CN102973277B - Frequency following response signal test system - Google Patents

Abstract

The invention relates to a frequency following response signal testing system, which is characterized in that it includes a computer, a D/A acquisition card, a multi-channel A/D acquisition card, a micro speaker, a micro microphone, a preamplifier, a body surface disc electrode, a high Impedance input stage, bioelectric amplifier and earplugs; ear canal sound pressure monitoring module and frequency following response signal extraction detection module are set in the computer; ear canal sound pressure monitoring module is used to collect and record the sound pressure signal in the ear canal, and collect The sound pressure signal is analyzed and processed offline, that is, the collected sound pressure signal is compared with the preset judgment criteria, and the signal segment that does not meet the normal sound pressure of the ear canal is eliminated. The frequency following response signal test platform is used to collect the FFR signal, and The collected FFR signal is analyzed and processed offline, that is, the FFR signal corresponding to the signal segment of the normal sound pressure of the ear canal is pre-screened and processed to complete the extraction and display of the subject's FFR signal. The invention can be widely used in the detection of FFR signals.

Description

A Frequency Following Response Signal Test System

technical field

The invention relates to an auditory and electrophysiological testing system, in particular to a frequency-following response signal testing system.

Background technique

Frequency Following Response (FFR) is to record the steady-state response of the brainstem to sound signals on the scalp. , ABR) were recorded in the same way, and the latency was slightly longer than the brainstem auditory evoked potential. It is a concentrated expression of the phase-locked response of brainstem neurons to periodic components in sound, and is closely related to the brain's perception of sound pitch and pitch intensity attributes.

The research and application of FFR can be roughly divided into two aspects, one is the brain's encoding of complex sounds, and the other is the brain's encoding and perception of sound pitch information. Complex sound refers to the sound with the characteristics of the human environment, including harmonic structure, dynamic amplitude modulation, and rapid time-frequency fluctuations, such as speech and music, which contain a large number of complex sound components. Both transient and steady-state sounds can be components of complex sounds. For example, for a syllable composed of consonant vowels, the consonant part is usually a transient component, while the vowel part is a periodic steady-state component. Other complex sounds containing periodic components include chords in music, etc. ABR induced by complex sounds (referred to as complex ABR in the literature, abbreviated as cABR) is an important means to study the encoding of complex sounds by the brain. It corresponds to the transient and steady-state components in complex sounds. cABR is also composed of transient And the steady-state continuous response, the steady-state continuous response is the frequency-following response, along with the study of cABR, the frequency-following response is applied to the study of the brain's coding mechanism for consonant vowels, as well as special language barriers, reading disorders and diseases such as autism spectrum disorder.

The research on pitch coding and perception is another important main line of FFR-related research. People's research on FFR has developed from a single pure tone as a stimulus to a compound sound of two pure tones, thus observing the distortion products in FFR. Then it is evoked by synthetic vowels, including vowels whose frequency components do not change with time and vowels whose pitch changes with time. In 2004, Krishnan used the four tones of the Chinese syllable "yi" as a stimulus to induce FFR, and used the autocorrelation graph method to extract the fundamental frequency information from the FFR signal. The obtained fundamental frequency was very consistent with the fundamental frequency information of the stimulus. It shows that the FFR signal carries the pitch information of the pitch time-varying speech, which reflects the coding function of the brainstem to the pitch information.

In the comparison of the pitch perception hearing performance of different hearing groups and their FFR signals, a series of studies have proved from several perspectives that the information contained in the FFR signals can reflect the differences in the pitch perception ability of these groups. This is well summarized in Krishnan and Gandour's 2009 review article. Krishnan et al. compared the FFR responses elicited by the four tones of the Chinese syllable "yi" in Chinese and English-speaking subjects, and found that the tone strength index extracted from the FFR of the Chinese-speaking subjects and the FFR signal The pitch-following accuracy of stimuli was better than that of native English speakers, which proved that FFR reflects the advantage of Chinese native speakers over non-Chinese native speakers in the perception of language-specific pitch features. The research of Wong et al. pointed out that among the people whose native language is non-tonal language, the frequency following response of musicians follows the pitch height of Chinese tones more accurately than that of non-musicians, which proves that FFR reflects the effect of listening training experience on pitch perception ability. Influence, not only that, Song et al.'s research also found that after a short-term training of native English-speaking adults using Chinese tones, their frequency-following responses became more accurate in following the pitch height of Chinese tones. After language training, this change in the FFR signal on the one hand explains the plasticity of the auditory brainstem, on the other hand, it also shows that the FFR signal can sensitively reflect the coding characteristics of the brainstem to the sound signal, and at the same time makes people more expect FFR Possibly a good correlation between the signal and a person's ability to perceive pitch. In addition to comparing different groups of people, Krishnan observed the relationship between the perception of pitch salience and FFR in the subject group under different sound conditions in the study of FFR and behavioral indicators of pitch salience. The research used the iterated ripples noise method to synthesize a series of sounds with different degrees of periodic regularity, which would cause different perceptions of pitch salience. Experiments indirectly measure the pitch salience of these sounds perceived by the subject's frequency resolution threshold for the fundamental frequency of the sound, and it is found that the pitch extracted from the FFR signal is significant when compared to the experimental data using a weighted correlation analysis. There are correlations between sexual indicators and their behavioral measures.

