Author Topic: What percentage of noise is flanking with a decoupled ceiling?  (Read 2985 times)

srj19

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What percentage of noise is flanking with a decoupled ceiling?
« on: December 24, 2015, 01:29:21 AM »
There are many factors in impact sound transmission, BUT I'm wondering if it's possible to say what percentage of sound heard below is flanking. I ask because I'm looking to do some work to reduce impact sound but I'm hesitant to use the same method as I did prior.

I put in a ceiling using channel and clips (and other materials) and didn't get the impact reduction I had hoped for.

I'm wondering if putting in a lumber  completely decoupled drop ceiling a couple inches below the existing joists, if the benefit would be same over all effect at lesser cost and time for the install. Anybody done both of these methods and can speak to the comparisons between the two?

My Drop ceiling would be lumber, decoupled from the floor joists. Two layers of drywall with Green Glue between attached to the lumber and held away from the perimeter of the room. The perimeter of the drop ceiling  framing would also not touch the existing structure direction but have some recycled rubber material between existing structure and new lumber. This would mean the highest level of decoupling from both immediate flanking sounds and immediate connection to the impact above.

Remaining impact would seem to then be what was able to travel across the floor above to the sides of the room, down the studs to the floor below. What level of impact sound would remain? Hopefully enough to make most of the impacts above (dropped light objects, walking hard on heels, taking off shoes and letting them fall the floor, etc) very much minimized.

Is there a way to test concepts like this prior to undertaking the tear out and new build?

Randy S

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Re: What percentage of noise is flanking with a decoupled ceiling?
« Reply #1 on: December 24, 2015, 04:42:11 PM »
That is not an easy question to answer. Normally I quantify flanking as 8-10 STC loss of a system.
The amount of DB heard from flanking would be indicative of the force of the impact, location on the floor above and surface area still coupled to the structure..

What is your floor ceiling assembly?  and what type of clip was used and did you treat the subfloor above before installing the soundproof ceiling? 

Anytime you build an isolated system it has less connections to existing structure you would yield a greater reduction.

Advise,

Randy S.


Randy Sieg

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srj19

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Re: What percentage of noise is flanking with a decoupled ceiling?
« Reply #2 on: December 24, 2015, 05:37:19 PM »
I could not find the exact clip on your site, what I used was a very heavy duty clip with rubber isolating boot where it connects to the ceiling joist and heavy hat channel. I put two layers of 1/2 drywall with green glue between and caulked the perimeter with acoustical sealant.

The structure upstairs was not accessible so it remained as is.
I screwed 2 layers of 5/8 drywall with green glue between to the the underside of the above subfloor between the joists and put R15 Roxul in the cavity.

The  sound transfer control is very good, probably in the high 60s to low 70s, but the impact is still there and I suspect it's because the ceiling itself still has dozens of contact points with the above floor, even though they are rubber dampened contact points. I was thinking that a properly decoupled lumber drop ceiling would probably give me the same or better result from the direct impact sound which would leave primarily flanking.

In addition to being less "impactful" and loud to the person down stairs, I'm assuming that flanking sounds are less intrusive because they are diffused through the walls instead of coming from a "hot spot" upstairs, is that generally true?

Randy S

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Re: What percentage of noise is flanking with a decoupled ceiling?
« Reply #3 on: December 24, 2015, 05:45:17 PM »
Very good! the system you installed should have delivered a highly noticeable reduction.
You doubled the mass if not more , you insulated the cavity and used green glue...This is a system we use as well. So with that being said I would have to say the clip was a RSIC clip and that is why you didnt get more reduction.
Did you mud and tape the perimeter after caulking the gap?

By chance was this lath and plaster before you started?

depending on the answer above, Your last statement is generally true however the walls are more surface area then the ceiling.

Randy S
Randy Sieg

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srj19

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Re: What percentage of noise is flanking with a decoupled ceiling?
« Reply #4 on: December 24, 2015, 06:50:25 PM »
What kind of clip will outperform the rubber insulated/dampening of an RSIC?

I did mud and tape the perimeter. I actually didn't use acoustical caulk on the perimeter. I used actual green glue compound.
I applied Fiber tape, then pushed a large amount of green glue up through the holes in the fiber tape. I used a drywall blade to smooth excesses until it dried a bit and the next day I applied mud.

This is an 1885 building so it did have plaster and lathe until I removed it. You said that may make my last statement true, (meaning that the flanking sounds from above will be dissipated and difused?

Randy S

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Re: What percentage of noise is flanking with a decoupled ceiling?
« Reply #5 on: December 24, 2015, 07:06:30 PM »
our clip is an isomax clip full neoprene clip, big difference in performance.
http://www.supersoundproofingsales.com/SSP-Clips-1/productinfo/09-IS/

The green glue will shrink essentially having a seal potentially open up over time.

Mud and tape on the perimeter just created a hard mount around the perimeter..drum head..lose in middle tight around perimeter.

Did you fully demo the walls also? if so your statement is true if not then you still have 5 sides of the room tied together.

Randy S.
Randy Sieg

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Fax.760-752-3040

srj19

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Re: What percentage of noise is flanking with a decoupled ceiling?
« Reply #6 on: December 24, 2015, 09:00:06 PM »
So the hat channel must be compressed into that neoprene? Does it work well on ceilings that must carry some double drywalled weight? If I remember correctly I went with channel that was heavier than I could get Home Depot, likely 12 gauge.

Before I did the green glue seal I mocked up the same scenario to see what would happen (if it expanded to fill the gap, etc) and it looked good but ultimately I can't say for sure because it's sealed now.

Can you explain more about the plaster and lathe/ 5 sides of the room? The new rocked ceiling does not touch the walls, I suppose the four walls all touch each other though in the corners, is that what you are referring to?

Randy S

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Re: What percentage of noise is flanking with a decoupled ceiling?
« Reply #7 on: January 04, 2016, 05:44:07 PM »
SRJ19

Sorry for the delay in response, I went on vacation.

Yes the hat channel goes into the neoprene clips.

Why don't you give me a call direct and we can discuss the particulars and I can send you pictures and cut sheets for you to review.

Randy S.
760-752-3030
Randy Sieg

Super Soundproofing Co
www.soundproofing.org
888-942-7723
Ph. 760-752-3030
Fax.760-752-3040

 

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