acoustic particle velocity applications in-situ surface ......the energy received by 1/3 low surface...
TRANSCRIPT
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Customer Report โ Scan & Paint for armored vehicle1
Microflown Technologies // PO Box 2205 // 6802 CE Arnhem // The Netherlands // www.microflown.com // [email protected]
Graciano Carrillo [email protected]
In-situ Surface Impedance and Reflection Coefficient Method
Acoustic Particle Velocity Applications
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1 2 3 4
CONTENT
Introduction to particle velocity
In-Situ absorption estimation based on
Equivalent Source Method
Practical applications Results and discussion
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INTRODUCTIONMicroflown sensor technology
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THE MICROFLOWN SENSORMeasuring particle velocity
1. Two platinum wires heated up to appr.200 oC
2. As the air flows through the upstreamwire, air temperature increases and thewire cools down.
3. Next, the heated air flows through thedownstream wire, again thetemperature of the wire drops.However, the decrease is lower than itwas with the first wire.
4. The different temperatures of the wirescause different electronic resistances.Finally, the resulting voltage differenceover the two wires is measured.
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Automatically reduces
the energy received by 1/3
Low surface velocity
and high surface pressure
High surface velocity
and low surface pressure
Fundamental physical differences between the two quantities
Figure of 8Near field effect
PRESSURE vs PARTICLE VELOCITY
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3D ACOUSTIC VECTOR SENSORPressure and particle velocity in the X, Y and Z axis
โข Acoustic vector sensors (AVS) can be created by using multiple orthogonal particle velocity sensors
โข Localization resolution and accuracy is preserved across the frequency spectrum.
โข Broad-banded response| 20 Hz- 20+kHz
โข Sound intensity can be obtained by combinations of all sensor elements
1 cm
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Practical applicationsMicroflown sensor technology
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Sensor ApplicationsExamples of customer applications
2D Sound Visualization In-situ absorption 3D Sound Visualization
Sound power Audio Design Transmission Loss
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SOUND FIELD VISUALIZATION
โข Vector field โข Sound field slices
Analyze results in vector view, scalar view or create as many 2D sound field slices
โข Sound pressure
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AUTOMOTIVE // AUDIO SYSTEM
Sound visualization around the driverยดs seat
Mid
-lo
w f
req
uen
cy
Hig
h f
req
uen
cy
Cav
ity
reso
nan
ce
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Perform End-of-Line noise tests for objective evaluation, eliminating the variability of the
subjective human perception
Measuring in the particle velocity in the near field allows vibro-acoustic characterization in a noisy environment.
End of Line // ML Fault Detection
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Time frequency spectrogram RPM signal Order based transform
RPM against frequency spectrogram
Order spectrum
Fourier Transform
Order Transform
Domain
Complex Exponential with RPM related
variation
Discrete VSDFT
MEASUREMENT METHODOLOGY: ORDER TRANSFORM
Velocity Synchronous Discrete Fourier Transform (VSDFT)
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MODEL LEARNING: GAUSSIAN MIXTURE MODELS
โข Model the distribution of the samples with the objective to will be able to distinguish GOOD from BAD samples.
โข Not many samples available 20/20.
โข Neural networks wasnโt applicable due sample limitations
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OUTDOORS LOCALIZATIONExample of application cases
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15 M2I project proposal
Real time source localization
Outdoors localization
Low frequency noise causes anxiety and insomnia
โข Complaints of about a tonal noise.
Deployment of a network of AMMS:
โข Geolocalization of the problem
โข Temporal and spectral analysis
Example: Cooling system of a factory in Veendam (Netherlands).
โข Tone located at 30 Hz.
โข The system is being replaced.
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Outdoors: Wind TurbineMoving sources beamforming
Sensor Array
Velocity potential can be calculated by convolving the excitation signals with the time-varying propagation functions
Sound pressure and particle velocity can be directly computed using time and space differentiation
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Wind Turbine: Beamforming resultsComparison of microphone array and AVS array : spacing 7 times over Nyquist limit
Microphone array 3D AVS array
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IN-SITU ABSORPTIONESM based method
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Customer Report โ Scan & Paint for armored vehicle19
Q
h
1
2
1r
Qโ
probe
2r
3r
3r
x
y
PU in situ method
โข Extend current in-situ method forimpedance estimation to an array of sensors.
Motivation
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(2)
(1)
Equivalent Source Method
Green functions pressure and particle velocity
โข G ๐ซ, ๐ซ๐ = ๐โ๐๐ ๐ซโ๐ซ๐
โข G๐ข ๐ซ, ๐ซ๐ =๐
๐๐งG ๐ซ, ๐ซ๐
1. Sound field and sources strength relationship
โข๐ฉโ1๐ฎโ1
=๐๐๐๐๐1โ1 ๐๐๐๐๐2โ1โ๐๐1โ1
๐ข โ๐๐2โ1๐ข
๐ช1๐ช2
Array of single later of p-u sensors. Problem definition
Microflown In-Situ Absorption
(1) (2)
(2)
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(2)
(1)
Equivalent Source Method
โข๐ฉโ1๐ฎโ1
=๐๐๐๐๐1โ1 ๐๐๐๐๐2โ1โ๐๐1โ1
๐ข โ๐๐2โ1๐ข
๐ช1๐ช2
2. Solving inverse problem for q (ill-posed)
โข ๐ช = ๐๐ +๐๐
Where the regularized pseudo-inverse is
โข ๐๐ + = ๐๐H ๐๐+ ฮป๐โ1
๐๐H
And the weighting matrix
โข ๐ =๐ฉโ 0
0 ๐ฎโ
โ๐
Equivalent sources strength estimation. Solving inverse problem.
