CN106124037B - A kind of near field acoustic holography test method and device based on spheric function elementary solution - Google Patents
A kind of near field acoustic holography test method and device based on spheric function elementary solution Download PDFInfo
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- CN106124037B CN106124037B CN201610424895.0A CN201610424895A CN106124037B CN 106124037 B CN106124037 B CN 106124037B CN 201610424895 A CN201610424895 A CN 201610424895A CN 106124037 B CN106124037 B CN 106124037B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H11/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
- G01H11/06—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties by electric means
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- G—PHYSICS
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/18—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using ultrasonic, sonic, or infrasonic waves
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Abstract
The present invention provides a kind of near field acoustic holography test method and device based on spheric function elementary solution, test method includes the number of microphone and position on the order N and spherical holographic measurement face for determine used spheric function elementary solution, sound pressure measurement is carried out to identified measurement point and utilizes the measurement result obtained, the reversed sound physical properties amount for reconstructing vibrational structure surface.Device includes pedestal (1), rotary shaft (2), semi-circular bracket (3), mechanism for testing (4), semi-circular bracket (3) can make circular-rotation with rotary shaft (2), mechanism for testing (4) is fixedly mounted on semi-circular bracket (3), can measure the sound pressure information on the spherical holographic measurement face for surrounding vibrational structure (5).
Description
Technical field
The invention belongs near field acoustic holography the field of test technology, are related to a kind of near field acoustic holography based on spheric function elementary solution
Test method and device.
Background technique
One key factor of noise analysis and control is to be accurately located noise source position.Near field acoustic holography (NAH:
Near-field Acoustic Holography) be acoustic investigation in the past 30 years one of hot spot, since near field acoustic holography exists
Evanescent wave (Evanescent Wave) ingredient is remained during signal acquisition as much as possible, keeps the reconstruction precision of sound field big
It has been more than greatly Rayleigh resolution criterion, this is that Wave beam forming and conventional acoustical holography technology cannot compare.Based on Helmholtz
The NAH of equation spheric function elementary solution is a kind of important method of Reconstruction of Sound Field.For such NAH, there are problems that two: one, such as
What determines the order of spheric function to different models and analysis frequency, this is concerning NAH inverting stability；Two, to the ball of specific order
Function determines the number and position of microphone needed for measuring how in the case where meeting certain precision.But existing open source literature,
There is no provide good solution to both of these problems with existing patent formula.
Summary of the invention
In view of the foregoing deficiencies of prior art, the purpose of the present invention is to provide a kind of based on spheric function elementary solution
Near field acoustic holography test method and device, for solving, spheric function order and microphone number, position cannot in the prior art
Scientifically determining problem.
In order to achieve the above objects and other related objects, it is complete to provide a kind of near field sound based on spheric function elementary solution by the present invention
Test method is ceased, following steps are included at least: (1) determining equivalent sphere source radius and the spherical holographic measurement face half of vibrational structure
Diameter；(2) the order N of used spheric function elementary solution is determined；(3) determine on the spherical holographic measurement face number of microphone and
Position is to obtain measurement point；(4) sound pressure measurement is carried out to measurement point determined by step (3)；(5) it is obtained using in step (4)
Measurement result, reversely reconstruct the sound physical properties amount on the vibrational structure surface.
Preferably, equivalent sphere source radius is calculated according to the external surface area of vibrational structure in the step (1), formula is such as
Under:
Wherein,For equivalent sphere source radius, S is the external surface area of vibrational structure；And according to the following formula
Calculate spherical holographic measurement radius surface:
Wherein, rhFor spherical holographic measurement radius surface, d be spherical holographic measurement identity distance equivalent source spherical surface away from
From.
Preferably, the order N of spheric function elementary solution is determined in the step (2) according to following formula:
Wherein, εNTo increase to N from N-1 when basic function order, structural body acoustical power radiation efficiency is about basic function order
Take relative increment when N-1；
For equivalent sphere source radius, k is wave number；
For spherical sound source n-th order mode radiation efficiency；
For ball Hankel function；
ε0For the error of setting.
