CN111510840A - Frequency-adjustable high-sound-pressure-level microphone calibration device - Google Patents
Frequency-adjustable high-sound-pressure-level microphone calibration device Download PDFInfo
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- CN111510840A CN111510840A CN202010294641.8A CN202010294641A CN111510840A CN 111510840 A CN111510840 A CN 111510840A CN 202010294641 A CN202010294641 A CN 202010294641A CN 111510840 A CN111510840 A CN 111510840A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R29/00—Monitoring arrangements; Testing arrangements
- H04R29/004—Monitoring arrangements; Testing arrangements for microphones
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Abstract
The invention discloses a frequency-adjustable high-sound-pressure-level microphone calibration device, which comprises a detuned standing wave tube and a loudspeaker; the detuning standing wave tube comprises a cavity, a piston, a thin tube and a microphone fixing device; one end of the cavity is closed, the other end of the cavity is provided with a movable piston, one end of the thin tube is fixed in a central through hole of the piston, and the other end of the thin tube is connected with the microphone fixing device; the variable cross-section closed space is formed by the closed end of the cavity, the piston, the thin tube and the microphone fixing device, and the resonant frequency of the detuning standing wave tube is changed by adjusting the position of the piston. The invention provides a high-sound-pressure-level (180dB) microphone calibration device with continuously adjustable frequency (100Hz-500Hz) and low distortion degree (less than 1%), which is based on the detuned standing wave tube principle, realizes output signal frequency adjustment through a standing wave tube with variable size, and meets the requirements of high-sound-pressure-level microphone frequency response measurement and calibration.
Description
Technical Field
The invention relates to the field of measurement and calibration of a high-sound-pressure-level microphone, in particular to a frequency-adjustable high-sound-pressure-level microphone calibration device.
Background
In recent years, the measurement requirement of the aviation/aerospace field on the noise parameters of the high-thrust engine is gradually increased, and the measurement and calibration requirements for the sound pressure level and the frequency response of the high-sound-pressure-level microphone are also increasingly increased. Most of the existing high-sound-pressure-level low-distortion microphones are based on the detuning standing wave tube principle, a standing wave field is formed in a multistage long tube through a loudspeaker to generate pure high sound pressure, wherein the frequency of a high-sound-pressure-level signal is determined by the resonance frequency of a sound cavity, and after the structure size of the sound cavity is fixed, the frequency of the high-sound-pressure-level signal is single and the bandwidth is narrow, so that the requirements of frequency response measurement and calibration of the high-sound-pressure level cannot be met.
For example, model 9719 high sound pressure calibrator manufactured by danish BK corporation, using a dual standing wave structure, with a maximum sound pressure level in the chamber of 174dB, a distortion factor of 0.5%, and a frequency of 500 Hz; the domestic Chinese academy acoustics Min et al develops a high-sound-pressure-level acoustic generator based on a gradually-changed cross-section detuned standing wave tube, the output sound pressure reaches 181dB, the distortion degree is 1%, and the frequency is 72 Hz; the above researches all have the problem that the output frequency of the high-sound-pressure level microphone is single. A frequency-adjustable high-sound-pressure microphone calibrator based on an electromagnetic drive diaphragm is researched by Arisaema, a research institute of Beijing space metering testing technology, and the like, wherein the frequency response range of the calibrator reaches 0.1Hz-5000Hz, and the maximum sound pressure level reaches 180dB, but when the sound pressure level is higher, the calibrator has poor distortion, cannot meet the calibration requirement of a microphone, and has the problem of microphone frequency response calibration under the condition of high sound pressure.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a high-sound-pressure-level (180dB) microphone calibration device with continuously adjustable frequency (100Hz-500Hz) and low distortion degree (less than 1 percent).
The technical scheme adopted by the invention is as follows: a frequency-adjustable high-sound-pressure-level microphone calibration device comprises a detuned standing wave tube and a loudspeaker; the detuning standing wave tube comprises a cavity, a piston, a thin tube and a microphone fixing device;
one end of the cavity is closed, the other end of the cavity is provided with a movable piston, one end of the thin tube is fixed in a central through hole of the piston, and the other end of the thin tube is connected with the microphone fixing device; the variable cross-section closed space is formed by the closed end of the cavity, the piston, the thin tube and the microphone fixing device, and the resonant frequency of the detuning standing wave tube is changed by adjusting the position of the piston.
Preferably, the closed end of the cavity is provided with an end cover, and the loudspeaker is positioned in the cavity and fixed on the end cover.
