Acoustics and flat construction

[Rip Van Winkle]

I’m going through the process of trying to help a theater (high school and younger) set their standards for flats. One factor of which I haven’t found any discussion: how does lauan vs. muslin affect sound on the stage?

Presumably the wood is reflective (and occasionally resonant) while the fabric is somewhat acoustically transparent. I don’t like the visible movement of fabric flats, but I also don’t understand how a set full of identical cajons isn’t a liability. Obviously every theater and every set is different, but I can’t quite figure out if or how all that needs to be taken into consideration.

Are there quick fixes to common complaints that should be implemented in the building of the flats (or the design of the sets)?

Does anyone have positive (or negative) experience with taking advantage the characteristics of one vs. another? (I’m thinking about a sort of incidental bandshell, for instance (for better or worse), or mic/speaker/FX placements.)

Does a set full of hard flats significantly influence GBF or the sound of wireless (or other) mics?

If you’ve toured shows with one or the other, have you observed differences with the same set in different rooms?

A more basic question which is possibly relevant to this topic: do hard and soft flats play nice together? That is, if I paint them at the same time, is a mix of materials obvious to the audience (leaving aside fluttering muslin)?

(ps — I had hoped to cross-post this to scenery/props/rigging; I don’t know if that’s at all possible or something an admin might help make happen?)

 

[MNicolai]

Acoustically, a wood flat will be more reflective across the full spectrum of frequencies. A fabric-covered flat will be more acoustically transparent -- however with a few layers of paint on them, they will be acoustically reflective for at least the higher frequencies related to speech intelligibility -- but will be more transparent in the low and mid frequencies.

If performers are generally angling their speech out toward the audience, probably no major consequences either way. If performers are facing away from the audience and speaking, a wood-covered flat will be at least a little bit more forgiving.

As for a mix of materials from an aesthetic perspective, the difference in texture/sheen/shadows could be noticeable. This depends mostly on the nature of the artwork though. Flats that are painted solid colors will show all of their sins. Flats with speckling/detail/etc, will be more forgiving when it comes to mix 'n match.

 

[TimMc]

I will use this opportunity to plug a favorite book, The Master Handbook of Acoustics, 7th, Everest and Pohlmann. Somewhere in all of that are many answers. {insert Obi Wan here}

{IMNSHO} The difference between muslin (after painting a few times) and wood veneer is how they respond to sound pressure; think sound board or bellows. Neither has sufficient mass to effectively reduce sound transmission through them at low frequencies (<200Hz) and both will be reflective in the speech range (300Hz-3kHz), with veneer likely being a bit more reflective in the higher end of that range. We're talking 1 or 2 dB, not a huge change. {/IMNSHO}

I'm pretty sure the rag traders have acoustic performance data for their raw goods, but for a "play along in the shop", stretch some muslin and get up close and personal with your voice, then do the same with a veneer panel. It's perceivable, but not dramatic.

 

[Rip Van Winkle]

Thanks for your replies. Had a chance to experiment and can confirm, “perceivable but not dramatic”. And of course in straight plays, virtually everything goes out to the audience. I was a little worried about weird buildups with monitors, orchestra, etc. on a busy musical set — the laws of unintended consequences — but it seems like maybe, just maybe, I’m overthinking a bit. Thanks again!

 

[TimMc]

Thanks for your replies. Had a chance to experiment and can confirm, “perceivable but not dramatic”. And of course in straight plays, virtually everything goes out to the audience. I was a little worried about weird buildups with monitors, orchestra, etc. on a busy musical set — the laws of unintended consequences — but it seems like maybe, just maybe, I’m overthinking a bit. Thanks again!

Don't sleep on it, Rip! You are right to be concerned about the amount of SPL on stage. There might be a couple really narrow uses where the reflective spectrum of a finish could be a factor but I see that mostly in video sets and location work rather than theater.

 

[MNicolai]

Thanks for your replies. Had a chance to experiment and can confirm, “perceivable but not dramatic”. And of course in straight plays, virtually everything goes out to the audience. I was a little worried about weird buildups with monitors, orchestra, etc. on a busy musical set — the laws of unintended consequences — but it seems like maybe, just maybe, I’m overthinking a bit. Thanks again!

That sounds about right.

Like 30% of my job as an acoustician is telling people "the physics say this" but "human perception and a host of other factors say that".

"Marginal" becomes a regular word in your vocabulary -- usually in reference to cost/benefit. What's the cost of doing {x} for a marginal improvement over {y}?