flanking.

 

Thanks. Yes, I've read all the flanking stuff from the SoundProofingCo. Still unsure how the sound is going to escape significantly up through the ceiling in this particular case. How would you see the sound flanking / through what physical mechanisms? Lets say you start vibrating the stud wall in front of the concrete. The concrete certainly is not going to move. The stud wall may vibrate and send the vibrations... where? The ceiling trusses rest on the foundation walls. I guess the stud walls do come in contact with the trusses since they are built real high - but the trusses actually physically rest on the concrete... Maybe the air behind the side wall resonates and causes the air in the upper cavity to resonate to some degree... But I have to imagine that the sound transmission at this point must be pretty low...

 

the flanking issue would be the sound going into the air cavity between the wall and concrete and traveling upwards. I have three concrete foundation walls surrounding my theater, but I still did DD + GG on all walls.


Sound is a funny thing, and its not always possible for anyone to say what is for sure "worth it" and what isn't. There are tried and true methods, and you can often get away with less in your application, but in this situation flanking is a real issue and I'd hate to see you be disappointed in your results after green gluing several of the walls but not some.

 

Your theater construction pics on your signature were pretty awesome. How did your final product turn out in terms of sound insulation? My main concern is sound traveling up into the house - just like yours was. Also, assuming I double drywall everything... where would you use acoustic caulk? Haven't done much research on that... where is that applied?


Anyone else have thoughts on the need for DD +GG on the concrete walls?

 



Quote:
Originally Posted by sthong /forum/post/18408381


Your theater construction pics on your signature were pretty awesome. How did your final product turn out in terms of sound insulation? My main concern is sound traveling up into the house - just like yours was. Also, assuming I double drywall everything... where would you use acoustic caulk? Haven't done much research on that... where is that applied?


Anyone else have thoughts on the need for DD + GG on the concrete walls?

I've hit a roadblock in my construction, I've had issues getting a carpenter to finish the woodwork on the columns and elsewhere just how I want it. So I can't say how the final product turned out yet. I'll be sure to post progress pics. Hat channel with isolation clips is even better, especially on the ceiling, but was beyond my budget and space restrictions. Acoustic caulk comes in handy plugging small little gaps and holes. But ideally you won't need much of it. The soundproofing company has brochures on the application of GG and acoustic caulk, and a few other items.

 

If cost is an issue, do 50% coverage of GG on all the walls and get 70% of the benefit. Don't design flanking paths intentionally. You will have plenty to contend with necessary flanking paths like HVAC and the door.


EDIT - here is a post from Dennis that discusses why not to go halfway (amongst other stuff):

Quote:
Originally Posted by Dennis Erskine /forum/post/18240007


You're going to "fill that room up" with sound. You're going to fill an aquarium full of water. It doesn't matter which wall (floor, side, etc) you build from plastic wrap, when that water comes pouring out of the aquarium, it's getting everywhere in the house. So you treat a common wall ... the vibrations get to the roof joists, which rest on the outside wall of the bedroom, and, you have sound in the bedroom ... through the floors, ceiling, attic, places you would not expect. A one or two sided aquarium is rather worthless.


Sound in or sound out. In the overall scheme of things, it doesn't make much of a difference. The isolation techniques used in typical construction are not one-way devices. On the other hand, isolation to reduce sound transmission out of the room is harder to do than the isolation required to prevent environmental sounds into the room (unless you live next to Hobby, Sugarland Airport, etc.)


A traditional metric is you don't want to raise the noise level in an adjacent space by more than 3dB. So if the ambient noise level in your room is 33dB (not unusual), then outside your room, you don't want the noise level to get above 36dB when you're playing your system. The usual sound track is recorded with a dynamic range from 22dB to 105dB (115dB for LFE). By that metric you have 105dB - 36dB is 69dB ... good luck. Even with GG, DD, Clips, Isolation, careful HVAC work, etc, etc, you're not going to get there from here unless the crew building that shell is expert in building isolated rooms. (Just as a reference ... going from 33dB SPL to 36dB SPL is a doubling of SPL.)


Let's go the other way ... ideally, you'd want the noise floor in your room (equipment and HVAC running) to be 21dB (just below the softest sound recorded on a CD, DVD, BD) so you can hear the softest sound without turning up the volume (and making your sound isolation problem even harder). If the ambient noise level in your home is 33dB, then your isolation requirements are 33dB - 21dB = 12dB ... a much easier problem to solve...but, even at that, it isn't going to be solved by half way measures.


Does sound isolation affect in room acoustics. Yes; but, indirectly. You have comfortable listening levels, enhanced dialog intelligibility, you're not running your system at levels upwards of 8 times intended volume (to raise the quietest sound above the background level), running your equipment to distortion and you don't have to buy as many bass traps from Ethan.

 

So, I'm about to build a new house, and I have set aside some space in the basement for a theater. I want to minimize sound coming up through the main-level floor -- any reason why I shouldn't put down an extra layer of plywood on the main floor, with GG between the two layers (at least in the rooms directly above the theater)? Or if not an extra layer of plywood and GG, some other type of soundproofing layer between the plywood and floor covering? It seems like most of the soundproofing tips I've seen deal with soundproofing in the theater room -- but maybe that's because people are adding a theater after the house is already built?


(I will, of course, also take measures in the theater room itself . . . .)

 

Generally you put your sound isolation efforts on the sound producing side, but there's no reason not to damp the floors as you've described.

 

If you can damp those floors do so. One of the more difficult sounds to abate are the patter of feet on hardwood floors.

 

My basement theater had two walls of solid poured concrete. Based on recommendations here, I built a wall with an inch gap between the studs and concrete, put in pink insulation and DD/GG on all four walls and ceiling. I also did clips/hat channel for the ceiling. I have an SVS PC13 sub and listen to movies and music at obnoxious levels (around -6 DB on my 140 watt Onkyo). You cannot hear anything on the first level unless you are in my bedroom closet and then it only sounds like decent thunder. If I listened at reference level of -15 DB, you would not hear a peep.

 

Nice...

 

Thanks, I appreciate the help. I will have hardwoods on the main floor over my theater (and kids), so the patter of feet is a concern for me. I've been doing a lot of reading over the past two days, and it looks like I have a lot to learn about soundproofing my theater.