CN105050020A - Free sound field device based on optical non-destructive monitoring technology - Google Patents
Free sound field device based on optical non-destructive monitoring technology Download PDFInfo
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- CN105050020A CN105050020A CN201510464431.8A CN201510464431A CN105050020A CN 105050020 A CN105050020 A CN 105050020A CN 201510464431 A CN201510464431 A CN 201510464431A CN 105050020 A CN105050020 A CN 105050020A
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Abstract
The invention provides a free sound field device based on an optical non-destructive monitoring technology and relates to a measurement technology. The free sound field device comprises a silencing box and an optical fiber collimator; a high-transmittance window piece and a lens are arranged on the two corresponding sidewalls of the silencing box, respectively; a light trap, a sound source and particles are arranged in the silencing box; laser light emitted by a laser is split into two beams of laser light of the same light intensity by use of a half transparent and half reflecting mirror, and the two beams of laser light enter the silencing box to be mixed together and then enter the light trap; scattered light in the silencing box enters the optical fiber collimator via the lens. The free sound field device based on the optical non-destructive monitoring technology is used for solving the technical problems that an interventional measurement manner is used for measuring the sound field of a microphone in the prior art, the measured sound field is affected by the microphone and the non-standard microphone cannot be calibrated. The free sound field device based on the optical non-destructive monitoring technology has the beneficial effects that the two light beams are used for measuring sound pressure and the sound field in the silencing box is the free sound field, particles are taken as a medium, and the sound speed and the sound pressure of a light beam interference point are accurately measured by use of an auto-correlation technique of scattering light by use of the particles. A receiving system is simple in structure and the signal-to-noise ratio of the system is high.
Description
Technical field
The present invention relates to test measurement device, especially relate to a kind of optics nondestructive technique that utilizes to the sound field device of microphone calibration measurement.
Background technology
Acoustic detection technology is in field extensive uses such as medical treatment, environmental protection, industry and oceans.Microphone, as a kind of important measurement instrument, is the key sensor of Acoustic detection.Calibration at present to microphone, mainly adopts standard source, utilizes microphone to calibrate the microphone be calibrated with the method for reciprocity.But there is two problems: (1) is because the size of microphone own is on the impact of sound field, can only calibrate (as 1/4 inch by the microphone in specific orientation to specific dimensions, 1/2 inch, 1 inch etc.), and some nonstandard microphones cannot be calibrated, as Mems microphone, fiber microphone etc., these nonstandard microphones are used widely in various electronic product, detection instrument, but cannot realize magnitude tracing; (2) utilize the mode of a microphone array or microphone repeatedly movement to measure, this metering system is a kind of mode getting involved measurement, and the sound field of measurement can be subject to the impact of microphone.Chinese patent Authorization Notice No. CN101895809B, authorized announcement date on July 3rd, 2013, the patent of invention that name is called " a kind of microphone calibration steps ", provides a kind of microphone calibrator.Comprise sound source, muffler, microphone construction section to be calibrated and standard microphone construction section, muffler, standard microphone construction section, microphone construction section to be calibrated and sound source adopt Flange joint from front to back successively; Microphone construction section to be calibrated has microphone installing hole to be calibrated, for installing microphone to be calibrated; Standard microphone construction section has at least three standard microphone installing holes, for installation code microphone; Thus microphone to be calibrated is arranged in the microphone installing hole on microphone construction section vertical section to be calibrated a week, then by keeper, microphone to be calibrated is positioned at microphone construction section to be calibrated.This metering system is also a kind of mode getting involved measurement, and the sound field namely measured can be subject to the impact of microphone.And as metering device, this influence amount is unacceptable often.Along with the development of science and technology, in recent years, obtain based on the acoustic field mode of optics and study widely.The researcher of Denmark, Japan, Britain and Germany have studied the mode that acoustooptical effect measures this sound-filed simulation, but this mode is suitable for ultrasonic wave, the sensitivity that the low-frequency sound wave for audible is measured and signal to noise ratio low.
Summary of the invention
In order to solve prior art, to there is measuring microphone sound field be a kind of mode getting involved measurement, the sound field measured can be subject to the impact of microphone, and the technical problem of nonstandard microphone can not be calibrated, the invention provides a kind of free found field device based on optics non-destructive monitoring technology.Measured the velocity of sound and the acoustic pressure of certain point in free found field by particle scattered light correlation technique, owing to being measured acoustic pressure by laser beam, in this sound field, do not introduce any barrier, make the sound field in anechoic chamber be free found field.This free found field device can also as calibrating installation, for the calibration of the microphone to non-size.