Previous studies have pointed out that FFR signals carry the information encoded by the brainstem on sound pitch. The FFR signal contains enough information to reflect the differences in the pitch perception ability caused by listening experience among different groups of people or the different representations of the subject groups on the pitch salience information under different sound conditions, and the FFR signal has sufficient sensitivity To reflect the changes in brainstem processing of sound information formed by short-term listening training. These phenomena indicate that the FFR signal may have potential application value in the evaluation of the pitch perception ability of cochlear implant wearers, and it may provide an objective evaluation method of the pitch perception ability that contains rich neural activity information, which is different from behavioral tests. . At present, psychoacoustic behavioral tests are widely used to evaluate the ability of pitch perception, and there are a series of shortcomings in the evaluation methods based on this. First of all, psychoacoustic experiments usually require the subjects to cooperate consciously to complete auditory-related tasks, and the experimental results are easily affected by many subjective factors, which reduces the reliability; secondly, accurate psychoacoustic measurements require the subjects to be ) tasks, the performance in the task is measured multiple times, the experimental process is more complicated, and it is difficult to carry out in the clinical population; thirdly, the psychoacoustic experimental methods vary widely, and it is difficult to unify the psychoacoustic experimental methods used in various studies. Among them, the corpora used are not the same, which makes the comparison between different research methods difficult; finally, the psychoacoustic experimental method can only evaluate the effect of the method used, and cannot provide information directly related to the perceived neural activity. information, which provides limited guidance for method development. Therefore, it is also of great significance to evaluate the ability of pitch height perception through the test of FFR signal.

In the existing domestic and foreign technologies, there is no system for testing the ability of pitch perception through FFR. At present, instruments related to FFR or ABR in domestic sales include Neuroscan, Biosemi and TDT. BioSemi is mainly a hardware system, not equipped with data acquisition and software support system for automatic signal screening and processing. It is difficult for psychology or medical users to process data later, so it is not suitable for automatic acquisition of FFR signals; TDT mainly It is used to collect click-induced ABR, which is used in many hospitals in China, and is also used in psychoacoustic experiments, but it is rarely used for FFR signal collection. In the existing research, Aiken et al. used TDT as the stimulation system and used Neuroscan to collect the FFR response of the scalp, but did not use TDT to collect the FFR signal. In addition, TDT itself is not equipped with stimulation software and automatic acquisition software, and it is not yet a system that can perform a complete FFR signal test. Neuoscan is the brand with the most users in China. It is currently used by nearly 70 laboratories, involving psychology, medicine, brain-computer interface, signal processing, sports psychology and other fields. However, the stimulation artifacts during signal acquisition and the screening of FFR signals need to be manually removed, and the price is expensive. In view of the current situation, it is urgent to develop a perfect and efficient FFR detection system that can automatically screen the original signal.

Contents of the invention

In view of the above problems, the purpose of the present invention is to provide a frequency follower response signal that can not only obtain a high signal-to-noise ratio simply and efficiently, but also has the function of monitoring the sound pressure signal of the ear canal and can automatically filter the FFR signal. Follow the response signal to test the system.

