The design of grommets is critical to the acoustic performance of any partition such as engine bay bulkhead.

Design Guidelines
  • Grommets should be of soft material (natural rubber recommended by a supplier though may not be suitable for high temperature areas) to ensure consistent fit.
  • Maximise grommet thickness.
  • High contact area to hose/harness, usually involves a sleeve.
  • High contact area to panel.
  • Grommet should be bonded to hose/harness to ensure good contact.
  • Hose/harness should be stress-free in area of grommet (i.e., is not at an angle or forced to one side of the grommet).
  • Overlaps acoustic treatment ensuring that no metal is visible.
  • For large areas, e.g., heater gaskets, do not use open cell foam, closed cell material provides a much better barrier.
  • Minimise size of hole in panel.
  • Put form in the panel around the grommet (i.e., a recess) to ensure a flat panel condition.
  • Ensure that the holes in the panel are remote from seam sealer, underseal and spot welds.
  • Harnesses - Wires bonded together under the grommet

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Subjects: Noise & Vibration