An analysis method for microphone sensitivity and sound leakage test

Abstract

The application discloses a kind of microphone sensitivity and sound leakage test analysis method, belong to electronic technical field, including building test system, the sound pressure calibration of loudspeaker, the generation of test excitation signal, signal acquisition of microphone to be measured, alignment processing, segmentation processing, fourier transform, extract the amplitude of characteristic frequency point, solve the technical problem of effective accurate test microphone sensitivity and identify microphone sound leakage situation, the sensitivity of the loudspeaker used for testing is iteratively corrected in the application, and the test excitation signal is generated in the application using splicing, solve the problem that test sound source is constant sound pressure, the application processes to the signal to be measured, such as alignment, segmentation and fourier transform, greatly improve accuracy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electronics, and particularly relates to a microphone sensitivity and sound leakage test analysis method. BACKGROUND

[0002] In the production process, the sensitivity and sound leakage of a microphone need to be tested to effectively distinguish the quality of the product. However, the current test method has a large data error, which affects the final quality of the product. SUMMARY

[0003] The purpose of the application is to provide a microphone sensitivity and sound leakage test analysis method, which solves the technical problem of effectively and accurately identifying the sensitivity and sound leakage of a microphone.

[0004] To achieve the above purpose, the application adopts the following technical solutions:

[0005] A microphone sensitivity and sound leakage test analysis method comprises the following steps:

[0006] Step 1: Build a test system, which includes a soundproof box, a loudspeaker, a power amplifier, a sound card, a test signal amplification module and a signal analysis module. The loudspeaker is placed in the soundproof box, and a standard microphone and a microphone to be tested are also placed in the soundproof box. The standard microphone and the microphone to be tested are electrically connected to the test signal amplification module through signal lines. The loudspeaker is connected to the power amplifier through a signal line. The power amplifier and the test signal amplification module are electrically connected to the sound card through signal lines. The sound card communicates with the signal analysis module through a data line.

[0007] The test signal amplification module is used to acquire and amplify the audio analog signals transmitted by the standard microphone and the microphone to be tested.

[0008] The sound card is used to convert the audio analog signals into audio digital signals and transmit them to the signal analysis module for processing. Meanwhile, the sound card also receives the audio test digital signals sent by the signal analysis module, converts the audio test digital signals into audio test analog signals through analog-digital conversion, and amplifies the audio test analog signals through the power amplifier and then emits them through the loudspeaker.

[0009] Step 2: Before testing the microphone to be tested, the loudspeaker is first calibrated for sound pressure. Specifically, the signal analysis module establishes a mathematical model between sound pressure and voltage. Through the mathematical model, multiple sound pressure frequency points are selected, and the digital voltage value corresponding to each sound pressure frequency point is calculated through the mathematical model. Then, the loudspeaker emits sound after conversion by the sound card and the power amplifier.

[0010] The test signal amplification module receives and amplifies the calibration signal transmitted by the standard microphone, and then transmits the calibration signal to the signal analysis module after digital-to-analog conversion by the sound card. The signal analysis module compares the calibration signal with the corresponding digital voltage value to obtain an iterative correction parameter. The iterative correction parameter is input into the mathematical model to calculate a calibration value, and the calibration value is used to calibrate the loudspeaker.

[0011] Step 3: After the calibration of the loudspeaker is completed, the signal analysis module generates a test excitation signal. The test excitation signal is spliced from the excitation signals corresponding to the sound pressures of multiple frequency points.

[0012] Step 4: The loudspeaker plays the test excitation signal. The test microphone collects the test excitation signal and generates a test analog signal. The test analog signal is amplified by the test signal amplification module and converted into a test digital signal by the analog-to-digital conversion of the sound card, and then the test digital signal is sent to the signal analysis module.

[0013] Step 5: The signal analysis module performs cross-correlation processing on the test digital signal and the test excitation signal to align the two signals.

[0014] Step 6: The signal analysis module divides the aligned test digital signal according to the step-scan frequency time to obtain a divided signal.

[0015] Step 7: The signal analysis module performs Fourier transform on the divided signal to extract the amplitude of the characteristic frequency point, converts the amplitude of the characteristic frequency point to obtain the sound pressure value, and outputs the result.

[0016] Preferably, when performing step 2, the specific steps are as follows:

[0017] Step 2-1: The signal analysis module establishes a mathematical model between sound pressure and voltage, and the formula is as follows:

[0018] SP = k·V + b;

[0019] where V represents voltage, k and b represent coefficient constants, and SP represents sound pressure.

[0020] Step 2-2: Select a frequency point sound pressure, calculate the voltage V corresponding to the frequency point according to the mathematical model, and record the values of k and b.

