Replies

1. 
   Jeff_Clarke_ | Oct 25, 2001 06:02pm | #1

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   i I've been in good hotels where you can't hear anything but I don't know how they managed it.

   Answer: Strescon concrete plank construction with floor topping (sorry). That's one of the reasons why good hotels are expensive.

   i What is the best sound-insulating material?

   Answer: Solid concrete - mass, mass, mass, since you are not dealing with 'absorption' within a space but 'tranmission' from one to the other. You're probably not building with 'the best sound-insulating material' therefore, but alternatives.

   However, you can do a good job with reducing sound transmission using alternative material - what is your construction type? Wood frame (worst)? Steel (better, since you can use concrete/steel deck)? Concrete (I doubt it)?

   Jeff

1. 
   Michael_Rimoldi | Oct 26, 2001 12:00am | #2

   *I just built a two story home with floor truss construction and I packed R 19 batts inside the floorceiling cavity and it dampens sounds from between floors very nicely. Didn't cost all that mush either as insulation is actually quite inexpensive.They also make a sound deadening subfloor board you can use between the ply and your finished flooring.Mike

1. 
   piffin_ | Oct 26, 2001 02:43am | #3

   *Strapping on lower cielings helps prevent transmition of sounds. Layering ply, homasote and underlayment helps buffer vibrations. Softening the surfaces (eg. carpet and suspended acoustic cielings) will absorb sounds. Sprayed foam is a pretty good sound buffer too but not an economical idea.So to satisfy her, lets use concrete floors, overgird them with homasote, underlayment and carpet. Then we'll go under neath and spray foam up at the concrete and suspend an acoustic tile.But she'll need a big piggy bank to build like a bank

1. 
   CaseyR_ | Oct 26, 2001 06:06am | #4

   *There have been a number of posts over the last couple of years regarding methods of decreasing sound transmissions. I have found Taunton's search function somewhat frustrating, but a search of the Breaktime archives may give you some additional information. Among the primary types of sound attention are methods that reflect and/or absorb sound waves (another would be active cancellation). Massive stone or concrete walls or floors tend to reflect sound waves back into the room in which they originate rather than passing them through and thus are effective in blocking noise that originates in the air before hitting the wall/floor. However, such materials are often very efficient conductors of impact noise such as a shoe hitting a floor or a hammer hitting a wall. (While steel may be effective in reflecting soundwaves in air impinging upon it, steel happens to be a more effective conductor of impact noise than is wood. I don't recall the transmission speed of sound in steel, but it is significantly greater than that in air and the sound waves tend to be channeled along the steel to possibly distant locations.) Blocking such impact or direct transmission noise requires isolation and dampening. Compliant materials such as "homasote" and various types of fiberboard change the soundwaves into heat and thus dampen the sound rather than allowing the vibrations to pass through the material. Carpeting can be very effective as can placing wood flooring or subfloors over various types of sound absorbing fiberous boards. Cork tile can be better than heavy carpet. Resilient channel material can assist in isolating upper floors from lower ceilings. A wood floor on wood sleepers can assist in gaining some degree of isolation. Filling between the joists with traditional insulation makes only minimal gains in sound absorption, but it does gain some. So let's see, a quiet floor - how about cork tile on sound absorbing fiber board over a 3/4" subfloor which is on 2x3 sleepers with rock wool insulation between the sleepers. (I think I once read that sand would do a fairly effective job of dampening sound transmission, so perhaps you could use sand instead of rock wool). Then you could use resilient channels or "Z"s to suspend an accoustical ceiling below the joists. Use lots of tapestries, heavy fabric wall hangings and heavy draperies as well as heavy rugs and overstuffed furniture in the room below to absorb any sound waves that manage to impinge. Should net you well over 20db (about the same as many earmuff style hearing protectors). This from the deaf guy who couldn't hear anything anyway...

1. 
   Tom_Laing | Oct 26, 2001 07:38am | #5

   *Don't know if it's still in print or not, but I've got a groovy little booklet put out by the Western Wood Products Association called "Wood Frame Design for Commercial/Multifamily Construction" that shows several different walls and floor assemblies and their corresponding STC (Sound Transmission Class) numbers. Plus, it's got a good, short primer on the physics of sound transmission. The Ph# for the WWPA (the booklet is pre-internet) is 503-224-3930 in Portland Oregon. One item that no one has mentioned in this thread is that doubling up on drywall is a great way to dampen sound. Tom Laing

2. 
   K_S_Wilbourne | Oct 27, 2001 08:44pm | #6

   *Thanks, everyone! All the ideas seem really helpful. One question: If we go with the concrete, what do you think would be the minimum thickness?

3. 
   Crusty_ | Oct 28, 2001 10:47pm | #7

   *My cellulose insulation contractor suggested shooting cellulose (with an adhesive mix) onto the underside of the upper floor. He says he does this in hotels and in a lot of houses as well. Well, we did, but I'm not sure it did a lot of good. I guess it has to help, but you can hear my kids walking around pretty good up there on the bare subfloor. The drywall is up, so adding batts is not an option now. I'm hoping a good pad and carpet are going to take care of it, and I suspect that other noise, such as talking and TV will probably not be troublesome.From what I see so far, I'd go with mass. Doubling up on the drywall on the lower ceiling would be pretty cheap.

4. 
   TLE_ | Oct 28, 2001 11:02pm | #8

   *I have had reasonable success strapping the ceiling with resilant-sound channel (also called RC-1).It is a metal channel that I first came across working on multiple-floor apartments.It works by isolating the ceiling from the floor system to break the path for sound to transmit through.It's cheap(1.75 for a 12' length), available at drywall supply houses, just nail to the joist and the board gets screwed to it.Terry

5. 
   steve_otto | Oct 29, 2001 04:11pm | #9

   *There is a good amount of info on soundproofing at http://www.soundproofing.org There trying to sell you some of their black magic, but you can learn alot about how to reduce sound transmission through walls and floors.WWW.usg.com also has some pretty good info. The cheap solution is fiberglass sound insulation in the joist bays, resilient channel (RC1), and thick drywall.Steve

2. 
   K_S_Wilbourne | Oct 29, 2001 04:11pm | #10

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   We are building a very small apartment building and since the owner will be living there too, she wants to be sure that noise doesn't travel from one floor to another: she doesn't want to hear people walking around, conversations, TV, loud music, etc. I've been in good hotels where you can't hear anything but I don't know how they managed it. Do you have to suspend the ceiling or is there a better and cheaper way? What is the best sound-insulating material?