of CE-Chirp signals was significantly lower than that of click signals in both males and females, with a significant difference (P < 0.01). The PETVFL of bone conduction short-duration signals in females was slightly lower than that in males, with a statistically significant difference (P < 0.05).

[0052] Table 1 Peak-to-peak equivalent threshold vibration force level of bone conduction short-term signals of different genders

[0053]

[0054] Note: *P<0.05, △ P<0.05

[0055] 2.2 Effective noise masking level of bone conduction short-term signals in young people with normal hearing

[0056] The stimulus levels, peak-to-peak equivalent vibration force levels, and bilateral and contralateral effective noise masking sound pressure levels of the short-duration bone-conduction click and CE-Chirp signals are shown in Table 2. The bilateral and contralateral effective noise masking levels of click and CE-Chirp sounds showed a positive linear correlation, with a significant correlation (P < 0.01), and both levels increased with increasing stimulus intensity.

[0057] Table 2 Effective noise masking levels of different types of bone conduction short-term signals (n=52)

[0058]

[0059] 2.3 Interaural attenuation of bone conduction short-term signals in young people with normal hearing

[0060] The interaural attenuation values for bone-conducted clicks and CE-Chirps in young adults with normal hearing were 3.46±2.34dB and 3.38±2.03dB, respectively. There was no statistically significant difference in the interaural attenuation values for the two bone-conducted short-duration signals (P>0.05). The interaural attenuation values for bone-conducted clicks and CE-Chirps by gender are shown in Table 3. The interaural attenuation values for both bone-conducted signals were slightly greater in women than in men (P<0.05).

[0061] Table 3 Interaural attenuation values of bone conduction short-term signals in different genders (n=26)

[0062]

[0063] Note: *P<0.05, △ P<0.05

[0064] 2.4 Effects of different stimulation rates on the output force level of bone conduction short-term signals

[0065] The output force levels of the B-81 bone vibrator were measured using a B&K3092 acoustic analyzer at 7.1, 11.1, 19.3, and 45.1 times / s. Table 4 shows the output force levels of the click and CE-Chirp bone conduction signals at different stimulation rates. At different stimulation rates, the output force levels of both the bone conduction click and CE-Chirp signals showed a linear relationship with the stimulation intensity (P < 0.01). The bone conduction output force level increased with increasing stimulation intensity, and no significant statistical differences were found between the different stimulation rates and the output force levels of the bone conduction short-term signals (P > 0.05).

[0066] Table 4 Peak-to-peak equivalent threshold vibration force levels of two bone conduction short-term signals at different stimulation rates

[0067]

[0068] In this experiment, the interaural attenuation of click and CE-Chirp sounds ranged from 0 to 8dB, with an average of 3dB. Therefore, it can be considered that the interaural attenuation of the click and CE-Chirp sounds output by the B-81 bone vibrator is very small. Cross-hearing is prone to occur in bone conduction ABR testing, and regular masking is required during bone conduction testing.

[0069] The results of this experiment indicate that women experience lower peak-to-peak equivalent threshold vibration levels for click and CE-Chirp sounds, and greater IA than men. This may be due to differences in the anatomy of the skull, brainstem, and peripheral auditory system between men and women. These differences may also be reflected in the energy transmission of bone vibrators.

[0070] Both click and CE-Chirp stimuli are broad-spectrum, so white noise, also broad-spectrum, is used for masking. However, unlike the narrowband masking noise reference levels for pure-tone audiometry, which are already documented in the GB / T 4854.4-1999 standard, masking for bone conduction ABR testing using short-duration signals remains largely undefined or standardized. The national standard GB / T 4854.6-2014 specifies standardized peak-to-peak equivalent threshold vibration force levels for the click output by the Radioear B-71 bone vibrator: 0 dB nHL for a click is equivalent to 51.5 dB peFL. Since there is currently no standardized reference threshold vibration force level for the click and CE-Chirp sounds output by the Radioear B-81 bone vibrator, the impact of using different bone vibrator models and different stimuli (such as the CE-Chirp) requires further investigation. Furthermore, during bone conduction ABR testing, the bone vibrator delivers a short-duration vibration signal, measured in dBpeRETVFL, with a baseline level of 1 μN. The masking signal delivered to the contralateral ear is typically a continuous noise signal delivered via air conduction (usually using insert earphones), measured in dB SPL, with a baseline level of 20 μPa. This is the effective masking level (EML) of the bone conduction ABR test, expressed in dB SPL. This requires individual laboratories to measure the specific EML value. Existing masking methods for bone conduction ABR testing vary. Some researchers recommend using 40-50 dB broadband noise for masking when conducting bone conduction auditory brainstem responses. Yu Chongxian et al., when testing infants and young children with normal hearing, chose to mask the non-test ear with white noise 20 dB higher than the stimulus level. Richy Lau et al. recommended that 500Hz 20 and 30dB nHL short pure tone stimuli be masked with 72 and 82dB SPL white noise respectively; 20, 30, and 40dB nHL short pure tone stimuli at 2000Hz be masked with 62, 72, and 82dB SPL white noise respectively.