[0021] Generate a calibration excitation signal according to the voltage V and output it by the loudspeaker. Then, the calibration excitation signal is collected by the standard microphone to generate a calibration signal, which is transmitted to the signal analysis module.

[0022] Step 2-3: The signal analysis module presets a sensitivity threshold to determine whether the calibration signal is within the sensitivity threshold. If yes, the loudspeaker sensitivity meets the standard; if no, the values of k and b are iteratively corrected according to the mathematical formula until the loudspeaker sensitivity meets the standard.

[0023] Step 2-4: Sensitivity calibration of the loudspeaker is performed according to the method of step 2-1 to step 2-3.

[0024] Preferably, in the execution of step 3, the sound pressure of the frequency point corresponds to the excitation signal calculated by the following formula:

[0025] S f =V f ·sin(2πf·t);

[0026] Wherein, t represents time sequence, f represents frequency, V f represents input voltage, S f represents the excitation signal of the frequency point.

[0027] Preferably, in the execution of step 4, the sound card is triggered to collect, and the collection duration is greater than the playing duration of the loudspeaker.

[0028] Preferably, in the execution of step 5, the cross-correlation value of the signal is calculated by the following formula, and then the time delay is obtained, so that the signals are aligned:

[0029]

[0030] Wherein, the excitation signal is x(t), the microphone response signal is y(t), T represents period, R represents cross-correlation value, τ represents continuous variable, and dt represents integral variable.

[0031] Preferably, in the execution of step 7, the formula of Fourier transform is as follows:

[0032]

[0033] Wherein, F(w) represents Fourier transform value, y(t) represents time domain signal, e represents natural logarithm, and i represents imaginary unit.

[0034] The microphone sensitivity and sound leakage test analysis method provided by the application solves the technical problem of effectively and accurately identifying the microphone sensitivity and sound leakage, greatly improves the accuracy of the test environment by iteratively correcting the sensitivity of the loudspeaker used for testing, saves the test time by generating the test excitation signal in a splicing manner, and greatly improves the accuracy by aligning, segmenting and Fourier transforming the to-be-tested signal. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is the architecture diagram of the test system of the application;

[0036] Figure 2 is the main flowchart of the application;

[0037] Figure 3 is a flow chart of step 2 of the present application;

[0038] Figure 4 is a schematic diagram of the test excitation signal of the present application;

[0039] Figure 5 is a schematic diagram of the signal after segmentation processing of the present application. DETAILED DESCRIPTION

[0040] is shown in the microphone sensitivity and sound leakage test analysis method, comprising the following steps: Figures 1-5

[0041] Step 1: Build a test system, the test system includes anechoic chamber, loudspeaker, power amplifier, sound card, test signal amplification module and signal analysis module, the loudspeaker is placed in the anechoic chamber, a standard microphone and a microphone to be tested are also placed in the anechoic chamber, the standard microphone and the microphone to be tested are electrically connected with the test signal amplification module through signal lines, the loudspeaker is connected with the power amplifier through signal lines, the power amplifier and the test signal amplification module are electrically connected with the sound card through signal lines, and the sound card communicates with the signal analysis module through a data line;

[0042] In this embodiment, the standard microphone is a microphone whose sensitivity and sound leakage data meet the standards in the production process.

[0043] In this embodiment, the signal analysis module is a computer, an industrial computer or a tablet computer.

[0044] The test signal amplification module is used to acquire and amplify the audio analog signals transmitted by the standard microphone and the microphone to be tested;

[0045] The sound card is used to convert the audio analog signals into audio digital signals and transmit them to the signal analysis module for processing, and the sound card also receives the audio test digital signals sent by the signal analysis module, converts the audio test digital signals into audio test analog signals, and amplifies the audio test analog signals through the power amplifier and then emits them through the loudspeaker.

[0046] Step 2: Before testing the microphone to be tested, first calibrate the sound pressure of the loudspeaker, which specifically includes that the signal analysis module establishes a mathematical model between sound pressure and voltage, selects multiple sound pressure frequency points through the mathematical model, calculates the digital voltage value corresponding to each sound pressure frequency point through the mathematical model, and then converts the digital voltage value through the sound card and the power amplifier and emits the sound through the loudspeaker.

[0047] ​The test signal amplification module receives and amplifies the calibration signal transmitted by the standard microphone, and then transmits the calibration signal to the signal analysis module after digital-to-analog conversion by the sound card.

[0048] During sensitivity and leakage testing of the microphone, the loudspeaker needs to output constant sound pressure, which means that the input voltage of the loudspeaker is different at different frequency points.