Microflown In-Situ Absorption
(2)
(2)(1)
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Equivalent Source Method
3a. Sound field reconstructed at the surface from estimated q
โข ๐ฉ๐ 0 = ๐๐๐ ๐๐1๐ 0๐ช1 + ๐๐2๐ 0๐ช2 ,
โข ๐ฎ๐ 0 = โ ๐๐1๐ 0๐ข ๐ช1 + ๐๐2๐ 0
๐ข ๐ช2
3b. Surface impedance Zs and reflection coefficient R is computed
โข ๐๐ 0 =1
๐ฯ๐=1๐ ๐๐ 0
(๐)
๐ข๐ 0(๐)
โข ๐ ๐ 0(๐) =๐๐ 0 cos ๐โ๐0
๐๐ 0 cos ๐+๐0,
Surface impedance and reflection coefficient reconstruction
Microflown In-Situ Absorption
(3)
(3)
(3)
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Equivalent Source MethodComparison: Single layer โ Double layer configuration
Microflown In-Situ Absorption
โข Valid for locally reactive samples only: The impedance doesnโt change with the angle of incidence)
โข Works for different types of sources: monopole / dipole
โข Doesnโt depend on wave model assumptions like plane wave
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Equivalent Source Method
Green functions pressure
โข G ๐ซ, ๐ซ๐ = ๐โ๐๐ ๐ซโ๐ซ๐
1. Sound field and sources strength relationship
โข๐ฉโ1๐ฉโ2
= ๐๐๐๐๐1โ1 ๐๐2โ1๐๐1โ2 ๐๐2โ2
๐ช1๐ช2
Double array of pressure transducers. Problem definition
Microflown In-Situ Absorption
(2)
(1)
(2)(1) (2)
(3)
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Acoustic field and impedance model
Microflown In-Situ Absorption
Pressure and velocity field model above an impedance plane ( Di & Gilbert)
โข ๐ ๐ซ =๐๐๐๐
4๐
๐โ๐๐ ๐ซโ๐ซ1
๐ซโ๐ซ1+
๐โ๐๐ ๐ซโ๐ซ2
๐ซโ๐ซ2โ 2๐๐ฝ 0
โ๐๐๐ฝ๐
๐โ๐๐ ๐1
2+ ๐1๐ง+๐๐งโ๐๐2
๐12+ ๐1๐ง+๐๐งโ๐๐
2๐๐
โข ๐ข๐ง ๐ซ = โ1
๐๐๐
๐
๐๐ง๐ ๐ซ
Porous media model (Delany and Bazley)
โข ๐๐ ๐ = ๐0 1 + 9.08103๐
๐
โ0.75
โ ๐11.9103๐
๐
โ0.73
Relative error in dB
โข ๐ธ{๐พest} = 20 log10๐พestโ๐พref 2
๐พref 2
Sketch of the geometric parameters
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Results and discussion4
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Results and DiscussionSurface Impedance PU vs PP (SNR 30 dB)
Real part Surface Impedance
Relative error
Microflown In-Situ Absorption
< 10 %
๐๐ 0 =1
๐
๐=1
๐๐๐ 0(๐)
๐ข๐ 0(๐)
< 10 % < 10 %< 10 %
Imaginary part Surface Impedance
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Results and DiscussionReflection coefficient PU vs PP (SNR 30 dB)
Microflown In-Situ Absorption
Real part Reflection Coefficient
< 10 %
Imaginary part Reflection Coefficient
๐ ๐ 0(๐) =๐๐ 0 cos ๐ โ ๐0
๐๐ 0 cos ๐ + ๐0,
< 10 %Relative error< 10 %< 10 %
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Results and DiscussionRelative error behavior Frequency vs SNR
Single Layer P-U method
โข P-U method: At 400 Hz, < 10 % relative error (-20 dB), -> SNR Needed: 15 dB
โข P-P method: At 400 Hz, < 10 % relative error (-20 dB), -> SNR Needed: 35 dB
Microflown In-Situ Absorption
Dual Layer P-P method
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Conclusions
Microflown In-Situ Absorption
โข Complex surface impedance and reflection coefficient have been calculated using ESM in two configurations: single-layer of p-u probes and a double layer of microphones.
โข The performance of ESM methods across the frequency for different SNR levels were studied.
โข Single layer p-u ESM method has significantly better performance, in special in the low frequency range, compared with the double layer of microphones ESM method.
โข In addition, the single layer p-u is also more robust against noise, achieving accurate results with relatively low levels of SNR.
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Customer Report โ Scan & Paint for armored vehicle31
Microflown Technologies // PO Box 2205 // 6802 CE Arnhem // The Netherlands // www.microflown.com // [email protected]
Contact us for further information or visit our website
Thank you for your attention
Graciano Carrillo Pousa