User benefits

• Non contact method

• No line of sight requirement

• Broad banded

• Measuring airborne sound

• Compact

• Trouble shooting tool

• Suitable for non cooperative materials

• No point of stability requirements
• Performs also with low level, low frequency signals

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Close to a vibrating surface (in the socalled very nearfield) the first layer of air is incompressible therefore the structural velocity of the surface and the acoustic particle velocity in the neighboring air are of the same magnitude.

• The very near field; theory, simulations and measurements of sound pressure and particle velocity in the very near field,
  H-E de Bree et al., ICSV11, St. Petersburg 2004

Non contact method

The Microflown is a non contact method, and thus a viable alternative to the scanning laser vibrometer. The Microflown doesn’t have the drawback of a massload of an accelerometer.

No line of sight requirement

A Microflown sensor doesn’t require the requirement of a scanning laser vibrometer, where the laserbeam has to see the surface to be tested.

Broad banded

The Microflown sensor is proven to work in the range from 0.1Hz up to 25kHz.

Measuring airborne sound

Scanning laser vibrometers and accelerometers cannot measure airborne do. However, Microflowns do.

Compact

The Microflown sensor has the similar size of an accelerometer, but is significantly smaller than a scanning laser vibrometer, and thus easy to operate.

Troubleshooting tool

The Microflown sensor is an intuitive tool that is easy to operate. Mode analysis can be done through with scanning the surface with the Microflown, listening to the Microflown, mapping the modes using for instance a white board marker. See e.g.:

• Application note 'scan and listen'

Suitable for non cooperative materials

Where scanning lasers black out, the Microflown sensor can be used to test non cooperative materials like

• scattering surfaces
• black surfaces
• foams

No point of stability requirements

Manual operation of the Microflown sensor without fixation is possible as long as the vibration of the hand is slow as compared to the frequency range of the vibrations to be tested.

Performs also with low level, low frequency signals

The Microflown is sensitive for vibrations (in m/s), accelerometers are sensitive for the derivative of the velocity (m/s²). Their sensitivity for vibrations is therefore proportional with frequency causing a low sensitivity (or S/N) at low frequencies. The Microflown is very sensitive at low frequencies.

• Application note 'scan and listen'
• Application Note Very Near Field Structural Dynamics (pdf),
• Chapter_7: Vibration measurements
• The very near field; theory, simulations and measurements of sound pressure and particle velocity in the very near field,
  H-E de Bree et al., ICSV11, St. Petersburg 2004
  
• The Very Near Field II, An introduction to Very Near Field Holography,
  H-E de Bree et al., SAE 2005 traverse city, USA
  
• Panel Contribution Analysis – An Alternative Window Method,
  Oliver Wolff and Roland Sottek,  SAE, 2005