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Acoustic sealing a door. Seeking recommendations and a little science with db meter.

JakeK

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I've lined my detached garage with insulation, OSB and plasterboard (drywall) to soundproof it and now I need to add seals to the door. The thin metal door did very little to stop sound and I've filled it with insulation, added two layers of solid wood and finally stuck on some thin acoustic tiles. It looks like this:

PXL_20240903_143744006.jpg

I have a bluetooth speaker I've been using as a ~100db noise source.

PXL_20240903_130420318.jpg

With the door open and the meter 1.2m from the doorway it's 87db with the door open.

PXL_20240903_144959592.jpg

67 db with the door shut so the door is absorbing/blocking ~20db as it is.

PXL_20240903_145049523.jpg

So what sort of strips are best for sealing this door? I've bought some 12mm batwing door strips and also some D shape foam and I intend to test before and after fitting. I think I can use both at once as I've made an extra edge on the inside of the door. So what will work best and how much difference could it make? The gaps are about 3 to 5mm all around.


I'm willing to buy other things to test out if the're not too expensive. Ideally if they have some science behind them. After all it's about audio science!
 
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Besides an airtight seal, sheer mass is key for sound proofing.

Stuff like mass loaded vinyl (MLV), Privacyshield Soundproofing Blanket, Green Glue, and adhesive sound deadening mats (link) can be used to give the door more inert mass.

You could also consider replacing the insulation filling inside the door with sand.

Of course, much depends on how much weight the door hinges can hold :)
 
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This kit is not exactly cheap. You may be able to get the ideas and try assembling a kit yourself. There are also a variety of other soundproofing door seal kits available. Do a web search for "soundproof doors" for more info.

 
Besides an airtight seal, sheer mass is key for sound proofing.

Stuff like mass loaded vinyl (MLV), Privacyshield Soundproofing Blanket, Green Glue, and adhesive sound deadening mats (link) can be used to give the door more inert mass.

You could also consider replacing the insulation filling inside the door with sand.

Of course, much depends on how much weight the door hinges can hold :)
The door is several times heavier than it was already and I don't know how much more the hinges can take so I'm only adding lightweight stuff now.

This kit is not exactly cheap. You may be able to get the ideas and try assembling a kit yourself. There are also a variety of other soundproofing door seal kits available. Do a web search for "soundproof doors" for more info.

Yeah at $300 that's not cheap and I'm not sure those felt strips would suit my door. I did some research as came up with 'batwing' seals and the D section foam. Has anyone tried this stuff and actually measured?
 
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You could sweep frequency and then design your treatment from that.

As others have mentioned, replace the door with a piano practice room, recording studio, or audiology test booth door, which would require replacing the jamb. Some highly energy efficient doors, like those designed for a pasivhaus, have multiple edge seals, again the jamb comes with the door. That may give you energy efficiency benefits too. I would ask for sound attenuation specs vs frequency to evaluate before investing. Occasionally you can find used audio booths or practice room doors used when remodeling is done. Recording studios close and surplus their remains too.

You could put 2 doors with seals back to back maybe 6 inches apart.

There is a Facebook Room Acoustics: Absorption, Diffusion, and Soundproofing group, https://www.facebook.com/groups/751477978587349, and likely acoustics and architecture discussion boards.
 
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You could sweep frequency and then design your treatment from that.

As others have mentioned, replace the door with a piano practice room, recording studio, or audiology test booth door, which would require replacing the jamb. Some highly energy efficient doors, like those designed for a pasivhaus, have multiple edge seals, again the jamb comes with the door. That may give you energy efficiency benefits too. I would ask for sound attenuation specs vs frequency to evaluate before investing. Occasionally you can find used audio booths or practice room doors used when remodeling is done. Recording studios close and surplus their remains too.

You could put 2 doors with seals back to back maybe 6 inches apart.

