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Microflown based Applications Microflown
Technologies The Netherlands www.microflown.com in
fo_at_microflown.com
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• Contents
• Introduction
• Microflowns
• Applications
• Scan Listen
• Near field acoustic camera
• Panel Noise Contribution Analysis
• In situ absorption
• Non contact vibration
• End of line testing

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• Introduction
• Microflowns
• Applications
• Scan Listen
• Near field acoustic camera
• Panel Noise Contribution Analysis
• In situ absorption
• Non contact vibration
• End of line testing

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Company Introduction
1994 Invention Microflown by Hans-Elias de Bree
at University Twente 1997 Ph.D. Hans-Elias de
Bree 1998 Founding Microflown Technologies B.V.
(de Bree, Koers) 2001 Industrializing
product 2003 Introduction broad banded sensor
element 2004 First applications scientifically
proven / first arrays sold 2005 Rapid growth in
(automotive aerospace) industry 2005 De Bree
appointed Professor Vehicle Acoustics at the
HAN University, Arnhem School of
Automotive Engineering 2008 12 FTE company 4
Ph.D. students, 1 MEURO turnover
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Company Introduction

• Main markets Microflown is focusing on are
  Automotive, Aerospace and Defense
• 12 FTE Company 4 PhD students
• lt1 million euro turnover
• Rapidly growing company
• Own faculty at the Han University of Automotive
  engineering in Arnhem

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References

• Automotive - OEM
• Audi, BMW, DAF Paccar, Daimler, Ford,
  Freightliner, Harley Davidson, Honda, Isuzu,
  Mazda, Nissan, PSA Group ( Peugeot - Citroën ),
  Renault Samsung, Toyota, Volkswagen
• Automotive - Others
• AISIN, Behr Group, Eaton USA, Faurecia, Fontijne
  Grotnes, Harman Becker Automotive Systems, ISM
  Automotive, Jatco, Mirror Controls International,
  Mitsuba, Rieter Automotive, Rietschle Thomas,
  Robert Bosch, Siemens VDO, Stankiewicz
• Aerospace
• Aeronautical Development Establishment
  Bangalore,  Airbus France, Airbus Germany, DLR (
  German Aerospace Center ), General Electric
  Propulsion Systems, Progency Systems Corporation

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References

• Defense Security
• Batelle, BBN, Dutch Ministery of Defense,
  University of the Federal Armed Forces (
  Germany), Naval Post Graduate School, Wehr
  Technische Dienst
• Test houses
• LMS International, Mueller-BBM, Ricardo UK,
  SPEKTRA
• Other Industries
• ASML, BOSE, CAE Engineering and Services, Canon,
  CNAM, EMPA, Fisher-Rosemount, INRS, INSA, KAZ,
  KNMI, Kobe Seitetsusyo, MSX International, Nippo
  Hoso Kyokai, Oticon, Pioneer, RION, Sick Maihak,
  Sony

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• Introduction
• Microflowns
• Applications
• Scan Listen
• Near field acoustic camera
• Panel Noise Contribution Analysis
• In situ absorption
• Non contact vibration
• End of line testing

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Microflown

• Microphone measures sound pressure (result)
• Microflown measures Particle Velocity (cause)
• Acoustical lt-gt electrical lt-gt energy
• Sound pressure lt-gt voltage lt-gt potential
• Particle velocity lt-gt Amperes lt-gt kinetic

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Microflown
PRESSURE WAVE
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Microflown
PRESSURE WAVE ? PARTICLE VELOCITY
(Source ISVR)
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Microflown
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Microflown

• Surface velocity measurement
• No background noise problems

Figure of eight
High surface velocity and low surface pressure
Low surface velocity and high surface pressure
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Microflown
Product range
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Microflown
Scanning Probes

• 1D velocity
• For small objects
• High temperatures

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PU Probes
Microflown

• Particle Velocity
• Sound Pressure
• 1D sound Intensity
• Impedance
• 1D Sound Energy

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PU Probes Placement of p and u
Microflown
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Microflown
Metal Mesh

• Wind shield, DC flow till 2 m/s
• Protection

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USP
Microflown

• 3D Particle Velocity
• Sound Pressure
• 3D sound Intensity
• Impedance
• 3D Sound Energy

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Microflown
3D Sound Chip
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Microflown

• Calibration standing wave tube
• Loudspeaker on one side,
• reference pressure microphone at the other side
• in the tube, known relation between pressure at
  the end and
• pressure and velocity in the tube

loudspeaker
Standing wave lt-gt
Reference microphone
PU probe
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Microflown
Calibration Piston on a sphere Known relation
between sound pressure and particle velocity in
front of the speaker. Use a reference pressure
microphone to calibrate the Microflown probe.
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• Introduction
• Microflowns
• Applications
• Scan Listen
• Near field acoustic camera
• Panel Noise Contribution Analysis
• In situ absorption
• Non contact vibration
• End of line testing

