CN103487135B - Microphone array optimum design method for closed wind channel aerodynamic noise measurement - Google Patents

Microphone array optimum design method for closed wind channel aerodynamic noise measurement Download PDF

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CN103487135B
CN103487135B CN201310446754.5A CN201310446754A CN103487135B CN 103487135 B CN103487135 B CN 103487135B CN 201310446754 A CN201310446754 A CN 201310446754A CN 103487135 B CN103487135 B CN 103487135B
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array
design method
sidelobe suppression
aerodynamic noise
optimum design
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CN103487135A (en
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周家检
郝璇
陈大斌
张卫民
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China Academy of Aerospace Aerodynamics CAAA
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China Academy of Aerospace Aerodynamics CAAA
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Abstract

Provided is a microphone array optimum design method for closed wind channel aerodynamic noise measurement. According to the method, aiming at the demand for a microphone array of closed wind channel aerodynamic noise measurement, under the condition that array installation conditions of a closed wind channel are met, with requirements of array sidelobe suppression levels as constraint conditions and with the array resolution ratio as an objective function, array unit coordinates are optimized in a simulated annealing method. The microphone array optimum design method overcomes defects in existing methods, and array unit arrangement adaptive to closed wind channel installation can be achieved, wherein the sidelobe suppression levels and the resolution ratio of the array unit arrangement can meet demands.

