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Author Topic: Emergency Exit doors that can stop very loud bass frequencies?  (Read 1749 times)

Chris Cox

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Emergency Exit doors that can stop very loud bass frequencies?
« on: February 14, 2017, 12:30:24 am »

Hi all,

Haven't posted on here in years because I sold my sound rig and got out of that side of the music biz. But I'm trying to help a friend with a problem, and this seems like the best place to find real answers from people who know a lot more than I do.

A friend of mine recently took over a venue here in Denver, and has been having some trouble with noise complaints from a neighboring apartment building. It's primarily a venue for DJs and electronic music, specifically styles that feature a lot of low bass - quite a bit more 30-50hz than even typical electronic music. The system in the main room has 8 Othorns for subs, in a line on the floor across the front of the stage. The capacity for that room is around 400 people.

The building is mostly brick/concrete, so it's overall pretty good at holding in the bass frequencies, but the side of the room closest to the street has an emergency exit:


            ________________________________
           |           __________________              |
 S        |          |            STAGE           |            |
 T        |          |__________________|            |
 R        X                       SUBS                         |
 E        |                                                         |
 E        |                                                         |
 T        |                                                         |
           |                                                         |
           |                                                         |
           |________________________________|
   

X is the emergency exit door.
(not to scale)

They've experimented with different sub placements, and the cluster on the floor seems to be the best at directing as much of the bass energy as possible forward onto the dancefloor, and minimizing the amount of bass washing to the street side - but it's not enough. The emergency exit door leaks a huge amount of bass. They are working on reinforcing the frame and wall around the door, sealing up gaps, etc. But it's pretty obvious that that's not going to be enough, because the door itself is just a fairly light wooden door. Unfortunately, taking the door out and sealing the hole with bricks isn't an option, because it needs to be a functional emergency exit.

So my question is: what is the best material for door construction, to stop large amounts of very low frequencies? Would a heavy steel reinforced door make a big difference? Or a solid door of a dense wood? Lead core/reinforced? I assume the higher the density, the better, but I'm just not sure what's available to buy (or feasible to build). I don't believe the door needs to have any specific emergency exit function, like triggering an alarm when opened or anything, it just need to be a functional door.

I've done a bit of googling, and everything I've found about soundproof type doors is focused on more typical applications - noisy neighbors, sleeping kids, etc. I haven't found anything that deals with trying to stop very low, very loud bass.

So if anyone has experience or insight, I'd be very grateful!
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Caleb Dueck

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Re: Emergency Exit doors that can stop very loud bass frequencies?
« Reply #1 on: February 14, 2017, 02:44:10 am »

Stopping bass requires physical decoupling and mass, lots of mass.  Stopping is relative, any given type of treatment will attenuate different levels at each frequency.

A thick, dense door is a start.  A double set of dense doors with a gap between is better.  Don't forget about the floors, walls, windows, ceiling, etc.  Bass behaves more like a pressure wave than a light ray.
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Ivan Beaver

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Re: Emergency Exit doors that can stop very loud bass frequencies?
« Reply #2 on: February 14, 2017, 07:04:38 am »

Stopping bass requires physical decoupling and mass, lots of mass.  Stopping is relative, any given type of treatment will attenuate different levels at each frequency.

A thick, dense door is a start.  A double set of dense doors with a gap between is better.  Don't forget about the floors, walls, windows, ceiling, etc.  Bass behaves more like a pressure wave than a light ray.
Just to add-the SEAL around the door is VERY VERY important.

It should basically be airtight.

 Agreed on the double SOLID THICK doors with gap and TIGHT seals.

Yes that costs money-but it is what is needed.
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Ivan Beaver
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Len Zenith Jr

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Re: Emergency Exit doors that can stop very loud bass frequencies?
« Reply #3 on: February 14, 2017, 10:28:18 am »

You also better check local building codes, most fire exits must be fire rated and have a placard indicating the rating.
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Robert Healey

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Re: Emergency Exit doors that can stop very loud bass frequencies?
« Reply #4 on: February 14, 2017, 10:43:42 am »

A friend of mine recently took over a venue here in Denver, and has been having some trouble with noise complaints from a neighboring apartment building. It's primarily a venue for DJs and electronic music, specifically styles that feature a lot of low bass - quite a bit more 30-50hz than even typical electronic music. The system in the main room has 8 Othorns for subs, in a line on the floor across the front of the stage. The capacity for that room is around 400 people.


Chris,

I am an acoustical consultant in Denver. I think I know what venue you are talking about - shoot me a PM if you are interested in looking at a proposal from us. We have worked on a few projects recently dealing with sound isolation of bass frequencies from EDM music and the city noise code.

There are good options for code complaint sound rated doors out there, but they are expensive. It would also be bad to spend the money on a sound rated door if the bass is actually going through the wall (either way, you would be wasting your money on a door that has a higher sound isolation rating than the wall).
« Last Edit: February 14, 2017, 10:46:39 am by Robert Healey »
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Kevin McDonough

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Re: Emergency Exit doors that can stop very loud bass frequencies?
« Reply #5 on: February 15, 2017, 07:18:50 am »

hey

yeah as people have said: a solid thick wooden door is key, properly airtight and sealed all around, is the minimum you'll need to do. A heavy, thick, sound deadening curtain hanging over this door can also sometimes help.

But as people have said, you'll probably find that to make any major difference you'll probably have to end up building a second door to make it a two door system. I assume you cant build out the way into the street, so you'll probably have to build in the way and add a second, similarly thick and airtight sealed door.

k
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Ivan Beaver

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Re: Emergency Exit doors that can stop very loud bass frequencies?
« Reply #6 on: February 15, 2017, 08:03:38 am »

A heavy, thick, sound deadening curtain hanging over this door can also sometimes help.


