Floor insulation for piano

[Uncle GroOve]

I posted this in another thread, but I realize it should actually have a life of it's own so...

Here's the problm. A friend of mine has rented (5 years, ouch!) space within a high rise where he plans to open a music school.
He has asked me for advice on the sound treatment of the rooms (PITA) - but the biggest problms I see are the pianos.
A total of 3 of them (2 uprights 1 coda) .
More sepcifically I see a problem of sound diffusing trough the floors to the offices below (local gov't by the way!).

What I am thing is of having a 3 layer platform built out of:
1) hard plywood (1 cm, appx 1/2")
2) a limp mass in sheet form and then
3) a last layer of gypsum board. (2.5 cm, appx 1")
The platforms would only cover the space occupied by the piano and the stool - also because budget IS a factor (Switzerland is more expensive than the US for just about everything, ahem).

How effective do you recon this solution could be? I know very well that the ideal and *best* solution would be to build the whole "floating room" thing - but realistically the budget isn't there to go all out on something like that, as there would be 4 rooms to build for a total of almost 100 sq. meters (900 sq ft?).

Thank y'all!

Paul

[bpape]

Unfortunately, whether budget allows or not isn't going to make the sound go down any less if you don't do a real isolated floor. I wish it was that easy.

What is the structure of the floor like right now between you and the lower tennants?

Bryan

[Uncle GroOve]

Hi Brian.
The floor is a commercial building from the mid 80s, which over here (Switzerland) implies poured concrete + rebar + supporting beams.

I know the situation is way less than ideal. I'm just trying to help to solve part of a miriad of problems....

Thx

Paul

[andrebrito]

If the problem is vibrations just build a platform for the piano using Sylomer or CDM similar products (check ressonance frequency of dampers) and raising it 5-10 cm from the floor. This won't stop airborne sound completely but will be valid for vibrational sound going through the concrete floor. You can even make a platform with 2 layers of MDF and vibroelastic damping material in it and will reduce even further.

[Uncle GroOve]

Originally Posted by andrebrito

If the problem is vibrations just build a platform for the piano using Sylomer or CDM similar products (check ressonance frequency of dampers) and raising it 5-10 cm from the floor. This won't stop airborne sound completely but will be valid for vibrational sound going through the concrete floor. You can even make a platform with 2 layers of MDF and vibroelastic damping material in it and will reduce even further.

Thx!
Yeah...that'd be my Plan A.
As for airborne sound ...it's a mess. The rooms are separated by plasterboard walls and they all share the same lowered ceiling - which means that "up there" there's a *huge* empty cavity. It just can't get any worse than that, I s'pose

Paul

[bpape]

I guess that was my point. I don't think the direct transmission will be as much as the airborne will be so I'm not sure it's a good way to spend limited funds. I mean realistically, if that's all it takes, you could simply build pads for where the piano actually contacts the floor.

Granted, a larger platform will spread the weight more evenly.

Bryan

[Uncle GroOve]

Originally Posted by bpape

I guess that was my point. I don't think the direct transmission will be as much as the airborne will be so I'm not sure it's a good way to spend limited funds. I mean realistically, if that's all it takes, you could simply build pads for where the piano actually contacts the floor.

Granted, a larger platform will spread the weight more evenly.

Bryan

Interesting, thx!

The airborne transmission will primarily disturb (IMO) the other music classes.
What I am concerned by, is the resonance of the pianos being actually able to resonate thru the concrete floor to the metal beams and then propagate very efficiently to the gov't offices below.

Granted - we know that gov't employees are not the most productive lot anyway and maybe they couldn't care less ....

[bpape]

Exactly. And most likely, if you built some GOOD isolating pads for the feet/legs of the pianos, you'll minimize the structural passage as much as you can short of floating a whole floor.

I'd want to do some calculations based on the weight of each and look at the pressure per sq ft to determine usable pad sizes. I mean realistically, if you're using something as an isolator that will crush flat at 50lbs/sq ft and you're putting 200 lbs/sq ft on it, doesn't do much good.

Bryan

[Uncle GroOve]

Yep, that's it, really.
In the "sandwich" I'm really looking to have one layer of superdense, heavy material especially manufactured for minimizing floor noise (several are available).
My only reserve is for the plaster board, which may indeed tend do disintegrate if/when subjected to heavy pressure. If anything I'll resort to a denser hardwood...

Thank you for the valuable input!

Paul

[andrebrito]

If your problem is a vibrations just make the platform for the piano and you can even place some absortion in it.

Regarding airborne sound, well you will have to build new walls :-)