One of the most common reasons for partitions failing the sound testing is down to noise flanking between partitions.

Noise Flanking is a term used by acoustic engineers wherein the sound passes over the top or under the primary partition separating the two spaces under test. Flanking sound transmission can be especially bothersome in multi-family residential buildings do to the sheer number of dividing partitions.

One way to reduce the chance of to flanking transmission/s is at the design phase of the dwelling. Unfortunately, by Simply specifying high performance wall and floor partitions between dwelling is no guarantee to a sound isolation and subsequently a successful sound test. APT Sound Testing offer both preconstruction and post construction design solutions to achieve the required sound isolation requirements of Part E of Building Regulations.

This Plate Shows The Main Air Leakage Paths


We also offer an acoustic onsite inspection service to ensure that the sound insulation elements are being installed as per manufactures guild lines and the quality of the workmanship is consistent with ‘best practice’ noise control procedures.

You can also undertake you own checks by asking the design consultant i.e. the architect or the builder what steps have been taken to insure your building will be sound adequately sound proofed from your neighbours and from noise intrusion through perimeter envelope from outside the building, after all there isn’t any point your dwelling having high spec acoustic insulation between the inner partitions if sound is transferring through the outer envelope.

 It is never safe to assume because the architect has specified high performance walls, windows and floor/ceiling assemblies that the materials and onsite workmanship will result in compliance with the anticipated results and ultimately a successful sound test. In all these instances successful sound isolation in your home depends on the workmanship during the sound insulation installation phase, the problem is the site installer may know little about noise control techniques unless he is give the right supervision and direction the construction phase.

Part E of Building Regulations stipulates the minimum standards for noise control between residential dwelling units. Upon completion of the building the Building inspection department will need the sound test certification prior to the issue a certificate of occupancy. This shows that the building meets minimum building code standards including sound isolation.

Typical Flanking Sound Transmission Pathways:

  • Dividing Floors – Through Floor and Floor Joist Space (if insulation has not been installed or direct fixing to joists without a drop ceiling below the partition under test)
  • Dividing Ceilings – Above and Through the Ceiling Space (where an adequate acoustic break has not been carried on through the ceiling void)
  • Through Structural Steel (structural steel beams are often a major cause of noise transmission as plasterboard is often fixed directly to the steel without sound breaks)
  • Shared Structural Building Components – Floor Boards, Floor Joists, Continuous Drywall Partitions, Continuous Concrete Floors, and Cement Block Walls.
  • Through Windows (if they are no double glazed or have secondary glazing as a minimum)
  • Fixtures & Outlets – Light Switches, Telephone Outlets, and Recessed Lighting Fixtures (if penetrations have been cut back to back with the opposite dwelling under test)
  • Structural Joints – Perimeter Joints at Wall & Floor, Through Wall & Ceiling Junctures (these should be filled with acoustic mastic)
  • Plumbing Chases – Junctures Between the Walls & Floor Slab Above or at the Exterior Wall Juncture (this should be filed with mortar etc. to add mass to this weakened area)
  • Around the End of the Partition Through the Adjacent Wall (acoustic mastic should be used to seal this junction)

Even if you your wall/floor has been designed so it should provide a high acoustic rating exceeding Part E requirements, this may not be enough. Unfortunately, sound will always find the weakest link, for instance construction workers will usually jack the plasterboard tight to the ceiling in order to achieve a nice tight joint at the ceiling. This often leaves a void or potential noise transference point at the floor/wall junction, which will eventually be covered with a piece of thin skirting board. Failure to fill the joint between the wall and the floor with acoustic mastic can reduce even a 50dB rated wall to under 40dB which will fail the minimum standard of 45dB for sound insulation testing as stipulated within the Building Regulations Part E.

This Video Clearly Shows Sound Flanking Through a Wall

Often the sound insulation manufacture will provide test lab results for their material. However, you should usually reduce the acoustic target by 4-5dB due to onsite construction. When the construction assembly is tested in the lab it is also certified and the installation techniques are described in detail.  Unfortunately it is not always possible to replicate the exact conditions on the site compared to the ideal conditions within in a lab setting, which is a far more controlled and scrutinised environment. This is the reason why a 5 point difference is allowed between the construction design on paper and the actual on site performance.

APT Sound Testing can advise on all types of acoustic design, whether it’s accomplished during initial construction or during a refurbishment/renovation project.  We have the technical experience to help identify and rectify your soundproofing or noise control problem.

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