Unless the curtain is REALLY THICK, it is going to do very little to nothing for the sub freq.

Yes those can help at mid and high freq, but as the freq goes lower, materials need to get larger and heavier to do any good
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dick rees

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Re: Emergency Exit doors that can stop very loud bass frequencies?
« Reply #7 on: February 15, 2017, 08:27:43 am »

Unless the curtain is REALLY THICK, it is going to do very little to nothing for the sub freq.

Yes those can help at mid and high freq, but as the freq goes lower, materials need to get larger and heavier to do any good

Ivan...

If this door exits directly to the outside, how would it work to put a 90 degree bend in the path by building on an 8' x 16' addition, beefing up the original door as suggested and adding another properly heavy door 16' to the side?  Addition could be block, concrete or other massive material.

I know those LLF waves push hard, but wouldn't a bend help even then?
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Keith Broughton

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Re: Emergency Exit doors that can stop very loud bass frequencies?
« Reply #8 on: February 15, 2017, 10:59:27 am »

Ivan...

If this door exits directly to the outside, how would it work to put a 90 degree bend in the path by building on an 8' x 16' addition, beefing up the original door as suggested and adding another properly heavy door 16' to the side?  Addition could be block, concrete or other massive material.

I know those LLF waves push hard, but wouldn't a bend help even then?
You theory is based (pun intended) on very low freq waves bending in that confined a space. Perhaps, if it was tuned to cancel a specific frequency...
Also, there might be building codes that prohibit that extra structure. Probably the density of the additional wall would help, bend or no bend.
It's more likely the whole wall on that side of the building might be passing low frequency anyway.
As mentioned earlier, fire rated doors with good seals would be the best place to start and figure it out from there.
« Last Edit: February 15, 2017, 11:01:45 am by Keith Broughton »
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Craig Hauber

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Re: Emergency Exit doors that can stop very loud bass frequencies?
« Reply #9 on: February 15, 2017, 11:03:38 am »

Hi all,

Haven't posted on here in years because I sold my sound rig and got out of that side of the music biz. But I'm trying to help a friend with a problem, and this seems like the best place to find real answers from people who know a lot more than I do.

A friend of mine recently took over a venue here in Denver, and has been having some trouble with noise complaints from a neighboring apartment building. It's primarily a venue for DJs and electronic music, specifically styles that feature a lot of low bass - quite a bit more 30-50hz than even typical electronic music. The system in the main room has 8 Othorns for subs, in a line on the floor across the front of the stage. The capacity for that room is around 400 people.

The building is mostly brick/concrete, so it's overall pretty good at holding in the bass frequencies, but the side of the room closest to the street has an emergency exit:


            ________________________________
           |           __________________              |
 S        |          |            STAGE           |            |
 T        |          |__________________|            |
 R        X                       SUBS                         |
 E        |                                                         |
 E        |                                                         |
 T        |                                                         |
           |                                                         |
           |                                                         |
           |________________________________|
   

X is the emergency exit door.
(not to scale)

They've experimented with different sub placements, and the cluster on the floor seems to be the best at directing as much of the bass energy as possible forward onto the dancefloor, and minimizing the amount of bass washing to the street side - but it's not enough. The emergency exit door leaks a huge amount of bass. They are working on reinforcing the frame and wall around the door, sealing up gaps, etc. But it's pretty obvious that that's not going to be enough, because the door itself is just a fairly light wooden door. Unfortunately, taking the door out and sealing the hole with bricks isn't an option, because it needs to be a functional emergency exit.

So my question is: what is the best material for door construction, to stop large amounts of very low frequencies? Would a heavy steel reinforced door make a big difference? Or a solid door of a dense wood? Lead core/reinforced? I assume the higher the density, the better, but I'm just not sure what's available to buy (or feasible to build). I don't believe the door needs to have any specific emergency exit function, like triggering an alarm when opened or anything, it just need to be a functional door.

I've done a bit of googling, and everything I've found about soundproof type doors is focused on more typical applications - noisy neighbors, sleeping kids, etc. I haven't found anything that deals with trying to stop very low, very loud bass.

So if anyone has experience or insight, I'd be very grateful!
I have seen improvements with just fastening a sheet of 3/4 MDF to the entire face of the door with construction adhesive.  (all edges router and sealed with really good weatherproof paint of course)  I'm sure that the hinges and frame were considered to be able to handle the extra weight. 
I actually saw this done to increase the security of the doors but the side-affect on the sound was a good bonus.  They also weatherstripped it really well and added a metal strip down the center to keep the gap between them sealed better.  It was all done on the outside (alley) side so the inside with panic-bars was the same as it always was and the emergency exit function wasn't impeded in any way.

Of course with Bass, the entire building pulsates from the energy contained within so any effort at soundproofing fastened to the building is just going to move along with the wall itself.  (think small storefront-sized places with more than 4 dual-18's)
Sympathetic vibrations can be eliminated -loud rattles and buzzes from structural elements on the exterior can go a long way in annoying the neighbors too.  Eliminating those and just having the remaining smooth fundamental bass tone emanating from the structure can sound more like an effort has been made to quiet things down -and excite the dB monitor's meter considerably less.

One customer of mine having major issues with his club has done everything he can with the outside of his heavy old masonry structure -to no avail, it was determined that the 100yr old single-layer uninsulated flat roof was letting more sound out no matter how much soundproofing was done to walls and doors!
In the end he just pulled the plugs out of the subs -making a choice between losing his licenses & business or keeping good sound wasn't hard for him.  It wasn't his fault that they build condos nearby after his place has been there for 25 years with no problems.  (Apparently the lack of 75Hz & below hasn't effected the cash registers at all.)
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Craig Hauber
Mondak Sound Design
-Live PA
-Installs
-Theatre
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