Design and Characterization of a Cylindrical Inertia Block for an Ultra-Low-Vibration Laboratory

Typical low-vibration facilities employ a rectangular concrete inertia block supported on pneumatic isolators that damp vertical oscillation. However, it has been shown that when the inertia block sides are parallel to the surrounding room walls, acoustic standing waves can exert pressure on the parallel faces of the slab that causes measurable motion. To address this problem, we have designed a new low-vibration laboratory room housing a cylindrical inertia block, with no parallel faces. Here we simulate and measure the acoustic modes of the room and place limits on their coupling to the cylindrical inertia block. We further measure the transfer function from the building foundation to the inertia block. Finally, we drive the flexural resonance modes of the cylindrical inertia block and compare their frequencies to more traditional block shapes.