Solid Wood Door treatment

[whitewatersound]

I am new to this forum and I am building a project studio and have a single 1 3/8 solid core door that separates my 11X16X10 control and 16X25X10 studio. It is new construction with no acoustical treatment. There is currently no threshold and I have solid hardwood floors that continue from one room into the other. What would be best without wasting my money? Also, I have french doors into the house that are untreated and would like to add something there too.

[Soundman2020]

Hi there "whitewatersound", and welcome to the forum!

You didn't say what the problem is with the door, but I'm assuming that it is not isolating as well as you want. If that's the case, then you will need to firstly ensure that it is sealed absolutely air-tight all the way around the perimeter, with suitable rubber seals that are correctly mounted. You can either search the forum to find DIY solutions for doing that on your own, or you can buy ready-made commercial seals that are specifically designed for this, and all you need to do is to install them. I recommend that you take a look a the Zero International catalog, so see what types of seals they have, especially for the threshold which is hard to do by yourself, but also for the sides and top of your door.

If you do that and still are not getting enough isolation, then you might need to add more mass to the door, as well as a second set of seals. "More mass" could just be a sheet of 3/4" MDF screwed or plywood and glued on top of the existing solid-core door. However, if you do that then you'll likely also need to replace the hinges with heavy-duty hinges, and you'll likely need 4 of them, not the usual 3. You can add the extra one a couple of inches below the top hinge.

If that still does not give you enough isolation, then the problem is probably not the door, but rather the entire isolation design: there's something wrong with the way the walls were designed and built, or the ceiling, or the floor, or the HVAC system, or the electrical system.

On the other hand, you mentioned "treatment" in your post, so maybe the issues is not isolation at all, and you have concerns about flutter echo or other forms of reflection from the door, messing up the acoustics within the room? There are solutions for that too, but it would be better if you could explain more clearly what the problem really is: is it isolation, or is it treatment?

Please provide as much detail as possible about the entire studio, so we can get a better idea of what you have, and what your goals are. Photos are a great help, and also a diagram or plan of the studio, with dimensions, shapes, and construction details.


- Stuart -

[whitewatersound]

Thanks Stuart,

These are both new normal residential constructed rooms with windows. I will try to post more specifics with some photos. Isolation is my problem right now, as I stated. There is no weatherproofing type of insulation at all right now. So I need to make the doors airtight. I understand that.

Are there special types of door thresholds or materials for making this air tight that I should be looking to buy or build?

[whitewatersound]

Zero International catalog.... got it. Thanks.

[Soundman2020]

Isolation is my problem right now, as I stated.

Actually, you didn't mention isolation at all! You said you needed "treatment", which is an entirely different aspect of acoustics. Isolation is what you do to a room to stop sound getting in and out, so isolation makes the room sound bad inside. Treatment is what you do after the isolation is completed, to make the room sound good again. They are frequently confused, but they are two very different and independent aspects of acoustics, and they are diametrically opposed. Isolation uses mostly massive, heavy, hard, rigid, stiff, reflective, air-tight materials. Treatment uses mostly light-weight, soft, flexible, fluffy, absorptive, porous materials. There is some overlap, yes, but in general they are at opposite ends from each other, and they do opposite things.

So you need isolation, and you suspect that the door is the issue, since it is not sealed. As I said, take a look at the Zero International catalog: they have an entire section on acoustic seals for doors, with a couple of pages on threshold seals. But I forgot to post the link! Sorry about that. Here it is:

http://www.zerointernational.com/

They are not the only manufacturer, but they make some really good stuff.

There is no weatherproofing type of insulation at all right now.

Excellent! Because normal weatherproofing products are not the best way of doing this. The type of weatherproof products that you buy at Home Depot will help to a certain extent, but they aren't really designed to be acoustic seals, so they are not as effective as the specially designed products. Here's a couple of direct links to pages in the Zero International catalog about proper acoustic door threshold seals:

http://www.zerointernational.com/catalo ... ?pageID=13
http://www.zerointernational.com/catalo ... ?pageID=14

The also offer the seals for the rest of the door perimeter:

http://www.zerointernational.com/catalo ... ?pageID=53


It would also help if you could specify how much isolation you need. I suspect that the the doors might not be the full extent of the problem. You said:

These are both new normal residential constructed rooms with windows.