Preferably, ε0It is set as 10-2。
Preferably, the order N according to determined by the step (2) is determined in the step (3) on spherical holographic measurement face
Required measuring point number is (N+1) × (2N+1), measuring point x on spherical holographic facetij(i=1,2 ... N+1；J=1,
2 ... 2N+1) spherical coordinates be (rh, θi, φj), wherein rhFor spherical holographic measurement radius surface, 0≤θi=acos μi≤
π, μiFor the i-th point of N+1 point Legendre-Gauss integral, -1≤μi≤1；φjFor the corresponding rectangular integration in the direction φ
Point, and0≤j≤2N。
Preferably, the step (5) specifically comprises the following steps:
(51) it is obtained by following formula and participates in the factor
Wherein,For the elementary solution of external acoustic problem；
hnFor ball Hankel function；
For ball cllipsoidal harmonics；
wiFor i-th of point weight of Legendre-Gauss integral；
p(xij) it is measuring point x in step (4)ijMeasurement acoustic pressure；
(52) according to the participation factor obtained in the step (51), the sound on vibrational structure surface is calculated by following formula
Pressure:
And normal velocity:
Whereinρ is medium averag density；C is the velocity of sound；N (x) is the outer normal direction at the x of position.
In order to achieve the above objects and other related objects, the present invention also provides a kind of near field sound based on spheric function elementary solution
Holographic test includes at least: one end of pedestal, rotary shaft, semi-circular bracket, mechanism for testing, the rotary shaft is mounted on
On the pedestal and can the relatively described pedestal make circular-rotation, one end of the semi-circular bracket is fixedly mounted on the rotary shaft
On, and the semi-circular bracket can make circular-rotation with the rotary shaft, the mechanism for testing is mounted on the semi-circular bracket
On, it can measure the sound pressure information on the spherical holographic measurement face for surrounding vibrational structure.
Preferably, the mechanism for testing includes at least one fixing seat, at least one test conduit, and the fixing seat can be consolidated
Dingan County in the semi-circular bracket, the test conduit installation on the fixing seat and can the relatively described fixing seat adjust
Its radial distance apart from vibrational structure.
Preferably, mounting hole is provided in the fixing seat, the test conduit is mounted in the mounting hole and can edge
The mounting hole sliding is to adjust its radial distance apart from vibrational structure.
Preferably, the number of the fixing seat and the test conduit that are mounted in the semi-circular bracket is N+
1, wherein N is the order of spheric function elementary solution.
As described above, it is of the invention, it has the advantages that
It (1) being capable of the scientific and effective order for choosing elementary solution and number of microphone and test position；
(2) in such a way that semicircle bracket is rotated around fixing axle, two polar angles of spherical coordinate system are separated, make its with
The determining measurement position of parsing matches, and conveniently, accurately realizes the sound pressure measurement in spherical measuring surface specific position.
(3) reconstruction of three-dimensional vibrating body surface face sound physical properties amount can be achieved, test operation is easy, and measuring point is few, rebuilds operation
Numerical stability is strong, and inversion accuracy is high.
Detailed description of the invention
Fig. 1 is shown as the rank of the spheric function elementary solution in the near field acoustic holography test of the invention based on spheric function elementary solution
Number N and εN、Relation schematic diagram.
Fig. 2 is shown as the near field acoustic holography test device schematic diagram of the invention based on spheric function elementary solution.
The structure that Fig. 3 is shown as the rotary shaft of the near field acoustic holography test device of the invention based on spheric function elementary solution is shown
It is intended to.
Fig. 4 is shown as the vertical view of the rotary shaft of the near field acoustic holography test device of the invention based on spheric function elementary solution
Figure.
Fig. 5 is shown as the left view of the rotary shaft of the near field acoustic holography test device of the invention based on spheric function elementary solution
Figure.
Fig. 6 is shown as the backsight of the rotary shaft of the near field acoustic holography test device of the invention based on spheric function elementary solution
Figure.
Fig. 7 is shown as showing for the semi-circular bracket of the near field acoustic holography test device of the invention based on spheric function elementary solution
It is intended to.
Fig. 8 is shown as the cross-sectional view in the direction F-F of the invention along Fig. 7.