To achieve the above object, the present invention takes the following technical solutions: a frequency following response signal testing system, characterized in that: it includes a computer, a D/A acquisition card, a multi-channel A/D acquisition card, an acoustic sensor, a preamplifier, Body surface disc electrodes, high-impedance input stage, bioelectrical amplifier and earplugs, the acoustic sensor includes a micro-speaker and a micro-microphone; the computer is connected to the D/A acquisition card and the multi-channel A/D acquisition card through a corresponding data interface , the input end of the micro-speaker is connected to the output end of the D/A acquisition card, the output end of the micro-speaker is inserted in the earplug through a sound tube, and the input end of the micro microphone is connected through a transmission sound tube Inserted in the earplug, the output end of the miniature microphone is connected to the input end of the multi-channel A/D acquisition card through the preamplifier; The recording electrode, the reference electrode set at the mastoid of the subject's earlobe on the same side as the earplug, and the ground electrode set at the brow center of the subject, the output terminals of the recording electrode, reference electrode and ground electrode are respectively connected to the The input end of the high-impedance input stage is connected, and the output end of the high-impedance input stage is connected with the input end of the multi-channel A/D acquisition card through the bioelectric amplifier; the frequency following response signal test is set in the computer Platform, the frequency following response signal test platform includes a test parameter setting module, a test signal generation module, a test signal stimulation module, an ear canal sound pressure monitoring module and a frequency following response signal extraction detection module; the test parameter setting module is used to set The frequency and intensity of the stimulation sound, the test signal generating module generates a corresponding digital stimulation signal according to the set stimulation sound parameters, and sends it to the test signal stimulation module, and the test signal stimulation module sends the digital stimulation signal to the The D/A acquisition card, the D/A acquisition card converts the digital stimulation signal into an analog voltage stimulation signal, and sends the analog voltage stimulation signal to the micro-speaker, and the micro-speaker converts the analog voltage stimulation signal into a sound Stimulate the signal, and send the sound stimulation signal to the human ear through the earplug, the ear canal sound pressure monitoring module and the frequency following response signal extraction detection module simultaneously collect the signal, and the ear canal sound pressure monitoring module is used for Collect and record the sound pressure signal in the ear canal, and analyze and process the collected sound pressure signal offline, that is, compare the collected sound pressure signal with the preset judgment criteria, and eliminate the signal segments that do not meet the normal sound pressure of the ear canal. The frequency following response signal extraction and detection module is used to collect FFR signals, and perform off-line analysis and processing on the collected FFR signals, that is, pre-screen and process the FFR signals corresponding to the signal segment of normal sound pressure in the ear canal, and complete the test or FFR signal extraction and display.

The ear canal sound pressure monitoring module includes an ear canal sound pressure acquisition module, an ear canal sound pressure recording module, an ear canal sound pressure judging module, an ear canal sound pressure elimination module, and a result display module; The acoustic signal is sent to the preamplifier after the acoustic-electric conversion, and the preamplifier amplifies the signal and sends it to the ear canal sound pressure acquisition module through the multi-channel A/D acquisition card. The ear canal sound pressure acquisition module sends the signal to the ear canal sound pressure recording module, and the ear canal sound pressure recording module is used to record the collected sound pressure value and send it to the ear canal sound pressure judgment module, the ear canal sound pressure judging module and the ear canal sound pressure elimination module perform off-line analysis and processing of the sound pressure signal, specifically: the ear canal sound pressure judging module analyzes the collected sound pressure according to a preset judging criterion The value is judged, and the judgment result is sent to the ear canal sound pressure elimination module, and the ear canal sound pressure elimination module rejects the sound pressure signals that meet the judgment criteria, and sends the remaining sound pressure signals after elimination to the result display module display.

The judgment criterion needs to meet the following three conditions at the same time: 1) The difference between the maximum value and the minimum value of the collected sound pressure signal is within the difference between the maximum value and the minimum value of the theoretical sound pressure corresponding to the stimulus sound intensity ±6dB SPL. 2) The maximum value of the collected sound pressure signal is greater than the maximum value of the sound pressure corresponding to the stimulus sound intensity + 6dB SPL; 3) The sound pressure signal in the ear canal recorded when the stimulus sound is emitted is averaged according to the acquisition time Divided into five sections, the maximum value of the sound pressure signal of a certain section is less than 75% of the maximum value of the overall sound pressure of the five sections, or the minimum value of the sound pressure signal of a certain section is greater than 75% of the minimum value of the overall sound pressure of the five sections.

The frequency following response signal extraction and detection module includes an FFR signal acquisition and recording module, an FFR signal processing module and a result display module; the recording electrode, reference electrode and ground electrode of the body surface optical disk electrode detect the FFR signal of the subject's head, and send it to the high-impedance input stage to obtain the FFR voltage signal, and the high-impedance input stage sends the FFR voltage signal to the bioelectric amplifier for filtering and amplification processing, and sends the filtered and amplified FFR voltage signal to The multi-channel A/D acquisition card, the multi-channel A/D acquisition card converts the FFR voltage signal into an FFR digital signal and sends it to the FFR signal acquisition and recording module, and the FFR signal acquisition and recording module sends the FFR digital signal To the FFR signal processing module, the FFR signal processing module performs off-line analysis and processing on the FFR digital signal data to obtain the subject's FFR signal, and sends the extracted FFR signal to the result display module for display.

