Author Topic: What percentage does MLV have to cover hardwoodfloors (with area rug over it?)  (Read 9339 times)

mozartlover

  • Guest
Hi, I'm about to move into a prewar co-op building (built in 1939 so I don't know how thick the floor/ceilings are, I know I won't be the only person w/a piano and I've been told there's also an opera singer in the building, but I'm pretty sure the co-op board's rules are that 75% of the apartment must have rug or carpet, I'm going to be on the top floor so I'm mainly concerned about the downstairs neighbors) and I plan to take my upright piano with me.
I've browsed through some of the threads on this forum suggesting getting MLV below the piano, but I've also read from soundproofing.org (or some other site, I forget which) that sound is like water, if you don't block all the paths/pores, it will find some other way to go through.

So my question is, let's say I have a 240SF living room (hardwood floor) and plan to put my upright piano against a wall (away from neighbors wall of course, but my main concern is the loudness and the sound that can travel downstairs).

1) Is there any way that I can just lay MLV on the hardwood floors and throw an area rug over it?
2) What percentage of the room's floor should it cover? Does the MLV have to cover the entire 240SF hardwood floor area? Can it be 75% or 60%, or just underneath the piano (I'm guessing no for the latter). What about the entry foyer?
3) Does the MLV have to be physically glued or adhered to the hardwood floors? Note, I'm renting the apartment and I don't want to mess up their floors.
4) Is wall-to-wall carpeting better for soundproofing? (like if I hire contractors to get MLV inside the carpet- how much would that cost?) If the apartment already has existing carpet (the landlord plans to take it out because it's really dirty/stained), is it better it stays? I plan to have area rugs anyway and I'm not concerned about impact noise, but I'm very concerned about airborne sounds that will come mainly from my upright piano.
5) If I order MLV from soundproofing.org, what would the shipping cost be? I couldn't find any shipping cost related info on the site.

Any input greatly appreciated.

Mark Daveis

  • Guest
You need to cover the whole (100%) floor as leaving even small areas uncovered will cause the sound to bypass through there and get past the mlv.
Also you will most likely need 5 or more layers to build up enough mass but mlv has a very low natural frequency so wont resonate at any frequency we can hear so you can use less mass than if you used solid materials like wood or concrete.
Try to leave the mlv as loose as possible so it can flex and convert the sound to heat energy instead of fixing it too rigidly.
Measure the sound level you will be producing with a meter first. :)

mozartlover

  • Guest
You need to cover the whole (100%) floor as leaving even small areas uncovered will cause the sound to bypass through there and get past the mlv.
-100% of the living room? (including the entry foyer that leads into the living room?) How bout attaching MLV to a large cloth and draping it over the piano? I don't think I'd be able to afford 240/280SF worth of MLV

Try to leave the mlv as loose as possible so it can flex and convert the sound to heat energy instead of fixing it too rigidly.
Measure the sound level you will be producing with a meter first.
- I thought only green glue converts sound to heat energy?
- Is there a table that illustrates how much mass is required to reduce the sound level by 1 decibel? Like if I want to reduce piano noise by 20-30 dB, what's the minimum mass per square foot of MLV required to do so?

johnbergstromslc

  • Guest
There's no way in hell you're gonna get 20+ dB reduction from MLV.  Even adding 2" of concrete wouldn't do that....

Mark Daveis

  • Guest
MLV is fine particles like barium compounds or even iron filings in a viscous matrix like vinyl.
The particles vibrate when sound hits them and causes a loss of sound energy by conversion to heat energy due to the massive viscous loss sort of similar to green glue.
The advantage of mlv and other limp materials such as neoprene is that they resonate at frequency's too low for humans to hear and resonant problems can be a big factor even in green glue or other soundproofing setups which use solids instead of limp mass. Also mlv gets closer to the mass law graph because it is damped all the way through. Think about it why do Quiet rock use a 11 layer damping drywall? Just because it damps the solid drywall more thoroughly all the way through and gives more sound proofing with less mass.

If you build a box or frame of wood or metal around the piano and cover this with 2 to 3 layers of mlv then this will get you about 20 db reduction and you can take it apart when you move. So its like a box or tent around the piano which will work much better than adding mass to your floor because of mass law.
You would need to put the box on a platform resting on 1 inch or more neoprene pads so it does not touch your floor.
All this will be cheaper since you are using much less mlv and only a small amount of neoprene.
Also you need to measure the sound level that you will be making with a sound meter. :)


mozartlover

  • Guest
If you build a box or frame of wood or metal around the piano and cover this with 2 to 3 layers of mlv then this will get you about 20 db reduction and you can take it apart when you move. So its like a box or tent around the piano which will work much better than adding mass to your floor because of mass law.
You would need to put the box on a platform resting on 1 inch or more neoprene pads so it does not touch your floor.
All this will be cheaper since you are using much less mlv and only a small amount of neoprene.
Also you need to measure the sound level that you will be making with a sound meter. :)

Can I glue (green glue?) MLV to a large cloth (tile it) and drape it all around the piano, and include MLV below the piano? are neoprene/vibration isolation pads under piano wheels still necessary if there's already MLV under it?

Mark Daveis

  • Guest
You don't need any green glue as the mlv is damped quite enough.
If you glue it to a cloth it will become very heavy and difficult to move about as even 2 sheets of mlv are heavy.
Yes you can drape it around the piano but it must be clear of the piano by at least 2 inches as if it touches then the sound will conduct into the mlv and outside so a 2 inch or more air gap is needed.
You need to raise the piano off the floor at least 2 inches of clear air space but its easy to do using a few planks of wood to get enough height then about 1 inch of neoprene or other dense rubber which will absorb shock put on top as a pad then a large piece of say thick plywood on the pads as the floor. Use as few plank supports as possible to hold the weight. Mlv wont work as pads as you need a springy dense material like thick rubber or even springs for the mounting as the pros do.

I built a iso booth for a friend who wanted something cheap with good performance so I used 2 layers of 18 mm plywood with some green glue between. For the corners I just used 2 cheap strong metal brackets and 8 mm steel bolts.
I got about 30 stc from this when tested with a sound meter. So you need to build some  portable panels around the piano to give you about 20 kg per metre sq of mass.
You could use 2 sheets of 18 mm plywood with or without the green glue and even without you will get more than 20 stc. Or you can use 1 18 mm plywood with 2 layers of mlv fixed loosely to it. The price of mlv and plywood is about the same.
You would bolt the panels together with just 2 holes on each panel and for the floor and roof just place down the same materials.
It may sound a bit complex but is straight forward and will give you a set of portable panels which will have a stc of over 20 to about 30 and as cheap as you can get. Just ask your wood supplier to cut the boards to the right size.
I have made other designs in the same way where I made a double walled box design and got over 50 stc performance without using large amounts of mass so it can work  really well if you set it up properly and at low cost. :)

joel

  • Guest
Green Glue is not a construction adhesive.  It is a damping compound.  It is to be used between rigid sheets of building materials - dry wall, OSB, plywood, cement board.  It is not used with sound deadening boad or other materials with a porous surface.  They call it Green "Glue" and classify it as "a visco elastic" material because it is sticky - even when fully cured.

 

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