Preferably, the frequency-adjustable high-sound-pressure-level microphone calibration device further comprises a standing wave tube displacement control system, wherein the standing wave tube displacement control system comprises a microphone to be tested, a standard microphone, a data acquisition unit and a control device;
the microphone to be tested and the standard microphone are symmetrically arranged on the microphone fixing device and are respectively connected with the data acquisition unit; the control device controls the thin tube to move according to the data collected by the data collector and drives the piston to move so as to adjust the resonance frequency of the detuning standing wave tube.
Preferably, the outer diameter of the piston is equal to the inner diameter of the cavity, and the inner diameter of the piston is equal to the outer diameter of the tubule.
Preferably, the piston is a graphite piston or a metal piston with a graphite collar.
Preferably, the cavity is made of borosilicate material.
Preferably, the tubule is a metal tubule, a glass tubule or a ceramic tubule.
Preferably, the standing wave tube displacement control system further comprises a displacement table, a displacement table slider and a displacement sensor, the thin tube is connected with the displacement table slider, the control device controls the displacement table slider to slide on the displacement table, and the displacement sensor is used for detecting the displacement of the displacement table slider.
Preferably, the thin tube is fixedly connected to the displacement table slide block through a support.
Preferably, the microphone further comprises a signal generator, and the loudspeaker is connected with the control device through the signal generator; the control device controls the signal generator to generate an acoustic signal having a certain frequency and output the acoustic signal via the speaker.
Preferably, the speaker is connected to the power amplifier through a lead wire.
Preferably, the standard microphone and the microphone to be detected are respectively connected with the data acquisition unit through lead wires.
The beneficial effects of the above technical scheme are that:
(1) the standing wave tube type acoustic generator based on the variable cavity length changes the length of the standing wave tube cavity by adjusting the position of the piston, changes the resonant frequency of the harmonic standing wave tube according to requirements by adjusting the length of the standing wave tube cavity, realizes frequency adjustment under the condition of high sound pressure level, and meets the requirements of frequency response measurement and calibration of a high sound pressure level microphone.
(2) According to the invention, the cavity and the piston form a mechanical sealing structure, and the clearance between the piston and the cavity is small enough to meet the requirement of the sealing degree of the cavity; meanwhile, the piston and cavity materials are reasonably selected, and the friction force is low enough on the premise of ensuring the sealing property, so that the displacement precision of the piston is improved, and the requirements of frequency response measurement and calibration of the high-sound-pressure microphone are met.
Drawings
Fig. 1 is a schematic structural diagram of a frequency-tunable high sound pressure level microphone calibration device according to the present invention.
Wherein: 1-end cover, 2-loudspeaker, 3-cavity, 4-piston, 5-tubule, 6-support, 7-microphone to be measured, 8-standard microphone, 9-microphone fixing device, 10-displacement table slide block, 11-displacement table, 12-base, 13-displacement sensor, 14-data collector, 15-displacement controller, 16-control device, 17-signal generator, 18-power amplifier and 19-reflection end face.
Detailed Description
The embodiments of the present invention will be described in further detail with reference to the drawings and examples. The following detailed description of the embodiments and the accompanying drawings are provided to illustrate the principles of the invention and are not intended to limit the scope of the invention, which is defined by the claims, i.e., the invention is not limited to the preferred embodiments described.
In the description of the present invention, it is to be noted that, unless otherwise specified, "a plurality" means two or more; the terms "upper," "lower," "inner," "outer," and the like, indicate orientations and positional relationships that are merely convenient or simple to describe, but do not indicate or imply that the referenced devices or elements must be in a particular orientation, constructed and operated, and thus are not to be considered limiting. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. The following description is given with reference to the orientation words as shown in the drawings, and is not intended to limit the specific structure of the present invention. In the description of the present invention, it should be further noted that the terms "mounted," "connected," and "connected" are to be construed broadly and their meanings in the present invention may be understood as appropriate by those skilled in the art, unless otherwise specifically defined or limited.
Example 1
As shown in fig. 1, the calibration apparatus for a frequency-adjustable high sound pressure level microphone disclosed in this embodiment includes a detuned standing wave tube, a speaker 2, a standing wave tube displacement control system, and a base 12; the detuning standing wave tube comprises an end cover 1, a cavity 3, a piston 4, a thin tube 5 and a microphone fixing device 9, wherein the cavity 3 is made of materials with smooth and wear-resistant surfaces, such as a glass cavity made of borosilicate materials, and a metal material made of ceramics or with a wear-resistant coating, and the glass cavity with mature processing technology and low price is preferably selected; the thin tube 5 is made of materials with smooth surfaces, such as metal, glass or ceramic materials, and the thin tube does not require the wear-resistant inner surface, so that metal materials which are easier to process and low in price are preferred; the standing wave tube displacement control system comprises a microphone 7 to be measured, a standard microphone 8, a displacement table slide block 10, a displacement table 11, a displacement sensor 13, a data acquisition unit 14, a displacement controller 15, a control device 16, a signal generator 17 and a power amplifier 18; the control device 16 is a computer.
