CN1119120C - Audibility measurement instrument emitting sound to ear and its test method - Google Patents

Abstract

The invention belongs to the technical field of electronics, computer and signal processing, and relates to an otoacoustic emission hearing detector and a testing method thereof, comprising a miniature probe for playing stimulation sounds and extracting otoacoustic emission signals, and performing an operation on the extracted otoacoustic emission signals. A pre-processing unit for filtering and amplifying processing, a computer system and control and processing software for processing the pre-processed signal, and a full-duplex sound card is installed in the computer system. Compared with the existing otoacoustic emission hearing detection device, the present invention not only greatly simplifies the hardware circuit, but also the system software has more powerful functions, and is more convenient and intuitive to use.

Description

Otoacoustic emission audiometer and testing method thereof

technical field

The invention belongs to the technical field of electronics, computer and signal processing, and in particular relates to an otoacoustic signal detection device and a detection method thereof.

Background technique

Otoacoustic Emissions (Otoacoustic Emissions referred to as OAEs) phenomenon was discovered in 1978 by British scientist Kemp.D.T. He observed in the experiment: Give the ear a short-term sound stimulus, and when the stimulus and the ear's reflex to the stimulus completely disappear, a sound will be recorded in the external auditory canal. Since then, it has been found that different sound stimuli are used, and the recorded sounds are also different; and even in the absence of external sound stimuli, a certain sound can be recorded. In patients with sensorineural deafness caused by cochlear lesions, the sound will be weakened or even disappear. Otoacoustic emission can quickly, non-destructively and objectively reflect the functional state of the cochlea, and has broad prospects in basic medicine, clinical diagnosis, and auditory physiology research.

The sound intensity of the otoacoustic emission signal is very weak and cannot arouse people's auditory awareness. A highly sensitive microphone placed in the external ear canal records the acoustic signal into the ear canal. This signal contains the otoacoustic signal, but because it is submerged in the noise, modern electronics, computer and signal processing technologies must be used comprehensively to detect the otoacoustic signal from the noise.

British patent GB2205430A has recorded a kind of otoacoustic emission hearing detection system, and its composition is shown in Figure 1, comprises: miniature probe (Speaker, Microphone), signal pre-processing unit, signal acquisition card, signal processing card and computer system and control and processing software. Among them, the micro-probe is responsible for playing the stimulation sound and extracting the otoacoustic emission signal. Signal pre-processing is responsible for pre-processing the otoacoustic emission signals extracted by the Microphone in the probe, including filtering, amplification and other links. The signal acquisition card is responsible for digitally sampling the pre-processed analog signal and generating stimulating sound at the same time. The signal processing card is responsible for digital processing of the quantized otoacoustic emission signals, including filtering, accumulation, coherent averaging, correlation and spectrum analysis. The system software is responsible for the control of the entire detection process, and at the same time completes functions such as display, printing and medical record management. The hardware circuit of this system is more complex, the function of the software is less, and it is not very convenient and intuitive to use.

Contents of the invention

The purpose of the present invention is to, in order to overcome the deficiencies of the prior art, on the basis of technological innovation and transformation of the hardware and software of the above-mentioned system, a new otoacoustic emission hearing detector is proposed, which not only has a large hardware circuit For simplicity, the system software has more powerful functions and is more convenient and intuitive to use.

The present invention proposes an otoacoustic emission hearing tester, which includes a micro-probe for playing stimulus sounds and extracting otoacoustic emission signals, a pre-processing unit for filtering and amplifying the extracted otoacoustic emission signals, and a pre-menstrual A computer system and control and processing software for processing the processed signal, characterized in that said computer system is provided with a full-duplex sound card that digitally samples the pre-processed analog signal and simultaneously produces stimulating sound . The connection relationship of each component is shown in Figure 2.

