Issue with sound transmission on a external wall

[Tomerf]

Hello,

I live in a top floor flat which is essentially silent apart from the living room. One of the external (i.e outside, no neighbouring flat) walls in the living room appears to have been altered at some point so that there is a plasterboard wall with a void (I'd say approx 5-10cm) behind it then the breeze block.

However I can hear sound from the downstairs flat through this external wall. It doesn't come through the floor. If I put my ear up against the plasterboard wall I can clearly hear the sound from downstairs (TV, talking, etc.). All the other walls don't have this void and I can't hear anything. Can't hear anything if I put my ear to the floor either.

Any ideas why someone would add this in the first place? Seem odd it's only on one wall.

Also any ideas how I can resolve the problem? Ideally without having to tear down the wall!

Thanks,

Tom

 

[motorbiking]

You could try injecting some expanding foam. Though 10cm might be a challenge to fill

 

[oldbutnotdead]

You might have to open it up to make sure it isn't a service duct....if it is it should be sealed where it passes through the floor & ceiling.

 

[Deluks]

It sounds like a great place for fire to travel upstairs from below, it would be worth inspecting to at least see if there's some sort of firestop between the properties.

To remedy the sound issue, you have the choice of tearing it down, or building on top of it, which would make your room smaller.