Capacitor microphone phase frequency response calibration device and method based on electrostatic excitation method

Abstract

The invention discloses a capacitor microphone phase frequency response calibration device and method based on an electrostatic excitation method, and the device comprises a signal source which is used for outputting a variable frequency electric signal; the electrostatic exciter power supply is used for amplifying the variable-frequency electric signal; the electrostatic exciter is used for generating constant electrostatic pressure on a vibrating diaphragm of the microphone; the microphone is used for outputting an acoustic-electric conversion signal under the action of the electrostatic exciter; the pre-amplifier is used for amplifying the signal and then outputting the signal; the adaptive amplifier is used for outputting an output electric signal of the pre-amplifier to the multi-channel sound analyzer; the multi-channel sound analyzer is used for analyzing and processing the received electric signal; and the computer is used for controlling the amplitude, the frequency and the duration of the variable-frequency electric signal output by the signal source. According to the invention, a dual-channel electrostatic exciter synchronous generation design is adopted, electrostatic excitation field signals with consistent phases are synchronously generated, rapid calibration of the relative phase frequency response of the condenser microphone is realized, and the problem of phase calibration of the condenser microphone is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of acoustic metrology, and in particular relates to a device and method for calibrating phase-frequency response of a capacitor microphone based on an electrostatic excitation method. Background Art

[0002] The earliest application of microphone phase calibration was to calibrate the phase error of the sound intensity sensor to study the reactive sound intensity in the sound intensity measurement caused by phase mismatch. In 1978, American scholar Chung proposed the microphone exchange method. The basic idea is to conduct two tests at the same measuring point. The second test is to flip the sound intensity probe 180 degrees, and indirectly calculate the transfer function of the two channels to calibrate the cross-spectrum. In 1981, Canadian scholar Krishnappa proposed the transfer function method, describing a sound intensity probe calibration method based on the cross-spectral density method. By exposing the two microphones to signals with the same phase and pressure level, the transfer function between the two microphone systems is measured, and the phase and gain mismatch errors can be calibrated over a wide frequency range. The residual sound intensity method was originally proposed by Jacobsen in Denmark. The basic principle is to subtract the residual sound intensity generated by the phase mismatch error from the total sound intensity value obtained by the test, thereby eliminating or reducing the influence of the phase mismatch on the sound intensity measurement. In 1984, Gade studied the influence of semi-reverberant field conditions on the phase mismatch error. Nielsen and Jacobsen et al. proposed to use the "sound pressure-residual sound intensity index" method to calibrate the phase mismatch error between the two channels. This method requires the use of professional sound intensity calibrators, such as B&K 3541 or B&K4297. The high price limits the promotion of this method in engineering. In 2005, Nagata et al. proposed the rotating microphone method. This calibration method is carried out in an anechoic chamber. It uses a reference sound intensity probe calibrated by a sound pressure phase difference calibrator to determine the deviation error during the comparative sound intensity measurement.

[0003] The methods described above are methods for correcting the phase mismatch error of cross-spectral sound intensity measurement. These methods aim to improve the sound intensity calculation formula to indirectly correct the phase mismatch error of the two microphones, but do not improve the phase matching degree of the two microphones, nor do they directly correct the phase mismatch error of the sound pressure signals collected by the two microphones. Summary of the invention

[0004] The technology of the present invention solves the problem: overcomes the shortcomings of the prior art, provides a condenser microphone phase-frequency response calibration device and method based on the electrostatic excitation method, adopts a dual-channel electrostatic exciter synchronous generation design, synchronously generates phase-consistent electrostatic excitation field signals, realizes rapid calibration of the relative phase frequency response of the condenser microphone, and solves the problem of condenser microphone phase calibration.

[0005] In order to solve the above technical problems, the present invention discloses a capacitance microphone phase-frequency response calibration device based on electrostatic excitation method, comprising: a computer, a signal source, an electrostatic exciter power supply, an electrostatic exciter, a microphone, a preamplifier, an adjustment amplifier and a multi-channel sound analyzer;

[0006] A signal source, used to output variable frequency electrical signals under computer control;

[0007] The electrostatic actuator power supply is used to amplify the variable frequency electrical signal, output the driving voltage, and drive the electrostatic actuator to work;

[0008] An electrostatic actuator, which is used to generate a constant electrostatic pressure on the diaphragm of the microphone when driven by an electrostatic actuator power supply;

[0009] A microphone, used to output an acoustic-to-electric conversion signal under the action of an electrostatic actuator;

[0010] A preamplifier is used to amplify the acoustic-to-electric conversion signal output by the microphone and then output it;

[0011] A conditioning amplifier is used to supply power to the preamplifier and the microphone; and output the output electrical signal of the preamplifier to the multi-channel sound analyzer;

[0012] Multi-channel sound analyzer, used to analyze and process the received electrical signals;

[0013] A computer is used to control the amplitude, frequency and duration of the variable frequency electrical signal output by the signal source.

