Airborne vs Impact Noise: Two Problems, Two Fixes

"We soundproofed the floor and can still hear the neighbours upstairs" is a complaint we hear often enough to know exactly what usually went wrong: airborne and impact noise were treated as one problem, when they're genuinely two.

Airborne noise: sound travelling through the air, then through the structure

Airborne noise is anything that starts as sound in the air, voices, music, television, before it reaches a wall or floor and sets it vibrating, which then re-radiates the sound on the other side. It's rated as Rw in laboratory conditions, or DnT,w as a field measurement in a completed building, and Approved Document E requires new-build separating walls and floors to achieve at least 45 dB DnT,w + Ctr. The way to stop airborne noise is mass, decoupling and sealing: heavier materials resist being set into vibration in the first place, an air gap between two independent layers stops vibration transferring directly across, and gaps or penetrations, sockets, pipes, gaps around doors, undermine even a well-built wall if they're not sealed.

Impact noise: vibration entering the structure directly

Impact noise is different in kind, not just degree. It's caused by something physically striking a surface, footsteps, dropped objects, dragged furniture, which injects vibration directly into the structure rather than through the air first. It's rated as Ln,w in the lab or L'nT,w in the field, and for this measurement, lower is better: Approved Document E requires new-build separating floors to achieve 62 dB L'nT,w or lower. Mass alone does very little against impact noise, what actually works is decoupling the impact source from the structure, resilient underlays, floating floor systems, isolation mounts, that absorb the vibration before it can travel into the building fabric.

Why a wall or floor can pass one test and fail the other

Because the physical mechanisms are different, a construction can perform well against airborne noise while performing poorly against impact, or the reverse. A dense concrete floor might block airborne sound effectively through sheer mass, but transmit footstep noise straight through unless it also has a resilient layer decoupling the finished floor surface from the structural slab. This is exactly why Part E tests both figures independently rather than relying on one combined score, and why a specification addressing only one will still fail the other.

What this means for a real specification

A separating floor between flats typically needs both an airborne solution, mass and sealed junctions, and an impact solution, a resilient underlay or floating floor layer, working together. Treating only the ceiling below with absorptive panels, a common but mistaken approach, does very little for either airborne or impact insulation, because absorptive treatment reduces reverberation within a room, it doesn't stop sound transmission between rooms. That's a different acoustic goal entirely, and confusing the two is one of the most expensive misunderstandings in residential acoustics.

Common questions

Will thicker carpet fix an impact noise problem? Carpet and underlay can meaningfully reduce impact noise at the source, but on their own they rarely bring an underperforming floor construction fully up to Part E's requirement, particularly in older buildings with lightweight timber floors.

Does soundproofing a ceiling help with impact noise from above? A resiliently mounted, mass-loaded ceiling can help, but addressing the floor construction above, where the impact actually originates, is almost always more effective than treating from below alone.

Diagnosing which problem you actually have

See our guide to Approved Document E or book a free survey to find out whether your noise complaint is airborne, impact, or both, before specifying a fix.

Related product guides: acoustic pods.