The structure that Fig. 9 is shown as the fixing seat of the near field acoustic holography test device of the invention based on spheric function elementary solution is shown
It is intended to.
Figure 10 is shown as the main view of the fixing seat of the near field acoustic holography test device of the invention based on spheric function elementary solution
Figure.
Figure 11 is shown as the left view of the fixing seat of the near field acoustic holography test device of the invention based on spheric function elementary solution
Figure.
Figure 12 is shown as the backsight of the fixing seat of the near field acoustic holography test device of the invention based on spheric function elementary solution
Figure.
Figure 13 is shown as the vertical view of the fixing seat of the near field acoustic holography test device of the invention based on spheric function elementary solution
Figure.
Figure 14 is shown as the vibration knot of the near field acoustic holography test method of the invention based on spheric function elementary solution and device
Structure surface acoustic pressure inversion result schematic diagram.
Figure 15 is shown as the vibration knot of the near field acoustic holography test method of the invention based on spheric function elementary solution and device
Structure surface acoustic pressure simulation result schematic diagram.
Component label instructions
1 pedestal
2 rotary shafts
21 column spinners
22 locking members
221 card slots
222 first fixation holes
3 semi-circular brackets
31 second fixation holes
311 frustum of a cone holes
312 cylindrical holes
4 mechanism for testing
41 fixing seats
411 mounting holes
42 test conduits
5 vibrational structures
6 connectors
61 third fixation holes
Specific embodiment
Embodiments of the present invention are illustrated by particular specific embodiment below, those skilled in the art can be by this explanation
Content disclosed by book is understood other advantages and efficacy of the present invention easily.
Fig. 1 is please referred to Figure 15.It should be clear that this specification structure depicted in this specification institute accompanying drawings, ratio, size etc., are only used
To cooperate the revealed content of specification, so that those skilled in the art understands and reads, being not intended to limit the invention can
The qualifications of implementation, therefore do not have technical essential meaning, the tune of the modification of any structure, the change of proportionate relationship or size
It is whole, in the case where not influencing the effect of present invention can be generated and the purpose that can reach, it should all still fall in disclosed skill
In the range of art content can cover.Meanwhile in this specification it is cited as "upper", "lower", "left", "right", " centre " and
The term of " one " etc. is merely convenient to being illustrated for narration, rather than to limit the scope of the invention, relativeness
It is altered or modified, under the content of no substantial changes in technology, when being also considered as the enforceable scope of the present invention.
The present invention provides a kind of near field acoustic holography test method based on spheric function elementary solution, includes at least following steps:
(1) the equivalent sphere source radius and spherical holographic measurement radius surface of vibrational structure are determined；(2) used spheric function elementary solution is determined
Order N；(3) determine that the number of microphone and position are on spherical holographic measurement face to obtain measurement point；(4) to step (3) institute
Determining measurement point carries out sound pressure measurement；(5) reversed to reconstruct vibrational structure surface using the measurement result obtained in step (4)
Sound physical properties amount.
Equivalent sphere source radius is calculated in step (1) according to the external surface area of vibrational structure, formula is as follows:
Wherein,For equivalent sphere source radius, S is the external surface area of vibrational structure；
And spherical holographic measurement radius surface is calculated according to the following formula:
Wherein, rhFor spherical holographic measurement radius surface, d is the distance of spherical holographic measurement identity distance equivalent source spherical surface.
The order N of spheric function elementary solution is determined in step (2) according to following formula:
Wherein,For equivalent sphere source radius, k is wave number；
For spherical sound source n-th order mode radiation efficiency；
For ball Hankel function；
ε0For the error of setting.
Formula (3) indicates that working as basic function order increases to N from N-1, and structural body acoustical power radiation efficiency is about basic function
Order takes relative increment when N-1.
WhenWhen, order N and ε as shown in Figure 1 can be drawn according to formula (3)N、Relational graph, looked into facilitating
It looks for.Preferably, acoustical power relative increment ε0It is set as 10-2, and then can determine the order N of the formula of meeting the requirements (3).