The FFR signal processing module includes a measurement screening module, a signal noise reduction module, a signal-to-noise ratio estimation module and a data selection module; The remaining signals are sent to the signal noise reduction module, and the signal noise reduction module performs Wiener filtering, coherent averaging and bandpass filtering on the FFR digital signals of each test segment tested by the subject, and processes The final signal is sent to the SNR estimation module; the SNR estimation module calculates the SNR of the FFR digital signal, and sets the SNR filter condition according to the SNR of the calculated FFR digital signal, and The signal-to-noise ratio screening condition is sent to the data selection module, and the data selection module rejects FFR signals with too low signal-to-noise ratio according to the signal-to-noise ratio screening condition.

The present invention has the following advantages due to the adoption of the above technical scheme: 1. The present invention includes various hardware measuring equipment and a frequency following response signal testing platform, and the subject uses the recording electrode, the ground electrode and the reference electrode of the disc electrode on the body surface during detection. Placed at the corresponding test site, the body surface disc electrode collects the FFR signal induced by the stimulus sound, and sends the collected FFR signal to the frequency follower response signal collection through the high-impedance input stage, bioelectric amplifier and multi-channel A/D acquisition card in turn. The extraction module performs processing, and the present invention only needs one acquisition channel (three electrodes) to realize the acquisition and processing of the frequency following response signal, so the FFR signal of the subject can be extracted objectively, simply and efficiently. 2. When the frequency following response signal acquisition and extraction module of the present invention processes the collected FFR signal, it can automatically complete the screening and elimination of the FFR signal through the measurement screening module, signal noise reduction module, signal-to-noise ratio estimation module and data selection module , compared with the existing manual removal method, not only the efficiency of extracting FFR signal is improved, but also the FFR signal with high signal-to-noise ratio can be obtained. 3. Due to the slight movement of the head of the subject during the test, which may cause a slight displacement of the earphone in the ear canal, or affect the good contact between the disc electrode on the body surface and the skin, for the current FFR test system Defects in the FFR detection method under stimulus response, the present invention is provided with an ear canal sound pressure monitoring module, through which the ear canal sound pressure signal collected and recorded simultaneously with the FFR signal can be analyzed and processed. The sound pressure signal in the canal that does not conform to the normal sound pressure of the ear canal is eliminated, so as to eliminate the frequency following response signal corresponding to the abnormal sound pressure signal segment of the ear canal, and only the FFR signal corresponding to the signal segment of the normal sound pressure of the ear canal is processed. Pre-screening and processing, the FFR signal processing module not only effectively solves the problem of alignment of stimuli and signal-to-noise ratio in subsequent signal processing through steps such as measurement screening, signal noise reduction, signal-to-noise ratio estimation, and data selection based on the basis of signal-to-noise ratio screening. Relatively low, complex testing and other issues, and further improve the signal-to-noise ratio of the detected FFR signal. The invention can be widely used in the detection of FFR signals.

Description of drawings

Fig. 1 is a structural representation of the present invention, wherein, the electroacoustic shielding room is an experimental environment;

Fig. 2 is a structural schematic diagram of the ear canal sound pressure monitoring module of the present invention;

Fig. 3 is a schematic structural diagram of a frequency following response signal extraction detection module of the present invention;

Fig. 4 is a schematic structural diagram of the FFR signal processing module of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, the present invention comprises a computer 1 that is loaded with windows system, a D/A acquisition card 2, a multi-channel A/D acquisition card 3, an acoustic sensor 4, a preamplifier 5, an integrated table CD Electrodes 6 , a high-impedance input stage 7 , a bioelectric amplifier 8 and a soft earplug (not shown in the figure); the acoustic sensor 4 includes a miniature speaker 41 and a miniature microphone 42 . In order to isolate the sound in the test subject's ear canal from the external sound, the output end of the micro-speaker 41 and the input end of the micro-microphone 42 are inserted into the same earplug.

