flanking sounds 07

What’s flanking transmission? (Why you hear your neighbours!)

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how sound can flanking in a home

Flanking transmission, or flanking noise, is when a sound travels around, over or under a partition. An example would be pipes traveling between two rooms under the floor. The sound can move between the room via the pipes.

Flanking noise can allow sound to travel around a building easily, even if walls and ceilings are thick. Pipes, electrics and fixings are all common culprits for you hearing your noisy neighbors.

Will soundproofing stop flanking transmission?

Soundproofing will stop flanking transmission only if you have identified the cause of your issue first. If you have, then it can be treated when the soundproofing takes place. However, should your flanking be caused by a light fitting but you are treating a wall, then the flanking transmission will continue.

In general, new soundproofing partitions should not cause flanking transmission along their length if they are installed correctly. You should always follow installation guides and take care around perimeters, sockets and fixings. We build in anti-flanking defenses to our systems such as isolation tapes, MuteClips and perimeter flanking band.

How to stop flanking noise transmission

To stop flanking noise transmission, first assess where the sound is leaking. When you have found the source of the issue, different steps can be taken to soundproof the weak area. In general, gaps should be acoustically sealed and if holes are large, insulation can also be used.

Below are a list of common flanking issues in homes and how to fix them.

flanking transmission infographic for soundproofing

Flanking noise from electric sockets

Flanking noise from electric sockets is very common as you have a large hole in the wall. The best option is to rewire the room so the socket is on a wall not connected to the noise source.

Your second option is to wall mount the socket which will reduce the size of the hole significantly. Acoustic sealant around the wire will strengthen this area and reduce potential flanking noise.

The last option for soundproofing a socket is to keep the recessed design but add an acoustic box around the socket. This helps to create a better seal but you will still have a larger weak area in your wall.

Flanking noise from light fittings

Flanking noise from light fittings will vary depending on the design. For simpler designs, acoustic sealant can be added around the opening to close gaps. If your lights have multiple ceiling fixing points, this will increase the weak areas in your structure and you may be better off opting for a simpler design.

For downlights, acoustic caps can be installed before the light itself. As downlights need a fairly large hole in the ceiling, it is worth adding this extra defense in.

Flanking noise from pipes

Flanking noise from pipes is common as pipes travel between various rooms. Metal is able to conduct sound and this allows it to travel between spaces easily. To prevent sound from traveling through pipes, you need to damp the vibrations.

By using a vibration-dampening membrane on pipes, they cannot vibrate with sound energy easily. We use pipe wraps to do this which are easy to install.

Flanking noise from impact and vibrations

Flanking noise from impact and vibrations is common, especially in flats or buildings with staircases joined to a party wall. Vibrations can travel through the whole building structure, not just the floor if left unchallenged.

One of the simplest methods is to install acoustic underlay as this treats the impact at the source. MuteMat 2 is best for impact control as it has a layer of closed-cell foam that never fully compresses. This is compatible with most flooring types and is only 10mm thick. This can be added to the tread of stairs, but we have a full blog on stair soundproofing for full information.

Flanking noise caused by cavities

Flanking noise caused by open cavity spaces can create an amplified ‘noisy’ version of the original sound. If sound is able to enter a space without insulation, then it can amplify and become an issue.

To avoid this, use acoustic-grade mineral wool in floor, wall and ceiling cavities. This will dampen the sound and help to prevent it from traveling and flanking through other structures.

Soundproofing materials for flanking transmission

Isolation Strips

Isolation strips are used to prevent flanking between large structures. We lay them on top of floor joists before a subfloor is installed to create a ‘floating floor’ effect. We also use them for stud frames so that the two rigid materials of the floor and wall are not in direct contact.

We have different isolation strips for different purposes. We have a full video about isolation strips, and which one you need over on YouTube.

Acoustic Sealant

Acoustic sealant is used in every soundproofing system. This will fill small gaps and create an air-tight finish. The sealant does not set solid and this flexibility allows it to dissipate vibrations.

Wall systems are always installed with a 2-5mm gap around the perimeter, as are floors. This ensures that the flanking structures are never in direct contact. Not allowing rigid materials to touch greatly reduces flanking noise.

Perimeter Flanking Band

Perimeter flanking band, as the name suggests, is purpose-made to control flanking transmission. This helps to ‘float’ your new floor and prevent sound from traveling up into the walls.

The band goes between the floor and the skirting board, which would usually be in direct contact. This small change makes a bigger difference.

Pipe Wrap

Pipe wraps are made of two materials; insulation to reduce reverberation in the hollow pipe and a membrane. The membrane absorbs vibrations and prevents sound from being conducted along the length of the pipe.

Pipe soundproofing is often needed in flats where living quarters can be closely interconnected.

Acoustic Downlight Covers

Acoustic downlights work in a similar way to socket boxes. While you should aim for a single point light fixing for a pendant light, sometimes you have to use what you’ve got!

These downlighters go behind the bulb to prevent the hole in your ceiling from allowing too much sound through.

Socket box inserts

As already discussed, it is best to either move your socket to another wall or use a wall-mounted socket. However, if neither option is possible you must use socket inserts.

These sit behind the socket box and help to insulate it. They are easy to install and should reduce weak gaps for sound to travel.

The best way to stop flanking transmission?

The best way to stop flanking transmission is to use a full system that uses the specialist product listed above. Before installation, make sure you are aware of areas which are ‘leaking’ sound and how to use your material correctly. Incorrect installed soundproofing, that allows rigid flanking structures (two walls, wall and ceiling, wall and floor), to meet, will compromise your solution.

The best way to ensure your new system works is to use an experienced installer. Make sure to check for flanking weaknesses before starting your work so the whole room can be strengthened, where needed.

Sales and Opperations Manager

Hi, I'm Richard Woodhouse, our sales and opperations manager. I've got over a decade of specialist soundproofing experience and knowledge that makes me well placed to help people install the best soundproofing for them.

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