Retrofit Sound Transmission

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Author Message David J. Wyatt, CDT Senior Member Username: david_j_wyatt_cdt Post Number: 93 Registered: 03-2011 Posted on Thursday, September 04, 2014 - 01:55 pm:    Has anyone successfully used blown-in or poured insulation in an existing wall to reduce sound transmission? The client has an office with a bathroom that apparently has no sound batts in the walls and it has become an issue. Any advice will be appreciated. Dave Metzger Senior Member Username: davemetzger Post Number: 532 Registered: 07-2001 Posted on Thursday, September 04, 2014 - 02:09 pm:    Sound transmission is reduced by mass, and by sealing of gaps (eg around cutouts in gypsum board for switch and outlet boxes, and around wall perimeter). Blown-in insulation is lightweight, so I wouldn't think it would contribute much to reducing sound transmission. If it is possible to add an extra layer of gypsum board, that would be more beneficial to improving the STC of the wall. ken hercenberg Senior Member Username: khercenberg Post Number: 822 Registered: 12-2006 Posted on Thursday, September 04, 2014 - 02:18 pm:    Agreed. Blow-in usually doesn't fill all the voids anyway. Adding gyp board, with correct placement of acoustical sealant per Gypsum Association would be my recommendation as well. Consider the new acoustical board from National Gypsum. It seems like it works pretty well. Jeffrey Wilson CSI CCS SCIP Senior Member Username: wilsonconsulting Post Number: 149 Registered: 03-2006 Posted on Thursday, September 04, 2014 - 02:32 pm:    I would argue for blown-in cellulose in addition to the treatments suggested by Dave and Ken. Cellulose is actually quite dense and completely fills the wall cavity when installed properly, and from experience in my own home, by itself produces substantial reduction in sound transmission. Jeff Wilson Wilson Consulting Inc Narberth PA William C. Pegues, FCSI, CCS Senior Member Username: wpegues Post Number: 921 Registered: 10-2002 Posted on Thursday, September 04, 2014 - 03:09 pm:    There is a very nice sound mat product that I have actually had a chance to use personally as well that I would not hesitate to recommend. http://www.unitedplastics.com/consumer-db-4flooring.php Though this is listed as a flooring product, this was the manufacturer's recommendation for heavier noise issues that I was facing. Maybe one of the other wall only products (made similarly) would be more suitable, but this stuff really works. My situation is a townhouse where there a common demising wall is well constructed, but we could hear their parties and they could hear my sound system. I put acoustical sealant continuously around the perimeter at floor and wall joints, all 4 sides. this sound mat which is a rubberized soft material on 1 side and a fluffy sound material on the other was then hung up, simply nailed to the top of the existing wall surface. Joints were taped. Then a layer of drywall was put on top of that. I chose the new drywall to be Type X board for the extra mass (my side has more base sounds where mass helps more), and had it be 5/8 inch thick as well. For the situation describe above, maybe the acoustical boards would work as well. The new layer of drywall was installed so that none of its edges touched the ceiling or the sides or the floor, and again, acoustical sealant to isolate the perimeter conditions for the new board. Then it was taped, finished, sanded and painted. Now totally silent. So, additional thickness in my case was the 5/8 inch drywall plus the thickness of the db4 material which was maybe the plus side of 1/4 inch. William C. Pegues, FCSI, CCS, SCIP Affiliate WDG Architecture, Washington, DC | Dallas, TX David E Lorenzini Senior Member Username: deloren Post Number: 160 Registered: 04-2000 Posted on Thursday, September 04, 2014 - 03:21 pm:    It should be noted that mass is effective in the reduction of low frequency sounds, and is used a lot for isolating mechanical equipment noise. David Lorenzini, FCSI, CCS Architectural Resources Co. David J. Wyatt, CDT Senior Member Username: david_j_wyatt_cdt Post Number: 94 Registered: 03-2011 Posted on Thursday, September 04, 2014 - 03:39 pm:    Thanks, everyone. This is a genuine community of professionals exchanging ideas. Scott Piper New member Username: spiper Post Number: 1 Registered: 08-2014 Posted on Thursday, September 04, 2014 - 04:27 pm:    I would agree with David that the frequency of sound that you are attempting to diminish is key. It should also be noted that if the bathroom is a smaller single user toilet with a hollow core door and a large undercut then all the work to sound-proof the walls may be for naught. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1588 Registered: 03-2002 Posted on Monday, September 08, 2014 - 10:27 am:    If the issue is bathroom sounds coming into the office area, these are probably higher-frequency sounds that would be blocked more easily. (Except for toilet flushing, which would have both high and low.) Blown-in insulation may help some. Adding drywall would probably have to be done on the office side, but would probably be more effective, but more expensive. If you add drywall (and have the space), you could mount two layers on properly-installed acoustic furring to get even better sound damping with minimal added cost.