Sound/acoustics folks, weigh in...

I'm constructing a tech booth for the theater.  Nothing fancy.  Up until now we just put a table in the extreme corner of the room which was far from ideal.  In the picture below, you'll see a black table in the top center of the photo labeled "sound/lights" which indicates where it is now.  The pink raised platform is where the new one will be.

I want to line the inside of the walls (luan or drywall over a short studwall) with acoustic foam to limit the amount of noise that makes it out from feet, chairs, key taps, etc.  I will also put carpet on the deck and ground the metal in the platform to prevent static build up. 

One of the things this theater needs is general sound dampening.  The whole space is basically a hard masonite floor and drywall walls.  Would adding acoustic foam and Duvetyne fabric around the outside of the booth be good, or would it just make a strange dampened field for one ear of patrons sitting near the booth?

I am not an expert, but I do have some education level experience. I have been shown that hanging heavy draperies and other things like that can really improve an otherwise live room without resorting to covering the entire wall.

In reply to tuna55 :

I'm far from an expert either just some classes years ago. 

My understanding is that your biggest gains will be from bass traps or acoustic foam mounted in corners followed by draperies or panels designed to muffle whatever frequency you're attempting to eliminate. 

Sorry... I was unclear.  I meant the walls of the sound booth.  Just the 6x8 platform.  I can't afford foam for the whole place :)

The large black unit behind the pink sound booth are pallet racks/shelves and they are covered with curtains, but they are just super light fabric to mask the ugly furniture on the shelves.  I was budgeted $450 to make curtains happen so I had to get something cheap.  That meant buying a few bolts of polyester fabric and taking my sewing machine to work. They baffle a tiny bit of sound but not much.  Long term goals are to get those shelves out and store my props in an off-site facility, but that is years down the road.  At that point, I have about 20 sheets of the woven fiber acoustic panels that will get hung.

So my thought was to put acoustic foam inside the walls of the 6x8 booth, but should I also put it on the outside?  I'm afraid the dead spot on that little booth won't do much for the whole room, and it might make strange acoustic things happen for patrons who sit near it... or for that matter, might make the sound that reaches the sound tech be damaged or inaccurate.  So what we're talking about is foam inside AND outside on the pink structure, or just inside?

So should I just dampen inside to prevent techie noises from getting out, or should I also dampen the outside of the booth to absorb some from the space?

Are they mixing for the house or for recording (or both)?

What are the dimensions of the space? I know you've mentioned it before but I just don't remember. 

I only ask because this might be slightly relevant. When I first moved out west I was living with an audiophile. The "living room" I guess you could call it was roughly 20x25 with easily 15 foot ceilings, and this was where all the sound was kept. 

He spent maybe a week measuring everything from his chair, the speakers, the walls and everything in between, then put up like 6 24"x24" panels of acoustic foam where his math told him. Which for an outsider looked completely random, btw. 

Some on the wall, some on the ceiling, but the way they were aimed to work with the speakers made everything louder and crisper(sorry, that's the best description I can think of at the moment). The echoes went away, truthfully it almost replicated surround sound.  And he was proud that he'd only spent like $150 on everything. 

On the total opposite end of the spectrum, when we were working on the recording studio in a television station, inside the walls, outside the walls, a foot thick on the ceiling, they had foam everywhere and were extremely picky about our wiring and fire alarms. 

Curtis:

Put the foam around the outside of the booth to give you some absorptive surface.  It will at least not add to the reverb problem.  I don't see it significantly affecting the audics at those seats - all the rest of the sound is going on through the curtain anyway, so it's out of the equation until it hits the back wall of the space and reflects.  Having the foam on the outside of the booth will prevent having a live surface immediately behind those folks.  And the engineer will be sitting with their head above the booth wall, so I don't think it will affect your mix much.

In the booth wall, put unfaced batt insulation in the stud cavity.  This will muffle some high-frequency noises from getting transmitted through from the station side.  Also, hang the drywall on 5/8" RC-1 resilient channel on one side or the other - that also reduces direct transmission through the wall.

Also, flare the end walls of the booth about 10 degrees outward.  That helps break up standing waves.

None of this is going to make a big difference one way or another due to the relative size of the surrounding space, but you can make small steps to improve it until you can refurb the main space.  I'm with Rev - anything at all you can do to add absorption to the perimeter side walls will help, even if it is only a little.  1" fiberglass board insulation - even the cheapest vinyl faced fiberglass lay-in ceiling tiles you can find - wrapped in a little fabric and glued to the walls will help.

From my experience with live sound and studio work, and my admittedly limited knowledge on the physics behind acoustic waves... anyway, I think you'd be fine just foaming the inside, maybe a little extra in the corners. The random foam bits around the room work when done properly but they can be unsightly.

Best trick I learned and still use is getting rid of 90* corners and eliminating the "square room effect", a frequency around 250hz that seems to reverberate in square rooms with hard surfaces. Think about the "noise" you hear in a gym or on a basketball court, how its never really silent. Simply cutting the EQ around 250hz helps eliminate extra noise and feedback most of the time, but pulling the frequency totally out can deaden the sound too so just play with it a bit.

https://www.zoro.com/armstrong-ceiling-tile-24-w-48-l-58-thick-pk16-2907/i/G0486696/feature-product?gclid=CjwKCAiAvMPRBRBIEiwABuO6qbLshrvkowFxZeINLeu_Z84d-EJe6Y_KVX2-PPrVZhio2Cy7T5ZnxhoC4YAQAvD_BwE

https://www.amazon.com/Auralex-RC8-Resilient-Channel-Lengths/dp/B0002D05OQ

scardeal said:

Are they mixing for the house or for recording (or both)?

