Sound Proofing Between Units

[Joel Florek]

I have a 4 unit building I bought this year and have been working on renovations. I just filled the last unit and am getting noise complaints about the sound. I popped a hole in the wall between the bedroom of one unit and the living room of the other and there is no insulation. There are two layers of drywall on each side so I would like to fill the cavity before trying to add an additional layer of sound proofing drywall.

I also have some considerable noise between the two floors. I have a drop ceiling which I could lay insulation on, or I could cut through the old ceiling with a layer of tin to blow in insulation. Any thoughts on what will be more effective?

Im looking for advice on the best type of blow in insulation for sound and suggestions on the ceiling issue.

[Mark Fedorov]

Not to crush your plans, but I worked in vibrational analysis for 5 years, sound has two characteristics that suck 1) they flow though both solid items and the air, and it is the connection between the solid items and the transition between solid items and the air that makes the difference in amplitude at the receiving end (so the way your joists and framing is connected to each other makes a major difference, that is also why drapes make a quieter room!). 2) sound is subjective based on the person hearing the sound and the frequency of the sound being transmitted.

Based on that, I would not do anything in the walls (which is expensive) unless ALL your tenants are complaining in this new building... don't ask them if it is ok, if they actively complain to you the problem is big enough for you to solve. Also, Keep in mind that affecting your tenants behaviors may be able to solve this for you. Does someone play the TV, but the have nothing on the walls, well that sound of the TV will go straight though the room to the other apartment, do you have hardwood floors? again nothing to stop the sound waves (my lease required 50% coverage by area rugs, I do not enforce that unless we get complaints).

If is quite possible you are chasing ghosts here, you can spend a lot of money sound insulating the place, and decrease all the sound frequencies above 125Hz, but not effect any sound at 50Hz and then your next tenant is a bass player and everyone complains.

You can get a professional sound meter from amazon for less than $20, those do not have frequency ranges, but they will let you know if the person who is complaining is crazy or not, and you can use that meter (that is calibrated) to compare against your local noise ordinance to see if there really is a problem. I suggest that be your first step.

Let's not forget that this may be solved by sending an email to the neighbors to listen to their music on headphones...