This was a hydraulic noise filter used in LIGO, the Laser Interferometer Gravity Wave Observatory that won the 2017 Nobel Prize in Physics.
The device works like a high-pass RC filter, but for a fluid system. It reduced hydraulic pump noise by 10x to 100x in the target frequency range, to a level only ~2x higher than ambient acoustic noise in the room.
- 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
Array of dampeners installed in LIGO (Hanford, WA facility)