There is a Facebook Room Acoustics: Absorption, Diffusion, and Soundproofing group, https://www.facebook.com/groups/751477978587349, and likely acoustics and architecture discussion boards.
Hi,

I'm not looking to replace the door, I've reinforced it instead. I guess buying a door with integrated seals is one way to go but I hope that adding sealing strips to this door will be enough. If not I'll add a heavy curtain inside the door.
 
You could sweep frequency and then design your treatment from that.

Not sure how I can do that as I don't have a calibrated microphone. Yet. I have considered getting a UMIK or similar but don't have a compelling reason at the moment. Nor do I have a good windows laptop which I think might be needed, only a chromebook. Also I'm not sure if this applied to door seals.

I'm planning to install and test the strips I have today once it's late enough in the morning to start sending 100db of noise through a closed door. Not sure if it's more valid to use pink noise or white noise. Pink noise has more bass but I don't think door seals will make much difference to bass.
 
sure if it's more valid to use pink noise or white noise.
Depends on what kind of noise you tend to emit from your garage :D

Ideally, record some of that and use it as your test tone.

If it's music, then use pink noise.
 
My internal doors are fire door and even without being airtight are very effective at stopping sound transmission. So I assume the mass of the door has a huge effect.
 
Depends on what kind of noise you tend to emit from your garage :D

Ideally, record some of that and use it as your test tone.

If it's music, then use pink noise.
Yes it's music I'm emitting mostly. I think I chose to use white noise previously as that plays louder on the Bluetooth speaker I'm using. I tried pink noise and that registers a few dB less on the meter at max volume. I'm worried now though as I just tried white noise and that's not reading as high as it did before when next to the speaker and the loudness is less consistent.
 
Welcome to the wonderful world of soundproofing. As people have said, sheer mass is the only realistic way to soundproof a door, other than having two of them of course. Studio doors are very heavy and expensive, mainly because of the issues with the seals around the doors which require an integrated frame and seal design. Any reputable studio will have two of them in a sound lock arrangement. But this is usually a bit much at home.

Comments about weighty dead damping materials are right on. But the hardest thing is the edge seals and the locks. Any hole bigger than 1mm will let quite a lot of sound in and out.

Suggestions:

- add an extra hinge to the door if it has only two
- add an extra hinge if it has three lightweight ones
- do add more damping
- add more weight
- that door handle/lock has to go. Most soundproof doors use wedge closures a bit like an old fridge. Holes through the door are a no-no. Separate non-piercing security lock required.

- door seals are a PITA. The bottom seal is usually the worst as it gets walked on or kicked.

For domestic purposes I have got reasonable results with products from some of the following:






Don't expect much more than 25 dB overall from one domestic-type door. Two of them in a lobby with acoustic absorption can give 40-50 dB depending on the quality of the doors, but that is I expect out of reach for you and probably unnecessary.

Did I mention that soundproofing is very hard, heavy and expensive? Sound treatment for acoustics is easy in comparison, and that's hard too... Good luck!

Former acoustic consultant, designed studios, rehearsal spaces and sound isolation... for money, natch.

PS After much pain and many flawed designs I generally found that a £1200 studio door that just worked was in fact the cheapest and quickest and least painful (except to the wallet) solution!
 
I had a bit of a problem getting consistent 99db white noise from the bluetooth speaker using bluetooth from my phone. It was varying from 93db to 96db per play which was odd as it has been a consistent 99db every time so I was worried the speaker might be failing due to being played so loud or maybe it was something with the sound subsystems on my phone as I had tried using a different, easier player on there. I moved to wired connection from a picoreplayer and that was more consistent so I stopped overthinking and just put up with the trailing cable across the room.

I read 69db outside which is up from 67db in my last test as the speaker is nearer the door than before due to the cable length and this might help accuracy slightly by having more signal over the ambient noise outside.

PXL_20240922_154132011.jpg

Then I added batwing seal strips all round but this meant the door wouldn't shut as there just wasn't enough clearance on the hinge side so I replaced it on the hinge side with the D section foam strip to have 3 sides batwing and 1 long side d-section and then I could close the door.
PXL_20240922_155917613.MP.jpg

After that I got 65db outside.

