Do I NEED to soundproof my new HT?

[stuartbrown21]

Hi guys

Have been reading through a lot of the threads in this section and there is a lot of information to digest!!

I will be moving house shortly and the room we have earmarked as the new Home Theatre is a bit 'cosier' than most, at a mere 13'x8'.

The room is upstairs in a detached house. We have no kids to worry about disturbing with noise, and if my wife isn't in the HT with me, she will most likely be below me in the living room.

I attach a diagram that shows the proposed layout of the room, drawn exactly to scale. There are a few issues undecided yet, such as the precise positioning and make up the the seating, the positioning of the projector, AV Rack & subwoofer, and whether or not the room can truly accommodate 7.1 surround (may end up making do with 5.1).

The most important issue to note is that the position of the screen and the four main surround speakers is a function of the size and shape of the room and therefore can't be changed. Given the width of the the screen and the floorstanding front speakers, there is literally just a couple of inches of spare width.

In terms of soundproofing, I am going to most likely use Cloud 9 underlay under the carpet to stop as much noise travelling downstairs as possible.

The reason for my posting this thread is that given the very tight width restriction with the current plan, I wouldn't be able to construct floating walls within the room, which I understand is the usual way to soundproof a HT. The only way I could implement this would be to step down to an 84" or even a 77" screen which I'm not willing to do, as in truth I'm already stepping down from a 106" screen which I use presently, which I'm a bit miffed about!!

I guess what I'm asking is, can I get away without soundproofing the room? Will the walls and the double glazed window prevent the noise from my HT spilling out into the street and will the underlay prevent the worst of the noise from polluting the living room below?

I think in theory, the most that I could do would be to build something approximating to a floating wall at the front and back of the room as I could afford to lose a little length. If there was anything that I could do to the sides of the room that would lose me no more than about an inch and a half on each side, then I guess I could also do this, if it would be worthwhile.

Also, just out of interest, how much width could I expect to lose from the room if I did relent and decide to build floating walls?

Any help would be much appreciated in this matter!!

Regards

Stu

[Docta teef]

Hi

Ive got more or less the same speaker setup which could throw out a fair bit of sound when cranked up. As far as sound proofing goes i think your missing the point a little. Assuming that the sound is going to radiate in all directions and that your in a detached house for starters i wouldnt worry about insulating the outside walls. My HC is in the cellar and i concentrated in insulating the ceiling to limit sound escaping you need to pack the floor with as much insulation as possible. After that you can think about internal walls

[ched]

Cloud 9 and its tredaire Dreamwalk type underlay arent really designed to reduce air borne noise. They are designed to reduce foot fall noise. So I dont really know how much of a difference they would make to reducing sound level to the downstairs. Cloud 9 reduces foot fall noise by 43db and Dreamwalk by 46db.

I am having dreamwalk fitted tomorrow to reduce footfall noise but will hopefully post about reductions in noise levels, unfortunately I dont have a sound pressure meter so it will just be subjective.

I think your best bet is, as has been said previously, put insulation under the cinema room floor between the joists and then make sure all gaps in floor boards are sealed to stop any air paths.

Good Luck

[Ted White]

Excessive packing of insulation will risk coupling the surfaces. Insulation then becomes a fairly effective conductor. Looking at the most comprehensive data will indicate:

Exotic insulations in a wall or floor do not improve the sound isolation any more than less expensive standard insulations.

A light application of insulation is best. More is not at all.

[Toonaroond]

I don't think the Cloud 9 will do it on its own. We've just had some fitted upstairs in a bedroom and even with a nice thick wool carpet on top of it I can still hear the radio from that room downstairs in the lounge below it, and the radio is only a mini hifi type on about half volume...

It's made my mind up that I need to go the whole hog when I get round to my HT....

Can you pull up the floorboards and insulate from below? What about an insulated false ceiling in the room below?

