Microflown Technologies - Source Path Contribution
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Source Path Contribution      

User benefits
 

  • Broad banded single transducer solution
  • Substantial time savings
  • More reliable results
  • Allows testing under real operating conditions
  • No foam required
  • Multipurpose tool

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Broad banded single transducer solution

Using only one type of sensor, cabin interior noise problems can be solved more accurately, in a wider frequency range and faster now. For a comprehensive, state of the art but time consuming analysis, two methods can be used for measuring the sound source and one method can be used for determining the transfer path. As far as measuring the sound source is concerned, for lower frequencies, the acoustic particle velocity radiating from a panel of a white body interior is measured.

Either accelerometers or a scanning laser are used. For higher frequencies, the radiated sound intensity from a panel of a white body interior is measured using a p-p sound intensity probe. PU probes cover the entire frequency range in one go, measuring the particle velocity in the lower frequency range and sound intensity at higher frequency range.

As far as determining the transfer path is concerned, usually a reciprocal method is used. With a volume velocity source placed at the drivers’ ears position, the transfer path to the interior white body panels is measured using sound pressure transducers placed near the wall. The same PU probes can capture the sound pressure signal as well.

So for a comprehensive analysis, PU probes replace accelerometers/scanning laser, sound pressure transducers and p-p sound intensity probes.

Substantial time savings

Traditionally used p-p sound intensity probes are susceptible to reflections as they occur in a vehicle interior. As a consequence, in order to measure the radiated sound intensity of a sound source, the entire cavity has to be covered by damping foam in order to create anechoic conditions. The corresponding time consumption is high and often even prohibitive.

As proven in a paper reviewed JASA paper PU probes are not susceptible to reflections, and thus the need to apply damping foam is eliminated.

As a consequence, with PU probes substantial time savings of more than 75 % can be realized.

More reliable results

PU probes eliminate the two adverse mass load effects as they normally occur during the measurement of the source strength for both frequency ranges. For the lower frequency range, the accelerometers causing a mass load effect are replaced by a non contact measurement method. For the higher frequency range, the damping foam is no longer required.

Allows testing under real operating conditions

Traditionally cars are tested in wind tunnels, semi anechoic rooms and chassis dyno’s to determine sound sources and transfer paths. The new PU method allows also testing on the road, since the windows are no longer blocked with damping foam. A new and complementary testing method emerges, with a new trade off to be made between standardization of measurement conditions applied and the costs of infrastructure involved.

For larger vehicle's (e.g. civil and business aircrafts, helecipters), where the application of damping foam was extremely time consuming / time consuming, now a broad banded source path contribution method comes in reach.

Multipurpose tool

The vary same PU probes can be used for other purposes as well, e.g. direct acoustic camera.

More info

Key papers