Computer 1 of the present invention connects the input end of D/A acquisition card 2 and the output end of multi-channel A/D acquisition card 3 respectively by corresponding data interface, and D/A acquisition card 2 converts digital signal into analog signal and sends it To the micro speaker 41, the multi-channel A/D acquisition card 3 converts the received multi-channel analog signals into digital signals and sends them to each module in the computer 1 for processing.

Microspeaker 41 of the present invention comprises two electro-acoustic transducers, and the input end of each electro-acoustic transducer connects the output end of D/A acquisition card 2, and the output end of each electro-acoustic transducer passes through The acoustic tube is connected to the earplug, and the electro-acoustic transducer converts the electrical stimulation signal into an acoustic stimulation signal, which is used to induce a frequency-following response signal. Miniature loudspeaker 41 can adopt the various products of prior art, adopt the ER2 plug-in type earphone that Etymotic Company produces when such as the present invention detects, and it has the continuous output capability more than 106dB SPL, 16kHz operating bandwidth and interaural isolation more than 70dB.

The miniature microphone 42 of the present invention includes an acoustic-electric transducer, which is used to convert the received acoustic signal in the subject's ear canal into an analog voltage signal, and the input end of the acoustic-electric transducer is inserted in the In the earplug, the output end of the acoustic-electric transducer sends the analog voltage signal to the preamplifier 5 through wires. The miniature microphone 42 can adopt various products of the prior art, such as the ER-10B+ produced by the U.S. Etymotic Company when the present invention detects.

The preamplifier 5 of the present invention is used to amplify the electrical signal output by the miniature microphone 41, the amplification factor can be adjusted according to actual needs, and the adjustment factor can be selected from 0dB, 20dB and 40dB. In order to avoid the impact of the ground loop, the present invention The Preamplifier 5 is powered by two 9V batteries. The input end of the preamplifier 5 is connected to the output end of the miniature microphone 42, and the output end of the preamplifier 5 is connected to the input end of the multi-channel A/D acquisition card 3 through a TRS interface.

The body surface disc electrode 6 of the present invention is used to collect frequency following response signals, and it includes a recording electrode arranged at the central point (forehead middle hairline) Cz of the subject's head, and a recording electrode arranged on the same side as the earplug A reference electrode at the earlobe mastoid of the subject and a ground electrode set at the center of the subject's brow Fpz.

The high-impedance input stage 7 of the present invention is used to increase the input impedance of the detection circuit, which is beneficial for recording bioelectrical signals.

The bioelectric amplifier 8 of the present invention is used for filtering and amplifying the frequency-following response signal collected by the disc electrode 6 on the body surface. Wherein, the input end of the high-impedance input stage 7 is respectively connected to the output ends of the recording electrode, the reference electrode and the ground electrode in the disc electrode 6 on the body surface, and the output end of the high-impedance input stage 7 is connected to the input end of the bioelectric amplifier 8. The output end of the amplifier 8 is connected to the input end of the multi-channel A/D acquisition card 3 through a TRS interface. The gain of the bioelectrical amplifier 8 of the present invention can be selected according to actual needs, and is not limited here.

A frequency follow response signal test platform 9 is set in the computer 1, and the frequency follow response signal test platform 9 includes a test parameter setting module, a test signal generation module, a test signal stimulation module, an ear canal sound pressure monitoring module and a frequency follower Response signal extraction detection module.

The test parameter setting module is used to set the frequency and intensity of the stimulation sound; the test signal generation module generates the corresponding digital stimulation signal according to the stimulation sound parameters set, and sends it to the test signal stimulation module; the test signal stimulation module sends the digital stimulation signal to D/A acquisition card 2, D/A acquisition card 2 converts the digital stimulation signal into an analog voltage stimulation signal, and sends the analog voltage stimulation signal to one of the electro-acoustic converters, and the electro-acoustic converter converts the analog voltage stimulation signal Convert it into an acoustic stimulation signal, and send the acoustic stimulation signal to the human ear through the earplug; the ear canal sound pressure monitoring module and the frequency following response signal extraction and detection module simultaneously collect the signal, and the ear canal sound pressure monitoring module is used to collect and record The sound pressure signal in the ear canal is analyzed and processed offline, that is, the collected sound pressure signal is compared with the preset judgment criteria, and the signal segments that do not meet the normal sound pressure of the ear canal are eliminated. The frequency following response signal extraction and detection module is used to collect FFR signals, and perform offline analysis and processing on the collected FFR signals, that is, pre-screen and process the FFR signals corresponding to the signal segment of the normal sound pressure of the ear canal, and complete the subject's FFR Signal extraction and display.