It is N by the elementary solution maximum order that step (2) determine, to guarantee that each rank mode can be recognized accurately, according to
Measuring point on spherical holographic facet should meet accurately calculating for following formula, to determine number and the position of microphone:
Wherein δ is Dirac function, works as n=l, and is 1 when m=t, and other situations are 0；It is harmonious for m ball of n rank
Function, expression formula are as follows:
Formula (5) are substituted into formula (4), and variable θ ∈ [0, π] and φ ∈ [0,2 π] is separated, thenWherein
By Nyguist sampling thheorem,It can be accurately calculated by m+1 point rectangular integration formula.It therefore, can be by φ
The measuring point in direction is placed at the point of rectangular integration formula, then needs 2N+1 measuring point to can satisfy I altogether1(| m-t |≤2N)
Accurate integration, point are as follows:
Corresponding weight are as follows:
I2Integral kernel function inN-order polynomial about μ when m is even number, be when m is odd number about
The n-1 rank multinomial of μ is multiplied byTherefore, as m=t, kernel function is integratedIt is the n+l (≤2N) about μ
Rank multinomial.N+1 point Legendre-Gauss integral formula is chosen, I can be completed2Accurately calculate.In θ ∈ [0, π] direction
Test point be N+1 point Gauss integration point.
According to above theory analysis, N+1 point Gauss integration point is chosen in [0, the π] direction θ ∈, and the direction [0,2 π] φ ∈ is chosen
2N+1 point rectangular integration point, can accurately calculateTherefore, the order N according to determined by step (2) determines ball in step (3)
Required measuring point number is (N+1) × (2N+1) on shape holographic measurement face, it is assumed that spherical holographic facet measuring point is expressed as xij(i=
1,2 ... N+1；J=1,2 ... 2N+1), then its spherical coordinates is (rh, θi, φj), wherein rhFor spherical holographic measurement
Radius surface, 0≤θi=acos μi≤ π, μiFor the i-th point of N+1 point Legendre-Gauss integral, -1≤μi≤1；φjFor
The corresponding rectangular integration point in the direction φ.Since test point has rotational symmetry about coordinate φ.Therefore it may only be necessary in spherical surface mother
N+1 microphone is arranged on line, equidistantly carries out sequence measuring around φ.
Step (5) specifically comprises the following steps: (51) according to the elementary solution of external acoustic problem on spherical holographic facet
It is orthogonal
Property, it is obtained by following formula and participates in the factor
Wherein,For the elementary solution of external acoustic problem；
hnFor ball Hankel function；
For ball cllipsoidal harmonics；
wiFor i-th of point weight of Legendre-Gauss integral；
p(xij) it is measuring point x in step (4)ijMeasurement acoustic pressure；
(52) according to the participation factor obtained in step (51), and according to mapping relations and modal superposition principle, by such as
Lower formula calculates the acoustic pressure on vibrational structure surface:
And normal velocity:
Whereinρ is medium averag density；C is the velocity of sound；N (x) is the outer normal direction at the x of position.
Thus inverting and imaging can be carried out to acoustic pressure by formula (10).
The present invention also provides a kind of based on the near field acoustic holography test device of spheric function elementary solution, it can be achieved that according to difference
Measurement condition, mechanism for testing is freely installed and freely adjusts the position of test point, to reach the technical effect flexibly tested.
As shown in Fig. 2, a kind of near field acoustic holography test device based on spheric function elementary solution of the invention, includes at least:
Pedestal 1, rotary shaft 2, semi-circular bracket 3, mechanism for testing 4, one end of rotary shaft 2 are mounted on pedestal 1 and can make with respect to pedestal 1
Circular-rotation, one end of semi-circular bracket 3 are fixedly mounted in rotary shaft 2, and semi-circular bracket 3 can make circumference with rotary shaft 2
Rotation, mechanism for testing 4 are mounted in semi-circular bracket 3, can test the acoustic pressure on the spherical holographic measurement face for surrounding vibrational structure 5
Information.Test device of the invention, when being measured on holographic facet, for measurement point coordinate (rh, θi, φj), pass through test
Measurement point (r is realized in the rotation of installation site and semi-circular bracket 3 of the mechanism 4 in semi-circular bracket 3h, θi, φj)
Positioning.As it can be seen that measuring device of the invention has the advantages that flexibly to install mechanism for testing and flexible modulation test point position.
