Wind noise
Wind noise is an aerodynamic noise related to the body design, and turbulence from rear view mirrors, wipers and cavities etcetera. It is most disturbing at speeds above 100 km/h but is becoming more and more important when powertrain and road noise is reduced. Careful design minimizes the problem so early concept studies are important. Wind noise is however often a late issue which requires fast and efficient analysis since measures like extended seal systems or sound packages are expensive.
Challenges:
The variation in production for critical design areas must be low. The tolerance chains need to be investigated and if necessary compensated for with good seal systems.
• Testing time has to be short since the access to prototypes is limited and The cost for wind tunnel testing is very high.
• Instrumentation must be fast and easy in a way to record repeatable results.
• The microphones must be installed to minimize structure borne sound.
• Microphone holders and cables shall not introduce any rattle noise.
• The installation shall be safe for the test engineer during vehicle test.
• Calibration verification must be easy to perform.
The transducers are often moved and unfortunately sometimes dropped.
This and also different environmental conditions as cold, heat and humidity must be handled without sacrificing performance or lifetime.
Example:
Wind tunnel tests with interior microphones measuring the contribution from a single system or component when all other possible sources are temporarily removed with tape, clay or similar.
Intensity microphone or surface microphones are used for noise source investigations.
Microphones used for wind noise testing shall be robust and also able to handle dust and humidity. Accessories like nose cones are needed for some tests.