advice for engine dyno cell

[bhays]

Hi all,
i'm putting together an engine testing cell. it is a dyno room and will be in a machine shop area. the dyno brake is rated to 2000 HP and will be testing high performance automotive engines. anything from 1.8L hondas to 702ci big blocks.
I am hoping someone has had some experience with a couple of things or can point me to some literature or other resources:

1) noise reduction- coustruction materials or techniques that keep the engine noise in the test cell from becoming a problem in the shop. the difference between standard gyp board construction and sound absorbing masonry block is something im interesd in.

2) engine noise analysis- what frequencies coming from the engine and exhaust are the loudest? i know the lower frequency noise is rather annoying, but is it at 125Hz, 200 Hz, 300Hz? this will help us tune our walls.

3) air handling- the room's ventilation will move 24,000cfm at a minimum. how can we be sure that ALL of the air is cycled through? i.e. no corners with stagnant air or build ups of fuel vapor or similar?

thanks in advance.
-bryan

 

[GregLocock]

1) Heavy walls, say a brick cavity wall are your best bet. Typical sound levels will be around 100 dBA at one metre.

2) main frequency is at firing order, so for a V8 that is rpm/60*8/2 Hz. There is a lot of broadband noise and harmonics as well.

3) don't know about other dynos, our noise dyno had extraction at all 4 corners.


Cheers

Greg Locock

 

[PFM]

Bryan,

We are just putting the finishing touches on a 2000 HP dyno cell. We recieved a lot of help with our goal of a quiet cell we could use any time day or night in the industrial complex without angry neighbors. First I doubt you will contain exhaust noise in the cell without great mufflers, search the web they are out there they are big, heavy and expensive, they will exit the cell. Next an engineer friend offered this info, 90% of the sound can escape through a 1% of area opening (walls and roof for total area). The above means build the cell like a boat, air tight (air system asside). The walls for our cell are sheet-rock, with a room inside a room, the inner walls floated on sound clips, the outer room isolated from the inner room, again search the web for info on sound rooms. Dual doors, with sound seals, dual isolated glass (Lexan), sound caulking details details details. The air system was handled by others, the short form is insulated duct work oversized and no straight line of sight paths for sound to excape without first hitting insulation. I can also suggest looking at some dyno cells and talk with the opperators most will show you what they have done.

Good luck.

Dave