[0071] Table 2 shows that the effective masking noise levels of both the bilateral and contralateral sides of click and CE-Chirp sounds increase with the increase of the stimulus level, showing a positive linear relationship. The comparison of the sound pressure levels of bone-conducted click and CE-Chirp sounds and contralateral white noise in young people with normal hearing found that the contralateral effective noise masking level L of the click sound at the nominal value of 0dB nHL (i.e. 51.5dB peRETVFL) is 0dB. EML-Contra The L of the CE-Chirp sound 0dB nHL nominal value (and 51.5dBpeRETVFL) is 36-39dB SPL, with an average of 38dB SPL. EML-ContraThe recommended masking method for bone conduction short-term ABR signals in young people with normal hearing is:

[0072] Click on the opposite side EML: L EML-Contra (dB SPL) = stimulus level (dB nHL) + 38dB;

[0073] Click on the opposite side EML: L EML-Contra (dB SPL) = stimulus level (dB peFL) - 14dB;

[0074] CE-Chirp contralateral EML: L EML-Contra (dB SPL) = stimulus force level (dB peFL) - 8dB.

[0075] Different laboratories use different bone conduction ABR stimulation rates in clinical practice. This study showed that the output levels of click and CE-Chirp bone conduction signals at different stimulation rates (7.1, 11.1, 19.3, and 45.1) were linearly correlated with the stimulus intensity (P < 0.01), with no statistically significant differences (P > 0.05). Therefore, stimulation rate does not affect the output level of the short-term bone conduction signal. Currently, when using clicks for bone conduction auditory brainstem response testing in this study, white noise at 30 to 40 dB SPL above the stimulus intensity in the contralateral non-test ear is typically used for masking. Combined with these experimental results, this method generally agrees with these findings.

[0076] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A method for masking a wide-spectrum, short-duration signal for bone-conduction auditory evoked potential testing, providing reference data for bone-conduction ABR masking by providing effective noise masking levels and interaural attenuation reference values for click or CE-Chirp stimuli for normal hearing. The method comprises: Step 1) measuring the stimulation force level of the subject's bone vibrator; Step 2) placing the bone vibrator of the evoked potential instrument on the mastoid process of one side of the subject and outputting a short-term signal at a set intensity as a stimulus sound, wherein the short-term signal is a click sound or a CE-Chirp sound; and delivering white noise of different intensities to both sides of the subject through the insert earphones of the pure tone audiometer; Step 3) Calculating the contralateral noise masking level that can just mask the bone conduction signal based on the stimulation level and the subject's response; When the short-term signal is a click sound, the contralateral noise masking level L EML-Contra for: L EML-Contra = stimulation level + first range value Among them, L EML-Contra The unit is dB SPL, the unit of stimulus level is dB peFL. The first range value is related to the contralateral hearing condition of the test ear. When the contralateral hearing of the test ear is normal or there is no difference between air conduction and bone conduction, the first range value is -16 to -12dB. When there is a difference between the contralateral hearing threshold of the test ear between air conduction and bone conduction, the first range value is -16 to -12dB + the difference between the contralateral hearing threshold between air conduction and bone conduction. When the short-term signal is CE-Chirp sound, the opposite side noise masking level L EML-Contra for: L EML-Contra = stimulation level + second range value Among them, the second range value is related to the contralateral hearing of the test ear. When the contralateral hearing of the test ear is normal or there is no difference between air conduction and bone conduction, the second range value is -10 to -6dB. When there is a difference between the air conduction and bone conduction hearing thresholds of the contralateral ear, the second range value is -10 to -6dB + the difference between the air conduction and bone conduction hearing thresholds of the contralateral ear.

2. The method for masking a wide-spectrum, short-duration signal for bone-conduction auditory evoked potential testing according to claim 1, characterized in that: The step 1) specifically involves measuring the stimulation force level of the subject's bone vibrator using an acoustic analyzer and a force coupler.

3. The method for masking a wide-spectrum, short-duration signal for bone-conduction auditory evoked potential testing according to claim 1, characterized in that: The method further comprises: before step 2), using a sound analyzer to calibrate the short-time signal.

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