[0049] Step 2-1: The signal analysis module establishes a mathematical model between sound pressure and voltage, and the formula is as follows:

[0050] SP=k·V+b;

[0051] Where V represents voltage, k and b represent coefficient constants, and SP represents sound pressure.

[0052] Step 2-2: Select a sound pressure at a frequency point, calculate the corresponding voltage V at the frequency point according to the mathematical model, and record the values of k and b.

[0053] According to the voltage V, a calibration excitation signal is generated and emitted by the loudspeaker, and then a calibration signal is generated by the standard microphone and transmitted to the signal analysis module.

[0054] Step 2-3: The signal analysis module presets a sensitivity threshold to determine whether the calibration signal is within the sensitivity threshold: if yes, the loudspeaker sensitivity meets the standard; if no, the values of k and b are iteratively corrected according to the mathematical formula until the loudspeaker sensitivity meets the standard.

[0055] Step 2-4: According to the method of steps 2-1 to 2-3, the sound pressures at multiple frequency points are selected to calibrate the sensitivity of the loudspeaker.

[0056] The loudspeaker sensitivity is calibrated in the present application, i.e., V-f (relationship between input voltage and frequency) is obtained.

[0057] Step 3: After the loudspeaker calibration is completed, the signal analysis module generates a test excitation signal, which is composed of excitation signals corresponding to sound pressures at multiple frequency points.

[0058] The excitation signal corresponding to the sound pressure at the frequency point is calculated by the following formula:

[0059] S f =V f ·sin(2πf·t);

[0060] Where t represents time series, f represents frequency, V f represents input voltage, and S fThe excitation signal represents the frequency point.

[0061] Step 4: the horn plays the test excitation signal, the microphone under test collects the test excitation signal and generates a to-be-tested analog signal, and then the test signal amplification module amplifies and the sound card performs analog-to-digital conversion to generate a to-be-tested digital signal and send it to the signal analysis module;

[0062] Since the test system has a delay, in order to ensure that the signal played by the horn is completely collected, simple processing is needed for signal collection. The method adopted by the present application is to trigger the sound card to collect first, and the collection time is longer than the playing time of the horn.

[0063] Step 5: the signal analysis module cross-correlates the to-be-tested digital signal and the test excitation signal to align the two signals;

[0064] Since the excitation signal is a step frequency signal, that is, the frequency of excitation is different in different time periods, the signal needs to be segmented when analyzed. The principle of segmentation is according to the excitation time of different frequency points.

[0065] The present application calculates the cross-correlation value of the signal by the following formula, and then obtains the delay time, so that the signals are aligned:

[0066]

[0067] Wherein, the excitation signal is x(t), the microphone response signal is y(t), T represents the period, R represents the cross-correlation value, τ represents the continuous variable, and dt represents the integral variable.

[0068] Preferably, when step 7 is performed, the formula of Fourier transform is as follows:

[0069]

[0070] Wherein, F(w) represents the Fourier transform value, y(t) represents the time domain signal, e represents the natural logarithm, and i represents the imaginary unit.

[0071] Step 6: the signal analysis module segments the to-be-tested digital signal after alignment according to the step frequency time to obtain a segmented signal;

[0072] Step 7: the signal analysis module performs Fourier transform on the segmented signal, extracts the amplitude of the characteristic frequency point, converts the amplitude of the characteristic frequency point to obtain the sound pressure value, and outputs the result.

[0073] The microphone sensitivity and sound leakage test analysis method provided by the application solves the technical problem of effectively and accurately identifying microphone sensitivity and sound leakage conditions, iteratively corrects the sensitivity of the loudspeaker used for testing, greatly improves the accuracy of the test environment, generates a test excitation signal in a splicing manner, saves test time, and greatly improves the accuracy by aligning, segmenting and Fourier transforming the to-be-tested signal.