[0014] In the above-mentioned condenser microphone phase-frequency response calibration device based on the electrostatic excitation method, the electrostatic exciter includes: a first electrostatic exciter and a second electrostatic exciter; the microphone includes: a standard microphone and a calibrated microphone; the preamplifier includes: a first preamplifier and a second preamplifier; the adaptive amplifier includes: a first adaptive amplifier and a second adaptive amplifier; wherein, during the test: first, the first electrostatic exciter, the standard microphone, the first preamplifier and the first adaptive amplifier are connected in sequence; the second electrostatic exciter, the calibrated microphone, the second preamplifier and the second adaptive amplifier are connected in sequence; then, the first electrostatic exciter, the calibrated microphone, the first preamplifier and the first adaptive amplifier are connected in sequence; the second electrostatic exciter, the calibrated microphone, the first preamplifier and the first adaptive amplifier are connected in sequence.

[0015] In the above-mentioned capacitor microphone phase-frequency response calibration device based on the electrostatic excitation method, the electrostatic actuator power supply is connected to the first electrostatic actuator and the second electrostatic actuator respectively through a tee; wherein the first electrostatic actuator and the second electrostatic actuator are two completely identical electrostatic actuators.

[0016] In the above-mentioned capacitor microphone phase-frequency response calibration device based on the electrostatic excitation method, the variable frequency electrical signal u output by the signal source is in For: in =A·sin(2πf·t); where f represents frequency, A represents amplitude, and t represents time.

[0017] In the above-mentioned capacitor microphone phase-frequency response calibration device based on the electrostatic excitation method, the driving voltage u output by the electrostatic exciter power supply is d Expressed as: d =U0+a·u in ; Among them, U0 represents the DC bias voltage, U0=800V; a represents the amplification factor, and the value of a is: 10~20.

[0018] Correspondingly, the present invention also discloses a method for calibrating the phase-frequency response of a capacitor microphone based on an electrostatic excitation method, comprising:

[0019] Step 1, connecting a computer to a signal source and a multi-channel sound analyzer respectively; connecting the signal source to an electrostatic actuator power supply; connecting the electrostatic actuator power supply to a first electrostatic actuator and a second electrostatic actuator respectively; connecting the multi-channel sound analyzer to a first conditioning amplifier and a second conditioning amplifier respectively;

[0020] Step 2, connecting the first electrostatic actuator, the standard microphone, the first preamplifier and the first adaptive amplifier in sequence; connecting the second electrostatic actuator, the calibrated microphone, the second preamplifier and the second adaptive amplifier in sequence;

[0021] Step 3, start the test, the signal source outputs a variable frequency electrical signal under the control of the computer; the variable frequency electrical signal outputs a driving voltage after passing through the electrostatic actuator power supply; the first electrostatic actuator and the second electrostatic actuator work under the drive of the electrostatic actuator power supply, and generate a constant electrostatic pressure on the diaphragm of the standard microphone and the calibrated microphone respectively;

[0022] Step 4: The acoustic-to-electric conversion signal output by the standard microphone is output to the multi-channel sound analyzer after passing through the first preamplifier and the first adaptive amplifier; the acoustic-to-electric conversion signal of the calibrated microphone is output to the multi-channel sound analyzer after passing through the second preamplifier and the second adaptive amplifier; the first electrical signal phase difference Δθ is obtained by analytical processing by the multi-channel sound analyzer 21 (f);

[0023] Step 5, swap the positions of the standard microphone and the calibrated microphone, that is, connect the first electrostatic actuator, the calibrated microphone, the first preamplifier and the first adaptive amplifier in sequence; connect the second electrostatic actuator, the standard microphone, the second preamplifier and the second adaptive amplifier in sequence; repeat the above steps 3 to 4, and obtain the second electrical signal phase difference Δθ through the multi-channel sound analyzer analysis and processing12 (f);

[0024] Step 6: According to Δθ 21 (f) and Δθ 12 (f) The phase difference Δθ between the calibrated microphone and the standard microphone is obtained by solving the equation.

[0025] In the above-mentioned electrostatic excitation method for calibrating the phase-frequency response of a capacitor microphone, Δθ = [Δθ 21 (f)-Δθ 12 (f)] / 2.

