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Need soundproofing ideas to keep confidential conversations confidential
August 26, 2014 5:50 PM   Subscribe

The nonprofit that I work with just moved into a new office. The walls between offices do a lousy job of blocking sound - I can hear conversations being held in the next room in a fairly normal tone of voice. Management understands this is a problem but every dollar spent on facilities is less money to care for clients. Need to know what to propose beyond the ubiquitous white noise machines.

I tried googling this question and found too much information of questionable origins. (Half seemed to be selling things and the other half didn't seem to have any expertise. The best idea as far as I can tell is to put up a second layer of drywall with a layer of dampening goop in between. (Is it really that simple?) Do we need specialty sound-deadening board? Or could we get by with acoustic dampening paint?? We also need to do something about doors between the office and halls and space where an interior wall meets a window.

So, management's first answer was white noise machines but if they are actually in the room, I find they interfere with conversation. So, i would like to propose something better. If people agree, they will probably hire a carpenter or handyman to do the actual work.

Help me! (1) practical ideas or (2) links to websites that are reputable and (3) ideally information about how effective the different options might be. It doesn't need to be truly soundproof, just deadened enough that you can't hear the words from adjoining rooms.
posted by metahawk to Home & Garden (11 answers total) 1 user marked this as a favorite
 
How is the sound getting out? Directly through the walls? Through gaps between the walls?

There are white noise machines that actually vibrate what they are attached to, i believe to inhibit the transmission of sound through the material, they make a slight audible noise, but its fairly quiet. I don't know if they work on walls though, i've only seen them for doors. They are probably spendy unfortunately.
posted by TheAdamist at 6:08 PM on August 26


I've looked into this a lot from the recording studio side, and it mainly comes down to this: To reduce acoustic transmission, you need to remove air gaps and increase mass, and possibly also incorporate absorbing materials.

If you want a room to be soundproof for the purposes of conversation, the most effective thing to do would be to first make sure there are no air gaps around doors or windows. Once that's done, adding a layer of drywall with the "goop" (I think it's called green glue, or something like that, but it's not actually glue) inbetween layers will help significantly. This is assuming you have a "real" ceiling, and not drop tiles, and that the flooring is solid. You will also want to make sure you have a solid door, since most interior doors are basically just cardboard honeycombs with a hard outer shell, and do very little to block sound.

The key here is mass. Drywall is really heavy, which is why it works well to stop sound. It is much more effective than putting up a layer of plywood (which I've heard about people doing because they thought it would be easier to do than drywall).

Any special things like acoustic dampening paint (is this a real thing?) are pretty much going to be pointless or scams. Things like having double walls or isolation brackets to hang the drywall aren't going to be nearly as effective or cheap as just hanging an additional layer of drywall, which will be the cheapest and easiest effective method. I've never used the green glue goop stuff, but I have read that it is somewhat effective, and the time to put it on is when you are adding drywall, so that's something you might as well do, since you can't do it after the fact.

There are a lot of more advanced things you will read about, but a lot of the real tricky soundproofing problems are for lower bass frequencies, and won't be vital when you are talking about conversations.

The two best sources for acoustic discussion I've found are the John L Sayers forum (I don't know how active this is currently, I haven't been there in a few years), and the gearsluts.com acoustic forums (don't be put off by the name, gearslutz is one of the best sources for info about the music recording industry).

Using foam or padding in the room may give you an ever so slight change, but not significant. If you are going to end up tearing out the drywall in the walls, though, adding a good fill of insulation in the walls will give you a little more isolation.

I think the route you take will also be determined by what type of institution and how confidential the info is. If this is a medical clinic you may need to do a little more than if it is a food bank, or an artist collective.
posted by markblasco at 6:08 PM on August 26 [1 favorite]


Is the room air conditioned? We had this issue and a single air con unit helped a lot because the counseling room had to be sealed for drafts and the air conditioner unit is white noise, as well as more comfortable, and it doesn't signal eavesdropping prevention.

Also get a sign for the door if you can't for procedure reasons lock the door during sessions. A big reversible sign that says do not disturb is a simple way to help cut down on thoughtless interruptions.
posted by viggorlijah at 6:09 PM on August 26


The cheap way to insulate for sound in a rental is to hang thick wall curtains. They'll make the room look softer which can be a bonus for counseling. You might be able to get the material donated if you don't care much about the specific colour/pattern. Add a laundry budget item for maintenance though as they will get dusty and need washing every 6 months or so.
posted by viggorlijah at 6:12 PM on August 26 [1 favorite]


In our office the person *who can hear the conversation* next door turns on their radio or white noise machine to allow the counselling session to carry on privately.
posted by ThatCanadianGirl at 6:57 PM on August 26 [1 favorite]


I've heard people recommend mass-loaded vinyl instead of green goop, but I don't know enough to make a confident recommendation for your circumstances. Maybe another term you could research?
posted by d. z. wang at 7:27 PM on August 26


I've looked into this a lot from the recording studio side, and it mainly comes down to this: To reduce acoustic transmission, you need to remove air gaps and increase mass, and possibly also incorporate absorbing materials. [...]

The key here is mass. Drywall is really heavy, which is why it works well to stop sound. It is much more effective than putting up a layer of plywood (which I've heard about people doing because they thought it would be easier to do than drywall).


Respectfully, this is actually all wrong. Having air gaps is super important for soundproofing, and two layers of plywood with an air gap between them would provide significantly more noise reduction than a single drywall wall of a larger mass.
posted by Jairus at 7:55 PM on August 26


Put the white noise machine outside of the room, near the door.
posted by oceanjesse at 8:03 PM on August 26 [1 favorite]


"Having air gaps is super important for soundproofing"

markblasco's description threw me at first too however when they say air gaps need to be eliminated they are talking about cracks around doors, windows, and at the wall floor intersection. And it is indeed a requirement to seal those gaps to minimize high frequency transmission.

One thing not mentioned in this vein so far is if you have receptacles/switches on dividing walls those foam draft seal things that go behind cover plates are cheap and can make a noticeable difference in transmission.

It's also important to have an air gap between layers of sound deading material in order to minimize vibrational transmission. This is where things like isolation/sound bars to separate layers of gyproc comes in.

TL; DR: Some gaps good, some gaps bad.
posted by Mitheral at 9:12 PM on August 26 [1 favorite]


Sorry, I did mean air gaps such as space around the edge of the doors. A doubled wall system with an air gap in between would be a better option than just adding mass, but would also be significantly more expensive, and due to the description saying this is for a non profit, and the cost would come out of their budget for helping people, I don't think it's a realistic option to have done correctly. If they just need to isolate one room than maybe it's feasible, but I got the impression this was for all of the offices.
posted by markblasco at 7:40 AM on August 27


How many offices are we talking about? If it is more than about half a dozen, I bet it would be worthwhile to bring in an acoustician for an hour or two consult. They will be able to tell you exactly how much and what kind of mitigation you need, and you will save their fee (a few hundred dollars, most likely) on over-doing acoustical improvements, or on coming back a second time to correct deficits in a first round of work.

An acoustician on-site listening critically to your situation can work magic -- they can identify the frequencies that are being transmitted, what level or improvements are required, the most cost-effective way to achieve the desired result, etc.

(if you memail your location, I can possibly suggest a local acoustician, if you happen in to live in one of a half-dozen cities)
posted by misterbrandt at 9:53 PM on August 31


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