Impact noises

[Seeoda]

I have a semi-D with relatively good soundproofing between my side and the neighbours. The wall build-up is block-on-flat, sand and cement on both sides and then steel hat channel and drywall on both sides. Mostly the party wall provides adequate soundproofing. Conversations and telly are not heard, however, some sounds do get through, such as the neighbour's front door shutting and stairs. See pic of their front door. It is a structure borne noise and I know these are hard to reduce. Given this unwanted noise is actually not loud, is there any hope to reduce it? Assuming there are no gaps in the cement coat, I am wondering could the drywall cavity on both sides be creating a 'triple leaf effect'? One person advised me that removing the drywall and wet plaster or to use drywall with fibreglass attached that is not touching the block wall. Would this make a difference? The triple leaf effect is something a lot of guides don't mention.

The house is three floors and really like a slice of the cake, cut from a cake, the rest of the terrace, given how tall, wide but shallow this house is. I think this shape might worsen the noise pollution transfer the house is acting like one large speaker. Smaller the air gap, the more the higher frequencies can resonance right?

I am also looking into convincing the neighbours to install some kind of rubber cushion on their front door but I do not what product to use. 

[saveasteading]

Never heard of the triple leaf effect.

More layers and more density will reduce air-borne sound, not amplify it.

Impact sound will come through because there is contact all the way.

 

To reduce airborne sound you need something separate from the solid wall, so changing to a dab connection is little benefit.

Any introduction of fibreglass between the leaves will help, but noise will still come through the connections.

Also there is flanking sound, where a surprising amount comes through the weakest point, such as cracks or joints at corners.

 

What is the floor made of? If concrete in a single slab, then the noise can reverberate from one house to the next.

 

For a much better sound barrier add another skin of wall, using studs that span floor to floor, and that don't touch the party wall. Fill with acoustic mineral wool, plasterboard and finish.

You have now lost 80 to 100mm of floor space.

 

The best improvement I have known was by fitting a special acoustic barrier of pvc sheet, containing lead,  hung loose down the 9 inch solid party wal, then stud and board. It resulted in not being able to ever hear babies or tv through the wall either direction. It was experimental and would be v expensive, and I don't know if it is available. It shows what can be achieved if it matters enough.

 

British Gypsum and Knauf have info on the noise reductions theoretically available, but an acoustics guy told me that the life levels are never as good as the lab figures..

 

Please note that you could do lots to the wall, only to have the noise come through the ceiling, or side walls....it depends so much on the construction.

[Mr Punter]

The inner leaf masonry where the door is connected runs into your house with no breaks.  That explains the front door noise.  The top hat should be resilient bar.  The stair may be fixed to the masonry.

Edited July 17, 2021 by Mr Punter

[ToughButterCup]

31 minutes ago, Seeoda said:

... looking into convincing the neighbours to install some kind of rubber cushion on their front door but I do not what product to use. 

 

Perhaps you meant ... suggest... above?   and

33 minutes ago, Seeoda said:

... Given this unwanted noise is actually not loud, is there any hope to reduce it? ...

 

I've tried the following technique on many occasions (while arbitrating between warring factions in the same building)....

 

If possible, get your neighbours to come round to your place, and at the same time, someone else to slam (close) your neighbour's  door (shut) while they are in your place. That way they'll understand your problem. There's a chance that they'll - on their own initiative -  close the door more carefully. Cheaper by far.

 

With care, the answer to your problem might cost nothing at all. Win, win.

[Seeoda]

1 hour ago, saveasteading said:

Never heard of the triple leaf effect.

More layers and more density will reduce air-borne sound, not amplify it.

Impact sound will come through because there is contact all the way.

 

To reduce airborne sound you need something separate from the solid wall, so changing to a dab connection is little benefit.

Any introduction of fibreglass between the leaves will help, but noise will still come through the connections.

Also there is flanking sound, where a surprising amount comes through the weakest point, such as cracks or joints at corners.

 

What is the floor made of? If concrete in a single slab, then the noise can reverberate from one house to the next.