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1. Scan Listen
With the Scan Listen device p and u can be
heard directly

• Easy finding of modes / vibration patterns
• Easy finding of sources
• Squeak Rattle
• Portable
• Simple to use

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1. Scan Listen
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1. Scan Listen
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1. Scan Listen
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1. Scan Listen

• The setup consists of two steel plates,
• the right one is vibrating
• the left one is steady
• p and u are measured at the same place on both
  plates with pu probes
• Two measurements are done
• without background noise
• with background noise

Gong
pu probes
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1. Scan Listen
Without background noise
Hard plate
Gong
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1. Scan Listen
With background noise
Hard plate
Gong
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Example 2 finding modeshapes
1. Scan Listen

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Example 2 finding modeshapes
1. Scan Listen



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• Introduction
• Microflowns
• Applications
• Scan Listen
• Near field acoustic camera
• Panel Noise Contribution Analysis
• In situ absorption
• Non contact vibration
• End of line testing
• Far field Acoustic Vector Sensors

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2. Near field acoustic camera
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2. Near field acoustic camera

• Features / Benefits
• Near field method
• Measured reliable acoustic particle velocity
  data
• Real time visualization of all relevant acoustic
  data
• One point methodology
• Free configuration of measurement grid
• Full bandwidth 20Hz-20kHz
• Large dynamic range gt40dB
• Low susceptibility to background noise and
  reflections
• No need for anechoic room or in anechoic
  conditions
• Visualization of transients
• Non coherent noise sources
• Multi purpose tool -gt probes can be used for
  other applications

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2. Near field acoustic camera
Each probe measures Sound Pressure and Particle
velocity (and thus Intensity) in one
spot Velocity and Intensity are directly
determined, without complex mathematics (like
near field holography)
Microphone opening
Velocity Microflown
Mini PU probe
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NAH Near field Acoustic Holography
2. Near field acoustic camera

• Measure pressure and calculate the velocity
  somewhere else
• Based on assumptions that are not met in practice
• Very difficult method
• - Only mid frequency
• - Relative low dynamic range
• Only planar or spherical sources
• Only used as an indication
• Results influenced by background noise or
  reflections

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2. Near field acoustic camera
JASA paper (Jacobsen) Velocity-based
predictions were consistently found to be better
than pressure-based predictions Test setup
for ideal condition -anechoic room -semi
infinite wall -flat surface -1000
measurements Conclusion Reconstruction of
particle velocity fails
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2. Near field acoustic camera
A simulation study radiation from a point driven
panel in a baffle
( Finn Jacobsen )
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2. Near field acoustic camera
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Beam forming arrays
2. Near field acoustic camera

• Low resolution
• Mainly suitable for high frequency
• Relative low dynamic range
• Results can be influenced by background noise or
  reflections
• simple method
• far field

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2. Near field acoustic camera

• SAE 2005 paper (Hald)
• Sound intensity method has no frequency
  limitations

Beam forming
Near field holography
Intensity method
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2. Near field acoustic camera
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Miniature PU match Acoustic Camera
2. Near field acoustic camera
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2. Near field acoustic camera

• 1cm x 1cm spacing
• Sound leak finding
• End of line control
• Real time movies

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2. Near field acoustic camera
Engine run up in an engine bay (not anechoic
environment) Spacing between probes will not
result in frequency limitations. So any probe
grid configuration can be defined
PU array with flexible grid
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2. Near field acoustic camera
Easy to deploy the measurement grid in the
software
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2. Near field acoustic camera
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2. Near field acoustic camera
FFT and a 3rd octave display on the left side to
show the frequency analysis of single probes in
detail
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2. Near field acoustic camera
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2. Near field acoustic camera
TATA Motors Noise Identification on the gear
lever panel Aim To identify the noise sources on
the Gear lever panel. The car was driven on the
test track to Identify the noise on the gear
lever panel. The measurements were done when the
vehicle was accelerated from Idle to full
throttle in 3rd gear.
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2. Near field acoustic camera
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(No Transcript)
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2. Near field acoustic camera
Measuring with a portable setup inside the
Eurocopter EC 120
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2. Near field acoustic camera
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2. Near field acoustic camera
Case Ricardo UK

• Replacing step scan SI sweeps for engine
  benchmarking
• Better occupational health
• Much faster
• More broad banded
• Higher spatial resolution

