windows into helmholtz resonators?

Paulkent · Post by **Paulkent** » Fri Dec 09, 2005 12:30 am

Hi there,

I've got some windows in my live room and control room and I'm considering ways to prevent them from being an issue by

1. Isolation problems (in and out)
2. Reflecting sound back into the room.

Bearing in mind that one of the windows sits almost parallel to the LR/CR window...

Is a window that's set back into a 30cm, 11.8" thick wall ripe for conversion into an angled Helmholtz Resonator?

am I just getting carried away because I like the spelling of Helmholtz?

would it be much more beneficial to create some kind of absorber?

is it better to do a second leaf of glass?

does it matter that it's double glazed (in relation to theory about three leaf walls)

I'm bearing in mind the cost of secondary window will be more than some MDF/Plywood and the Rockwool that I already have.

I appreciate anybody that can string together my strangled thoughts process.

Paul

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=4786

(another thread that has a picture of my space..)

knightfly · Post by **knightfly** » Sun Dec 18, 2005 9:00 am

Paul, almost let this one slip thru the cracks -

am I just getting carried away because I like the spelling of Helmholtz?

Yes. Definitely. You are never to use that word again

Seriously, a Helmholtz is a tunable trap - any and all resonant traps will actually WEAKEN your isolation thru the wall at that location, by providing an easier path for the specific frequencies to get through.

If the window is already double-glazed, then adding another pane would weaken the low frequency isolation. With that thick a frame, tilting might help flutter though; somewhere around 2" in 10" would give a 12 degree angle, which should minimise flutter even if the opposing wall is plumb... Steve

Paulkent · Post by **Paulkent** » Tue Dec 20, 2005 8:05 pm

thanks knightfly.

as with all things... it seems really obvious once you know the answer... of course a resonator increases sound leakage at that frequency.. duh!

ho humm. I stand by my comment. The 'H' word is a thing of beauty in every respect. Let me ellaborate :

1. It kind of rolls off the tongue
2. It's never used outside the acoustician circle and therefore makes you seem right clever..
3. It sounds european - which conjurs an image of sophistication and mystique.
4. It uses the letter Z. Which, by the fact that it's a rarity, adds Kudos!
5. I believe it is derived from the German 'Helm' (Helmet) 'Holt' (gets) and means something like 'armour bearer' - and therefore plays on my innate manly instinct to wear armour and swing a sword.

so there you see..

this definitely proves it's a cool word.

it also proves I'm bored at work..

Paul

bert Stoltenborg · Post by **bert Stoltenborg** » Tue Dec 20, 2005 8:57 pm

How thick is this double glazing?
Is it a thermal isolated double pane or does it have a large gap already?
If you have double glass with a gap of just a couple of mm, and you add a second pane at a large distance (30 cm or so), TL will benefit, AFAIK.

Paulkent · Post by **Paulkent** » Tue Dec 20, 2005 9:19 pm

Yeah, that would work it's only a couple of mm.

but would it work better than just stuffing it with rockwool and covering it with plywood. Then forgetting about it? I'm not too worried about the light.

Although if the isolation is comparable I could be tempted.

I would of course have to build a third pane inside the inner wall though and then it would be a three leaf disaster...

I'm presuming isolation will be best if I block it off?

Paul

bert Stoltenborg · Post by **bert Stoltenborg** » Wed Dec 21, 2005 3:37 am

A decent pane of glass, as heavy or heavier than the plywood (or the wall construction) will perform as good as anything, and natural light and view is also worth something, IMO.

When you have a thermopane window and place another pane in front of that on 30 cm you will have better TL, the effect of the 3 leafs will be a few dB i the 125 Hz range. Niothing to worry about.