[0026] In the above-mentioned capacitance microphone phase-frequency response calibration method based on electrostatic excitation method,

[0027] Δθ 21 (f)=[S φDUT (f)-S φREF (f)]+ε φ

[0028] Δθ 12 (f)=[S φREF (f)-S φDUT (f)]+ε φ

[0029] Among them, S φREF (f) represents the phase sensitivity of the standard microphone, S φDUT (f) represents the phase sensitivity of the calibrated microphone, ε φ Represents the phase measurement error introduced by the preamplifier, conditioning amplifier, and multi-channel acoustic analyzer.

[0030] The present invention has the following advantages:

[0031] (1) The present invention discloses a phase-frequency response calibration scheme for a condenser microphone based on an electrostatic excitation method, which is different from the prior art coupling cavity pressure field comparison method calibration scheme. Since the phase consistency in the pressure field coupling cavity is determined by the ratio of the volume in the cavity to the wavelength of the sound wave, that is, when the volume in the coupling cavity remains unchanged, the higher the sound wave frequency, the smaller the wavelength, and the worse the consistency of the sound pressure in the cavity, which generally does not exceed 25kHz, the relative phase value of the calibration technology based on the electrostatic excitation method described in the scheme of the present invention is determined by the consistency of the electrostatic field, and the electrostatic field is determined by the phase consistency of the excitation electrical signal, and the consistency of the excitation electrical signal is much higher than the consistency of the sound pressure. Therefore, the relative phase calibration result has a higher accuracy.

[0032] (2) The present invention discloses a phase-frequency response calibration scheme for a capacitor microphone based on an electrostatic excitation method, with a wide frequency range of 10 Hz to 100 kHz.

[0033] (3) The present invention discloses a phase-frequency response calibration scheme for a capacitor microphone based on an electrostatic excitation method, which uses a standard microphone as a reference and can achieve relative phase traceability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of a capacitor microphone phase-frequency response calibration device based on an electrostatic excitation method in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] Reference Figure 1 In this embodiment, the phase-frequency response calibration device of the capacitor microphone based on the electrostatic excitation method includes: a computer, a signal source, an electrostatic exciter power supply, an electrostatic exciter, a microphone, a preamplifier, an adaptive amplifier and a multi-channel sound analyzer. Among them, the signal source is used to output a variable frequency electrical signal under the control of the computer; the electrostatic exciter power supply is used to amplify the variable frequency electrical signal, output a driving voltage, and drive the electrostatic exciter to work; the electrostatic exciter is used to work under the drive of the electrostatic exciter power supply to generate a constant electrostatic pressure on the diaphragm of the microphone; the microphone is used to output an acoustic-to-electric conversion signal under the action of the electrostatic exciter; the preamplifier is used to amplify and output the acoustic-to-electric conversion signal output by the microphone; the adaptive amplifier is used to power the preamplifier and the microphone; the output electrical signal of the preamplifier is output to the multi-channel sound analyzer; the multi-channel sound analyzer is used to analyze and process the received electrical signal; the computer is used to control the amplitude, frequency and duration of the variable frequency electrical signal output by the signal source.

[0037] In this embodiment, the microphone includes: a standard microphone and a calibrated microphone; based on the standard microphone and the calibrated microphone, the present invention adopts a dual-channel electrostatic actuator synchronous generation design. That is: the electrostatic actuator includes: a first electrostatic actuator and a second electrostatic actuator; the preamplifier includes: a first preamplifier and a second preamplifier; the adaptive amplifier includes: a first adaptive amplifier and a second adaptive amplifier. Wherein, during the test: first, the first electrostatic actuator, the standard microphone, the first preamplifier and the first adaptive amplifier are connected in sequence; the second electrostatic actuator, the calibrated microphone, the second preamplifier and the second adaptive amplifier are connected in sequence; then, the first electrostatic actuator, the calibrated microphone, the first preamplifier and the first adaptive amplifier are connected in sequence; the second electrostatic actuator, the standard microphone, the second preamplifier and the second adaptive amplifier are connected in sequence.

[0038] In this embodiment, the electrostatic actuator power supply is respectively connected to the first electrostatic actuator and the second electrostatic actuator through a tee; wherein the first electrostatic actuator and the second electrostatic actuator are two completely identical electrostatic actuators.

[0039] In this embodiment, the variable frequency electrical signal u output by the signal source in For: in =A·sin(2πf·t); driving voltage u output by the electrostatic actuator power supply d Expressed as: d =U0+a·u in ; Among them, U0 represents the DC bias voltage, U0=800V; a represents the amplification factor, the value of a is: 10~20; f represents the frequency, the value is 10Hz~40kHz; A represents the amplitude, the value is 3V~8V; t represents time.