As shown in Fig. 2, mechanism for testing 4 includes at least one fixing seat 41, at least one test conduit 42, fixing seat 41 can
It is fixedly mounted in semi-circular bracket 3, test conduit 42, which is mounted in fixing seat 41 and can fix seat 41 relatively, adjusts its distance
The radial distance of vibrational structure 5.
As shown in figure 3, being the structural schematic diagram of rotary shaft 2, rotary shaft 2 includes a column spinner 21 and a locking member 22, rotation
The lower end surface of rotary column 21 is mounted on pedestal 1 and can make with respect to pedestal 1 circular-rotation, and upper surface is fixedly connected with the one of locking member 22
End, locking member 22 are provided with a card slot 221 along longitudinal direction, and the part that 221 two sides of card slot are located on locking member 22 is provided with first and fixes
Hole 222.As shown in Fig. 4, Fig. 5, Fig. 6, the respectively top view, left view and rearview of rotary shaft 2, as shown in figure 4, card slot
221 are positioned away from the position of 2 rotation axis of rotary shaft, and the eccentric distance that card slot 221 deviates 2 axis of rotary shaft is L.
As shown in fig. 7, being the structural schematic diagram of semi-circular bracket 3, multiple second fixation holes are provided in semi-circular bracket 3
31, it can be used for being fixedly mounted mechanism for testing 4.Fig. 8 show the sectional view in the direction F-F along Fig. 7, and as seen from the figure, second is fixed
Hole 31 penetrates through a cylindrical hole 312 by a frustum of a cone hole 311 and forms, and the depth in two holes is identical.As shown in fig. 7, semi-circular bracket 3
One end be connected with a connector 6, connector 6 may be stuck in card slot 221, and being provided on connector 6 can be with the first fixation hole 222
This end of semi-circular bracket 3 is fixed in rotary shaft 2 by the third fixation hole 61 of connection using screw or other connection types.
By Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 7 it is found that after semi-circular bracket 3 is mounted in rotary shaft 2, it is located off the rotation of rotary shaft 2
The eccentric distance of axis is the position of L and plane where it is parallel with the rotation axis of rotary shaft 2.
As shown in figure 9, being the structural schematic diagram of fixing seat 41, it is provided with mounting hole 411 in fixing seat 41, tests conduit 42
It is mounted in mounting hole 411 and can slide along mounting hole 411 to adjust its radial distance apart from vibrational structure 5.Figure 10, figure
11, Figure 12, Figure 13 are respectively main view, left view, rearview and the top view of fixing seat 41, from left view 11 it can be seen that solid
The bottom of reservation 41 is the shape to be adapted to frustum of a cone hole 311, and the bottom of fixing seat 41 can be stuck in frustum of a cone hole 311,
The part of fixing seat 41 being fitted in outside frustum of a cone hole 311 is provided with mounting hole 411.As shown in Figure 13, in mounting hole 411
The heart deviates 41 bottom of fixing seat, and the distance deviateed is L.It follows that fixing seat 41 is mounted on the second fixation hole 31 and surveys
After examination conduit 42 is mounted on mounting hole 411, the eccentric distance that the longitudinal center line of test conduit 42 deviates semi-circular bracket 3 is equal to
Semi-circular bracket 3 deviates the eccentric distance of the rotation axis of rotary shaft 2, is L, and then the rotation axis of rotary shaft 2 is located at
In plane where test conduit, when vibrational structure 5 to be placed in the rotation axis direction of rotary shaft 2, by adjusting test
Position of the conduit 42 in semi-circular bracket 3 may make test conduit 42 to be located at envelope in the spherical holographic facet of vibrational structure 5
In radial line, that is, the end for the test conduit 42 being mounted in semi-circular bracket 3 is located on a bus of spherical holographic facet,
Microphone is installed in this end, the measurement of the measuring point on a bus on spherical holographic facet can be realized, due on holographic facet
Symmetry of the measuring point about coordinate φ, then the setting of the achievable φ of rotation by semi-circular bracket 3, finally can be realized entire
The measurement of measuring point on holographic facet.Further, the test conduit 42 in the present invention can fix seat 41 relatively and adjust its distance vibration
The adjustment of the different measuring distances between holographic measurement face and vibrational structure, further body can be realized in the radial distance of structure 5
The convenience of test flexibility and operation possessed by the device of the invention is showed.