Ricardo UK /
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2. Near field acoustic camera
Case Ricardo UK
FEAD Tensioner
Crank pully
Calculated Sound Power, obtained through method
utilizing the Microflown
Sound Power obtained through swept PP sound
intensity probe method
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2. Near field acoustic camera
Case TATA Motors
TATA Motors Door Rattle Aim To locate the door
rattle noise of the left door of a Car. The
vehicle was excited on a Squeak and Rattle four
poster. The array was scanned around the door
from outside. The location of the rattle was
identified and shown.
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2. Near field acoustic camera
Case TATA Motors
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2. Near field acoustic camera
Case WKK
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2. Near field acoustic camera
Case WKK
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2. Near field acoustic camera
Case WKK
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2. Near field acoustic camera
Case BMW
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• Introduction
• Microflowns
• Applications
• Scan Listen
• Near field acoustic camera
• Panel Noise Contribution Analysis
• In situ absorption
• Non contact vibration
• End of line testing
• Far field Acoustic Vector Sensors

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3. Panel Noise contribution
DISPLAY
3D DIGITIZER
MEASUREMENT
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3. Panel Noise contribution

• Measure the contribution of each source to the
  total amount of noise at the listener position
• Two complete separate measurements
• Source strength measurement
• Path measurement

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Traditional panel noise contribution methods
3. Panel Noise contribution

• Traditional methods
• Two methods required for full acoustic bandwidth
• High installation time for both methods
• Different equipment for both methods
• Low frequency LASER or accelerometer
• Laser is difficult to use
• Accelerometer massload and cable errors
• Accelerometer high installation time,
  airborne leaks cannot be handled
• High frequencies very much measurement points
• High frequencies PP intensity probe
• PP intensity probe has p/I problems
• One need damping foam to reduce p/I problems
• Damping foam installation is very time consuming

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3. Panel Noise contribution
THEORY
The Kirchoff-Integral-Equation reads ...
... Since in our case no internal sources exist
...
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3. Panel Noise contribution
THEORY
... it follows
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3. Panel Noise contribution
THEORY
If the Greens function is now identified...
... with the reciprocally measured transfer
function P/Q ...
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3. Panel Noise contribution
THEORY
... and the gradient ...
... with the reciprocally measured transfer
function V/Q ...
... by using
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3. Panel Noise contribution
THEORY
... and if the pressure gradient...
... is related to the directly measured volume
velocity v...
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3. Panel Noise contribution
THEORY
... and if ...
... is identified with the directly measured
pressure P ...
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3. Panel Noise contribution
THEORY
... the following formula results
The right side of this formula contains only
measurable quantities (PU-sensor data).
No extra assumptions required concerning the
Greens function (like e.g. free field
condition).
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3. Panel Noise contribution
THEORY
Approximation for hard backed wall
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3. Panel Noise contribution
THEORY
With a discrete number of sensors
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3. Panel Noise contribution
Transfer Functions P/Q
Microflown Sensors
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3. Panel Noise contribution
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3. Panel Noise contribution
Sensor mounting for PNCA measurement Decoupling
the probe from surface
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3. Panel Noise contribution
Data hardware
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Omnidirectional volume velocity sourcesvolume
velocity particle velocity Area
3. Panel Noise contribution
High freq. source100Hz-7kHz
Low freq. source30Hz-300Hz
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3. Panel Noise contribution
3D DIGITIZER
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3. Panel Noise contribution
LOADING 3D GEOMETRY MODEL
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3. Panel Noise contribution
COMBINING MEASURED ACOUSTIC DATA ...


WITH THE 3D GEOMETRY MODEL
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3. Panel Noise contribution
RESULTS DETAILED ANALYSIS
180 individual panel contributions
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3. Panel Noise contribution
FREQUENCY DOMAIN

• Frequency can be set
• Time slot can be set
• Display range can be set

? full flexibility
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3. Panel Noise contribution
TIME DOMAIN

• Frequency can be set
• Time slot can be set
• Display range can be set

? full flexibility
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3. Panel Noise contribution
VALIDATION AVERAGED SPECTRA
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3. Panel Noise contribution
Transfer Functions P/Q
Microflown Sensors
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PNCA FEATURES

• Unique sensor ? unique method
• Ideal for Sound Package Optimisations or Trouble
  shooting
• Very fast Measurement of whole vehicle
  takes max. 2 ½ days. 3D geometry
  measurement takes less than 4 hours.
• Very flexible road measurements (wind, rain,
  gravel, etc.) are easy
• Frequency range 100 Hz 2 kHz
• Very high degree of detail 180 single surface
  contributions
• Method maintains the structure and the
  absorption properties of the car. (No heavy
  spring mass system needed anymore!)

