Wave Dynamics GuidesWhy Sound Insulation Tests Fail and How to Avoid It
The most common reasons separating walls and floors fail sound tests, from flanking and gaps to bridged floating floors, and how to avoid them.
In Short
Most sound test failures are caused by construction details rather than the wall or floor type itself. Gaps, back-to-back sockets, bridged floating floors, poorly sealed service penetrations and flanking through connected walls let sound bypass an otherwise good separating construction.
- Small air gaps can cost several decibels of airborne performance.
- Impact failures usually come from floating floors or screeds touching the structure.
- Flanking through façades, ceilings and internal walls is a major cause of failure.
- An early first test set finds problems before they are repeated through the building.
Airborne Failures: Walls and Floors
- Air paths: gaps at wall heads, around steel beams, behind kitchen units and at the junction with the façade.
- Back-to-back services: sockets, switches and pipes in the same position on both sides of a separating wall.
- Unsealed penetrations: pipes, ducts and cables passing through without acoustic sealant or collars.
- Incorrect linings: wrong board density, missing layers, or linings fixed rigidly where resilient fixings were specified.
Impact Failures: Floors
- Screed or floating floor touching the perimeter walls because the edge strip is missing or trimmed.
- Skirting boards fixed down onto the floating floor.
- Resilient layers that are torn, overlapped incorrectly or the wrong product.
- Ceiling hangers or services in the void bridging the ceiling to the slab where an isolated ceiling was intended.
Flanking Transmission
Flanking is sound travelling around the separating element through connected parts of the building: the external leaf, lightweight internal walls, continuous ceilings and floor voids. It is common in timber frame, light gauge steel and modular buildings, and where internal walls run past the end of a party wall. The cure is in the junction details, which should be designed at the drawing stage and inspected on site.
What Happens After a Failure
We carry out diagnostic testing, which can include sound intensity checks and visual inspection, to find the weak point. Remedial options range from sealing and replacing linings to adding an independent lining or ceiling. The pair is then retested, and other similar rooms are reviewed so the fix is applied consistently.
How to Avoid Failures
Have an acoustic consultant review separating constructions and junctions at design stage, carry out a site inspection before linings close up, and test an early sample. These steps cost little compared with stripping out finished apartments.
Frequently Asked Questions
Can a failed wall be fixed without demolition?
Usually yes. Most failures are fixed with sealing, extra lining layers or an independent lining, without removing the main wall.
Do failures always mean the design was wrong?
No. Many failures come from workmanship or late changes on site, such as relocated sockets or substituted products.
This guide gives general information and is not a substitute for project-specific advice. Requirements change, so always check the current regulations, guidance and your planning conditions. Ask our team about your project.
Jon Maguire (BSc Hons MIOA) brings over 8 years of expertise in acoustic consultancy, specialising in environmental acoustics with a focus on 3D modelling, assessments, and detailed design for industrial, commercial, and energy projects. He has lead noise assessments for key clients while thriving in multidisciplinary environments. Jon’s diplomatic communication skills are ideal for stakeholder consultation.
Jack is a Field Engineer at Wave Dynamics, supporting the delivery of environmental monitoring and acoustic consultancy services through detailed on-site fieldwork. He has hands-on experience in noise monitoring, vibration monitoring, and dust monitoring across a variety of infrastructure, construction, and environmental projects. Jack is involved in the setup, operation, and maintenance of monitoring equipment, ensuring accurate data collection in line with relevant standards and project requirements. He works closely with consultants and project teams, providing reliable field support that underpins high-quality assessments and reporting.
Aidan is the Director for all U.K Operations and has worked in multiple industries including for clients in the UK and internationally operating in the residential, industry, healthcare, education, and construction sectors.
