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Objective

The objective of this investigation was to visualize the noise sources on a car door module during window operation.

Test Procedure

  1. A conformal array with 63 microphones in 7x9 arrangement was used
  2. Test was first conducted on fully dressed door and then on the door module after removing the trim
  3. Measurements were acquired for 2 Sec between start and end of window travel and data was averaged over these 2 seconds
  4. Intensity was visualized to identify noise sources

Results

Intensity reconstruction after a quick test revealed a hot spot under the arm rest.

On physical inspection, it was found that the retainer bolt was missing.
After replacing the retainer bolt, the test was done again.

Intensity destribution showed that after replacing the retainer bolt, another louder hot spot appeared above the arm rest.

A spacer was found to be acting as an enery bridge and transmitting vibration from the door module to the trim panel
The test was then conducted on the door module after removing the trim.

Contrary to the popular belief, the motor did not turn out to be the major source of sound. Most of the noise was seen to be coming from the module panel. Even though the motor is the source of energy in the system, it is not a significant source of noise.