The signal preprocessing unit in the present invention is composed of an integrated analog electronic circuit including a preprocessing circuit, a signal filtering circuit, and a signal grading and amplifying circuit, as shown in FIG. 3 . Its working principle is briefly described as follows: In the preprocessing circuit, the receiving and preprocessing of the physiological signals extracted by the acoustic sensor (probe) are completed, and the normal working power supply voltage is provided to the acoustic sensor. The physiological signal converted by the sensor is a mixed signal, which not only contains otoacoustic emission signals, but also contains a large number of interference signals. The composition of the preprocessing circuit includes band-pass filtering and voltage amplification, and its function is to perform preliminary voltage amplification and noise filtering on the signal. After the otoacoustic emission signal is preprocessed, it is sent to the signal filtering processing unit. In the signal filtering and processing circuit, the high frequency band and the low frequency band of the signal are respectively processed, and the interference signals other than the specific frequency of the otoacoustic emission signal are filtered out for further processing. Entering the step-by-step amplification circuit unit, the signal is amplified to different voltage values respectively. After passing through the A/D, it is analyzed and processed by the multimedia computer and control and processing software.

The system control and processing software of the present invention are Windows application programs written by Delphi, including two major functional modules of signal detection and medical record management, said signal detection is made up of a test interface module, a multimedia control module and a signal processing module, said The medical record management consists of a medical record establishment module, a medical record preservation module, a printing test result module, and a medical record retrieval module.

The present invention adopts a kind of otoacoustic emission signal testing method of above-mentioned instrument, and its concrete steps comprise:

1) Create a medical record for a new patient, and open the original medical record and create a new record for a review patient;

2) Place the probe and check whether the probe is properly placed. If the probe is properly placed, the noise spectrum should be evenly distributed and the amplitude spectrum should be flat. Otherwise, it should be relocated;

3) If the probe is placed properly, go to step 4) to start the test; if it is not placed properly, adjust the position of the probe and continue the inspection of step 2);

4) According to the requirements of transiently evoked otoacoustic emissions, pitch-shifted otoacoustic emissions, and pitch-shifted otoacoustic emissions audiogram, respectively set the stimulation parameters, emit stimulating sounds, set the noise threshold according to the noise histogram, and start the formal test;

5) recording otoacoustic emission signals;

6) Judging whether the stimulus is valid and whether the noise level is lower than the noise rejection threshold according to the changes in the displayed effective times, and adjust the noise rejection threshold appropriately; if the stimulus is valid and the noise is lower than the noise rejection threshold, go to the 7th ) step; otherwise, discard this result and go to step 8);

7) Store the otoacoustic emission signal into the corresponding data buffer, and perform the above-mentioned real-time signal processing;

8) Judging whether the required number of stimulations is reached or whether the user requires to stop the test; if so, go to step 9); otherwise, go to step 5) for the next test;

9) Stop the test, perform post-processing, and display the test results;

10) Store the medical records, and the test ends.

The present invention has following characteristics:

First, the hardware circuit of the system is greatly simplified. The present invention adopts a full-duplex sound card, which replaces the necessary signal acquisition cards (A/D, D/A) for digital signal processing in the traditional sense, and the sound card can complete all the functions of the signal acquisition card in the prior art. At the same time, since the sound card is a standard component of the computer, its control is more convenient, the system is also more functionally modular, and the function expansion is also more convenient. The pre-processing circuit of the present invention uses an integrated analog electronic circuit chip to complete filtering and amplification. At the same time, the signal processing card in the prior art is omitted, and all its functions are completed by the signal processing function in the system software.

Second, the system control and processing software of the present invention are more convenient to use. In terms of function, two detections of otoacoustic emission signals are added, so that it can detect transient evoked otoacoustic emissions, pitch distortion otoacoustic emissions and pitch distortion otoacoustic emission audiograms, while existing technologies can only detect transient evoked otoacoustic emissions. Acoustic emission.

Its three, the medical record management database that the present invention establishes. Multiple inspection results can be entered to record multiple medical visits. It can search according to the medical record number, name, age, occupation, medical history, date, etc., and print out relevant information for diagnosis and research by clinicians.

Description of drawings

Fig. 1 is a system block diagram of the prior art.

Fig. 2 is a system block diagram of the present invention.

Fig. 3 is a block diagram of the signal pre-processing unit of the present invention.

FIG. 4 is a schematic diagram of the preprocessing circuit of this embodiment.

FIG. 5 is a schematic diagram of the filter processing circuit of this embodiment.

FIG. 6 is a schematic diagram of the low-magnification amplifier circuit of this embodiment.

