Impact noise is the thud of footsteps, the bang of a dropped object, the vibration of a chair being dragged across the floor. Unlike airborne noise — which travels through the air and loses energy passing through walls — impact noise is introduced directly into the building structure and travels efficiently through solid materials. Adding mass to a floor does not stop it; what you need is decoupling.
Acoustic underlay sits between your finished floor (timber, laminate, engineered wood, LVT) and the subfloor below, acting as a resilient isolation layer. When something impacts the floor surface, the energy has to pass through this resilient layer before it can reach the structure — and a significant proportion of it is absorbed and lost in that transition. The floor above becomes quieter to people below.
How acoustic underlay works
Standard foam underlay is designed for comfort and thermal performance — it provides minimal acoustic isolation. Acoustic underlay is engineered for resilience: it is denser, more dimensionally stable, and specified to provide measurable sound attenuation under load. It remains effective under the weight and traffic of normal floor use, where softer products quickly compress and lose their isolation properties.
Performance is measured by the impact sound improvement value, ΔLw, under BS EN ISO 717-2. A higher ΔLw figure means greater reduction in impact noise transmission. Products range from ΔLw 14dB for basic acoustic grades up to ΔLw 28dB or more for high-performance specifications. The finished floor you choose also affects total system performance — published data is available on request for specific floor system combinations.
Installation disruption level: low. Acoustic underlay replaces standard underlay in a conventional floating floor installation. No structural work required.
Typical use cases
- Upper-floor flats — the most common application: reducing the impact noise from your floor that is heard as footfall thud and scraping by people in the flat below
- Timber floor retrofits — replacing or relaying a timber floor gives an opportunity to upgrade the underlay to an acoustic specification without further disruption
- New build and conversion compliance — Part E of the Building Regulations sets minimum impact sound performance for new residential separating floors; acoustic underlay is a standard component in Part E compliant floor systems
- Home offices and home studios on upper floors — reducing footfall transmission below a working space that has equipment (chairs, tripods, studio monitors on stands) with frequent movement
- Commercial tenancies — reducing impact noise between office floors in multi-storey commercial buildings where a lease change triggers a fit-out
Technical notes
Acoustic underlay performance is measured under BS EN ISO 717-2 (impact sound insulation). ΔLw figures and full system test data are available on request. Product selection should account for the total floor system: subfloor type, finished floor material, and any existing resilience in the construction. For new build or conversion projects where Part E compliance is required, we can advise on the appropriate specification.
What's the difference between acoustic underlay and a resilient floor system?
Acoustic underlay is a single layer added between the finished floor and the subfloor. It is quick to install and adds meaningful impact noise reduction in most situations. It is the right solution when you are laying or relaying a floating floor and want to significantly improve impact sound performance.
A resilient floor system (using Resilient Clips & Channels or a fully decoupled floating floor system) provides a higher degree of structural decoupling — the floor surface is isolated from the structure not just by a compressible layer but by a mechanical break. This approach adds more construction depth and cost, but it is appropriate for situations with very demanding performance targets, severe impact or airborne noise problems, or Part E compliance requirements where standard underlay does not achieve the required Ln,w figure.
If you are unsure which approach is appropriate for your situation, describe your floor and noise problem and we'll advise on the right specification.