# Sound dampening advice needed



## steel1 (Oct 16, 2008)

We have a toilet drain pipe running down a family room wall and are looking to add some noise-dampening insulation that we can do ourselves. Can anyone make some recommendations? I have tried to do some research online and by talking to local contractors and ideas are all over the map: foam self-sealing wrap, bubble wrap, sound batt in the walls, polystyrene in the walls in addition to standard insulation...(or as one person suggested not using the toilet)? What is the most effective method. Some folks have said standard fiberglass insulation is useless. Any thoughts appreciated. Thanks.


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## iMisspell (Jun 2, 2007)

Heres some info ive learned while looking (and some experience) into sound "proofing" a music room.
Thicker is *not *always better, shape and material is what matters.

A 8" cinder block foundation will dampen sound better then a 8" poured. When a sound wave hits something solid the wave will continue, but when a sound wave hits layers, pockets and uneven suffuces it dissipate. Being a block has two walls and the pourceness, it will deaden sound better then a solid poured wall. If you have ever been in or seen pictures of music studios you will see "egg-create" foam on the walls. The sound waves hits the creators and breaks up which deadens the sound.

If your looking for an inexpensive way, i would try something like this.
Bobble wrap the pipe, then around that bobble wrap, wrap one of them egg-create mattes people sleep on with smooth surface out "knobs" in touching the bobble wrap, and then if you can fur out and then box in the pipe with sound board. 

You might have a second problem though. The toilet might be "sending" sound waves/vibrations to the floor and carrying that way also, not sure how you would combat that. With a music room you would make a floating "sub-floor" (dont seam like a good idea for a toilet though  ).

Just some more food for thought.

_


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## Nestor_Kelebay (Jun 17, 2008)

iMisspell said:


> Thicker is *not *always better, shape and material is what matters.
> 
> A 8" cinder block foundation will dampen sound better then a 8" poured.
> 
> When a sound wave hits something solid the wave will continue, but when a sound wave hits layers, pockets and uneven surfaces it (will) dissipate.


I think it's best to start with the basics. Sound is nothing more than a pressure wave traveling through the air. As such, it obeys all the laws of physics.

When you push on a heavy object with the same force as you push on a light object. You will find that the heavy object doesn't accelerate as quickly (because of it's inertia) and it doesn't move as far either. (And I think that's got something to do with Work = force X distance, but I'm having trouble explaining in my own mind why something heavy wouldn't move as far when you push on it as something light. In outer space, it should move just as far, regardless of how small the force is. It just wouldn't move as fast.)

That is ALL you need to understand the very basics of sound transmission as outlined by Quirt in his paper:

http://irc.nrc-cnrc.gc.ca/pubs/bsi/85-3_e.html

(The CNRC is the Canadian National Research Council.)

The most basic thing you need to know about accoustics is the Mass Law, which says that for every doubling of either the mass per unit area of a wall or the frequency of the sound waves hitting a wall, the noise level on the other side of a wall is reduced by 6 decibels. Decibels are a logarithmic funtion defined below:

dB = 10 times the log (base10) of (P1/P2)

where P1 and P2 are two sound pressure levels (one on each side of the wall), and therefore P1/P2 is the ratio of those two sound pressure levels.

so 6 dB = 10 log (P1/P2) or 0.6 = log (P1/P2) or inverse log (0.6) = P1/P2

From Windows Calculator, inverse log of 0.6 is 3.98107

So, the Mass Law says that for every doubling of either the mass per unit area of a wall or doubling of the frequency of the sound wave hitting that wall, the sound pressure level on the opposite side of the wall from the source is 1/4 of what it is on the source side of the wall.

Thus MASS is what matters.

And, we can prove that by explaining a very common experience. You're laying in bed in your apartment at 2:00 AM on a Saturday night, and you can't sleep because you're hearing the BOOM-BOOM_BOOM from a loud stereo being played at a party in a different apartment. However, when you open the window, you can hear the music clearly from cars that are considerably further away.

This is explained by the extremely simple way sound moves through walls:

1. The sound wave hits the wall.

2. The impact of the sound wave makes that wall move.

3. The movement of the wall recreates the sound wave on the opposite side of the wall.

4. If you're on the opposite side of the wall, it's that recreated wave that you hear, NOT the original.

So, if you double the mass per unit area of the wall, you double the mass of the wall and it doesn't move as far due to the impact of the sound wave hitting it. That smaller movement of the wall means that the reproduced sound wave has a smaller amplitude, which means it's quieter than the original sound wave that hit the wall.

Also, if you double the mass of the wall, you double the inertia the wall has and you reduce the wall's ability to reverse it's direction of motion. Consequently, as a wall gets heavier OR the frequency of the sound wave hitting it increases, it is inertia that reduces the walls ability to respond to the sound wave. As the frequency of the incident sound wave increases, the inertia of the wall very quickly limits it's ability to move in response to (and thereby reproduce) that sound wave.

The reason why our sleeping tenant hears "BOOM-BOOM-BOOM" from the apartment stereo (whereas he can hear car stereos properly) is because the Mass Law effectively prevents the midrange and higher frequencies from being reproduced except in buildings constructed with very light materials (like 3/8 inch drywall on metal studs). The building's walls and ceilings are heavy enough that they simply can't vibrate at midrange and treble frequencies.