[Paul_T]

The false ceiling is an option of what we have to install in new flats these days (I work in an architect's), and I've been doing a bit of digging around for information on the best way of insulating a single room within a house.

My problems slightly different to the OP's as my new AV room is on the ground floor - I'm kind of fortunate in that mine is new build, trying to work with what's already there can be expensive - but I still have insulate the floor above as there'll be a kids bedroom.

The main rule of thumb is that a good dense mass will reduce impact sound (footsteps) and sealing airgaps will reduce airborne sound - you more or less have to make the room airtight, so you need a mixture of the 2.

I'm lucky as can build the new walls up with a dense concrete block and wet plaster on top (plasterboard on dabs is a no-no as its porous which means air can travel through, if air can pass through - so can sound)

In the old days you could get away with a standard floor joists with floorboards above and plasterboard below, now you can't mainly because of fire regs and more recently sound. Getting the sound insulation up to scratch if working with an existing floor gives you 2 options - lose room height upstairs or downstairs - the latter is the better or you'll be making a step up into the room otherwise, better to have a slightly decreased ceiling height downstairs as it'll be less noticable.

There's a few links that might give you some handy info.

http://www.soundstop.co.uk/solutions...solution_1.php

http://www.british-gypsum.com/PDF/wb...0sil_07_05.pdf

"Resiliant Bars" are a kind of shock absorber - they sit between the joist and the ceiling and absorb any vibrations that might otherwise pass through.

You'll certainly need some insulation between the joists - 100mm is usually enough, anything more would be a bonus dont pack it in (like compressing 250mm deep insulation into a 200mm floor).

You may also get benefit from stiffening the existing floor - add a row of strutting down the centre of the room, and replace your current floor floorboarding upstairs with the densest you can get hold of - we usually specify a layer of Gypsum 19mm Soundbloc plasterboard between the joists and the floorboard, but this will give a small step also.

Something else that gets overlooked is the door opening, we'll usually specify a rubber strip around the door which is more widely used in fire resistance, and on the floor a weatherbar from an external door!

Apologies if some of this is a repeat, hope you find it useful.

[Ted White]

http://www.soundproofingcompany.com/...m_construction

http://www.soundproofingcompany.com/...icles/flanking

Different materials will work better in some locations than others. For example super thick insulation works well in a thermal insulating project, but not in acoustics. There is only a very marginal increase in performance going beyond R19 (15cm) in the ceiling. This isn't an opinion. There's a great deal of data from the NRC labs in Canada.

"Filling the cavity with absorptive material can increase the transmission loss substantially, especially when the cavity is large... The density of the sound-absorbing material is not very important and using batts thicker than two-thirds of the cavity depth provides little additional increase in STC."

from Sound Transmission Through Building Components by
J.D. Quirt of the NRC. So we needn't get too obsessed with the thickness nor density of the insulation.

Another example of more ideally places materials is resilient bars. They are a problematic material in general. They are designed to introduce decoupling and resiliency (spring). There is no single design spec on the flexibility, so some are made too stiff and don't maintain a spring. Others are too floppy and sag, also not maintaining a spring. If you theoretically had a good resilient bar that would perform with the weight, the ideal location is on open studs and joists, not on finished surfaces. That application will help a bit in the upper frequencies, but at the distinct cost of the low frequency performance. I can provide the lab data for that if anyone cares. The point is to use resilient bars in instances where you don't trap a thin air pocket. So on a finished wall = bad, whereas on an open frame system = good.

Lastly, block is great for many cosntruction applications, but isn't a great acoustic isolator, though it is intuitive that it would be. Better, simpler and generally cheaper to build a double stud wall system and plasterboard. The resulting mass-air-mass system outperforms a pure mass system.

[Ted White]

Another small piece too keep in mind is that we are much more effective if we install isolation on the sound producing side of the partition. So if you had a home cinema in the basement you would rather install the soundproofing on the ceiling. We're trying to keep the sound vibration from entering the original framing.