Super Soundproofing Community Forum

Soundproofing Forum Topics => Soundproofing your Condo, Townhouse or Bed & Breakfast => Topic started by: Brrrrian on February 07, 2006, 04:39:29 AM

Title: hardwood floor
Post by: Brrrrian on February 07, 2006, 04:39:29 AM
If MLV can block out airborn sound because of its mass, then theoratically, shouldn't heavy hardwood floor (the nail down kind) be effective against airborn sound as well??

It's because wood transmits sound so well- 1200 times better than air!  Same principal as hearing a train coming through it's track long before you hear it through the air.

BJ Nash
Title: Re: hardwood floor
Post by: brrian on February 08, 2006, 07:57:17 PM
Thanks for the reply, but I am talking about airborn noise, not impact noise. You can hear a train on the track before you can hear it in the air because the train is physically touching the track. so thats more like impact noise, right?
Title: Re: hardwood floor
Post by: john bergstrom on February 20, 2006, 04:00:08 AM
You're both wrong and right, Brian.  MLV doesn't block sound due to it's mass, but it's molecular matrix.  It is a 'visco-elastic' material, meaning it exhibits both the properties of an elastic solid with viscous properties.  When sound energy deforms the molecules in MLV, they don't immediately spring back, but they kind of 'flow' (think of taffy...)  This delay takes a lot of energy out of the sound wave and turns it into heat - tiny amounts of heat, but heat nonetheless.  This is what dampens the sound.  
As for the hardwood question, you are right.  Any material with high mass will provide airborne noise reduction, but the problem is, as you said, you nail it down to the subfloor, providing a rigid mechanical connection.  The airborne sound will vibrate the hardwood and that vibration will readily transfer to the other framing elements of the house.  What is needed is decoupling - if you put a foam pad under the hardwood (or any finish flooring) and make sure there is no rigid connection to the subfloor, then you will get much better soundproofing.  But if your serious about noise reduction, installing the hardwood on a layer of gypsum concrete on a foam pad will do a lot better....

So remember, mass + decoupling works best.
Title: Re: hardwood floor
Post by: percept on February 22, 2006, 07:11:47 AM
i currently have carpet in my basement studio apartment, and plan on switching to hardwood.  i have a theater system with a subwoofer and would like the subwoofer not to rattle the whole house while i'm watching a movie.  So is the best way to prevent this adding a layer of MLV, then a layer of gypsum then nailing the hardwood on top of that?
Title: Re: hardwood floor
Post by: brrian on February 23, 2006, 08:22:25 PM
hi John,

Thaks for clearing that up. I did some research on gypsum concrete and it seems very labor intensive and expensive.  I was thinking putting dow 1lb MLV, then foam pad, and then 3/8" lamninated floor ( mass +decoupling is acheived). What do you think? Is there a cheaper alternative to MLV? Thanks.
Title: Re: hardwood floor
Post by: johnbergstromslc on February 25, 2006, 01:07:52 AM

There are companies that sell a foam pad pre-glued to a layer of MLV.  I think you install it with the foam side down, MLV up.  (I've never used it)  You can install wood flooring directly on top of it.  
But before you do that, get a couple tubes of silicone caulk and seal up all the seams, nail/screw holes and the perimeter of the floor (where the bottom 2X4 of the wall meets the floor.)  Pretend you're building an aquarium - anywhere water can leak through the floor, seal it up!  It will definitely make a difference!
Here's a company that makes a foam/MLV composite product:
If you fill out the 'contact us' screen, they will phone you, determine what you're trying to do and will send you samples of their products.  (I got a free t-shirt, too...)