FIG. 7 is a schematic diagram of the high magnification amplifier circuit of this embodiment.

Fig. 8 is a block diagram of system control and processing software in this embodiment.

Fig. 9 is a basic flowchart of otoacoustic emission signal testing in this embodiment.

Detailed ways

The present invention proposes an embodiment of an otoacoustic emission hearing tester, which is composed of hardware circuit and software. The detailed description is as follows in conjunction with the accompanying drawings:

The overall structure of the hardware circuit of this embodiment is shown in Figure 2, including a miniature probe made of a miniature microphone and one or two miniature speakers, a signal pre-processing unit and a multimedia computer with a full-duplex sound card inside. Wherein, the signal pre-processing unit is composed of an integrated analog electronic circuit including a pre-processing circuit, a signal filter processing circuit, and a signal grading and amplifying circuit, as shown in FIG. 3 .

The preprocessing circuit selects the integrated high-precision instrumentation amplifier AD624. The device has a three-op amplifier amplifier circuit inside. The circuit principle is shown in Figure 4. The amplification factor is optional and the common-mode rejection ratio (CMRR) is high. The physiological signal extracted by the acoustic sensor is sent to the pre-amplification circuit, after amplification and high-frequency filtering processing, the amplitude of the signal is increased, the low-frequency interference is reduced, and the signal-to-noise ratio of the signal is improved.

The filter processing circuit in the signal pre-processing unit of this embodiment is a band-pass filter composed of a high-pass filter and a low-pass filter. Its circuit principle is shown in Figure 5. The bandpass filter uses an integrated universal filter chip UAF42, and the parameters of external components are designed by special software to determine the cutoff frequency of the filter. The accuracy of the internal capacitance of the chip is 0.5%, and the accuracy of the resistance in the external circuit is 0.1%.

In this embodiment, after the signal is processed by the pre-amplifier and filter, it is respectively sent to the low-magnification amplification circuit and the high-magnification amplification circuit composed of LF444 linear amplifiers, as shown in Fig. 6 and Fig. 7 . The precision of the resistance in the circuit is 0.1%, and the signal is finely adjusted through these two parts of the circuit to make it meet the data processing requirements.

The software part of this embodiment realizes the overall control of the test system, including the detection and processing of various otoacoustic emission signals, multimedia control and case management. Its composition is shown in Figure 8, including two parts to signal detection and medical record management, said signal detection is made up of test interface module, multimedia control module and signal processing module, said medical record management is made up of medical record module, medical record preservation Module, print test result module, medical record retrieval module. Each part is described as follows: signal detection part:

This part includes the detection, processing and result display of transiently evoked otoacoustic emission signals, tone-shifted distortion otoacoustic emission signals and tone-shifted distortion otoacoustic emission audiograms. The specific functions are:

1. Test interface: including the detection interface of the probe position, the detection interface of transient evoked otoacoustic emission, pitch-shifted otoacoustic emission and pitch-shifted otoacoustic emission audiogram, as well as the detection parameters and detection results of various otoacoustic emission signals Real-time display, such as noise level, noise threshold, otoacoustic emission signal strength, test times, correlation rate, etc. Before each test, the test parameters can also be set and adjusted according to the actual situation.

2. Multimedia control: control the full-duplex sound card, emit various stimulation sounds (click sound or pure tone), adjust the stimulation sound intensity and frequency and other parameters, and realize the recording of otoacoustic emission signals at the same time.

3. Signal processing:

(1) General algorithm: an algorithm that must be used when detecting various otoacoustic emission signals. They are digital filtering, fast Fourier transform (FFT), AR spectral analysis, coherent averaging, and noise estimation, among others.

(2) Special algorithm: a special signal processing method used when detecting different otoacoustic emission signals. Including the non-linear difference averaging used in the detection of transiently evoked otoacoustic emissions, the phase alignment algorithm used in the detection of pitch-distorted otoacoustic emissions, and the probe position detection algorithm, etc.