Typical residential walls will provide about 30 dB of isolation. Most studios need about 50 dB of isolation, which implies that they need to block one hundred times more energy. Getting to that level of isolation is possible, but not with normal home walls. Sealing the door perimeter is very necessary, and you will need to do that anyway, no doubt at all, but that won't provide more isolation than the walls are providing. For example, if you complete your door such that it gives you 45 dB of isolation, but the walls are providing only 30 dB of isolation, then your TOTAL isolation is 30 dB: Sound is a bit like water, in the sens that it takes the easiest path out of the room. So if you have a great door, it will ignore that and go through the wall. And if your doors and walls are both great, then it will take a path through the HVAC system, or electrical system, or the ceiling, or the windows. You have to isolate ALL parts of the room to the same level, in order to get good results.

Also, I have french doors into the house that are untreated and would like to add something there too

Are those the typical sliding glass patio doors that you see in Home Depot and similar stores? If so, then you'll need to replace those with proper acoustic-rated doors. Ordinary patio doors have thin glass in them, thin frames, and no seals, or just simple brush seals and thin rubber strips to stop water getting in: That's totally inadequate for acoustic isolation. The glass has to be thick laminated glass, the frames have to match the surface density of the glass, and there need to be multiple hermetic seals around the edges.

I have solid hardwood floors that continue from one room into the other.

What is under that? Is it laid directly on the sub-floor, or is there an air gap under it? Hardwood floors generally do have an air gap under them, which is a problem. Also, what is the sub-floor made of? Is it a concrete slab on grade, or is it plywood over joists over another room, or over a crawl space?

Those are all very different scenarios. If this is a typical residential home, then I'd suspect that you have the worst-case scenario: joists over air with plywood on top, then the hardwood over that. If so, then that is a major flanking path between rooms: regardless of how well you seal the door, sound will simply "flank" around it through the floor structure, and into the other room. This is especially true for impact sounds, but also still very problematic for airborne sounds. If you need high levels of isolation, then that will need fixing too.


- Stuart -

[whitewatersound]

It would also help if you could specify how much isolation you need.

This is what I am trying to determine. I do know that I will have to beef up the door with seals,etc. (thanx for the links).

Also, what is the sub-floor made of? Is it a concrete slab on grade, or is it plywood over joists over another room, or over a crawl space?

The whole of these two rooms, while they are very nice living spaces, are built over a 6 ft crawl space with CB foundation and the joist floor has a sub floor and real wood hardwood slats installed (no air gap). When they attached the ductwork for the HVAC (which I might add is very quiet since it is new and physically exists in another portion of the house) they screwed them to the joists and this causes creaking. I am not happy about that! Also there undoubtedly is the problem you mentioned about the flowing of sound vibrations (flanking) through from room to room.

Are those the typical sliding glass patio doors that you see in Home Depot and similar stores?

The french doors swing independently into a tiled 8 ft. breezeway attached to the house. They are two separate doors with 16 panes each, but isolating them is not critical due to the fact that I do not plan to be using the other side for recording unless for a vocal booth possibly. This is my entrance into the control room. There is a lot of glass there and it may become useful for an highly reflective echo type of sound if this entire space is salvageable at all.

[Soundman2020]

This is what I am trying to determine.

The best way of doing that (in fact, the only accurate way) is with a sound level meter. You can buy a good one for around US$ 100 on eBay or Amazon (just don't buy the cheap Chinese garbage! They are little more than toys...) Look for an Extech or Galaxy in that range, and make sure it has both "A" and "C" weighting, and both "Fast" and "Slow" response. Additional features are good to, but it must have at least those.