Technical scheme of the present invention is: a kind of free found field device based on optics non-destructive monitoring technology, it comprises laser, semi-transparent semi-reflecting lens, speculum, silencer box and optical fiber collimator, silencer box is cuboid airtight cavity structure, the corresponding two side of silencer box is respectively equipped with high diaphragm and lens thoroughly, light trapping is provided with in silencer box, sound source and particle, laser sends laser and is divided into through semi-transparent semi-reflecting lens the laser that two-beam is equal by force, two bundle laser are reflected through high diaphragm thoroughly through speculum and inject silencer box and incide in light trapping after crossing, optical fiber collimator is incided by the light scioptics of particle scattering in silencer box.Measure acoustic pressure by dual-beam, without any barrier in this sound field, make the sound field in silencer box be free found field; Utilize finely ground particles in silencer box as medium, by the autocorrelation technique of particle scattered light, the velocity of sound at Measurement accuracy beam interference point place and acoustic pressure.Adopt back scattering, by a slice lens and an optical fiber collimator receiving scattered light, receiving system structure is simple, makes the signal to noise ratio of system higher.
As preferably, two bundle laser inject the geometric center that silencer box joint is silencer box, and the angles that two bundle laser are formed are θ, θ value is between 12 ° to 18 °; Ensure that two bundle laser interferencefringeses have better visibility and uniformity, signal to noise ratio is high.
As preferably, sound source is arranged on the longitudinal axis of symmetry of silencer box above two bundle laser joints, and the central shaft of sound source is arranged in the plane that two bundle laser are formed; The sound pressure at favourable raising measured point place.
As preferably, lens are convex lens, and diameter is 45-55mm, and focal length is 100-150mm, and lens are positioned on silencer box lateral symmetry axis; Scattered light is converged to optical fiber collimator.
As preferably, silencer box inwall is provided with wedge absorber, wedge absorber wedge-shaped in cross-section, and wedge shape height is 30-42cm; Silencer box cut-off frequency is made to be 200Hz.
As preferably, laser is the single longitudinal mode laser of wavelength 532nm, and beam divergence angle is 0-1.2mrad; Beam divergence angle is being less than within the scope of 1.2mrad, reduces interference fringe spacing inhomogeneities.
As preferably, particle is smoke particle thing, and particle size is 0.1-2um; Within the scope of this, smoke particle produces stronger scattered light, and produces light intensity and change the Doppler frequency shift caused.
Compared with prior art, the invention has the beneficial effects as follows: with smoke particle thing for medium, utilize laser beam as measurement means, by measuring the auto-correlation time of scattered light, obtaining the velocity of sound and the acoustic pressure of beam interference point place sound field, in silencer box, not introducing solid obstacle, sound field in silencer box is made to be free found field, and demarcate acoustic pressure by harmless optical detection means, for the demarcation of free found field provides technological means, the calibration for the microphone of non-size provides device and calibration steps.Adopt back scattering, by a slice lens and an optical fiber collimator receiving scattered light, receiving system structure is simple, makes the signal to noise ratio of system higher, improves sensitivity.
Accompanying drawing explanation
Accompanying drawing 1 is connection diagram of the present invention;
Accompanying drawing 2 is 1kHz for working as frequency of source, autocorrelation function graph when intensity is 125dB.
In figure: 1-laser; 2-semi-transparent semi-reflecting lens; 3-speculum; 4-silencer box; 5-optical fiber collimator; 6-photon counter; 7-autocorrelation function analyzer; The high diaphragm thoroughly of 41-; 42-lens; 43-light trapping; 44-sound source; 45-wedge absorber.
Embodiment
Below by embodiment, and by reference to the accompanying drawings, technical scheme of the present invention is described in further detail.