These signal processing methods can also be divided into real-time processing and post-processing according to the real-time processing. Real-time processing algorithms include nonlinear differential averaging, coherent averaging, noise estimation, digital filtering, FFT, AR spectrum analysis, etc. Post-processing includes elimination of stimulus artifacts, cross-correlation of waveforms, calculation of cross-spectrum and difference spectrum, etc. Case management part:

Systematic database management of the subjects' medical records. The database of this embodiment is an all-Chinese medical record management database established according to the clinical needs of otology in China. Using the Delphi database engine, it can realize the establishment, preservation, retrieval, modification and other functions of medical records. The basic process of the otoacoustic emission signal test of the present embodiment is as shown in Figure 9, and is applicable to various test functions (modules) of the otoacoustic emission signal, such as the "test probe position" and "test TEOAE" of the test interface in Figure 8 , "Test DPOAE", "Test DP_GRAM" and "Result Display", the specific steps include:

1) Create a medical record for a new patient, and open the original medical record for a reexamination patient, and create a new record (see "Medical Record Establishment" and "Medical Record Retrieval" under the block diagram of "Medical Record Management" in Figure 8);

2) Place the probe and check whether the probe is properly placed (see "Test Probe Position" under the block diagram of "Test Interface" in Figure 8). If the probe is placed properly, the noise spectrum should be evenly distributed and the amplitude spectrum should be flat. Otherwise, it should reposition;

3) If the probe is placed properly, go to step 4) to start the test; if it is not placed properly, adjust the position of the probe and continue to check in step 2);

4) According to the requirements of Transient Evoked Otoacoustic Emissions (TEOAE), Distorted Pitch Otoacoustic Emissions (DPOAE), and Distorted Pitch Otoacoustic Emission Audiogram (DP_GRAM), respectively set the stimulation parameters (stimulation frequency, stimulation waveform, stimulation times, stimulation intensity ), send a stimulating sound, set the noise threshold according to the noise histogram, and start the formal test (see "stimulus" under "multimedia control" in Figure 8);

5) Record otoacoustic emission signals (see "Response" under "Multimedia Control" in Figure 8);

6) Judging whether the stimulus is valid and whether the noise level is lower than the noise rejection threshold according to the changes in the displayed effective times, and adjust the noise rejection threshold appropriately; if the stimulus is valid and the noise is lower than the noise rejection threshold, go to the 7th ) step; otherwise, this result is discarded, to step 8) (see "General Algorithm" under the "Signal Processing" block diagram in Figure 8);

7) Store the otoacoustic emission signal into the corresponding data buffer, and perform the above-mentioned real-time signal processing (see "special algorithm" under the block diagram of "signal processing" in Fig. 8);

8) Judging whether the required number of stimulations is reached or whether the user requests to stop the test. If so, go to step 9); otherwise, go to step 5) for the next test (see Figure 8 "signal processing");

9) Stop the test, carry out post-processing, and display the detection results (see "result display" under the "general algorithm" under the "signal processing" block diagram in Figure 8, "general algorithm" and "test interface" block diagram);

10) The medical records are stored, and the test ends (see "Medical Record Storage" under the block diagram of "Medical Record Management" in Figure 8).

The implementation method of the functional module of this embodiment:

1. Detection of transient evoked otoacoustic emissions (TEOAE):

Transient evoked otoacoustic emissions are otoacoustic emission signals evoked by short transients (80 microseconds). It can be recorded after 5 ms from the stimulus. Since the transiently evoked otoacoustic emission signal is often submerged in strong background noise, it must first pass through an analog filter with a bandwidth of 0.3-10kHz before A/D sampling. And use nonlinear differential averaging, digital filtering, set noise rejection threshold, and increase sine window to eliminate the influence of noise. In order to confirm the existence of transient evoked otoacoustic emissions, the response signal is stored in two different buffers in odd and even times, and superimposed respectively to obtain two independent coherent average results. By calculating the correlation of these two results The repeatability of the transiently evoked otoacoustic emission signal can be seen from the rate. A higher correlation ratio indicates that there is indeed a deterministic evoked response, rather than random noise, which is unlikely to exhibit such a correlation.