PXL_20240922_165241253.jpg

I had thought about using both types of strip together but it became clear this wouldn't work so I ripped off the batwing and binned it which removed plenty of paint. Then I made it d-section foam strip all round. This did make the door need a firm pull to close but it's OK and it should be worth it as long as the hinges don't break!

PXL_20240922_173014573.jpg

After that I got approx 64 db outside.

PXL_20240922_172718322.MP.jpg

I also tried adding some extra layers of a rectangular foam strip inside as a secondary seal but that made no measurable difference. One strip of d-section foam strip all round the door has made approx 5db of difference which is worthwhile as I can play music 5db louder while still not being noticeable outside. The door now blocks/absorbs 25db of sound compared to being open.

I've learned that d-section foam is more effective than 'batwing' type which some people recommend but not that different and that two types of seal together makes no measurable difference on my door. This might be different with a much heavier door which may be able to benefit from better types of seal and multiple seals. I think the door itself is now the limiting factor.
 
As others have mentioned, replace the door with a piano practice room, recording studio, or audiology test booth door, which would require replacing the jamb. Some highly energy efficient doors, like those designed for a pasivhaus, have multiple edge seals, again the jamb comes with the door. That may give you energy efficiency benefits too. I would ask for sound attenuation specs vs frequency to evaluate before investing. Occasionally you can find used audio booths or practice room doors used when remodeling is done. Recording studios close and surplus their remains too.
Using a heavier door and frame is probably the best advice!
 
Welcome to the wonderful world of soundproofing. As people have said, sheer mass is the only realistic way to soundproof a door, other than having two of them of course. Studio doors are very heavy and expensive, mainly because of the issues with the seals around the doors which require an integrated frame and seal design. Any reputable studio will have two of them in a sound lock arrangement. But this is usually a bit much at home.

Comments about weighty dead damping materials are right on. But the hardest thing is the edge seals and the locks. Any hole bigger than 1mm will let quite a lot of sound in and out.

Suggestions:

- add an extra hinge to the door if it has only two
- add an extra hinge if it has three lightweight ones
- do add more damping
- add more weight
- that door handle/lock has to go. Most soundproof doors use wedge closures a bit like an old fridge. Holes through the door are a no-no. Separate non-piercing security lock required.
These probably are the best advice but I don't want to go through that extra work just yet.
- door seals are a PITA. The bottom seal is usually the worst as it gets walked on or kicked.
Yes I found it a right pain carefully cutting and installing the batwing type only to end up ripping it all off. The whole thing was right fiddle!

Don't expect much more than 25 dB overall from one domestic-type door.
I've probably done the best I can if I've achieved near to 25db then!

Did I mention that soundproofing is very hard, heavy and expensive? Sound treatment for acoustics is easy in comparison, and that's hard too... Good luck!

Former acoustic consultant, designed studios, rehearsal spaces and sound isolation... for money, natch.

PS After much pain and many flawed designs I generally found that a £1200 studio door that just worked was in fact the cheapest and quickest and least painful (except to the wallet) solution!
That all sounds very true, thanks. I'm not ready to spend that much on the door yet though! Is that 1200 including fitting or will I have to pay someone a few hundred to install the thing as well? Fitting won't be that easy as the basic structure is thin concrete prefab panels.
 
These probably are the best advice but I don't want to go through that extra work just yet.

Yes I found it a right pain carefully cutting and installing the batwing type only to end up ripping it all off. The whole thing was right fiddle!


I've probably done the best I can if I've achieved near to 25db then!


