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Acoustic advice needed for performance in gym

   I teach music K-6 and choir, and strive--within the limitations of the elementary school environment--for high level choral singing.  My classroom has satisfactory acoustics, but our only performance space is a huge open gym, 105 x 80 feet, with poorer acoustics than any other gym I've had to use.  As with all of these spaces, the walls are so far away, and the reverberation so long, that the singers can't hear themselves.  I know a shell would help vocal production by the singers, but is this worth buying when the sound still goes out into an unimproved, cavernous gym?  I know carpet and acoustical panels would help, but don't know where to begin.  Does anyone have advice, preferably based on experience, about effective modifications I can make and install myself on a very low budget?  Are any of you acoustical engineers?    
   We have no budget for any of this, so the cost would be born by donations, the PTA and myself.  I am a carpenter of long experience, and aware of the building codes, the requirements for fireproof materials, and the necessity of clearing any work with the physical plant people in the school district, so my question is only about possible acoustic improvements.  We also have a large theater stage (concrete and block) centered on, and projecting beyond, the 105 foot long side.  This is unimproved and unused, except for storage, and available to me to use with a shell, either portable, or made to fit and permanently installed.
   There must be some general acoustical rules that apply.  Here are some specific questions that have come to mind:  Is there a certain percentage of wall that must be covered?  A specific shape, size and orientation of ceiling panels?  What if we temporarily rolled out carpet over the unused floor area in front of the shell and beyond the chairs?  Would it help to hang 10 x 10 foot squares of canvas or flannel vertically over the closed bleachers?  How much would it help if we surrounded the seating area with those folding, rolling, portable dividers made for school use?  How much less effective is a portable, plastic shell, compared to a totally enclosed, customized wooden shell?
   Thanks for any advice you can give.
 
Bart Brush
Humboldt Elementary School
Humboldt, Arizona    
Replies (3): Threaded | Chronological
on December 19, 2013 5:15pm
Hi Bart,
 
I've worked in some similar spaces, including a very similar sounding gym with a stage on the long side. Here are a few thoughts:
  • If you can place the singers on risers on that stage, you'll give yourself a good head start. Because you would be in an enclosed space, you'd have an easier (and more effective) experience with choral shells (rented or purchased). You would also be able to provide other hard/reflective surfaces behind and above the singers, should you want to use them. These can be purchased at a store like Home Depot for not that much; and they're easy/fun to build and install.
  • My current gym and the one I mentioned above (with the stage) both had their ceilings sprayed with some sort of acoustical foam that had a DRAMATIC positive effect on the acoustics. If you can afford it, doing so could be a great second step.
  • Another thing you can do on the relative cheap-and-easy is to hang a combination of absorptive and reflective surfaces from the ceiling, having them hang at various heights around the audience perimeter. (They would be high enough so that the audience couldn't jump to touch them.) These would hang vertically....
  • You could also hang hard surfaces in the air between the stage and the audience (over the audience's heads), with the angle reflecting the sound back to the audience. (See any modern symphony hall for fancier panels that do this.)
  • Your idea of surrounding the audience (or just backing them) with rolling portable dividers would probably also help. 
  • RE carpeting, I would wait until you try some of these other options first, then carpet as fine-tuning. (As you probably know, the audience will be absorbing some of this floor-bounce as well.)
Best of luck!
 
Tom
on January 17, 2014 5:22pm
Thank you Tom.
 
Regarding your suggestion of hanging  absorptive and reflective surfaces of different heights from the ceiling,  why hang these only around the audience perimeter?    And can you hazard a guess how many hanging surfaces or how much area I need to reach some sort of "critical mass" that begins to change the acoustics?  Would simple banners of canvas or other fabric work? (No supports or paneling, just fabric.)
 
Shell on stage: I'm thinking that the low cost shells like the Wengert Legacy, with the top 3' section that tilts forward, would be of limited effectiveness.  Wouldn't most of our sound still be lost above the stage, lost to the audience and the singers?  It seems to me that having a shell with a complete ceiling is very important, but I have no experience with the Legacy variety and maybe I'm not giving this type of shell enough credit.
 
The more I think about this, the more I realize I need to know what the most important defect is in this space.  Is it the hardness of the surfaces?  Is it their flatness and regularity?  Is the area immediately around the choir more important than the space in which the audience sits?  If you have anymore thoughts, thank you in advance.
 
On the pessimistic side, a musical friend not involved in music education and school concerts opined, "Acoustical science is very inexact--just look at Philharmonic/Avery Fisher Hall in NYC."
on January 18, 2014 1:01pm
Bart, I just moved back to the Northwest from Scottsdale - !
 
You can reach me at meljr-la(a)hotmail.com.
 
I am a degreed Choral Conductor who happens to make my living doing acoustics  :-)
 
As to Fisher Hall it should be pointed out that he original spec. presented to the City of New York got "value engineered" before that infamous first attempt!  Subsequent work has rendered it much more fri9endly and useable.
 
I may be able to help - within limits.
 
Cheers
 
Gene Lysinger
LYSINGER ASSOCIATES
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