 

For a much better sound barrier add another skin of wall, using studs that span floor to floor, and that don't touch the party wall. Fill with acoustic mineral wool, plasterboard and finish.

You have now lost 80 to 100mm of floor space.

 

The best improvement I have known was by fitting a special acoustic barrier of pvc sheet, containing lead,  hung loose down the 9 inch solid party wal, then stud and board. It resulted in not being able to ever hear babies or tv through the wall either direction. It was experimental and would be v expensive, and I don't know if it is available. It shows what can be achieved if it matters enough.

 

British Gypsum and Knauf have info on the noise reductions theoretically available, but an acoustics guy told me that the life levels are never as good as the lab figures..

 

Please note that you could do lots to the wall, only to have the noise come through the ceiling, or side walls....it depends so much on the construction.

 

The floor is poured concrete and screed. The minimum a stand alone wall could be is 80mm? Is this the same with steel or wooden studs? I guess the current drywall and cavity is about 25mm so I guess Id lose around 60mm more if I replaced it with stand alone wall. 

[nod]

The main issues with sound transfer is the stairs fixed directly against the party wall

Housing associations have recognised this as a problem and don’t fix against the party wall Usually Leaving a 10 mil gap between the plasterboard and the stairs 

Covered with a decorative fillet 

Spec house builders don’t care 

[Seeoda]

2 hours ago, nod said:

The main issues with sound transfer is the stairs fixed directly against the party wall

Housing associations have recognised this as a problem and don’t fix against the party wall Usually Leaving a 10 mil gap between the plasterboard and the stairs 

Covered with a decorative fillet 

Spec house builders don’t care 

 

Luckily the stairs isn't so bad. Its more perpendicular to the party wall then parallel which probably helps. Thanks for the tip though. I will be looking to see if the timbers touch the wall. 

5 hours ago, saveasteading said:

Never heard of the triple leaf effect.

More layers and more density will reduce air-borne sound, not amplify it.

Impact sound will come through because there is contact all the way.

 

To reduce airborne sound you need something separate from the solid wall, so changing to a dab connection is little benefit.

Any introduction of fibreglass between the leaves will help, but noise will still come through the connections.

Also there is flanking sound, where a surprising amount comes through the weakest point, such as cracks or joints at corners.

 

 

 

Just to answer this, the wall would already be nearly nine inches of dense block, and sand and cement on both sides, so the challenge is to know whether adding more mass would have any meaningful impact. The triple leaf effect is supposed to be significant when you have multiple narrow cavities that each further amplify each other. I wonder if it applies to here. 

[saveasteading]

The cost of sorting the neighbours door slam is so small that you might offer to do it for them.

 

Thickness of an extra skin of wall? 20mm gap with rockwool slab therein, normally a 70mm stud, with fibreglass roll or batt between,  then plasterboard and skim or joint. 

you might turn the studs 90 degrees, put twice as many in, and accept some deflection.

 

Testing if noise is flanking through the floor is rather undignified. It involves you lying on the floor with an ear on the solid floor surface while a noise is created next door. 

It is worst with impact on the floor, and much reduced if there is carpet.

[Seeoda]

On 18/07/2021 at 12:35, saveasteading said:

The cost of sorting the neighbours door slam is so small that you might offer to do it for them.

 

Thickness of an extra skin of wall? 20mm gap with rockwool slab therein, normally a 70mm stud, with fibreglass roll or batt between,  then plasterboard and skim or joint. 

you might turn the studs 90 degrees, put twice as many in, and accept some deflection.

 

Testing if noise is flanking through the floor is rather undignified. It involves you lying on the floor with an ear on the solid floor surface while a noise is created next door. 

It is worst with impact on the floor, and much reduced if there is carpet.

At some stage I want to take down the dry wall anyway for fitting speaker wire and a TV so I might use that opportunity. If I go ahead and end up installing a lot of soundbloc plasterboard I hope it helps keep the house in future heat waves

[saveasteading]

Soundblock plasterboard AND acoustic mineral wool insulation.