In a kind of foregoing near field acoustic holography test method based on spheric function elementary solution, to spheric function elementary solution
The determination that science has been made in order N, the number of measurement point and position on this basis, can when carrying out near field acoustic holography test
It is N+1 that the fixing seat 41 being mounted in semi-circular bracket 3, which is arranged, and tests the number of conduit 42, wherein N is spheric function base
The order of this solution.And by the equidistant semi-circular bracket for being rotatably installed with N+1 test conduit, (N+1) × (2N can be completed
+ 1) the spherical envelope measurement of a point.
Specific embodiment is given below, and to be further described the near field sound of the invention based on spheric function elementary solution complete
Cease test method and device.
The side length that one regular hexahedron vibrates sound source is 0.2m, and analysis frequency is 601Hz, then based on the close of spheric function elementary solution
Field acoustical holography test process is as follows:
(1) the equivalent sphere source radius and spherical holographic measurement radius surface of vibrational structure are determined:
The equivalent sphere source radius of vibrational structure can be calculated by formula (1),Set spherical measuring surface away from
Equivalent source spherical surface 0.1m, then spherical holographic measurement radius surface rh=0.2382m.
(2) the order N of used spheric function elementary solution is determined:
CauseEnable ε0=10-2, then according to Fig. 1 or formula (3), N=3 is selected.
(3) determine that the number of microphone and position are on spherical holographic measurement face to obtain measurement point:
Due to N=3, so, the measuring point number needed for determining in spherical shape measuring surface is (N+1) × (2N+1)=28, wherein
N+1=4 fixing seat and measurement conduit are installed in semi-circular bracket, i.e., need 4 Mikes on the bus of spherical envelope measurement
Wind.
For measuring point xij(i=1,2,3,4；J=1,2,3 ..., 7), spherical coordinates is (rh, θi, φj), 0≤θi=
acosμi≤ π, μiFor the i-th point of 4 point Legendre-Gauss integral, -1≤μi≤1；φjFor the corresponding rectangle in the direction φ
Point, and0≤j≤2N。
Therefore, θiAnd weight is as follows accordingly:
For φj, since 0 degree, measurement rotates about the axis 51.4286 degree every time, carries out 7 sequence measurings altogether, obtains
28 measuring points.
(4) sound pressure measurement is carried out to measurement point determined by step (3).
(5) using the measurement result obtained in step (4), the sound physical properties amount on vibrational structure surface is reversely reconstructed:
It is calculated by formula (9) and participates in the factorAccording to formula (10) and formula (11) calculate vibrating body surface acoustic pressure and
Normal velocity, and then be imaged in body structure surface.
It is as shown in figure 14 the inversion result carried out according to formula (10) to acoustic pressure, Figure 15 show simulation result.
Comparison diagram 14, Figure 15 are measured using envelope it is found that satisfied using method and device imaging results of the invention
Preferable sound source distribution character can be reconstructed, and acoustic pressure maximum amplitude error is less than 25%.
To sum up, the present invention effectively overcomes various shortcoming in the prior art and has high industrial utilization value.
The above-described embodiments merely illustrate the principles and effects of the present invention, and is not intended to limit the present invention.It is any ripe
The personage for knowing this technology all without departing from the spirit and scope of the present invention, carries out modifications and changes to above-described embodiment.Cause
This, institute is complete without departing from the spirit and technical ideas disclosed in the present invention by those of ordinary skill in the art such as
At all equivalent modifications or change, should be covered by the claims of the present invention.