[0040] On the basis of the above embodiments, the present invention further discloses a method for calibrating the phase-frequency response of a capacitor microphone based on an electrostatic excitation method and implemented based on the above device, comprising:

[0041] Step 1, connect the computer to the signal source and the multi-channel sound analyzer respectively; connect the signal source to the electrostatic actuator power supply; connect the electrostatic actuator power supply to the first electrostatic actuator and the second electrostatic actuator respectively; connect the multi-channel sound analyzer to the first conditioning amplifier and the second conditioning amplifier respectively.

[0042] Step 2, connecting the first electrostatic actuator, the standard microphone, the first preamplifier and the first adaptive amplifier in sequence; connecting the second electrostatic actuator, the calibrated microphone, the second preamplifier and the second adaptive amplifier in sequence.

[0043] Step 3, start the test, the signal source outputs a variable frequency electrical signal under the control of the computer; the variable frequency electrical signal outputs a driving voltage after passing through the electrostatic actuator power supply; the first electrostatic actuator and the second electrostatic actuator work under the drive of the electrostatic actuator power supply, and generate a constant electrostatic pressure on the diaphragm of the standard microphone and the calibrated microphone respectively.

[0044] Step 4: The acoustic-to-electric conversion signal output by the standard microphone is output to the multi-channel sound analyzer after passing through the first preamplifier and the first adaptive amplifier; the acoustic-to-electric conversion signal of the calibrated microphone is output to the multi-channel sound analyzer after passing through the second preamplifier and the second adaptive amplifier; the first electrical signal phase difference Δθ is obtained by analytical processing by the multi-channel sound analyzer 21 (f). Where Δθ 21 (f)=[S φDUT (f)-S φREF (f)]+ε φ , S φREF(f) represents the phase sensitivity of the standard microphone, S φDUT (f) represents the phase sensitivity of the calibrated microphone, ε φ Represents the phase measurement error introduced by the preamplifier, conditioning amplifier, and multi-channel acoustic analyzer.

[0045] Step 5, swap the positions of the standard microphone and the calibrated microphone, that is, connect the first electrostatic actuator, the calibrated microphone, the first preamplifier and the first adaptive amplifier in sequence; connect the second electrostatic actuator, the standard microphone, the second preamplifier and the second adaptive amplifier in sequence; repeat the above steps 3 to 4, and obtain the second electrical signal phase difference Δθ through the multi-channel sound analyzer analysis and processing 12 (f). Where Δθ 12 (f)=[S φREF (f)-S φDUT (f)]+ε φ .

[0046] Step 6: According to Δθ 21 (f) and Δθ 12 (f), the phase difference Δθ between the calibrated microphone and the standard microphone is obtained by solving the equation. Where Δθ=[Δθ 21 (f)-Δθ 12 (f)] / 2.

[0047] When connecting the microphone to the electrostatic actuator, first remove the microphone protective cover and then place the electrostatic actuator on the microphone surface; since the electrostatic fields are consistent, the phase difference of the electrical signals output by the two preamplifiers is the phase difference of the phase sensitivities of the two microphones.

[0048] According to the above method, the measurement accuracy of this device is as follows:

[0049] <0.5°@10~10kHz

[0050] <4°@10~40kHz.

[0051] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0052] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A condenser microphone phase-frequency response calibration device based on electrostatic excitation method, characterized in that: include: Computer, signal source, electrostatic actuator power supply, electrostatic actuator, microphone, preamplifier, conditioning amplifier and multi-channel sound analyzer; A signal source, used to output variable frequency electrical signals under computer control; The electrostatic actuator power supply is used to amplify the variable frequency electrical signal, output the driving voltage, and drive the electrostatic actuator to work; An electrostatic actuator, which is used to generate a constant electrostatic pressure on the diaphragm of the microphone when driven by an electrostatic actuator power supply; A microphone, used to output an acoustic-to-electric conversion signal under the action of an electrostatic actuator; A preamplifier is used to amplify the acoustic-to-electric conversion signal output by the microphone and then output it; A conditioning amplifier is used to supply power to the preamplifier and the microphone; and output the output electrical signal of the preamplifier to the multi-channel sound analyzer; Multi-channel sound analyzer, used to analyze and process the received electrical signals; A computer is used to control the amplitude, frequency and duration of the variable frequency electrical signal output by the signal source.