So, to effectively stop noise from a toilet drain pipe, you either need to contain the noise with heavy materials to box in the drain pipe (so the heavy materials the box is made of will contain the noise), or you have to prevent the drain pipe from vibrating, which is what's making the noise in the first place.

My advice would be to consider replacing that plastic toilet drain pipe you have with a cast iron drain pipe if possible. The iron is much heavier and less flexible and simply wouldn't move as far or as quickly in response to the water running through it. That is, apply the Mass Law to your pipe. The heavier the pipe, the less it's gonna move, and the lesser it's ability to change it's direction of motion, so the lower the frequency any noise it does produce will be.

So, just from the basics of accoustics, it's clear that when a sound wave hits a solid object, it doesn't continue through it. Instead it bounces off that object. If it did continue through it, our sleepless tenant would be able to hear the mid-range and treble frequencies of the offending stereo, and know what song it was. That doesn't happen. He hears "BOOM-BOOM-BOOM" until he gets close enough to the inconsiderate neighbor that he can hear the higher frequencies through the much lighter apartment door (or, very likely, the small air gap under the door).

Also, a solid poured concrete foundation will move much less when hit by a sound wave than a relatively light concrete block foundation. Consequently, it will produce a much smaller amplitude sound wave when it does move, and the frequency of the sound waves it CAN reproduce will be comensurately lower.

Hope this helps.


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## Termite (Apr 13, 2008)

After all that, the third paragraph from the bottom is the answer (albeit difficult and impractical for most DIYers)! High-end homes almost always have cast iron in the walls to avoid exactly what you're experiencing. The stuff is silent, and PVC sure isn't.


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## MrShadetree0222 (Oct 4, 2008)

Well before going death in my right ear i was one of those idiots you hear going down the road with the BOOM BOOM BOOM loud car stereos, and you look at me and think what is his problem, and why does he need it that loud..
well i dotn have the smarts or intelligence to explain how or why i needed that loud but let me tell you the louder the better! Actually it was so loud I won 1999-2000 stereo competition for the eastern us 1st place 2 yrs in a row!
Now with thta said, vehicles do not provide any sound deadeneing objective, so you would have ot deaden the sound yourself!
Now vehicles without sound deadeners, you could hear the music and the rattles of every part in the car from a distance of 100' And thos eof us that chose to go ahead and forth out the money we had what was known in the industry as sound deadener! The top of the line product back in the day was Dynomat, and let me tell you what, you couldn't hear my 1st place stereo system, or rattles from the vehicle from outside of the car with windows rolled up form 10 feet away! This product allowed us the ability to contain without loss of any decibals with the vehicle cabin compartment! No sound could exscape the cabin becouse of this product!
This is a stickon product, that adhears to anything, the stickyness level is about as sticky as mastic if you ever used mastic*three times stickier then duct tape)

So my suggestion for sure deadening of the toilet waste system would be to sound deaden the pipe, and back your sheetrock( or whatever wall covering you are choosing to use) with the product, so you can enjoy your family room in piece and quite!

Again I dont understand the laws or physics of sound UNLIKE Nestor_Kelebay ! All I know is it works!
Maybe if Nestor_Kelebay, could explain how this product works then Maybe I would have a better understanding aswell, never to death to learn how something works, just wish he would explain it in english, he used some pretty technical words up thier in his post! lololol just kidding!
For those stereo techies, back in the day under the _IAASCA _old measurement system for db(decibals) I was pushing 143.4 db, with the windows rolled up!


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## Chagres (Oct 13, 2007)

Are you saying the pipe is outside the wall? If so, I would just build a a chase around it. I was doing some research not long ago for noise solutions (a blog topic) and found a site for "soundproof" drywall. I've never used it myself but judging by their list of people that have used it it sounds like it does a good job. So you could use that on the chase. I think the name of the manufacturer is Quiet Solution.

Chagres
http://www.icanfixupmyhome.com


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## iMisspell (Jun 2, 2007)

Something to keep in mind, theres a difference in absorbing or dampening sound and redirecting / bouncing / containing sound.


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## aaron.klimchuk (Sep 30, 2008)

> The top of the line product back in the day was Dynomat


While this works well in cars, I think the price tag is a bit impractical for home improvement use.


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## MrShadetree0222 (Oct 4, 2008)

aaron.klimchuk said:


> While this works well in cars, I think the price tag is a bit impractical for home improvement use.


 
Yes pricy, but the best sound deadening idea I could come up with!


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## HandyPete (Mar 23, 2008)

Nestor is a genius but, Mr. Shade nailed the solution....IMHO

I used Dynamat on my drain pipes and man, it works! (does such a small cost really matter?)

I bought a large sheet and cut ribbons 1" wide so I could "tape" the stuff around the pipe using the half-lap technique so you actually get two layers.

GO FOR IT!!!!!

-pete

Alpine... 2 amps @ 250 watts each, 12" sub, Ipod...and Dynamat!


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## Nestor_Kelebay (Jun 17, 2008)

I have absolutely no clue why sticking this Dynomat stuff to a plastic sewer pipe would make it quieter.

The Lord works in mysterious ways.


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