Embodiment 1:
As shown in Figure 1, in figure, dotted line represents light path.Based on a free found field device for optics non-destructive monitoring technology, it comprises laser 1, semi-transparent semi-reflecting lens 2, speculum 3, silencer box 4, optical fiber collimator 5, photon counter 6 and autocorrelation function analyzer 7.Laser 1, semi-transparent semi-reflecting lens 2 and speculum 3 are arranged on the outer front end of silencer box 4.Laser 1 is the single longitudinal mode laser of wavelength 532nm, and beam divergence angle is less than 1.2mrad.Laser 1 power is 200mW, spot diameter 2mm.Semi-transparent semi-reflecting lens 2 one, speculum 3 has two.Silencer box 4 is cuboid airtight cavity structure, and the present embodiment adopts 2m × 2m × 2m overall dimension.The corresponding two side of silencer box 4 is respectively equipped with high diaphragm 41 and lens 42 thoroughly.Silencer box 4 left side wall is provided with the window film perforation of two through left side walls, and two window film perforations are symmetrical with the horizontal axis of silencer box 4.High diaphragm 41 thoroughly has two pieces, and the light transmission rate of high diaphragm 41 couples of 532nm is thoroughly greater than 99.5%.Two pieces high diaphragms 41 embed window film perforation respectively and are tightly connected with window film perforation.Silencer box 4 right side wall is positioned at silencer box 4 lateral symmetry axis and is provided with lens opening.Lens opening through silencer box 4 right side wall.Lens 42 are convex lens, and diameter is 50mm, and focal length is 150mm.Lens 42 embed lens opening and are tightly connected with lens opening.Light trapping 43, sound source 44, wedge absorber 45 and particle is provided with in silencer box 4.Light trapping 43 has two, fixes respectively with silencer box 4 right side wall.Two light trappings 43 are symmetrical with the horizontal axis of silencer box 4.Sound source 44 is positioned on the longitudinal axis of symmetry of silencer box 4.Sound source 44 is connected with silencer box 4 top board.Generating plane aims at the geometric center of silencer box 4, and the axis that the central shaft of sound source is vertical with silencer box 4 overlaps, and namely drops in the plane of two bundle laser formation.Wedge absorber 45 wedge-shaped in cross-section.Bottom surface and silencer box 4 internal chamber wall of wedge absorber 45 wedge shape are fixed.The point of wedge shape is the height of wedge shape to the distance of bottom surface.The present embodiment is 200Hz to make silencer box 4 cut-off frequency, and the height of wedge shape is 40cm.Particle is smoke particle thing, and particle size is 0.1-2um, and specifically determined by the width of two bundle laser interferencefringeses, particle size is less than the width of two bundle laser interferencefringeses.Particle is full of whole silencer box 4 inner chamber.Optical fiber collimator 5, photon counter 6 and autocorrelation function analyzer 7 are arranged on the outer rear end of silencer box 4.Optical fiber collimator 5 by coupling fiber to photon counter 6.The signal output part of photon counter 6 is connected with the input of autocorrelation function analyzer 7.The output of autocorrelation function analyzer 7 is connected with computer (not shown).The process software that autocorrelation function analyzer 7 is supporting is housed in computer.
Theoretical according to auto-correlation function, velocity of sound u and the relation with the auto-correlation time can be obtained:
Wherein, λ is optical maser wavelength, and θ is the angle of light beam, t
minfor the time that auto-correlation coefficient first minimum value is corresponding.
Acoustic pressure P can be expressed as
P＝uρc(b)
Wherein, ρ is Media density, and c is the velocity of sound.
The present embodiment silencer box 4 is operated in the laboratory of constant temperature and humidity.Laser 1 sends laser directive semi-transparent semi-reflecting lens 2, is divided into through semi-transparent semi-reflecting lens 2 laser that two-beam is equal by force.Two bundle laser reflect respectively through two speculums 3, then are each passed through two high diaphragms 41 and inject in silencer box 4.Two bundle laser form identical angle with the horizontal axis of silencer box 4, and two bundle laser joints are the geometric center of silencer box 4, i.e. the crosspoint of the horizontal axis of silencer box 4 and longitudinal central axis line is also two-beam interference position.The angle that two bundle laser are formed is θ, θ value is 13.8 °.Incide respectively in light trapping 43 after two bundle laser cross.Open aerosol producer (not shown), the smog of generation is filled with silencer box 4, allow smoke particle thing be full of whole silencer box 4 inner chamber.Incide optical fiber collimator 5 by the light scioptics 42 of particle scattering, signal is exported to autocorrelation function analyzer 7 by photon counter 6 by optical fiber collimator 5.Observing the count intensity shown in autocorrelation function analyzer 7 software, when reaching about 50kcps, cutting off aerosol producer, allow smog stablize about 1min in silencer box 4.Drive sound source 44 to send certain frequency, the voice signal of some strength, operating software, generate autocorrelator trace (as Fig. 2).Extract the time t that correlation function value reaches first minimum value
min, calculate according to formula (a), (b) acoustic pressure that two-beam interference is pointed out.Close laser 1, tested microphone is placed into two-beam interference position, sensitive face aims at sound source 44, drives sound source 44, sends the acoustical signal with same frequency and intensity when not putting into microphone, record microphone acoustic pressure.Place the acoustic pressure before and after two-beam interference position according to tested microphone, provide the test of tested microphone or calibration result.