Claims

1. A method of analyzing a microphone sensitivity and sound leakage test, the method comprising: The method comprises the following steps: ​ Step 1: build a test system, the test system comprises a soundproof box, a loudspeaker, a power amplifier, a sound card, a test signal amplification module and a signal analysis module, the loudspeaker is placed in the soundproof box, a standard microphone and a microphone to be tested are also placed in the soundproof box, the standard microphone and the microphone to be tested are electrically connected with the test signal amplification module through signal lines, the loudspeaker is connected with the power amplifier through a signal line, and the power amplifier and the test signal amplification module are electrically connected with the sound card through signal lines; the sound card communicates with the signal analysis module through a data line; The test signal amplification module is used for acquiring and amplifying audio analog signals transmitted by the standard microphone and the microphone to be tested; The sound card is used for converting the audio analog signals into audio digital signals and transmitting the audio digital signals to the signal analysis module for processing; meanwhile, the sound card also receives audio test digital signals sent by the signal analysis module, converts the audio test digital signals into audio test analog signals through analog-digital conversion, and amplifies the audio test analog signals through the power amplifier and then sends the audio test analog signals out through the loudspeaker; Step 2: before testing the microphone to be tested, the loudspeaker is first calibrated in terms of sound pressure, specifically comprising the following steps: the signal analysis module establishes a mathematical model between sound pressure and voltage, selects multiple sound pressure frequency points through the mathematical model, calculates the digital voltage value corresponding to each sound pressure frequency point through the mathematical model, and then converts the digital voltage value into a sound through the sound card and the power amplifier; The test signal amplification module receives and amplifies the calibration signal transmitted by the standard microphone, and then transmits the calibration signal to the signal analysis module through the digital-analog conversion of the sound card; the signal analysis module compares the calibration signal with the corresponding digital voltage value to obtain an iterative correction parameter, inputs the iterative correction parameter into the mathematical model to obtain a calibration value, and calibrates the loudspeaker through the calibration value; Step 3: after the calibration of the loudspeaker is completed, the signal analysis module generates a test excitation signal, the test excitation signal is spliced from excitation signals corresponding to multiple frequency points of sound pressure; Step 4: the loudspeaker plays the test excitation signal, the microphone to be tested collects the test excitation signal and generates a to-be-tested analog signal, and then generates a to-be-tested digital signal through the amplification of the test signal amplification module and the analog-digital conversion of the sound card and sends the to-be-tested digital signal to the signal analysis module; Step 5: the signal analysis module performs cross-correlation processing on the to-be-tested digital signal and the test excitation signal, so that the two signals are aligned; Step 6: the signal analysis module divides the to-be-tested digital signal after the alignment processing according to a step-scan frequency time to obtain a divided signal; Step 7: the signal analysis module performs Fourier transform on the divided signal, extracts the amplitude of a characteristic frequency point, converts the amplitude of the characteristic frequency point into a sound pressure value, and outputs the result.

2. The method of claim 1, wherein: the microphone sensitivity and acoustic feedback test is performed by the microphone sensitivity and acoustic feedback test module; and the microphone sensitivity and acoustic feedback test is performed by the microphone sensitivity and acoustic feedback test module. When step 2 is performed, the specific steps are as follows: Step 2-1: the signal analysis module establishes a mathematical model between sound pressure and voltage, and the formula is as follows: SP=k·V+b; Wherein, V represents voltage, k and b represent coefficient constants, and SP represents sound pressure; Step 2-2: select a frequency point of sound pressure, calculate the voltage V corresponding to the frequency point according to the mathematical model, and record the values of k and b; Generate a calibration excitation signal according to the voltage V and send the calibration excitation signal out through the loudspeaker, and then generate a calibration signal through the standard microphone and transmit the calibration signal to the signal analysis module; Step 2-3: The signal analysis module presets a sensitivity threshold to determine whether the calibration signal is within the sensitivity threshold: if yes, the horn sensitivity is up to standard; if no, the values of k and b are iteratively corrected according to the mathematical formula until the horn sensitivity is up to standard; Step 2-4: The sound pressure of multiple frequency points is selected according to the method of step 2-1 to step 2-3 to calibrate the sensitivity of the horn.

3. The analytical method for microphone sensitivity and sound leakage testing as described in claim 1, characterized in that: When step 3 is performed, the excitation signal corresponding to the sound pressure of the frequency point is calculated by the following formula: S f = V f • sin(2πf · t); where t represents a time series, f represents a frequency, V f represents an input voltage, S f represents the excitation signal at this frequency point.

4. The analytical method for microphone sensitivity and sound leakage testing as described in claim 1, characterized in that: When step 4 is performed, the sound card is triggered to collect, and the collection duration is greater than the playing duration of the horn.

5. The analytical method for microphone sensitivity and sound leakage testing as described in claim 1, characterized in that: When step 5 is performed, the cross-correlation value of the signal is calculated by the following formula, and then the time delay is obtained to align the signals: Wherein, the excitation signal is x(t), the microphone response signal is y(t), T represents the period, R represents the cross-correlation value, τ represents the continuous variable, and dt represents the integral variable.

6. The analytical method for microphone sensitivity and sound leakage testing as described in claim 1, characterized in that: When step 7 is performed, the formula of Fourier transform is as follows: Wherein, F(w) represents the Fourier transform value, y(t) represents the time domain signal, e represents the base number of natural logarithm, and i represents the imaginary unit.

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