As shown in Figure 2, in the above embodiment, the ear canal sound pressure monitoring module includes an ear canal sound pressure acquisition module 911, an ear canal sound pressure recording module 912, an ear canal sound pressure judging module 913, an ear canal sound pressure elimination module 914 and Result display module 915; Miniature microphone 41 sends to the preamplifier 5 after the acoustic signal in the ear canal that receives is converted into electricity, and the preamplifier 5 amplifies the signal and sends it to the multi-channel A/D acquisition card 3. The ear canal sound pressure acquisition module 911, the ear canal sound pressure acquisition module 911 sends the signal to the ear canal sound pressure recording module 912, and the ear canal sound pressure recording module 912 is used to record the collected sound pressure value and send it to the ear canal sound pressure recording module 912. The canal sound pressure judging module 913, the ear canal sound pressure judging module 913 and the ear canal sound pressure eliminating module 914 perform off-line analysis and processing on the sound pressure signal, specifically: the ear canal sound pressure judging module 913 judges all The collected sound pressure value is judged, and the judgment result is sent to the ear canal sound pressure elimination module 914, and the ear canal sound pressure elimination module 914 rejects the sound pressure signals that meet the judgment criteria, and sends the remaining sound pressure signals after elimination to the result display module 915 for display.

The judgment criterion can be set according to the actual experimental situation. The judgment criterion of the embodiment of the present invention needs to meet the following three conditions at the same time: 1) The difference between the maximum value and the minimum value of the collected sound pressure signal is within 83dB SPL of the stimulus sound intensity adopted. (The intensity of the stimulating sound can be set according to the actual situation. The value of the stimulating sound intensity used in the embodiment of the present invention is 83dB SPL) ±6dB SPL is outside the range of the difference between the maximum value and the minimum value of the theoretical sound pressure; 2) the collected The maximum value of the sound pressure signal is greater than the maximum value of the sound pressure corresponding to the stimulus sound intensity 83dB SPL+6dB SPL; 3) The sound pressure signal in the ear canal recorded when the stimulus sound is emitted is divided into five segments on average according to the acquisition time, and the sound pressure signal of a certain segment The maximum value of the pressure signal is less than 75% of the maximum value of the overall sound pressure of the five segments, or the minimum value of the sound pressure signal of a certain segment is greater than 75% of the minimum value of the overall sound pressure of the five segments.

As shown in Figure 3, in above-mentioned each embodiment, the frequency following response signal extraction detection module comprises FFR signal collection record module 921, FFR signal processing module 922 and result display module 923; FFR signal processing module 922 comprises measurement screening module 9221, signal Noise reduction module 9222, signal-to-noise ratio estimation module 9223 and data selection module 9224; the recording electrode, reference electrode and ground electrode of the body surface optical disk electrode 6 detect the FFR signal of the subject's head and send it to the high-impedance input stage 7 to obtain the FFR voltage signal, the high-impedance input stage 7 sends the FFR voltage signal to the bioelectric amplifier 8 for filtering and amplification processing, for example, a hardware band-pass filter of 1-3000 Hz can be selected and amplified by 50000 times, and the filtered and amplified The FFR voltage signal is sent to the multi-channel A/D acquisition card 3, and the multi-channel A/D acquisition card 3 converts the FFR voltage signal into an FFR digital signal and sends it to the FFR signal acquisition and recording module 921, and the FFR signal acquisition and recording module 921 converts the FFR digital signal Sent to the FFR signal processing module 922, the FFR signal processing module 922 performs off-line analysis and processing on the FFR digital signal data to obtain the subject's FFR signal, and sends the extracted FFR signal to the result display module 923 for display.

