Sound
Structure-Borne Sound
Sound carried as vibration through solid building elements rather than through air. It re-radiates from surfaces far from the source, which is why adding mass to one wall often fails to stop it.
In more detail
Structure-borne sound travels as vibration through solid building elements — framing, slabs, pipes, ducts, equipment supports — rather than as pressure waves in air. It becomes audible when a surface set in motion by that vibration radiates sound into a room, which can be a long way from the source.
That is what makes it confusing to diagnose. A pump in a mechanical room can be clearly audible in an upstairs bedroom and inaudible in the hallway outside the mechanical room, because the path is the structure rather than the air. Adding mass or absorption to the wall nearest the noise treats an airborne path that was never the problem.
The remedies are about interruption: resilient mounts and pads under equipment, flexible connections at pipe and duct penetrations, resilient hangers, or a deliberate discontinuity in the framing. Structure-borne energy is also concentrated at low frequencies, which is why it passes through assemblies that measure well on airborne ratings.
Why it matters
Almost every mechanically dense home — heat pumps, circulation pumps, ERVs, elevators, gym equipment, pool systems — carries a structure-borne noise risk, and it is typically discovered at commissioning or later. Isolation at the point of attachment costs little at installation and is disruptive to retrofit, because it means unmounting equipment and reworking connections that are finished around by then.
The common misunderstanding
That noise is loudest closest to its source. Structure-borne sound radiates from whichever surfaces the vibration reaches and excites, so the room where it is most audible may be several away. Chasing the sound where it is heard, rather than tracing the path back to the attachment, is how these problems stay unsolved for years.
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.