Just house.  I suppose recording might happen, but it would just be pulling a channel off the console into a recorder for archival purposes

RevRico said:

What are the dimensions of the space? I know you've mentioned it before but I just don't remember. 

I only ask because this might be slightly relevant. When I first moved out west I was living with an audiophile. The "living room" I guess you could call it was roughly 20x25 with easily 15 foot ceilings, and this was where all the sound was kept. 

He spent maybe a week measuring everything from his chair, the speakers, the walls and everything in between, then put up like 6 24"x24" panels of acoustic foam where his math told him. Which for an outsider looked completely random, btw. 

Some on the wall, some on the ceiling, but the way they were aimed to work with the speakers made everything louder and crisper(sorry, that's the best description I can think of at the moment). The echoes went away, truthfully it almost replicated surround sound.  And he was proud that he'd only spent like $150 on everything. 

On the total opposite end of the spectrum, when we were working on the recording studio in a television station, inside the walls, outside the walls, a foot thick on the ceiling, they had foam everywhere and were extremely picky about our wiring and fire alarms. 

 

50 wide, 60 length.  Barrel ceiling from 19' at the walls to 26' at the peak.  Ceiling is acoustic tile but has a coat of black paint on it that probably isn't helping.

for what it is worth, I have never been in a theater that had sound deadening around the sound booth. most people mix from the Front of House (FOH) position just so they can hear what the audience hears. I understand wanting to put dampening in the half walls of the booth and the floor though. Spray Foam may be your friend in this case, just fill those open spaces and seal, should do a decent job of dampening the sound.

the "music box" at the Borgata has the sound booth out in the open like you show. I think your best bet is to do something about the slap you are getting from the back wall and prop storage. Heavy Duvateen or used curtains from a theater or prop house might help

mad_machine said:

for what it is worth, I have never been in a theater that had sound deadening around the sound booth. most people mix from the Front of House (FOH) position just so they can hear what the audience hears. I understand wanting to put dampening in the half walls of the booth and the floor though. Spray Foam may be your friend in this case, just fill those open spaces and seal, should do a decent job of dampening the sound.

 

the "music box" at the Borgata has the sound booth out in the open like you show. I think your best bet is to do something about the slap you are getting from the back wall and prop storage. Heavy Duvateen or used curtains from a theater or prop house might help

Agreed on the heavy fabric.  Only problem is that its about 100 linear feet of shelves that are 15' high.  We're talking really big money for that project.  Just to buy the Duve for the project would be nearly $3000 for the non-fireproof stuff which I would have to salt, or $4000 for the fireproof stuff.  Then I would need a week to sew it all together.  To put it in perspective, the last set I built was in a 40' proscenium, it was 18' high, had three houses with two levels, and it cost me $673.  We just don't have the money right now to even consider such a project.  The tech booth won't cost me anything since I have so much scrap material here.

I also wish I could put a finger on exactly where the "life" was coming from in there.  Its fortunately pretty even given its symmetry... which means that most of the productions here can be equally misinterpreted from any seat.  Here is another view of the space:

Years ago (around 1999) this building was converted from a proscenium theater into a production center.  All of our productions for a while took place at a new, larger theater downtown.  That proved to be not cost-effective, so we moved some of the productions back home here.  When I took over three seasons ago, there were more exposed shelves with no curtains, no seating risers, and no lighting.  The lights were literally halogen work lights hanging on trusses that were suspended from the ceiling.  The light board was a piece of plexiglass with 12 residential slide dimmers in it with a snake of THHN hardwired into a subpanel.  That firetrap was the first thing to go.

In 99 when this was converted, the main space you see above was a raked audience seating.  The floor was raised up level with the stage.  Now the former audience area is a black box theater, the former stage is now the lobby, and the former lobby is now costume storage.  So the old proscenium arch is now covered with a curtain and people enter and exit through it.  So, the shelving you see in the photo is covered with a lightweight (maybe 6oz) polyester woven fabric.  It isn't quite opaque, but when you have lights on you can't see through it.  Looks wonderful, but doesn't do much for sound.  I think the upholstered furniture on the shelves does more.  Walls are all drywall and portions of it are angled back and forth a bit (maybe 10 degrees).

I have a couple dozen of the 4'x8' sheets of hard woven fiber panels which I think I won't install until I get the shelves out.  Not much wall space to install them right now.

For right now I'll likely just put foam inside the booth.  I have enough for that.  I may temporarily install some on the outside and just see what it does.  I just don't want to make it worse for patrons or have a sound tech chew me out for doing something dumb.

ok.. for the booth itself. The Booth's walls in the Music Box are carpeted inside and out. I am sure that helps some. It's nothing special looking, just some loop glued to the half walls and finished off nice. As for your "life" I would start looking at the ceiling. Between the hard walls and the curve of the roof, I am betting you are getting some bounce off of it. I worked in a nightclub that was under a glass dome 90' across (the Pool at Harrahs) you could speak to somebody across from you in a normal speaking tone, it bounced up into the dome and came back down the other side clear as day