Description

Be applied to the microphone array optimum design method that Closed Tunnel aerodynamic noise is measured
Technical field
The present invention relates to a kind of microphone array optimum design method, particularly a kind of microphone array optimum design method being applied to Closed Tunnel aerodynamic noise and measuring.
Background technology
Utilize Mike's wind facies array measurement technology in Closed Tunnel, carry out civil aircraft Study of Aerodynamic and receive increasing concern at home, and different test models requires different Array Design.Array has two main performance index: resolution and Sidelobe Suppression level.Resolution is relevant with array bore, and bore is larger, and resolution is more excellent.Sidelobe Suppression level is relevant with the density degree that array element is arranged, arranged in arrays must be closeer, and Sidelobe Suppression level is more excellent.Therefore for the array of given microphone number, between resolution and Sidelobe Suppression level, there is certain paradox.The object of Array Design is exactly optimization array cell layout, and its performance index are all met the demands in frequency range to be measured.
The optimal design of array must handle the cooperate optimization relation of resolution and these two performance index of Sidelobe Suppression level well, if single optimization performance index, is then difficult to obtain the optimum results that another performance index also meet the demands.Existing array optimization method for designing is all be optimized using Sidelobe Suppression level as objective function usually, reckons without the resolution index of array, cannot obtain optimum array.
And for Closed Tunnel noise measurement, microphone array installation site, bore and shape all receive the restriction of the condition that wind-tunnel is installed, placed on array design proposes new requirement.
Summary of the invention
Technology of the present invention is dealt with problems and is: overcome now methodical deficiency, provide a kind of microphone array optimum design method being applied to Closed Tunnel aerodynamic noise and measuring, the method measures the demand to microphone array for Closed Tunnel aerodynamic noise, when meeting array mounting condition in Closed Tunnel, with the demand of pair array Sidelobe Suppression level for constraint condition, take array resolution as objective function, utilize simulated annealing, optimization array unit coordinate, the array element that acquisition resolution and Sidelobe Suppression level all satisfy the demands is arranged.
Technical solution of the present invention is: a kind of microphone array optimum design method being applied to Closed Tunnel aerodynamic noise and measuring, comprises the following steps:
(1) stochastic generation microphone array, utilizes this array initialization microphone array column unit coordinate, initialization simulated annealing temperature T and k=1;
(2) whether the array in determining step (1) meets Closed Tunnel constraint condition, does not meet constraint condition and then jumps to step (4), otherwise go to step (3);
(3) the Sidelobe Suppression level of computing array, judges whether the criterion meeting Sidelobe Suppression level, to the array meeting Sidelobe Suppression level requirement, is accepted as new array, jumps to step (5), otherwise jumps to step (4);
(4) stochastic generation new array in former array neighborhood, jumps to step (2);
(5) calculate the resolution of new array, judge whether the resolution of new array is better than old array, if more excellent, accept new array, otherwise calculate acceptance probability, acceptance probability is greater than set-point and then accepts new array and go to step (6), otherwise jumps to step (4);
(6) judge whether the resolution of accepted array reaches end condition, reach end condition and then export current array unit coordinate, optimize and terminate, otherwise reduce simulated annealing temperature, make k:=k+1 :=represent assignment operation, repeat step (4) and start next circulation.
Array Sidelobe Suppression level in described step (3) is relevant with analysis frequency, only judges whether the Sidelobe Suppression level under maximum analysis frequency meets the demands.
The criterion MSL of array Sidelobe Suppression level in described step (3) dsetting SNR is greater than, along with simulated annealing temperature T in iterative process early stage in iteration kreduction progressively reduce, at T k≤ T dtime reach setting SNR, its formula is wherein T dfor preset value.
In described step (4), in former array neighborhood, the method for the new array of stochastic generation is: x i=x k-1 i+ RandomrL, wherein: Random is the random number between 0 to 1, r is the unit vector of random direction, and L is the radius of neighbourhood.X ifor generating the planimetric coordinates vector of new array; x k-1 ifor k-1 walks the planimetric coordinates vector of array.
The described radius of neighbourhood reduces along with the reduction of simulated annealing temperature, and computing formula is l 0the neighborhood initial radium that representative is preset.
Array resolution in described step (5) is relevant with analysis frequency, only judges whether the resolution under minimum analysis frequency meets the demands.
The present invention's beneficial effect is compared with prior art:
(1) the present invention passes through the constraint condition of the demand of pair array Sidelobe Suppression level as optimization problem, take array resolution as objective function, optimization array unit coordinate, thus the array element that array Sidelobe Suppression level and resolution all satisfies the demands can be provided arrange.
(2) the present invention is by the constraint condition by relaxing Sidelobe Suppression level early stage in iteration, and strengthen the constraint condition of Sidelobe Suppression level gradually along with the reduction of simulated annealing temperature, thus reduce the impact of initialization array, and Optimization Progress is carried out smoothly.
(3) the present invention passes through the constraint condition of restrictive condition in Closed Tunnel as optimization problem, thus makes given array element arrange the installation that can adapt in Closed Tunnel.
Accompanying drawing explanation
Fig. 1 is array optimization method for designing process flow diagram of the present invention.
Fig. 2 is the schematic diagram of array plane and sound source surface grids.
Fig. 3 is the Wave beam forming schematic diagram of the unit sound source of array.
Embodiment
The modeling of array optimization problem:
min(R(x i))，（x i∈Ω，MSL(x i)≤SNR，|x i-x g|≥d）
Wherein:
R (x i) be resolution performance function, be objective function;
X i(i=1, M) is array element coordinate, and M is array element number;
X i∈ Ω is constraint condition, the region that Ω determines for array installing space in wind-tunnel, array
Unit coordinate must not exceed region Ω;
| x i-x g|>=d is constraint condition, g=1, M and g ≠ i, minimum spacing between adjacent two unit
Setting d must not be less than;
MSL (x i)≤SNR is constraint condition, MSL (x i) be array Sidelobe Suppression level function,
Be better than setting SNR.
As shown in Figure 1, the present invention is applied to the process flow diagram of the microphone array optimum design method that Closed Tunnel aerodynamic noise is measured, and concrete steps are as follows:
(1) initialization array element coordinate x i 0(i=1, M), the array used in Closed Tunnel is generally planar array, thus x i 0be positioned at same plane.For reducing Optimal Parameters, array co-ordinates can be limited in coordinate plane.X i 0the mode of stochastic generation can be adopted to obtain.As shown in Figure 2, Fig. 2 is the schematic diagram of array plane and sound source surface grids.The two shares a coordinate system, such as, can adopt cartesian coordinate system.Initialization simulated annealing correlation parameter, comprises initial temperature T.Start iteration, k=1, makes x i=x i 0.
(2) judge whether array meets Closed Tunnel constraint condition x i∈ Ω and | x i-x g|>=d, does not meet constraint condition and then jumps to step (4), accepts the array meeting wind-tunnel constraint condition, continues next step.
Wherein, Closed Tunnel constraint condition comprises array element border, unit minimum spacing, x i∈ Ω and | x i-x g|>=d.In Closed Tunnel, carry out Mike's wind facies array aerodynamic noise measure, the installation of array is restricted, usually be restricted to position and the size of certain block portable plate on wind tunnel wall, microphone can only be installed in the region of restriction position and size, and then have array element coordinate x i(i=1, M) is defined in the Ω of region, i.e. x i∈ Ω.This restrictive condition needs to judge whether each unit coordinate exceeds the border of region Ω seriatim.In actual mechanical process, the region Ω of a comparatively rule can be chosen in the region limiting position and size, be convenient to provide zone boundary.Microphone itself and stationary installation thereof all have a certain size, make microphone space | x i-x g| setting d can not be less than, otherwise cannot install, namely | x i-x g|>=d.Array element spacing as shown in Figure 2.This restrictive condition needs to calculate array element spacing between two | x i-x g|, all can not be less than limits value setting d.
(3) the Sidelobe Suppression level of computing array, judges whether to meet MSL (x i)≤SNR, to the array meeting Sidelobe Suppression level requirement, is accepted as new array, jumps to step (5), otherwise jumps to step (4).
Sidelobe Suppression level, also claims maximum side lobe levels, and be the maximal value of secondary lobe in the Wave beam forming figure of the unit sound source of array, computing formula is:
MSL ( x i ) = 10 · log 10 { max y j ∈ D ′ f L ≤ f ≤ f H [ psf ( x i , y j , f ) ] }
Wherein:
F is analysis frequency, f lfor analysis frequency lower limit, f hfor the analysis frequency upper limit;
D is sound source surface grids region, is generally the plane domain being parallel to array plane, and region D ' is the region of region D rejecting main lobe, and the schematic diagram of sound source surface grids and array plane as shown in Figure 2.；
Y jfor sound source surface grids coordinate; J=1, N, N represent sound source surface grids and count
Psf (x i, y j, f) be array x ianalysis frequency f under the Wave beam forming figure of unit sound source.
Psf (x i, y j, the analysis frequency caused by unit sound source be the frequency of position, sound source face being f) f is the Beamforming result of f, describes the basic response of array.Fig. 3 is the Wave beam forming schematic diagram of the unit sound source of array, and in figure, horizontal coordinate face is sound source face, and the unit of diaxon is m, and the longitudinal axis is psf, and unit is dB.In figure, 1 is main lobe, and 2 is secondary lobe.Its calculation procedure is, places unit point sound source in sound source surface grids, is usually positioned over directly over array center, and calculate the cross-spectrum matrix that this point sound source causes on array, then carry out Beamforming, computing formula is:
psf ( x i , y j , f ) = 10 · log 10 { G ( x i , y j , f ) * AG ( x i , y j , f ) | G ( x i , y j , f ) | 2 }
Wherein:
A is y 0the cross-spectrum matrix that unit sound source in position causes on array, computing formula is:
A = G ( x i , y 0 , f ) G ( x i , y 0 , f ) * | G ( x i , y 0 , f ) | 2 ;
G is adjustment vector, and computing formula is: G ( x , y , f ) = 1 4 π | x - y | e i 2 πf 340 | x - y | ;
" * " represents that plural number gets conjugation.
Psf is at y 0position obtains maximal value zero, and thus maximum side lobe levels is minus value.Array Sidelobe Suppression level is relevant with analysis frequency, and analysis frequency is higher, and Sidelobe Suppression level is poorer, therefore usually only needs to judge whether the Sidelobe Suppression level under maximum analysis frequency meets the demands.
For reducing the impact of initialization array, suitably relaxing the requirement of Sidelobe Suppression level in iteration early stage, getting the decision content MSL of Sidelobe Suppression level dbe greater than setting SNR, and progressively reduce along with the reduction of simulated annealing temperature, and drop to setting T in simulated annealing temperature dreach time (can get 0.5T) and remain setting SNR, its formula is:
MSL D = min ( T D T k , 1 ) · SNR
(4) the new array of stochastic generation in former array neighborhood, jumps to step (2).Former array neighborhood is the set of arranging close array with former array element.The structure of neighborhood is diversified, adopts random fashion to generate new array:
x i=x k-1 i+Random·r·L
Wherein:
Random is the random number between 0 to 1;
R is the unit vector of random direction
L is the radius of neighbourhood.
Random number between 0 to 1 calculates and is easy to realize, such as usual all with the intrinsic function of random number in Fortran compiler.In the optimization problem of planar array, the unit vector in available following formulae discovery direction immediately:
r=(cos(θ),sin(θ)),θ=2π(Random-0.5)
The radius of neighbourhood reduces along with the reduction of simulated annealing temperature, and computing formula is
L 0the neighborhood initial radium that representative is preset, such as, can get 2d, generally get (1-3) d.
(5) the resolution R (x of new array is calculated i), judge whether the resolution of new array is better than old array R (x i)≤R (x k-1 i), if more excellent, accept new array, x k i=x i, otherwise calculate acceptance probability acceptance probability is greater than decision content 0.2 and accepts new array, x k i=x i, otherwise jump to step (4).
Array resolution takes from the main lobe width of main lobe peak value decline 3dB position, and its computing formula is:
R(x i)=2imin(|y j-y 0|),psf(x i,y j,f)=-3dB
Array resolution is relevant with analysis frequency, and analysis frequency is lower, and resolution is poorer, therefore usually only needs to judge whether the resolution under minimum analysis frequency meets the demands.
(6) judge whether the resolution of accepted array reaches end condition R (x i)≤R t, R tfor the desired value of array resolution.Reach end condition and then export current array unit coordinate, optimize and terminate, otherwise reduce simulated annealing temperature, T k+1=0.99T k, k:=k+1, (:=represent assignment operation) repeat the next circulation of step (4) beginning.
Principle of work of the present invention: the optimal design of array must handle the cooperate optimization relation of resolution and these two performance index of Sidelobe Suppression level well.The present invention using array Sidelobe Suppression level requirement as constraint condition, and consider the restrictive condition of Closed Tunnel array installation, utilize global optimization method---simulated annealing, optimization array resolution, thus the array that acquisition Sidelobe Suppression level and resolution all meet the demands.
The unspecified part of the present invention belongs to general knowledge as well known to those skilled in the art.