As shown in Figure 4, the processing process of the FFR signal processing module 922 is: the measurement screening module 9221 is used to eliminate the measurement data that does not meet the setting conditions in each test section, and the setting conditions can be set according to actual experiments. The setting condition of the example is: the maximum or minimum value of the measured FFR digital signal is removed outside 95% of the range of the hardware measurement device (such as the voltage saturation value of the A/D acquisition card or bioelectric amplifier), and will be removed The remaining signals are sent to the signal noise reduction module 9222, and the signal noise reduction module 9222 performs Wiener filtering, coherent averaging, and bandpass filtering on the FFR digital signals of each test section tested by the subject, and processes the processed The signal is sent to the signal-to-noise ratio estimation module 9223; the signal-to-noise ratio estimation module 9223 calculates the signal-to-noise ratio of the FFR digital signal, and sets the signal-to-noise ratio filter condition according to the calculated signal-to-noise ratio of the FFR digital signal, and the SNR The filter conditions are sent to the data selection module 9224, and the data selection module 9224 rejects FFR signals with too low SNR according to the above-mentioned SNR filter conditions; wherein, the SNR estimation module 9223 can reduce the signal-to-noise ratio when setting the SNR filter conditions. Spectrum analysis is performed on the FFR digital signal of a certain length (for example, 133.6ms long) intercepted after noise processing, and the square of the highest spectral peak amplitude of the spectrum is used as the signal energy estimate, and the passband range of the bandpass filter is between 70 and 210Hz. The mean square value of other frequency spectrum amplitudes except the largest spectrum peak is used as the filtering condition of the noise ratio.

The noise in the FFR signal collected by the FFR signal acquisition and recording module 921 includes the components of the non-corresponding stimulus sound response in the subject's EEG components. Interference, and the random noise of the hardware device and the frequency follow response signal test platform of the present invention, etc. Therefore, after the measurement screening by the measurement screening module 9221 is completed, it is necessary to perform signal noise reduction on the FFR signals of each test section of the subject, including Wiener filtering, coherent averaging and bandpass filtering, and then average the signals of all test sections, Among them, the specific working principle of Wiener filtering:

The remaining measurement signal after the signal of a certain test section is eliminated by the measurement screening module 9221 is expressed as x _i (n), i=1~N, N is the number of repeated measurements retained in the test section, and n is each The number of points of the measured signal corresponds to the duration of the signal, then the measured signal is:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, is the signal component in the i-th measurement signal, is the noise component in the i-th measurement signal.

Averaging the power spectrum P _i of the signal x _i (n) for all single measurements gives an estimate of the sum of the power spectrum of the signal component and the power spectrum of the noise component, given by express:

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula, P _s represents the power spectrum of the signal component, P _n represents the power spectrum of the noise component, and P _i represents the power spectrum of the signal obtained from the ith measurement.

Time-domain stack averaging of all N measured signals:

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

According to the assumption that the signal component is a deterministic component and the noise component is a stationary random process, after superposition and averaging, the power spectrum of the signal component remains unchanged, while the power spectrum of the noise component is reduced to one-Nth of the original, that is power spectrum for,

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

The power spectrum of the signal component and the noise component can be solved immediately by combining the above formulas (2) and (4). According to the theory of Wiener filtering, under the condition that the aforementioned assumptions are established, the signal obtained by superimposing and averaging N measurement signals is the signal obtained after passing through the filter with amplitude-frequency response H(w) shown in formula (5), which is the optimal estimate of the aforementioned deterministic signal components.

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; w</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

The above-mentioned embodiments are only used to illustrate the present invention, wherein the structure and connection mode of each detection system can be changed, and all equivalent transformations and improvements carried out on the basis of the technical solutions of the present invention should not be excluded. outside the protection scope of the present invention.

Claims (1)

