Echo in the ceiling

Tao_teh_ching · Post by **Tao_teh_ching** » Fri Dec 30, 2005 2:35 am

Dear all,

A friend of mine was making his studio. He approached me with a problem that he is facing, I thought I should post the problem here for all to help.

The recording rooms size is H x W x L= 10ft x 11.4ft x 10.6ft. There is a 5ft gap above the false ceiling, after the five feet gap is the concrete ceiling. Now, the false ceiling is made up of 1inch of plyboard + 2inches of Glasswool, then there is a layer of cloth + a layer of egg crate shaped foam. Additionaly on top of the plywood, there is about 3inches of additional glasswool. Well, the room is not dead. I have been inside it, it resonates and there is an echo formed at the ceiling. But this only happens when a warm sounding vocalist sings in the room. It does’nt happen with my voice, which is shrilly. But my friend whose voice is deep and ‘bassy’ resonates the place and the echo is dominant.

Any idea what can I add to the roof without causing much damages to the existing roof and his pocket.

I was thinking… if I can reach the area on top of the false ceiling, then I can add another layer of loose glasswool to further deaden the place.

There are no bass traps present in the floor, should I use any?

len-morgan · Post by **len-morgan** » Fri Dec 30, 2005 7:16 am

Are you sure it's not the drop ceiling that's causing the problem? Some of it can rattle pretty good.

len

Post by **kendale** » Fri Dec 30, 2005 9:40 am

Aloha Tao,

A couple of questions/thoughts:

- What/how is the room itself constructed?

- What kind of treatment has been done to the interior of the room, i.e. absorbers, traps, or is it none at all?

Aloha

Tao_teh_ching · Post by **Tao_teh_ching** » Fri Dec 30, 2005 4:56 pm

Dear Kendale,

1. The walls- My friend placed wooden grids (stud walls) on all the four walls, inside that grid he placed a 12mm layer of thermacole. Ontop of the thermacole he stuffed 2inches of glasswool. Ontop of the grid he placed a layer of cheap white cloth, and ontop of that he placed a layer of designer cloth. (There is no gap between the thermacol and glasswool), so i think the glasswoll has become pretty rigid reducing its effectivness.

2. The floor is nothing special, just a layer of 12mm construction thermacole, and ontop of that a layer of carpeting.

3. The roof i have explained.

He was'nt trying anything special, due to his limited knowledge he just went for an all out dead room. So he just concentrated on giving the room a general layer of high absorption. There are no diffusors, bass traps or reflectors. He has placed these wierd triangular shafts on the walls, he claims they will destroy the standing waves (if any).

The same goes for the Control room. However, in the control room, he placed a wooden grid on the ceiling, and did not close it with a plyboard. He just stuffed a lot of loose glasswool, held it with a wire mesh and placed a layer of cheap white cloth and egg crate shaped foam (Keeping a 5ft height above the cieling). It does not echo as much as the recording room, i guess this is so because the glasswoll it working both ways. The sound passes through it on its way up, then after bouncing from the concrete cieling it again gets absorbed by the same glasswoll on its way down. This is what i think.

Anyways, i hope this has helped you. I need some pointers on this thing guys, the man is desperate...

Post by **kendale** » Fri Dec 30, 2005 8:11 pm

Aloha Tao,

Have you & your friend studied and/or considered using the acoustic hangers/panel absorbers described at the SAE website? http://www.saecollege.de/reference_material/index.html

Click on "absorbers" in the left hand column and then on low frequencies at the top of the page.

Aloha

Tao_teh_ching · Post by **Tao_teh_ching** » Fri Dec 30, 2005 10:06 pm

Dear Kendale,

Thanks for the drawings. This might be easy for me to execute as i have all that space above the false ceiling. I should use these hangers for both the recording floor and the PCR right? I think it will work well in both cases as the main aim is to make the rooms as dead as possible. Thanks a lot

Post by **kendale** » Sat Dec 31, 2005 12:46 am

Aloha Tao,

I should use these hangers for both the recording floor and the PCR right?

Uh, what exactly do you mean by "recording floor" and "PCR"?

In regard to the link to the SAE site: be sure to check out the other tabs (high & mid frequencies) as well as the rest of the site. There's a wealth of information to glean from.

Here's a couple of recent pics of some hangers and another diagram for you to reference.

Aloha

Dan Fitzpatrick · Post by **Dan Fitzpatrick** » Sat Dec 31, 2005 11:24 am

are you sure it isn't standing bass waves from insufficient bass absorption inside the room? i'm no expert on this, but if that's the problem, adding hangers or anything else in the ceiling cavity won't do anything. something to rule out before going forward with opening the ceiling.

usually people fill the corners with bass traps, and i think you said there aren't any in this room.

Tao_teh_ching · Post by **Tao_teh_ching** » Sun Jan 01, 2006 7:11 pm

Dear Dan,

Yes your observation is right... there are no bass traps in the room. My friend just went for an all out absorption. I wont mind placing any bass traps in the room, it won't hurt if they are there. But the real problem is in the ceiling, you can clearly make out the echo is formulating in that 5ft gap, so i'll also go with the hangers (Thanks Kendale). So, can you give me any drawings for bass traps.

Post by **kendale** » Sun Jan 01, 2006 8:36 pm

Aloha and Happy New Year!

Hey, you're welcome Tao.

Here's a link with some bass trap plans: http://www.johnlsayers.com/HR/index1.htm

and here: http://www.ethanwiner.com/acoustics.html

Food for thought: It's probably a lot easier to build and install the bass traps in the room than it will be installing them in the ceiling, so perhaps it might not be a bad idea to start there and see what kind of difference it makes and then move on to the ceiling, yes?

Aloha