Advice on soundproofing an existing floor?

[GrendelsMum]

We have a couple of rooms with very noisy floors - they let both impact and airborne sound through. The problem seems to be that they're just chipboard laid onto beams and then floorboards laid directly on the chipboard. The timber beams are a major feature of one of the rooms, so we don't want to cover them up there at least. What can we do to sort out the noise? (Apparently you can hear by husband typing in the study from the guest bedroom above.) We've been looking at acoustic underlays - does anyone have any experience and advice?

GrendelsMum,

I like to bore people with acoustical theory!

Airborne insulation - generally:

a) Insulation performance increases with increase of mass (i.e. weight);
b) Improving airborne insulation has more effect in reducing high rather than low frequency airborne noise transmission;
c) Airborne insulation performance can be degraded by airborne "leakage" paths" - gaps in ceiling/flooring around piping between rooms etc.

Structureborne noise reduction (for impact noise) - generally:
a) Use vibration "isolation" (from rubber underlay to "floating floor" construction for worst case)
b) Improving structureborne insulation has more effect in reducing high frequency rather than low frequency structure-borne noise;
c) Insulation performance can be degraded by structureborne "flanking" paths.

So to reduce the noise of type writer to room above - need to improve airborne insulation, and to reduce footstep noise from room above - need to improve structureborne insulation.

A possible solution could be a thick rubber underlay under a false floor in room above.

apologies in advance for typos

Obviously too boring!!

No, on the contrary, you were too helpful and informative! I read your message this morning, got very excited , and went to poke around the room to try to put it into context, so I could write you a proper reply this pm. Thank you!

I spotted that there were gaps in the flooring around the piping, so that would obviously be one problem.

The problem is that the ceiling in the room above is low, so we need to keep the solution as thin as possible.

So does this sound right

• whatever we do, it will muffle more high frequency noise than low frequency noise, and that's just something to be aware of

• noise can sneak round via 'flanking' paths (but I don't think there are any of those in this case, due to the odd layout of the house, but I will check)

• we need to make sure there are no 'leakage' paths between upstairs and downstairs, so around pipes and wires must be carefully filled.

• more mass = better airborne insulation

• we need to cut down the amount of vibration coming through to the floorboards above, e.g. with underlay or with a floating floor (prob not possible because of existing low ceiling).

So we should go for some kind of underlay that's very high in mass? What would this be?

Thanks again for taking the time and trouble to help me with this - it's very much appreciated!

Sorry, had a stressful week!

To cut down on vibration from above you need a thick rubber type underlay. Add a high mass layer to this to reduce airborne noise transmission.

You may be able to get some "sandwich" type material, that has a rubber layer in it.