One end of the cavity 3 is fixed on the end cover 1, the other end is connected with the piston 4, the outer diameter of the piston 4 is equal to the inner diameter of the cavity 3, and the inner diameter of the piston 4 is equal to the outer diameter of the thin tube 5; one end of the thin tube 5 is fixed in the central through hole of the piston 4, and the other end is arranged on the microphone fixing device 9; the reflection end face 19 of the end cover 1, the cavity 3, the piston 4, the thin tube 5 and the microphone fixing device 9 form a variable cross-section closed space, the two-stage variable cross-section standing wave tube belongs to a detuning standing wave tube, the cavity 3 and the piston 4 form a mechanical sealing structure, the gap between the piston 4 and the cavity 3 is small enough to meet the requirement of the sealing degree of the cavity, and the sealing structure ensures the acoustic sealing performance, so that the sound leakage cannot be generated in the cavity; the piston 4 can be a graphite piston or a metal piston with a graphite lantern ring, the piston material contacting with the cavity is guaranteed to be graphite, the graphite has good self-lubricating performance, the friction coefficient can be effectively reduced, and the piston 4 is guaranteed to have extremely low friction force during movement.
The thin tube 5 is fixed on a displacement table slide block 10 through a bracket 6 and is connected with a control device 16 through a displacement controller 15; the control device 16 controls the displacement table slide block 10 to move horizontally on the displacement table 11 through the displacement controller 15, so that the thin tube 5 and the piston 4 are driven to move in the cavity 3 through the bracket 6; along with the position change of the piston 4, the volume and the resonant frequency of the variable cross-section closed cavity are changed; the displacement sensor 13 is connected to the displacement stage slide 10 and is configured to measure the displacement of the displacement stage slide 10 and transmit displacement data thereof to the control device 16.
The loudspeaker 2 is positioned in the cavity 3 and fixed on the reflecting end surface 19 of the end cover 1; the loudspeaker 2 is connected with a power amplifier 18 through a lead wire, and the power amplifier 18 is connected with a control device 16 through a signal generator 17; the control device 16 controls the signal generator 17 to output the frequency of the sound signal, the frequency of the sound signal is amplified by the power amplifier 18 and then output by the loudspeaker, namely, the control device 16 can control the frequency and amplitude of the output sound signal of the loudspeaker 2, when the frequency of the sound signal output by the loudspeaker 2 is equal to the resonance frequency of the closed cavity, a high sound pressure standing wave field is formed in the cavity, and at the moment, the maximum sound pressure level at the microphone fixing device 9 reaches 180 dB.
Simultaneously placing the microphone 7 to be measured and the standard microphone 8 for measuring the required sound pressure on two adjacent measuring points in a sound field by adopting a simultaneous comparison method, namely symmetrically installing the microphone 7 to be measured and the standard microphone 8 on a microphone fixing device 9, and respectively connecting the data acquisition device 14 through lead wires, wherein the data acquisition device 14 is connected with a control device 16; the data collected by the data collector 14 are transmitted to the control device 16, and the control device 16 respectively controls the displacement controller 15 and the signal generator 17 according to the collected acoustic signal feedback, so that the output frequency of the loudspeaker 2 is consistent with the resonant frequency of the cavity.
In order to realize the output sound pressure frequency adjustment, the cavity length l of the cavity needs to be obtained through calculationASo as to change the volume and resonant frequency F of the closed cavity, then collect output signal sound pressure level L by standard microphone, feedback control the output frequency F of the loudspeaker, make the sound signal frequency equal to the resonant frequency of the closed cavity, at this moment, form high sound pressure standing wave field in the closed cavity, the distortion degree and sound pressure level both meet the calibration requirement (1%, 180dB), the length and sectional area of two standing wave tubes are l respectivelyA、sAAnd lB、sBThe sound velocity is c, and the resonance condition of the detuned standing wave tube meets the following relational expression:
after the standing wave tube is fixed in size, sA、lBAnd sBAre all fixed values, and can therefore be varied by varying the piston positionAThe resonant frequency f is adjusted.
