Hydraulic Noise Filter
To help reduce vibration in the LIGO gravity-wave observatory
Exploded CAD model including mounting flanges and window


The device works like a high-pass RC filter, but for a fluid system. It reduced noise by 10x to 100x in the target frequency range, to a level only ~2x higher than ambient acoustic noise in the room.

It includes:

  • mounting point for an "accumulator" (a fluid equivalent of a grounded capacitor)
  • fluid resistor (a series of disks separated by .014" spacers)
  • mounting point for a pressure gague
  • window to monitor fluid level and bubbles