That all sounds very true, thanks. I'm not ready to spend that much on the door yet though! Is that 1200 including fitting or will I have to pay someone a few hundred to install the thing as well? Fitting won't be that easy as the basic structure is thin concrete prefab panels.
I think you are doing pretty well there so far. It's always a question of balancing cost versus effectiveness. You probably don't need to buy a studio door in the circumstances, and if the fancy door is more soundproof than the building the cost (+ installation!) is wasted funds. What loss are you getting through the walls/roof? Perhaps 35 dB? Money should be targeted at the weakest link in the whole chain, until sufficiency is achieved. Have you got to a point where you can play/rehearse/record without being overly bothered by external noise and without bothering the near neighbours? Then that's probably good enough. Also, the 80/20 pareto rule usually applies: most of the improvement comes from a small part of the work. Figure out where there is still a problem, if there is, and attack that. Don't forget you need air to breathe ;) Oh, a hint: I have previously made a secondary door "seal" consisting of a sheet of 19 mm chipboard (OSB, plywood, MDF, what have you) with thick felt all over one side of it (perhaps acoustic foam other side), which I could hang on heavy hooks/stand on floor, pressing on the inside of the door and frame (felt to inside against door) covering the whole door and frame for another 10-12 dB reduction. Might work for you. And don't forget the breathing bit! And leaks through the keyhole! Cheers.
 
I think you are doing pretty well there so far. It's always a question of balancing cost versus effectiveness. You probably don't need to buy a studio door in the circumstances, and if the fancy door is more soundproof than the building the cost (+ installation!) is wasted funds. What loss are you getting through the walls/roof? Perhaps 35 dB?
35db is a pretty good ballpark figure of what the walls and roof are doing. Roughly 100db inside and I measure 56db outside (on the other side from the small door). I measured 13 db difference due to just the distance from inside to outside where I'm measuring so that leaves around 31db from the walls and roof. That would make a door system that does ~50db a waste of time and money as you say.

Money should be targeted at the weakest link in the whole chain, until sufficiency is achieved. Have you got to a point where you can play/rehearse/record without being overly bothered by external noise and without bothering the near neighbours? Then that's probably good enough. Also, the 80/20 pareto rule usually applies: most of the improvement comes from a small part of the work. Figure out where there is still a problem, if there is, and attack that.
I think it's pretty much good enough. My wife thinks there is a problem when she can hear music stood just outside the door. I think that if I play music at 90db inside it's 46db directly outside (apart from right outside the door) which is only a couple of DB over ambient noise while I can just hear it in my garden I find it hard to imagine that will bother the neighbours. So the door is the focus.
Don't forget you need air to breathe ;) Oh, a hint: I have previously made a secondary door "seal" consisting of a sheet of 19 mm chipboard (OSB, plywood, MDF, what have you) with thick felt all over one side of it (perhaps acoustic foam other side), which I could hang on heavy hooks/stand on floor, pressing on the inside of the door and frame (felt to inside against door) covering the whole door and frame for another 10-12 dB reduction. Might work for you. And don't forget the breathing bit! And leaks through the keyhole! Cheers.
That secondary door seal is not a bad idea apart from I don't know where I would put it when not in place. I'm going to have a look at the keyhole and door handle area next as that may be worth a couple of db.
 
How about a 2nd door with an air gap? One that opens inwards and the existing one, that opens outwards.
I don't have space for that unfortunately. I have been considering an acoustic door curtain as that won't take up much space. I'm not sure how many db a curtain could do but if it does about 5 or more that will be enough. It's something I mean to research and I would appreciate advice on. May be a new thread for that though.
 
The other thing that might be worth doing is a spectral analysis of the noise that is escaping. This does not need to be fancy. You can do this two ways: either compare the spectrum of noise inside the building and out, or do a sweep (REW can do this, or there's sweeps online) inside and out. The aim is to work out what frequencies are escaping. As a hint, bass is the hardest to stop: the only thing that stops it is mass, lots of. This is why you can often hear the disco down the road from some distance as thumps. If you generate white noise inside, outside it should fall off in roughly a straight line from bass to treble. If there are any bumps there is more sound leaking at that frequency (same applies to sweeps, should be a straight line falling off with frequency). Of course it never is, but you can get a clue to what the problem is from this. If there's bass lumps, tough, more mass needed. If middle, then there may be something resonating which can be damped. If high, it's a leak. This is very approximate of course. Good luck again.
 
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