Once you have your meter, a good way of determining how much isolation you have at present is by simply making a noise and measuring it! Set up some good full-range speakers inside each of the rooms in turn, and play loud music through the system. Use the type of music that you'll normally be recording / mixing in your studio. Play it at around 100 dB as measured inside the room at least three feet away from the speaker(s) (use "C" weighting, "slow" response on the meter). And wear ear protection while you do that. You might also want to warn your neighbors in advance that you'll be doing an isolation test for a few minutes with loud music. Then Walk around the rest of the house taking careful measurements in the other parts of the studio, and the other rooms in the house: Make notes about where you take each reading, and what the reading was. Do the same outside: walk around all sides of your house, measuring about three feet away from the walls, and also at your property line, in several different locations. This part of the test will give you a god indication of how good the isolation is right now.

The second part of the test is to then go back to the place where you recorded the LOWEST level outside your house (quietest) and get someone else to slowly turn down the volume on the speakers until you can't hear it any more when standing in that location and keep it at that level. Now walk around to all the other points where you took measurements before, and note down the new lower level for each location.

The final part of the test is to then go back to the place where you recorded the HIGHEST level outside your house originally in the first test, and once again get someone to slowly turn down the volume on the speakers until you can't hear it any more when standing in that location, or at least until you think it is at a reasonable and acceptable level for that location. Now with the system still playing at that new lower level, go back inside and measure 3 feet from the speakers once again, to see how loud they are playing.

You now have enough data to figure out how much isolation you have, and how much more you need.

All of those tests should be done with the windows and doors tightly closed, or course.

The whole of these two rooms, while they are very nice living spaces, are built over a 6 ft crawl space with CB foundation and the joist floor has a sub floor and real wood hardwood slats installed (no air gap).

That's sort of what I was expecting you'd say... Not the best situation, since basically both rooms are sitting on top of the same "drum head". So any sound or resonance in either room will get through the crawl space to the other room, either via airborne transmission or by structure-borne flanking. If you plan on recording drums, bass guitar, piano, or anything else that has potential impact noise, I'd suggest that are going to need a "drum riser" type of platform to improve the impact isolation.

Also, is you have access to the crawl space, you might want to consider getting in there to "beef up" the floor from below, with extra mass and damping. (Assuming you need good isolation).

When they attached the ductwork for the HVAC (which I might add is very quiet since it is new and physically exists in another portion of the house) they screwed them to the joists and this causes creaking.

So they did it the "quick and cheap" way, not the right way! You seriously should consider re-hanging those ducts on isolation hangers, to help prevent sound form your studio from flanking into the rest of the HVAC system, and hence the rest of the house. You'll also need to install silencer boxes between the main ducts and the branches that go to/from your studio rooms: HVAC is a major source of sound transfer between rooms. You can have the best isolated walls, doors, windows, ceilings and floors, but if you have ordinary HVAC installation with no silencers, then you don't have any isolation at all. Even normal speaking voices in one room will be audible in the other room.

When you take those photos around your place, see if you can get a few inside the crawl space, showing how those ducts are mounted, and how they connect to the registers.

The french doors swing independently into a tiled 8 ft. breezeway attached to the house. They are two separate doors with 16 panes each, but isolating them is not critical due to the fact that I do not plan to be using the other side for recording unless for a vocal booth possibly. This is my entrance into the control room. There is a lot of glass there and it may become useful for an highly reflective echo type of sound if this entire space is salvageable at all.

Ahhhh! OK, I thought you were talking about sliding glass doors. It might be possible to seal up those a bit better, to improve isolation.

I'm sure your rooms can be "salvaged" for a studio! They are decently sized, and one of the good things is that they have very high ceilings: 10 feet is unusual in typical houses these days. That allows for a lot of options, for both isolation and for treatment.

Anyway, if you can provide photos and more details, and also do those tests to determine how much isolation you need (in decibels) then we'll be able to help you figure it all out!


- Stuart -

[whitewatersound]

This floor plan drawing seems to be a preliminary work in progress but is close to accurate. There is an outside door in the lower right corner not shown where a window is drawn (the window was replaced with a door). Also, the french doors are added, but the breezeway has two opposite heavy duty sliders instead of what is shown. The entire addition including the bath is 10 foot ceiling height except for the breezeway which is 7 foot 10 inches. Also, I think the room sizes are more accurate than I first stated - 10X15X10 (closet included) and 25+X15X10. Thanks for all your comments up until now Stuart. Proceeding with the SPL meter measurements.

floorplan.jpg