Non-destructive soundproofing for doorways

Hello! I have been feverishly reading up on the wealth of information on this site for the past week, thanks to all contributors. This is my first post, and I am seeking advice on the best way to soundproof 2 wooden doors that lead to my studio (in Los Angeles, CA). I am only concerned with preventing sound from getting into the studio from the kitchen and entryway which are common areas shared by my 6 housemates. I am a cellist and I primarily record acoustic orchestral instruments, so the sound I produce will not bother my housemates, but the sound they make (footsteps and voices primarily) will certainly disturb my low volume recording. Now the bad news is that I am a renter and cannot alter the construction of the doors at all. However the good news is that there is a 3rd door that leads outside, thus I do not need to use the other 2 doors so I can seal them off. So the question what is how to stop as much sound transmission as possible through these doorways without causing any damage to the wood of the doors, frames, or walls. I am no soundproofing expert, but from reading up on the subject I came up with 2 potential solutions that might combine to attenuate enough noise: 1) sealing the cracks between the doors and the door frames with rubber or putty, and 2) building broadband absorption panels that cover the entire area of both the inside and the outside of the doorways. I am completely open to any other solutions, but here are my specific questions about this method: What substance is best for sealing cracks and not damaging wood? This is to fill the gaps between the closed doors and the door frames. These cracks are extraordinarily uneven, ranging from a tiny slither to a 1/2 inch gap. I am assuming that all kinds of caulking, acoustic or otherwise would damage the wood but please correct me if I am wrong. Out of the potential 4 large panels to build (interior and exterior of each doorway), 3 of them have a 5 inch recess that could potentially be a slot to slide the panel into. For example Door 1 is 83'' wide, 72" tall, and 2.5" thick. I am thinking that I would slide a 83" x 72" x 6" panel into the doorway recess (so the panel would stick out 1 inch. The other option I can see would be to build the panel slightly larger than the dimensions of the doorway (maybe 96" x 84" x 6" and leave the 83" x 72" x 5" gap). I am not sure whether or not it would advantageous to leave such a gap in this situation. The dimensions of Door 2 are 82" x 27" by 1.5". This door also has a glass pane which allows even more sound transmission. I am thinking basically the same plan for this one. Also, I am wondering if it might be effective to use wood on the outside face of the 2 panels that would face the common areas. Since they would be facing the source of the problematic noise in this case, wouldn't a large amount of reflectivity help? I am planning on following the basic construction outline of the DIY sound absorption panels, just with increased dimensions, but I am wondering if using a large piece of plywood (or medium density fiberboard?) on those 2 outward facing panels might help. I am also trying to figure out what kind of insulation to use. Maybe Roxul Mineral Wool, maybe fiberglass, maybe denim. It would be ideal to spend less than $400 on these 4 panels, but if cheap insulation is going to make these panels totally ineffective than I might bite the bullet and spend around $800. Any advice would be greatly appreciated. Thanks so much!

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I knew that I had to provide my location but didn't realize it needed to be in the profile section. Sorry, my mistake.

Hi Chris, and welcome.

1) sealing the cracks between the doors and the door frames with rubber or putty,

Sealing cracks will help, but it probably wont be enough. You need mass, and those doors don't have it.

2) building broadband absorption panels that cover the entire area of both the inside and the outside of the doorways.

contrary to popular belief (and intuition), absorption does not stop sound. Think of it this way: can you stop the water coming out of a tap by putting a sponge over the tap? There's your answer: the sponge soaks up water really well, but cannot stop water getting through. Same with sound: you cannot stop sound by putting an acoustic "sponge" in the way. You need mass. Acoustic absorption is a necessary part of treatment and isolation, but it cannot isolate all on its own, in any reasonable thickness. The normal way of dealing with a problem like yours is to build a "plug". Basically, a large piece of wood, or maybe a wooden frame with drywall on it, rubber seals around the edge, and absorption attached to the back (mineral wool, pink fiberglass, 703, etc). You build it carefully so that it is a tight fit into the frame around those doors, and so that the rubber seals tightly. That will do the trick. HOWEVER! That may not be the entire problem. You mention. "but the sound they make (footsteps...". Footsteps. That is impact noise, not just airborne noise, so it might be flanking through the building structure itself. If so, then the door isn't the problem: the entire building is the problem. I'd suggest that you should try to determine if the footstep sounds really are coming only through the doorway, or if they might be coming through the floor/wall/ceiling structure itself. I'd start with that, before spending too much money on building the plug. - Stuart -

The footsteps are on the hardwood floor most likely, not in an overhead area. Any door that you can shut off, that does not have to be used, then you should at minimum stuff loose insulation into the cracks around the perimeter of the door(s) as a start. Doors that glide on a track or slide require modifications. It could be as simple as a rubber seal nailed into the door edge to reduce the flow of sound through the crack. The bottom of the door, being elevated might take something as simple as a dense material pushed up to the bottom of the door to slow those areas. Doors are difficult and need attention that cannot be administered directly if you cannot modify the door so you have to go with simple things that produce mass as Stuart suggested but do not alter the interior environment and can also be easily removed. Weather stripping on the door edges at the jamb area might help as well.

Thanks so much for the replies! I don't believe there is not much that I can do about noise flanking through the structure since I can't do any structural modifications, so perhaps building the plugs and getting my roommates to tread softly by my doors is going to be the way to go! So figuring out exactly what design and materials to use for these plugs is the next step. It seems like this DIY Gobo Design DIY Gobo Design is approximately the right structure. How might I modify this for maximum effectiveness? It seems like adding additional layers of drywall would help by adding more mass.... Thanks again!

