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Soundproofing Bedrooms

Robert Car | Posted in General Questions on

What’s the general consensus for economically soundproofing bedrooms for guests/family comfort during normal daily life? I’m aware of using more than one layer of drywall, and would like to avoid this option.

Any ideas?

Thanks in advance for your advise,

Robert

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Replies

  1. Riversong | | #1

    The most economical way is to give out disposable foam earplugs to your guests and family members.

    Second to that would be to install insulation in the stud cavities and/or soundboard (Homasote) or resilient channels behind the drywall. Dense wall coverings limit low-frequency sounds. But the most important strategy is to avoid "sound flanking" through direct pathways, such as under doors, through HVAC vents, or back-to-back electrical outlets.

  2. Michael Chandler | | #2

    One solution we have used is to cover one side of the wall with therma-ply 1/8" structural cardboard sheathing such as is used by insulators to close the backs of knee walls in attics and spray it with a very thin, one inch "flash" layer of open cell spray foam. We generally do this on the "noisy side" of the wall esp in laundry rooms and bath rooms. the foam is a lousy sound emitter and it helps seal up electrical openings and flanking paths. Robert is right that you should look for those flanking paths under doors and through duct-work and electrical openings and we also sometimes will caulk the base plate to the floor.

  3. Riversong | | #3

    If the partitions are not yet built, you can also use staggered studs or an air gap between two 2x3 partitions.

    I am curious, though, why you've ruled out doubling the drywall thickness.

    Here are some good rules of thumb:

    - When the mass of a barrier is doubled, the isolation quality (or STC rating) increases by approximately 5 dB, which is clearly noticeable.
    - Installing insulation within a wall or floor/ceiling cavity will improve the STC rating by about 4-6 dB.
    - An airspace of 1½" will improve the STC by approximately 3 dB. An air space of 3" will improve the STC by approximately 6 dB.

  4. Ted White | | #4

    Robert, there's really no way around this. You're going to have to add significant mass to the wall as Robert Riversong suggested. I would avoid soundoard and resilient channels for several reasons.

    The lightweight foam and foil method mentioned would not provide a measurable benefit. No mass is why.

    Small point Robert R., but it's the entire wall whose mass would need to be doubled to increase isolation by 5 points. That means adding up the weight of both sides of drywall, the wall studs and insulation. Many people believe that doubling the drywall from one to 2 sheets is doubling the mass. It is not.

  5. Robert Car | | #5

    Many thanks to all for replying.

    I didn't want to use a second layer of drywall so space wouldn't get smaller. I thought perhaps stuffing some kind of insulation would do the trick (like Bonde Logic recycled denim, etc.), but after reading the answers, it seems clear to me that another layer is the way to reduce noise transmission, and it's probably the most economical one.

    If I go this route, should I use green glue to attach the extra drywall?

    If I were to use any insulation in addition, what would you recommend?

  6. TJ Elder | | #6

    Insulation in the stud bays definitely improves sound containment. Denser fiber is better, but even a standard fiberglass batt works. The denim batt you mention is a good choice. I think the highest performing material would be mineral wool, e.g. Roxul or Thermafiber. Dense-packed cellulose would also work well and has the best green cred (lowest energy embodied, highest recycled content).

  7. Ted White | | #7

    If you are going to the effort to add a second sheet of drywall (5/8" is best) then it would be a missed opportunity to also damp the wall with Green Glue.

    Interestingly, insulation in a single stud wall is good, but not great. The framing limits the contribution of the insulation. Since the wall is already drywalled, you're limited to blown-in cellulose or perhaps fiberglass. Just take care that the insulation doesn't get compacted during installation.

    If the walls were not drywalled, your best route would be standard R13 fiberglass. Why? Because it works best in the low frequencies. Mineral fiber has a slight edge in the upper frequencies, but that wall will not have high frequency issues. It will have low frequencies as the only significant frequency issue. Since fiberglass has the edge there, we use it.

    Surprisingly, the insulations that market themselves as "acoustic" have no lab data that supports they are a better choice. On the other hand, a great deal of work has been done by the NRC of Canada (finest acoustics lab in North America) gives us the data that shows cheap ol' fiberglass is actually the way to go. Go figure.

  8. Andy Ault, CLC | | #8

    Also, if you're going to go the "double board" route then consider three other options in lieu of gyp board only.

    First would be a product from Celotex called Sound Stop: http://www.blueridgefiberboard.com/pages/soundstop/pdfs/SoundStop-brochure.pdf
    We practically make this our SOP in walls between master baths and nurseries / adjoining bedrooms, etc. We bond the Sound Stop to the framing using an acoustical sealant running horizontal to the framing. Then we tape the joints with butyl tape. Next we layer the gyp board over that in a vertical orientation. It's quick, easy, and relatively cheap and gets very high marks from our clients.

