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Flanking noise down a UK cavity wall

Flanking noise down a UK cavity wall

Flanking noise down a UK cavity wall

Hi there

I am really struggling to find decent advice. I am willing to pay for advice but cannot seem to find the correct professional who really understands the issue.

I have a 3 story apartment building which was built in the 1990's. It has solid concrete floors with a 20cm slab between each flat. The slab sits in 150mm pumice thermal blocks. In many other countries, the concrete slab would rest on the outside blocks. In the UK it is common to stop the intermediate floor to rest on the inside blocks so that the 50mm cavity is maintained from top to bottom of the building. See photo enclosed

The windows on each floor are above each other and when the flats were built, the cavities were not closed as they would be today. In addition, if the flats were built today there would be an acoustic flanking "sausage" of rockwool (covered in plastic) at each floor layer.

It has plastic windows which sit in the cavity. They are attached with a few "groundings" but I believe as there is only a section of PVC between the window and the cavity, sound is travelling up and down the 50mm cavity.

I have two ideas. One is to fill the cavity with the thermal insulation "beads". I know these are not designed for acoustic insulation but my idea is the clear air gap would be filled. Surely these beads would acts in a similar way to acoustic Rockwool which is not that dense?

A second idea is to remove the skirting boards and drill the wall at 100mm centers. Then to inject a small amount of filler foam to re create a solid flanking strip. I have a Borescope with a rotating camera so I could confirm that the foam strip was continuous with no air gaps.

Does anybody have any suggestions where I can look for advice or acoustic properties for thermal insulation beads? I don't want to blow in Rockwool due to lots of reported issues with wicking and retaining water. The beads are waterproof.

Any advice welcome?

RE: Flanking noise down a UK cavity wall

I have not worked on this noise control situation (noise control engineer with 40+ years experience in USA), so I did a quick search:

Cavity Wall Noise Control

Cavity Wall Insulation

From <https://www.cavitech-uk.com/cavity-wall-insulation...;

What is bonded bead cavity wall insulation ?

From <http://www.yorkshireinsulation.co.uk/bonded-bead-c...;


Problem Free Cavity Wall Insulation

From <https://certainfilcavityinsulation.co.uk/cavity-wa...;

What is Partial Fill Cavity Wall Insulation?

From <https://certainfilcavityinsulation.co.uk/partial-f...;

Problems With Cavity Wall Insulation (Part 2)

From <https://www.eco-home-essentials.co.uk/problems-wit...;


Does cavity wall insulation reduce noise? If so, how?

From <https://www.quora.com/Does-cavity-wall-insulation-...;


Injected Cavity Wall Insulation

From <https://www.diydoctor.org.uk/projects/pumped-cavit...;

I could not find relevant noise control performance for Flanking Noise in a Cavity Wall. Perhaps one or more sales/installation vendors can provide case histories based on professional measurements. Foam beads injected with adhesive appear to be common in the UK. I would consider justifying project cost based on thermal energy loss reduction and with noise reduction an added benefit. The sound reduction provided by the cavity fill may not meet your full sound level requirement, so other measures may be needed. I would take close look at where sound gets into and out of the wall cavity; such as window frames and pipe/conduit penetrations.

A UK consulting firm that may be of assistance:
Industrial Noise and Vibration Centre Ltd
889 Plymouth Road – Slough – Berks – SL1 4LP – United Kingdom
Tel: +44 1753 698800 Fax: +44 1753 567988 Email: consult@invc.com


RE: Flanking noise down a UK cavity wall

I have an idea that I will get a lay flat PVC water hose and I can stuff this with Acoustic Rockwool which has a density of 45Kg per meter cubed

The 45 kg density Rockwool is what they use in professional cavity closer "socks" which are covered in very thin plastic. The plastic is 50 micron = 0.05mm


I called Timloc technical and they say they have no acoustic test data available which I find slightly suprising!!

My retrofit solution would have a PVC tube with a 1 mm thick walls as it has to be robust enough to over pack to say 65 mm width then and stuff in in the block walls without ripping. It would be a tight fit and the Rockwool would spring out a bit after to make a tight seal. So the question is could 1mm flexible PVC cause issues compared to 0.05mm PVC

Also has anybody got any software to calculate the attenuation that a sock 50mm x 270mm would cause (that would be the final shape of my retrofit solution in the wall)

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