Sound
Vibration Isolation
Interrupting the path that carries vibration from equipment into the structure, using resilient mounts, pads or breaks. Performance depends on matching the isolator to the load and the frequency involved.
In more detail
Vibration isolation interrupts the path from vibrating equipment into the building structure, using springs, elastomeric mounts, pads, resilient hangers, or a break in the supporting element.
It works by frequency, not by softness. An isolator has a natural frequency set by the supported load and its own stiffness, expressed in practice as static deflection. Isolation is achieved only when the disturbing frequency sits well above that natural frequency; a common design target is a ratio of at least three to one. Below that ratio the mount does little, and near it the mount amplifies — which is why an undersized or oversized isolator can make a vibration problem worse rather than better.
Isolation also fails at its bypasses. A well-mounted pump connected by rigid pipe, rigid conduit or a hard duct connection transfers vibration through the connection instead. Complete isolation means the mounts, the flexible connectors, and the absence of any incidental hard contact — including contact added later by another trade.
Why it matters
Isolation is the difference between mechanical equipment that is inaudible and equipment that defines the acoustic character of a floor. Selection depends on the equipment's weight, its operating speed and the structure supporting it, which is why it is engineered rather than chosen by category. It is also inspectable: a mount compressed solid, or a rigid pipe run crossing an isolated base, is visible before the ceiling closes.
The common misunderstanding
That a rubber pad under a machine is isolation. Whether a mount isolates depends on the relationship between its natural frequency and the equipment's operating frequency, and a pad too stiff for the load can transmit nearly everything while looking like a solution. A mount matched to the wrong load can also amplify vibration at some operating speeds.
Related terms
On Compound
Where this term does real work — and where the decisions get made.
Sources
Last reviewed July 2026 by Compound Editorial. Definitions are educational and not project-specific engineering or medical advice.