Claims (7)
1. the free found field device based on optics non-destructive monitoring technology, it comprises laser (1), semi-transparent semi-reflecting lens (2), speculum (3), silencer box (4) and optical fiber collimator (5), it is characterized in that: described silencer box (4) is cuboid airtight cavity structure, silencer box (4) corresponding two side is respectively equipped with high diaphragm (41) and lens (42) thoroughly, light trapping (43) is provided with in silencer box (4), sound source (44) and particle, laser (1) sends laser and is divided into through semi-transparent semi-reflecting lens (2) laser that two-beam is equal by force, two bundle laser are reflected through high diaphragm (41) thoroughly through speculum (3) and inject silencer box (4) and incide in light trapping (43) after crossing, optical fiber collimator (5) is incided by the light scioptics (42) of particle scattering in silencer box (4).
2. the free found field device based on optics non-destructive monitoring technology according to claim 1, it is characterized in that: described two bundle laser inject the geometric center that silencer box (4) joint is silencer box (4), the angle that two bundle laser are formed is θ, θ value is between 12 ° to 18 °.
3. the free found field device based on optics non-destructive monitoring technology according to claim 1 and 2, it is characterized in that: sound source (44) is arranged on silencer box (4) longitudinal axis of symmetry above two bundle laser joints, and the central shaft of sound source (44) is arranged in the plane of two bundle laser formation.
4. the free found field device based on optics non-destructive monitoring technology according to claim 1, it is characterized in that: described lens (42) are convex lens, diameter is 45-55mm, and focal length is 100-150mm, and lens (42) are positioned on silencer box (4) lateral symmetry axis.
5. the free found field device based on optics non-destructive monitoring technology according to claim 1, it is characterized in that: described silencer box (4) inwall is provided with wedge absorber (45), wedge absorber (45) wedge-shaped in cross-section, wedge shape height is 30-42cm.
6. the free found field device based on optics non-destructive monitoring technology according to claim 1, it is characterized in that: the single longitudinal mode laser that described laser (1) is wavelength 532nm, beam divergence angle is 0-1.2mrad.
7. the free found field device based on optics non-destructive monitoring technology according to claim 1, it is characterized in that: described particle is smoke particle thing, particle size is 0.1-2um.
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Cited By (6)
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| CN108801439A (en) * | 2018-07-10 | 2018-11-13 | 河海大学常州校区 | A kind of sound field measuring device and measurement method |
| CN109974641A (en) * | 2019-04-15 | 2019-07-05 | 天津大学 | A kind of acoustic sounding device, system, method, computer equipment and storage medium |
| CN110260968A (en) * | 2019-07-09 | 2019-09-20 | 中国计量科学研究院 | Air ultrasound acoustic pressure recurrence system based on the measurement of sound particle vibration velocity |
| CN110290454A (en) * | 2019-07-19 | 2019-09-27 | 中国计量科学研究院 | Microphone high temperature calibration system based on optical method |
| CN112461719A (en) * | 2020-11-19 | 2021-03-09 | 南京工程学院 | Non-uniform sound field testing method for main particle size of wide-screening particles |
| CN113091881A (en) * | 2021-04-13 | 2021-07-09 | 河南省计量科学研究院 | Method for improving air sound pressure measurement precision of photon correlation method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112461719A (en) * | 2020-11-19 | 2021-03-09 | 南京工程学院 | Non-uniform sound field testing method for main particle size of wide-screening particles |
| CN113091881A (en) * | 2021-04-13 | 2021-07-09 | 河南省计量科学研究院 | Method for improving air sound pressure measurement precision of photon correlation method |
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