Claims (6)

1. be applied to the microphone array optimum design method that Closed Tunnel aerodynamic noise is measured, it is characterized in that comprising the following steps:
(1) stochastic generation microphone array, utilizes this array initialization microphone array column unit coordinate, initialization simulated annealing temperature T and k=1;
(2) whether the array in determining step (1) meets Closed Tunnel constraint condition, does not meet constraint condition and then jumps to step (4), otherwise go to step (3);
(3) the Sidelobe Suppression level of computing array, judges whether the criterion meeting Sidelobe Suppression level, to the array meeting Sidelobe Suppression level requirement, is accepted as new array, jumps to step (5), otherwise jumps to step (4);
(4) stochastic generation new array in former array neighborhood, jumps to step (2);
(5) resolution of new array is calculated, judge whether the resolution of new array is better than old array, if more excellent, accept new array, otherwise calculate acceptance probability, acceptance probability is greater than set-point and then accepts new array and go to step (6), otherwise jumps to step (4);
(6) judge whether the resolution of accepted array reaches end condition, reach end condition and then export current array unit coordinate, optimize and terminate, otherwise reduce simulated annealing temperature, make k:=k+1 :=represent assignment operation, repeat step (4) and start next circulation.
2. the microphone array optimum design method being applied to Closed Tunnel aerodynamic noise and measuring according to claim 1, it is characterized in that: the array Sidelobe Suppression level in described step (3) is relevant with analysis frequency, only judge whether the Sidelobe Suppression level under maximum analysis frequency meets the demands.
3. the microphone array optimum design method being applied to Closed Tunnel aerodynamic noise and measuring according to claim 1, is characterized in that: the criterion MSL of array Sidelobe Suppression level in described step (3) dsetting SNR is greater than, along with simulated annealing temperature T in iterative process early stage in iteration kreduction progressively reduce, at T k≤ T dtime reach setting SNR, its formula is wherein T dfor preset value.
4. the microphone array optimum design method being applied to Closed Tunnel aerodynamic noise and measuring according to claim 1, is characterized in that: in described step (4), in former array neighborhood, the method for the new array of stochastic generation is: x i=x k-1 i+ RandomrL, wherein: Random is the random number between 0 to 1, r is the unit vector of random direction, and L is the radius of neighbourhood, x ifor generating the planimetric coordinates vector of new array; x k-1 ifor k-1 walks the planimetric coordinates vector of array.
5. the microphone array optimum design method being applied to Closed Tunnel aerodynamic noise and measuring according to claim 4, is characterized in that: the described radius of neighbourhood reduces along with the reduction of simulated annealing temperature, and computing formula is l 0the neighborhood initial radium that representative is preset, T kfor the simulated annealing temperature in iterative process.
6. the microphone array optimum design method being applied to Closed Tunnel aerodynamic noise and measuring according to claim 1, it is characterized in that: the array resolution in described step (5) is relevant with analysis frequency, only judge whether the resolution under minimum analysis frequency meets the demands.
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