    Next is a pricier, but conceivably better engineered, option, which is QuietRock: http://www.seriousmaterials.com/html/quietrock.html We've only used this in high-end home theatre applications, but it did perform as advertised.

    Third, and last, would be Mass Loaded Vinyl: http://www.soundproofing.org/infopages/flooring.htm
    We use this around plumbing chases to eliminate the "flush factor" We haven't used it in a whole-wall application yet, but another design-build contractor I trust has and says he gets great results with less dimensional gain than using something like Sound Stop or QuietRock. Again, it is a pricier option, but if that extra 1/2 - 3/4 inch of floor space is that critical, then it may be something to look at.

  9. Ted White | | #9

    I would disagree with all three of those choices for many reasons. Here are a few:

    #1 Sound Stop is simply another generic "sound board." Soundboard does not decouple, has very little mass and is to dense for proper absorption. Also the very limited if non-existent acoustic data makes this product all but abandoned by the acoustic community.

    #2 Any pre-damped drywall will perform well. The $85 a sheet material is a good performer. The $45 board is about the same as two layers of standard 1/2" drywall. You will always be able to field assemble your own board using standard 5/8" drywall and a damping compound. The resulting wall will be 1/2 the cost, and much higher performance. REams of independent lab data (including theirs) proves this. The product is fine, but the cost and waste makes this utterly wasteful.

    #3 MLV is simply mass. Drywall is mass, plywood is mass, etc. Mass is mass. At $1+ a square foot, you're better off using standard drywall from Home Depot.

    Andy I appreciate the fact that you've used these materials, however when we look at the raw data, these options are not at all optimal.

  10. Robert Car | | #10

    I'm finding that prices for options other than adding another layer of drywall can get expensive. Audimute offers a recycled rubber membrane that seems like a great performer, but by the time shipping is added, it goes for about 2 bucks sq/ft.

    I'm not trying to setup a recording studio, home theater, or anything like that. Still at framing stages, l'm looking for the best bang for the buck to help reduce noises before covering the sticks.

    So, to get the best result of the double drywall sheets, are there any recommendations on how should these be attached for best performance and keeping the budget low?

  11. Andy Ault, CLC | | #11

    Ted, thanks for the feedback. A few follow-on questions:

    1) you refer to "damping compund" - I haven't run across this before. Do you have a link(s) to a specific product I can learn more about for a field assembled solution? If there's something that's higher performing at a lower cost then I'd like to add that to our options.

    2) You mention the lab data which backs up certain solutions. I've looked at the basic STC wall assembly options when designing simple solutions as mentioned above, but haven't seen much else which goes into the details of alternate routes. Can you post links to some of this info that might be helpful in learning alternate designs and how they perform?

    3) You mentioned the "missing" acoustic data for the Sound Stop product, The PDF link I provided gives specific STC performance expectations based on prescriptive wall assemblies. Is this information inaccurate? If so, why, because i don't want to refer to it if it's flawed.

    Obviously we're using all of these options now and seem to be getting desirable results, but if we should be doing something different, I'd rather figure out alternatives sooner than later.

  12. TJ Elder | | #12

    I have worked on multifamily projects with acoustical consultants who specify wall assemblies, and their usual material palette is 5/8" gyp board, resilient furring, acoustical caulk and fiberglass acoustic batts. For certain applications with particularly high noise to suppress (e.g. adjacent to a machine room) the basic 1/2" RC furring gets replaced by RSIC furring, which is more reliable but takes more space. The caulk is for sealing along the perimeter of the gyp board. This approach is intended to be cost effective and repeatable for relatively large projects.

    Double layers of gyp board are typical for one or both sides of sound rated partitions. Electric outlets or switches should not be located back to back in the same stud bay, and they're often wrapped with putty pads or boxed out with sub-enclosures inside the wall. Sometimes there is felt or rubber weatherstripping at the door jamb.

  13. Garth Sproule | | #13

    I believe Ted White works for the "Green Glue" company and probably should identify himself as such. I have no experience with the product but all reports are that it is an excellent product for use as an acoustic damping compound. Works especially well on lower frequencies, even lower than those frequencies included in an STC rating. Their website is an excellent resource...

  14. Riversong | | #14

    At almost $15 per quart tube, that Green Glue better be magic.

    And "green" seems to refer to the color, not the ecological footprint or the health impacts - there is apparently no MSDS sheet available on their website and nothing indicating its ingredients.

    Additionally, their website is misleading and deceptive, since it claims that it "dissipates up to 90% of noise". Of course, anytime an advertiser claims "up to", that means "don't expect these results". But, more importantly, nothing can claim to stop 90% of some undefined "noise". STC ratings are all relative - they measure only the number of decibels of sound reduction compared to another material or assembly, and only over a specific weighted frequency spectrum.

  15. Garth Sproule | | #15
  16. Ted White | | #16

    Hi Andy. Sure thing.

