School Cafeteria Acoustics

Posted by AcousticalSurfaces on 11/21/2008 3:11 pm | 2 Comments

A.K. from Portland, OR writes:

Hi Ted,

I just started investigating our options for reducing noise levels in my kids’ school cafeteria and came across your excellent blog. Thanks for providing easy-access education. I’m intrigued primarily by the 1″ Echo Eliminator. I would go for the 2″, but like all public schools we are on a shoestring budget and would have to fund-raise/write grants for anything like this. My questions to you are:

1. Our school is near the top of the list in receiving a top down renovation in the next few years, and chances that this will happen are pretty good. Thus, my thought is that it would be great if we could take down the panels and reinstall them where needed after whatever renovation we receive. Since they are not finished, would it impair the panels’ acoustical performance if we covered them in fabric and hung them from the walls/fastened them to the ceiling – kind of like cushions? That way, they could easily be removed and reused later. Another option would be to have them adhere to, say 4′ x 8′ panels that similarly could be taken down and reused.
2. This may be kind of obvious, but hey… Since they bond directly to the surface, I’m assuming that anyone (including parent volunteers) can do it. Am I correct?

I haven’t yet measured and sketched up the space, but will do so in the next week, or so. In case having a visual would help determine your answer to my first question, please let me know and I’d be happy to provide numbers when I get them.

Thank you so much for your time!

Cheers,
A.K.

A.K.,

It’s great to hear that my online ramblings are helping people. A friend of mine recommended that I organize my replies a bit better so readers could jump around – so I’m going to give that a shot. I’ll jump right into it, but feel free to contact me directly if you have any specific questions or if you don’t understand what in the heck I’m writing about. Here goes.

Type of room:
Cafeterias are generally extremely loud places, so the situation is quite normal. Stuff a bunch of kids into a concrete room and even though they’re supposed to be filling their mouths, the noise level will be ear splitting. These cafeterias are almost always made out of vinyl tile flooring and painted concrete block walls, both extremely reflective surfaces. Noisy kids plus reflective surfaces equals headaches.

Which Thickness?:
You mentioned that you would go for the 2″ panel, but I am going to try to talk you out of that. I would ONLY recommend that the 1″ panel be used in this type of situation for two main reasons, performance and cost. I can show you the test numbers to back up the information here, but the only real advantage to the thicker panel is the increase in absorption in the low frequencies. If you are dealing with mid and high frequencies, the 1″ and the 2″ panels will perform about the same. There are only a few types of rooms that will require a thicker panel and these tend to be recording rooms, home theaters, studios, band rooms, etc. So, considering the type of noise that you are dealing with in the cafeteria, the 1″ and 2″ panels (for the most part) are going to give you about the same performance. Because there is twice as much cotton in the thicker panel and it is twice the thickness, it is more expensive for the product is to ship because it is more boxes or a bigger pallet.

Mounting:
As far as mounting goes, that is going to be up to you. Temporary installations are a bit tricky but they are definitely possible. I would say that 99% of the panels that we sell are adhered directly to the structure (the ceiling or the walls of the room). I have, however, helped a few people in similar situations come up with creative ways to mount panels so that they can be removed for one reason or another. This is typically done by pounding grommets through the panels and hanging them from hooks or nails that extend out from the wall. The panel can be taken off of the hook and stored then put back when the work is done.

Wrapping with Fabric:
I would not recommend covering the cotton panels directly with fabric, these panels are generally installed as-is. They are not a rigid enough board to be able to hold the tension of the fabric and would end up looking like a canoe. If you want something that is wrapped with, we would use a rigid board of fiberglass which will hold it’s shape much better than the cotton. These panels are quite a bit more expensive though.

Colors:
The cotton panels are available in nine different colors, which we have found works well enough for most cases. You also mentioned 4′ x 8′ panels which is possible in some cases, but our standard panel size is 2′ x 4′. The smaller panels are a lot easier to handle on site and are usually a lot more economical to ship. We have a limited inventory of 4′ x 8′ panels, so if that is a route that you want to explore, please contact me and we can discuss it.

Installation:
These panels are extremely easy to install, regardless of which mounting type you end up going with. Most installations are done by in-house people, and if your “in-house handy people” aren’t comfortable dong it, I’m sure that you could convince some parent volunteers to handle the installation. There is not necessarily a “right or wrong” way to install the panels. For all practical purposes as long as you have the right number of panels in the room, based on the acoustical needs for that room, the panels can be anywhere and do the same job. I would recommend trying to space the panels as evenly throughout the space to make the room look and feel balanced, as well as exposing all four edges of the panels. By exposing the edges you will increase the overall absorption for each panel because some sound will hit the sides of the panels as well as the surface.

Conclusion:
I would be happy to make a couple recommendations specifically for the room, but to do so, I would need the measurements of the room (height, width and depth) along with a picture of the space if there is anything out of the ordinary. If it is a standard, run of the mill cafeteria, no picture is needed, I already have one in my head. The measurements will help me make a recommendation as to the overall square footage needed to effectively treat the space. I can also get some samples and supplemental literature to you if you could send me your address and phone number.

Additional Resources

Creating Better-Sounding Rooms

Download eBook

Solutions to Common Noise Problems

Download eBook

CAD, CSI, & Revit Library

Access Product Cad Files