Sir, I believe I explained that flanking in respect to an overhead situation is not your problem. what you are dealing with, and you correct any time I am incorrect, is that you have hard wood floors and walking around on them is causing vibration that moves directly under the door, around the door and into what ever penetration are at the doors there may be. Back to the gobos...not much help at this point. You have to stop the sound at the source of penetration which is the cracks around the doors...you can trust that:)

Yes Xspace you are correct, sorry I suppose I misused the term flanking. I just meant the sound of footsteps going through the hard wood floors. However, that is definitely not the only sound I am trying to stop. My housemates are all musicians and they make all kinds of noise, from walking to talking to playing all varieties of instruments (guitars, bass, drums) both amplified and acoustic. I know that keeping all sound out is probably impossible without modifying the construction of the house or having a bigger budget (mine is $800 max), but I want to stop as much sound of all kinds as much as possible. So I am thinking that I will get the best results if I combine the sealing of the cracks around the doors with adding mass with the gobos. For the sealing of the cracks: Weather stripping or any kind of rubber seal seems impossible to install without nailing it to the door. I am wondering if it might work to use painters tape to protect the door and door jamb so I can use acoustical caulking to seal the cracks. A bit risky, but it seems like if the tape easily stops paint it could stop caulk as well..... also expanding foam seems like it might work for the same purpose. For adding mass with a gobo: Here is a tentative plan for doorway 2 (the one with heavy sliding doors, see pics in first post): I would build 4 gobos, 2 to cover the inside and 2 to cover the outside. I'd build them to these specifications here, just modified to the dimensions of the doorway so that each gobo is the size of each door. I could also try to seal the gobos into the doorway with either a rubber seal nailed to the gobo, or using the painters tape with caulking/expanding foam technique mentioned above. Would leaving a gap between the door and the gobo be advantageous? It seems like facing the reflective side towards the unwanted noise source would be most effective, but what about the interior side? All advice on how to modify or completely revise this plan is most welcome. Also, thanks for help thus far!

I have the perfect idea, I had to implement this some years ago myself. Get rid of the room mates :) I'm kidding...I meant you need to move. Still kidding...

So I am thinking that I will get the best results if I combine the sealing of the cracks around the doors with adding mass with the gobos.

You seem to be missing the point of isolation: Gobos are not meant to isolate a room, and indeed cannot isolate it. Gobos are treatment. Putting a couple of gobos in the room will do nothing at all to keep the footsteps and other noise out of the room. All that gobos will accomplish is to maybe improve the acoustics of the room itself. Yes, sealing the gaps around door will help, and yes you need mass, but unless you put the mass into the doorway so that it seals tightly all around, then you will not get the isolation. That's why I mentioned the concept of plugs.

also expanding foam seems like it might work for the same purpose.

If you are talking about the typical closed-cell polyurethane foam that comes in a spray can, then that isn't very useful acoustically, and sticks like crazy! Even better than caulk. You also seem to be missing the point of sealing: If you put masking tape on the door then aply some type of sealant on top of the tape, trying to stop it from touching the door, then you are defeating the purpose of the exercise! To "seal the door" means that you seal the door! Not the tape. The sealant has to contact the door and the jamb, all the way around, to be effective. If you absolutely cannot stick any sealant to the door, then just buy several meters of rubber seal, the kind the use around car doors, and stuff that up all around the edges of the door, on both sides, then put tape on TOP of that, to keep it in place. The tape does not seal: the rubber does that. The tape is just there to keep the rubber in place. You'll probably need about 30 meters of rubber strip to do that. Get the very flexible soft spongy kind, just like you find around the edge of your car door. Don't get a hard rubber.

I'd build them to these specifications here,

Once again, that's a gobo, not a plug. It won't help to isolate, since it is treatment. What you need is a plug, not a gobo. And yes, you do need to seal it in place with the same kind of rubber strip that you use on the door. It must be an airtight seal, all around the door frame. So you will have two seals: once around the edge of the door itself, and one around the plug.

2 to cover the inside and 2 to cover the outside.

Bad idea! that would make a three-leaf system, which would REDUCE your isolation for low frequencies. The footsteps and drums would be louder like that, not quieter. Although the voices would be gone, for sure! [quote]It seems like facing the reflective side towards the unwanted noise source would be most effective, quote]It would make no difference at all. If you went with gobos, instead of a plug, you could face it either way, and the result would be exactly the same: no isolation. - Stuart -

Thank you for your detailed reply Stuart! I was attempting to follow the suggestion in your previous post and build a plug, You described a plug as: "a large piece of wood, or maybe a wooden frame with drywall on it, rubber seals around the edge, and absorption attached to the back (mineral wool, pink fiberglass, 703, etc)" I was trying to find an alternative to the rubber seals, but other than that the gobo sealed into the doorway seemed to fit that description pretty well. Obviously I was not correct. So the plug is a simpler structure, right?. In its simplest form it would be a single piece of wood as big as the entire doorway with a layer of absorption attached to the back (and rubber seals along the edges). The slightly more complex form substitutes the single piece of wood for a single piece of drywall in a frame built out of wood. I am wondering which of these 2 options has more stopping power, and how thick each layer should be in either case. I have 5 inches of depth in the frame so perhaps 5/8 inches of drywall or wood and 4 inches of insulation? Should I press the absorption side all the way against the door or leave a small gap? Thanks again!