1. A frequency following response signal test system, it comprises computer, D/A acquisition card, multi-channel A/D acquisition card, acoustic sensor, preamplifier, body surface disc electrode, high impedance input stage, bioelectricity amplifier and Earplugs, the acoustic sensor includes a micro-speaker and a micro-microphone; the computer is connected to the D/A acquisition card and the multi-channel A/D acquisition card through a corresponding data interface, and the input of the micro-speaker is connected to the D/A The output end of the acquisition card is connected, the output end of the miniature speaker is inserted in the earplug through the sound tube, the input end of the miniature microphone is inserted in the earplug through the transmission sound tube, and the output of the miniature microphone terminal is connected with the input terminal of the multi-channel A/D acquisition card through the preamplifier; The reference electrode at the mastoid of the ear lobe and the ground electrode arranged at the center of the brow of the subject, the output terminals of the recording electrode, the reference electrode and the ground electrode are respectively connected to the input terminals of the high-impedance input stage, and the high-impedance The output end of the input stage is connected with the input end of the multi-channel A/D acquisition card through the bioelectrical amplifier; It is characterized in that: a frequency follow response signal test platform is set in the computer, and the frequency follow response signal test platform includes a test parameter setting module, a test signal generation module, a test signal stimulation module, an ear canal sound pressure monitoring module and a frequency follow response Signal extraction detection module; The test parameter setting module is used to set the frequency and intensity of the stimulus, and the test signal generation module generates a corresponding digital stimulus signal according to the stimulus parameter set, and sends it to the test signal stimulus module, the test signal stimulation module sends digital stimulation signals to the D/A acquisition card, and the D/A acquisition card converts the digital stimulation signals into analog voltage stimulation signals, and sends the analog voltage stimulation signals to the miniature Speaker, the micro-speaker converts the analog voltage stimulation signal into a sound stimulation signal, and sends the sound stimulation signal to the human ear through the earplug, and the ear canal sound pressure monitoring module and the frequency following response signal extraction and detection module simultaneously The ear canal sound pressure monitoring module is used to collect and record the sound pressure signal in the ear canal, and perform offline analysis and processing on the collected sound pressure signal, that is, compare the collected sound pressure signal with the preset judgment criteria Compare, remove the signal segment that does not meet the normal sound pressure of the ear canal, the frequency following response signal extraction detection module is used to collect the FFR signal, and perform offline analysis and processing on the collected FFR signal, that is, the signal segment of the normal sound pressure of the ear canal The corresponding FFR signal is pre-screened and processed to complete the extraction and display of the subject's FFR signal; The ear canal sound pressure monitoring module includes an ear canal sound pressure acquisition module, an ear canal sound pressure recording module, an ear canal sound pressure judging module, an ear canal sound pressure elimination module, and a result display module; The acoustic signal is sent to the preamplifier after the acoustic-electric conversion, and the preamplifier amplifies the signal and sends it to the ear canal sound pressure acquisition module through the multi-channel A/D acquisition card. The ear canal sound pressure acquisition module sends the signal to the ear canal sound pressure recording module, and the ear canal sound pressure recording module is used to record the collected sound pressure value and send it to the ear canal sound pressure judgment module, the ear canal sound pressure judging module and the ear canal sound pressure elimination module perform off-line analysis and processing of the sound pressure signal, specifically: the ear canal sound pressure judging module analyzes the collected sound pressure according to a preset judging criterion The value is judged, and the judgment result is sent to the ear canal sound pressure elimination module, and the ear canal sound pressure elimination module rejects the sound pressure signals that meet the judgment criteria, and sends the remaining sound pressure signals after elimination To the display of the result display module; the judgment criterion needs to meet the following three conditions at the same time: 1) the difference between the maximum value and the minimum value of the sound pressure signal collected is within the theoretical sound pressure corresponding to the stimulus sound intensity ± 6dB SPL 2) The maximum value of the collected sound pressure signal is greater than the maximum value of the sound pressure corresponding to the stimulus sound intensity + 6dB SPL; 3) The ear recorded when the stimulus sound is issued The sound pressure signal in the channel is divided into five sections on average according to the acquisition time. The maximum value of the sound pressure signal of a certain section is less than 75% of the maximum value of the overall sound pressure of the five sections, or the minimum value of the sound pressure signal of a certain section is greater than the overall sound pressure of the five sections 75% of the minimum; The frequency following response signal extraction and detection module includes an FFR signal acquisition and recording module, an FFR signal processing module and a result display module; the recording electrode, reference electrode and ground electrode of the body surface optical disk electrode detect the FFR signal of the subject's head, and send it to the high-impedance input stage to obtain the FFR voltage signal, and the high-impedance input stage sends the FFR voltage signal to the bioelectric amplifier for filtering and amplification processing, and sends the filtered and amplified FFR voltage signal to The multi-channel A/D acquisition card, the multi-channel A/D acquisition card converts the FFR voltage signal into an FFR digital signal and sends it to the FFR signal acquisition and recording module, and the FFR signal acquisition and recording module sends the FFR digital signal To the FFR signal processing module, the FFR signal processing module carries out off-line analysis and processing to the FFR digital signal data, obtains the FFR signal of the subject, and sends the extracted FFR signal to the described result display module for display; the FFR The signal processing module includes a measurement screening module, a signal noise reduction module, a signal-to-noise ratio estimation module and a data selection module; The signal is sent to the signal noise reduction module, and the signal noise reduction module performs Wiener filtering, coherent averaging and bandpass filtering on the FFR digital signals of each test segment tested by the subject, and the processed signal Sent to the SNR estimation module; the SNR estimation module calculates the SNR of the FFR digital signal, and sets the SNR filter condition according to the SNR of the calculated FFR digital signal, and the The signal-to-noise ratio filter condition is sent to the data selection module, and the data selection module rejects the FFR signal with too low signal-to-noise ratio according to the signal-to-noise ratio filter condition.