2. Detection of Pitch Distortion Otoacoustic Emissions (DPOAE):

The pitch-distorted otoacoustic emission signal is an otoacoustic emission signal evoked by two continuous pure tones or a pure tone pulse (100ms) with a long time delay. Stimulus intensity is 70dBspl. The overall effect is best when the frequency ratio f2/f1 of the two stimuli is generally 1.22. The frequency range of stimulation sound is above 0.3-6kHz, so the sampling rate is 22.05kHz. The frequency separation method is used to detect pitch-distorted otoacoustic emissions. The processing before A/D sampling is the same as that of transiently evoked otoacoustic emissions. After sampling, the whole period interception method is used to align the phase, the coherent averaging is used to eliminate the noise, and the FFT is used to extract the frequency component of the otoacoustic emission signal.

3. Test of tone shift distortion otoacoustic emission audiogram (DP_GRAM):

The testing method of the tone-shifting distortion otoacoustic emission audiogram is essentially the same as that of the tone-shifting distortion otoacoustic emission audiogram, except that the frequency of the stimulus is changed sequentially from low to high at intervals of 1/2 octave when testing the tone-shifting distortion otoacoustic emission audiogram Yes, the results of the tone shifting distortion otoacoustic emission of each frequency point are integrated on a graph. Among them, since there are many frequency points in the tone shift distortion otoacoustic emission audiogram test, we select one of the stimulating sounds of a specific frequency for automatic volume adjustment. Before the test, the user can set parameters such as the stimulus intensity, the start and end range of the stimulus frequency, and the frequency interval; can choose the coherent averaging method (time domain or frequency domain); can choose whether to automatically adjust the volume during the test. During the test, there are two test methods to choose from (fixed frequency and frequency sweep). If the fixed-frequency method is adopted, the frequency of the stimulation sound will not change, but multiple stimulations and multiple accumulations will be performed at the frequency selected by the user, so as to better eliminate noise and highlight the pitch-distorted otoacoustic emission signal. If the frequency sweep mode is selected, the frequency of the stimulating sound will change from low to high.

Claims (4)

1. An otoacoustic emission hearing tester, comprising a microprobe for playing stimulus sounds and extracting otoacoustic emission signals, a pre-processing unit for filtering and amplifying the extracted otoacoustic emission signals, The computer system and control and processing software for processing the processed signal are characterized in that said computer system is provided with a full-duplex sound card for digitally sampling the pre-processed analog signal and simultaneously generating stimulating sound. 2. The otoacoustic emission hearing detector according to claim 1, wherein said signal preprocessing unit is composed of an integrated analog electronic circuit including a preprocessing circuit, a signal filtering circuit, and a signal grading and amplifying circuit. 3. The otoacoustic emission hearing detector as claimed in claim 1, wherein said control and processing software includes two major functional modules of signal detection and medical record management, and said signal detection consists of a test interface module, a multimedia It is composed of a control module and a signal processing module, and the medical record management is composed of a medical record establishment module, a medical record preservation module, a test result printing module, and a medical record retrieval module. 4. an otoacoustic emission signal testing method that adopts the otoacoustic emission hearing detector as claimed in claim 1, its concrete steps comprise: 1) Create a medical record for a new patient, and open the original medical record and create a new record for a review patient; 2) Place the probe and check whether the probe is properly placed. If the probe is properly placed, the noise spectrum should be evenly distributed and the amplitude spectrum should be flat. Otherwise, it should be relocated; 3) If the probe is placed properly, go to step 4) to start the test; if it is not placed properly, adjust the position of the probe and continue the inspection of step 2); 4) According to the requirements of transiently evoked otoacoustic emissions, pitch-shifted otoacoustic emissions, and pitch-shifted otoacoustic emissions audiogram, respectively set the stimulation parameters, emit stimulating sounds, set the noise threshold according to the noise histogram, and start the formal test; 5) recording otoacoustic emission signals; 6) Judging whether the stimulus is valid and whether the noise level is lower than the noise rejection threshold according to the changes in the displayed effective times, and adjust the noise rejection threshold appropriately; if the stimulus is valid and the noise is lower than the noise rejection threshold, go to the 7th ) step; otherwise, discard this result and go to step 8); 7) Store the otoacoustic emission signal into the corresponding data buffer, and perform the above-mentioned real-time signal processing; 8) Judging whether the required number of stimulations is reached or whether the user requires to stop the test; if so, go to step 9); otherwise, go to step 5) for the next test; 9) Stop the test, perform post-processing, and display the test results; 10) Store the medical records, and the test ends.

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