Assume that there is l in the initial stateA＝l1，F＝f＝f1，L1180dB, the system output sound pressure level is 180dB, and the frequency is f1Is adjusted to f2The steps are as follows:
1) calculating the resonance frequency f from the resonance condition2Length of pipe l corresponding to time2；
2) The position of the slide block is adjusted to ensure that the cavity length l of the glass cavity bodyA＝l2；
3) Measuring the resonance frequency f of the closed acoustic cavity at this time, ifSatisfy f ═ f2Jumping to step 5); if f is not satisfied2Jumping to step 4);
4) at the current slide position l2Fine-tuning on the basis ofA＝l2+ Δ l, where Δ l is a fine tuning distance, which may be determined empirically, and jumping to step 3 after the adjustment is completed);
5) adjusting the output power of the speaker to output a sound pressure level of L2＝180dB。
The invention provides a high-sound-pressure-level (180dB) microphone calibration device with continuously adjustable frequency (100Hz-500Hz) and low distortion degree (less than 1%), which is based on the detuned standing wave tube principle, realizes output signal frequency adjustment through a standing wave tube with variable size, and meets the requirements of high-sound-pressure-level microphone frequency response measurement and calibration.
The standing wave tube acoustic generator based on the variable cavity length changes the length of the standing wave tube cavity by adjusting the position of the piston, changes the resonant frequency according to requirements by adjusting the length of the standing wave tube cavity, realizes frequency adjustment under the condition of high sound pressure level by the resonant frequency of the standing wave tube, and meets the requirements of frequency response measurement and calibration of a high sound pressure level microphone; according to the invention, the cavity and the piston form a mechanical sealing structure, and the clearance between the piston and the cavity is small enough to meet the requirement of the sealing degree of the cavity; meanwhile, materials of the piston and the cavity are reasonably selected, so that the friction force is low enough on the premise of ensuring the sealing property, and the requirements of frequency response measurement and calibration of the high-sound-pressure microphone are met.
While the invention has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (10)
1. A frequency-adjustable high sound pressure level microphone calibration device is characterized by comprising a detuned standing wave tube and a loudspeaker (2); the detuning standing wave tube comprises a cavity (3), a piston (4), a thin tube (5) and a microphone fixing device (9);
one end of the cavity (3) is closed, and the other end of the cavity is provided with a movable piston (4); one end of the thin tube (5) is fixed in a central through hole of the piston (4), and the other end of the thin tube is connected with a microphone fixing device (9); the variable cross-section airtight space is composed of the closed end of the cavity (3), the piston (4), the thin tube (5) and the microphone fixing device (9), and the resonance frequency of the detuning standing wave tube is changed by adjusting the position of the piston (4).
2. Microphone calibration device according to claim 1, characterized in that the closed end of the cavity (3) is provided with an end cap (1), and that the loudspeaker (2) is located inside the cavity (3) and fixed to the end cap (1).
3. The microphone calibration device according to claim 1, further comprising a standing wave tube displacement control system, wherein the standing wave tube displacement control system comprises a microphone (7) to be tested, a standard microphone (8), a data collector (14) and a control device (16);
the microphone (7) to be tested and the standard microphone (8) are symmetrically arranged on the microphone fixing device (9) and are respectively connected with the data acquisition unit (14); the control device (16) controls the thin tube (5) to move and drives the piston (4) to move according to the data collected by the data collector (14) so as to adjust the resonant frequency of the detuned standing wave tube.
4. Microphone calibration device according to claim 1, characterized in that the outer diameter of the piston (4) is equal to the inner diameter of the cavity (3), and the inner diameter of the piston (4) is equal to the outer diameter of the tubule (5).
5. Microphone calibration device according to claim 1, characterized in that the piston (4) is a graphite piston or a metal piston with a graphite collar.
6. Microphone calibration device according to claim 1, characterized in that the cavity (3) is made of borosilicate material.
7. Microphone calibration device according to claim 1, characterized in that the capillary (5) is a metal capillary, a glass capillary or a ceramic capillary.
8. The microphone calibration device as claimed in claim 3, wherein the standing wave tube displacement control system further comprises a displacement table (11), a displacement table slider (10) and a displacement sensor (13), the thin tube (5) is connected with the displacement table slider (10), the control device (16) controls the displacement table slider (10) to slide on the displacement table (11), and the displacement sensor (13) is used for detecting the displacement of the displacement table slider (10).
9. Microphone calibration device according to claim 8, characterized in that the tubule (5) is fixedly connected to the displacement table slide (10) by means of a bracket (6).
10. Microphone calibration device according to claim 1, characterized by a signal generator (17), by which the loudspeaker (2) is connected to the control device (16) via the signal generator (17); the control device (16) controls the signal generator (17) to generate an acoustic signal with a certain frequency and output the acoustic signal through the loudspeaker (2).
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Cited By (3)
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| CN113405650A (en) * | 2021-05-29 | 2021-09-17 | 西北工业大学 | Vector sensor correction method based on standing wave tube and sound absorption material |
| IT202000028430A1 (en) * | 2020-11-25 | 2022-05-25 | Leonardo Spa | MICROPHONE CALIBRATION METHOD, PARTICULARLY MICROPHONE FOR AERONAUTICAL USE |
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| Publication number | Priority date | Publication date | Assignee | Title |
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