Claims (8)
1. a kind of near field acoustic holography test method based on spheric function elementary solution, which is characterized in that include at least following steps:
(1) the equivalent sphere source radius and spherical holographic measurement radius surface of vibrational structure are determined；
(2) the order N of used spheric function elementary solution is determined；The order N of spheric function elementary solution is determined according to following formula:
Wherein, εNTo increase to N from N-1 when basic function order, structural body acoustical power radiation efficiency takes N-1 about basic function order
When relative increment；
For equivalent sphere source radius, k is wave number；
For spherical sound source n-th order mode radiation efficiency；
For ball Hankel function；
ε0For the error of setting；
(3) determine that the number of microphone and position are on the spherical holographic measurement face to obtain measurement point；According to the step (2)
Identified order N determines that required measuring point number is (N+1) × (2N+1), spherical holographic facet on spherical shape holographic measurement face
Upper measuring point xij(i=1,2 ... ... N+1；J=1,2 ... ... 2N+1) spherical coordinates be (rh,θi,φj), wherein rhIt is spherical complete
Breath measurement radius surface, 0≤θi=acos μi≤ π, μiFor the i-th point of N+1 point Legendre-Gauss integral, -1≤μi≤
1；φjFor the corresponding rectangular integration point in the direction φ, and0≤j≤2N；
(4) sound pressure measurement is carried out to measurement point determined by step (3)；
(5) using the measurement result obtained in step (4), the sound physical properties amount on the vibrational structure surface is reversely reconstructed.
2. the near field acoustic holography test method according to claim 1 based on spheric function elementary solution, it is characterised in that: described
Equivalent sphere source radius is calculated in step (1) according to the external surface area of vibrational structure, formula is as follows:
Wherein,For equivalent sphere source radius, S is the external surface area of vibrational structure；
And spherical holographic measurement radius surface is calculated according to the following formula:
Wherein, rhFor spherical holographic measurement radius surface, d is the distance of spherical holographic measurement identity distance equivalent source spherical surface.
3. the near field acoustic holography test method according to claim 1 based on spheric function elementary solution, it is characterised in that: ε0If
It is set to 10-2。
4. the near field acoustic holography test method according to claim 1 based on spheric function elementary solution, which is characterized in that described
Step (5) specifically comprises the following steps:
(51) it is obtained by following formula and participates in the factor
Wherein,For the elementary solution of external acoustic problem；
hnFor ball Hankel function；
For ball cllipsoidal harmonics；
wiFor i-th of point weight of Legendre-Gauss integral；
p(xij) it is measuring point x in step (4)ijMeasurement acoustic pressure；
(52) according to the participation factor obtained in the step (51), the acoustic pressure on vibrational structure surface is calculated by following formula:
And normal velocity:
Whereinρ is medium averag density；C is the velocity of sound；N (x) is the outer normal direction at the x of position.
5. a kind of test device using the near field acoustic holography test method described in claim 1 based on spheric function elementary solution,
It is characterized in that, including at least: pedestal (1), rotary shaft (2), semi-circular bracket (3), mechanism for testing (4), the rotary shaft (2)
One end be mounted on the pedestal (1) and can the relatively described pedestal (1) make circular-rotation, the one of the semi-circular bracket (3)
End is fixedly mounted on the rotary shaft (2), and the semi-circular bracket (3) can make circular-rotation with the rotary shaft (2), institute
It states mechanism for testing (4) to be mounted on the semi-circular bracket (3), can measure the spherical holographic measurement face for surrounding vibrational structure (5)
On sound pressure information.
6. test device according to claim 5, it is characterised in that: the mechanism for testing (4) includes that at least one is fixed
Seat (41), at least one test conduit (42), the fixing seat (41) can be fixedly mounted on the semi-circular bracket (3), institute
State test conduit (42) be mounted on the fixing seat (41) and can the relatively described fixing seat (41) adjust it apart from vibrational structure
(5) radial distance.
7. test device according to claim 6, it is characterised in that: be provided with mounting hole on the fixing seat (41)
(411), the test conduit (42) is mounted in the mounting hole (411) and can slide along the mounting hole (411) to adjust
Its radial distance apart from vibrational structure (5).
8. test device according to claim 6 or 7, it is characterised in that: the institute being mounted on the semi-circular bracket (3)
The number for stating fixing seat (41) and test conduit (42) is N+1, wherein N is the order of spheric function elementary solution.
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| CN101251412A (en) * | 2008-04-17 | 2008-08-27 | 上海交通大学 | Method for rebuilding circulation calm sound source by overlapping spherical wave |
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