2. The electrostatic excitation method-based condenser microphone phase-frequency response calibration device according to claim 1, characterized in that: The electrostatic actuator comprises: a first electrostatic actuator and a second electrostatic actuator; the microphone comprises: a standard microphone and a calibrated microphone; the preamplifier comprises: a first preamplifier and a second preamplifier; the adaptive amplifier comprises: a first adaptive amplifier and a second adaptive amplifier; wherein, during the test: first, the first electrostatic actuator, the standard microphone, the first preamplifier and the first adaptive amplifier are connected in sequence; the second electrostatic actuator, the calibrated microphone, the second preamplifier and the second adaptive amplifier are connected in sequence; then, the first electrostatic actuator, the calibrated microphone, the first preamplifier and the first adaptive amplifier are connected in sequence; the second electrostatic actuator, the standard microphone, the second preamplifier and the second adaptive amplifier are connected in sequence.

3. The device for calibrating phase-frequency response of a capacitor microphone based on electrostatic excitation method according to claim 2, characterized in that: The electrostatic actuator power supply is respectively connected to the first electrostatic actuator and the second electrostatic actuator through a tee; wherein the first electrostatic actuator and the second electrostatic actuator are two completely identical electrostatic actuators.

4. The electrostatic excitation method-based condenser microphone phase-frequency response calibration device according to claim 1, characterized in that: The variable frequency electrical signal u output by the signal source in For: in =A·sin(2πf·t); where f represents frequency, A represents amplitude, and t represents time.

5. The device for calibrating phase-frequency response of a capacitor microphone based on electrostatic excitation method according to claim 4, characterized in that: The driving voltage u output by the electrostatic actuator power supply d Expressed as: u d =U0+a·u in ; Wherein, U0 represents the DC bias voltage, U0=800V; a represents the amplification factor, and the value of a is: 10~20.

6. A method for calibrating the phase-frequency response of a capacitor microphone based on an electrostatic excitation method, characterized in that: include: Step 1, connecting the computer to the signal source and the multi-channel sound analyzer respectively; Connect the signal source to the electrostatic actuator power supply; Connecting the electrostatic actuator power supply to the first electrostatic actuator and the second electrostatic actuator respectively; connecting the multi-channel sound analyzer to the first conditioning amplifier and the second conditioning amplifier respectively; Step 2, connecting the first electrostatic actuator, the standard microphone, the first preamplifier and the first adaptive amplifier in sequence; connecting the second electrostatic actuator, the calibrated microphone, the second preamplifier and the second adaptive amplifier in sequence; Step 3, start the test, the signal source outputs a variable frequency electrical signal under computer control; The variable frequency electrical signal outputs a driving voltage after passing through the electrostatic actuator power supply; The first electrostatic actuator and the second electrostatic actuator work under the driving of the electrostatic actuator power supply to generate constant electrostatic pressure on the diaphragms of the standard microphone and the calibrated microphone respectively; Step 4: The acoustic-to-electric conversion signal output by the standard microphone is output to the multi-channel sound analyzer after passing through the first preamplifier and the first adaptive amplifier; the acoustic-to-electric conversion signal of the calibrated microphone is output to the multi-channel sound analyzer after passing through the second preamplifier and the second adaptive amplifier; the first electrical signal phase difference Δθ is obtained by analytical processing by the multi-channel sound analyzer 21 (f); Step 5, swap the positions of the standard microphone and the calibrated microphone, that is, connect the first electrostatic actuator, the calibrated microphone, the first preamplifier and the first adaptive amplifier in sequence; connect the second electrostatic actuator, the standard microphone, the second preamplifier and the second adaptive amplifier in sequence; repeat the above steps 3 to 4, and obtain the second electrical signal phase difference Δθ through the multi-channel sound analyzer analysis and processing 12 (f); Step 6: According to Δθ 21 (f) and Δθ 12 (f) The phase difference Δθ between the calibrated microphone and the standard microphone is obtained by solving the equation.

7. The method for calibrating phase-frequency response of a capacitor microphone based on electrostatic excitation method according to claim 6, characterized in that: Δθ=[Δθ 21 (f)-Δθ 12 (f)] / 2.

8. The method for calibrating phase-frequency response of a capacitor microphone based on electrostatic excitation method according to claim 6, characterized in that: Dth 21 (f)=[S φDUT (f)-S φREF (f)]+e φ Dth 12 (f)=[S φREF (f)-S φDUT (f)]+e φ Among them, S φREF (f) represents the phase sensitivity of the standard microphone, S φDUT (f) represents the phase sensitivity of the calibrated microphone, ε φ Represents the phase measurement error introduced by the preamplifier, conditioning amplifier, and multi-channel acoustic analyzer.

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