    1) There are many damping compounds out there Swedak, Decibel Drop, Green Glue and Quiet Glue to name a few. Some work better than others. These are used in between standard drywall or plywood. They remove resonance in the panels, making them less able to transmit vibration. Some products are standard drywall panels with a damping compound applied in between at the factory. Examples are ComfortGuard, SoundBreak, QuietRock and Supress.

    2) Here’s a link to lab data for various assemblies: http://www.soundproofingcompany.com/library/green_glue_testing/
    http://www.soundproofingcompany.com/library/whisperclip_testing/

    These give you raw lab data (rather than a single STC figure) for walls with damping compound and resilient clips & channel.

    3) Giving a static STC figure is only a glimpse into what’s really happening. STC does not measure low frequencies, so when designing a room, we have to see all the raw data, preferably below 125Hz.

    As a side note look at the recommended attachment:
    -Secure the SoundStop to the stud with screws. That part is great
    -Laminate drywall (with a glue) to the soundboard, and secure to framing on the top and bottom (only) with screws. The rest is secured “intermittently” at 32” OC.
    -Building code dictates no more than 24” spacing to secure drywall.

    For wood framing, they require you to ractually emove the fasteners holding up the drywall after the laminating glue dries. This just isn’t reasonable construction, however the significant lack of fasteners is the only way to get remotely reasonable Transmission Loss test data. The problem is we don’t build buildings this way. Other “Sound Board” manufacturers require the drywall to be screwed into the soundboard only, not the framing. Sound boards are too soft to anchor drywall.

    Thomas Jefferson, I agree with your comments, however resilient channel isn’t spec’d by the SSMA (Steel Stud Manufacturer’s Association) so any manufacturer bending steel is free to come up with their own design for the RC-1. Some are too stiff, some are too flexible. It’s rolling the dice, and Resilient Channel acoustic tests that are sometimes throw around were done in the 70s and 80s by USG, who hasn't made the product since the 80s. Everyone else with their own designs is riding on that old data. Not appropriate at all.

    Garth, I don’t work for the Green Glue Company, and have taken care to avoid any reference to specific products. I am discussing data and principles, and only reference a product that someone else might bring up.

    Robert Riverstrong, If you’re interested, have a look at the data in my previous link. Damping as a method for acoustic isolation isn’t new. I agree that STC is nearly useless, as it does not look at data below 125Hz. I can’t speak to the verbiage on that website that bothers you.

    Thanks all.

  17. Ted White | | #17

    Garth, I'm with the Soundproofing Company, for full disclosure. I had not meant to make my posting here seem commercial, so again, unless someone else had a product-specific comment, I avoided any overt commercial reference. Some feel that this sort of full disclosure is itself marketing and some forums frown on it.

  18. Kelvin Joel | | #18

    i FOUND A COMPANY CALLED AUDIMUTE...http://www.audimutesoundproofing.com/Sound-Absorption-Sound-Blocking-Sound-Insulation-Material-Sound-Proofing-Material-Acoustic-Soundproofing.aspx... THE HAVE A Product called peacemaker, and that has worked wonders for me... you simply put it directly on the studs, and put a sheet of 5/8" sheetrock on top and your set... it makes the room almost completely sound proof... I put cardboard first, then lined it with the peacemaker, and put the sheet rock on top...

  19. Steve Knapp CZ 3A Georgia | | #19

    I want to see if I can resurrect this thread instead of starting a new one. Ted White's advice seemed focused on adding mass and sealing opening as the optimal approach for reducing noise. That's essentially what I'm considering for my new house (without getting carried away). Here is what I am considering as an approach.

    Putty packs on interior wall electrical outlets and switches.
    Double layers of drywall with Green Glue between the floor joists.
    Double layers of drywall with Green Glue on interior partition walls and on the basement and first floor ceiling.
    Sealing the first layer of drywall on all four sides.

    Thoughts? I considered using sound clips and resilient channel, but that might be more complication than I can handle. Would it be worthwhile to also add Rockwool?

  20. Margareta Svensson | | #20

    In such case you have to focus on absorption and acoustic treatment. Any kind of insulation within a wall's cavity will help to absorb some sound. When trying to reduce sound it is advantages to apply the soundproofing materials on the noise producing side of the wall. You can add extra dry wall to your existing wall. There is no need to build real wall. While thinking on soundproofing, damping is the main thing which is very efficient process with great soundproofing results.

  21. Expert Member
    Malcolm Taylor | | #21

    Steve,

    The basics: Fill the cavities with Roxul Safe and Sound and seal all penetrations and the perimeter.
    If you want to go further: de-couple the drywall by using resilient channels.
    Still not satisfied: Add layers of drywall.

    I'd suggest avoiding Green Glue. It is in the same category as roofing goo and acoustical sealant. If you are the one boarding the house you will end up with it everywhere. If you are employing a drywall contractor they will probably quit.

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