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3. Panel Noise contribution
Helicopter interior measurements at PZL Swidnik,
Poland
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3. Panel Noise contribution
PZL Swidnik
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PNCA inside TGV train
3. Panel Noise contribution
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• Introduction
• Microflowns
• Applications
• Scan Listen
• Near field acoustic camera
• Panel Noise Contribution Analysis
• In situ absorption
• Non contact vibration
• End of line testing

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Traditional methods
4. In situ absorption

• Current methods have disadvantages
• Kundts tube
• Sample cut-out acoustic properties are affected
• Sound leakage due to mounting problems
• Only under 90 degrees incidence
• Reverberant room / alpha cabin
• Large and expensive facilities required
• Large samples several square meters
• Absorption values larger than 100 is experienced
• Microphone based free field (e.g. Tamura)
• Large samples 10 square meter
• Slow method 4 hour
• Influence of background noise

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4. In situ absorption

• Microflown standard calibration tube can be used
  as Kundts tube
• lower frequencies
• can be measured
• More accurate

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R. Lanoye et al, a practical device to determine
the reflection coefficient of acoustic materials
in-situ based on a Microflown and microphone
sensor, ISMA, 2004.
4. In situ absorption
PU based Kundts tube method has more broadbanded
and continuous results
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4. In situ absorption

• Reverberant method

• Large setup
• Only diffuse result
• LF problems
• Not accurate

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4. In situ absorption

• Free field method Tamura

• Free field
• Large sample (10m2)
• Slow method (4 hours)
• Oblique angles possible
• Anechoic room required

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4. In situ absorption

• New Microflown based method

• In situ
• Portable
• Real time
• No Kundts tube
• Broad band 200Hz-10kHz
• Normal and oblique angles
• High spatial resolution
• Flat and curved surfaces

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4. In situ absorption

• Impedance is the ratio of sound pressure and
  particle velocity

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Surface impedance setup
4. In situ absorption
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2 channel SC DAQ Surface impedance
software
4. In situ absorption
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User-friendly software
4. In situ absorption
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Measurementscreen
4. In situ absorption
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Load your measurements
4. In situ absorption
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Plot options
4. In situ absorption
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Curve example Absorption Reflection
4. In situ absorption
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Sample with three quarter lambda resonators
High spatial resolution
4. In situ absorption
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4. In situ absorption
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4. In situ absorption
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4. In situ absorption

• Conclusion Kundts tube
• High flow resistivity and soft (i.e. foams)
  deviated results in the tube
• Tubes requires uniform samples
• Difficult materials (concrete, car parts)cannot
  be measured in a tube
• No oblique measurements possible
• Frequency limitation

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25 VW GOLF test cars
4. In situ absorption
Case VW Golf carseats
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1 reference car
4. In situ absorption
Case VW Golf carseats
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4. In situ absorption
Reference car
25 test cars
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• Introduction
• Microflowns
• Applications
• Scan Listen
• Near field acoustic camera
• Panel Noise Contribution Analysis
• In situ absorption
• Non contact vibration
• End of line testing

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Vibration measurements
5. Non contact vibration

• Surface velocity (vibration) measurement
• Traditionally by laser or accelerometer
• Also possible with microflown

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5. Non contact vibration

• Surface velocity (vibration) measurement
• Laser
• no mass load (contactless)
• - expensive, large, not always possible (30)
• Accelerometer
• low cost
• - Must be fixed to structure, cables, time
  consuming, mass load, cable induced errors

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5. Non contact vibration

• Surface velocity (vibration) measurement
• Microflown
• medium cost
• contactless
• all surfaces (also foam, air etc.)
• can be done by hand (no stability problems)
• Not affected by background noise

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5. Non contact vibration

• Very close to surface structural
• velocity and acoustic particle coincide
• Very close typical dimension of the source / 6
• Maximum underestimation 2dB

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5. Non contact vibration
Low frequencies
Thin steel plate

Onera (FR)
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5. Non contact vibration
Thin steel plate

University of Twente
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5. Non contact vibration
On foam
Rieter Automotive
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Modes of turbo
LMS
5. Non contact vibration
High frequencies
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• Introduction
• Microflowns
• Applications
• Scan Listen
• Near field acoustic camera
• Panel Noise Contribution Analysis
• In situ absorption
• Non contact vibration
• End of line testing

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6. End of line control

• Acoustic check of products

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6. End of line control

• Audio example
• background noise
• reduction

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6. End of line control

• Acoustic check of products
• Not always possible with microphone
• Microflown no influence of background noise
• Laser and accelerometer are difficult to use

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Noise radiation Benefits Microflown sensor
6. End of line control

• No influence background noise
• Fast
• Non contact
• Easy to install

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Comparison test
6. End of line control
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6. End of line control
Comparison test Order tracking
Accelerometer
Microflown
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Mirror Power actuatorMirror controls Int. (Eaton)
6. End of line control

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6. End of line control
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• Not the absolute SPL but the sound quality is of
  importance
• 6 different spectrograms with 6 different noise
  issues
• 1) Good
• 2) Grinding
• 3) Waving
• 4) Ticking
• 5) Vibrating
• 6) Buzzing

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• Are there any questions ?