I know that these types of questions have been posted in the past. I live in a condo and , truthfully, the soundproofing between units is actually pretty good. We cannot hear things like people talking, TVs, and things like that. We did have some issues with low frequency bass from music, but one ticket from the cops put that issue to bed.

My question involves the use of dense packed cellulose. My wife and I were going to do some painting and crown molding, but before we did, we thought about seeing if there was any additional sound dampening we could do. I am familiar with the decoupling method which seems too expensive and involve.

I have heard really good things about dense packed cellulose. I had an insulator come out, who provided references for other people who used cellulose for noise reduction, and was actually surprised when he drilled some holes in our wall to learn that we had 6 inch open cavity in our walls with nothing but air. Am I wrong to assume that filling that with any type of Insulation, such as densed packed insulation would provide benefit ( ie something better than nothing). The insulator seemed to think we'd get a lot of benefit given the amount of unfilled space there. He claims cellulose performs well with lower frequency sound. Anyone have any experiences??

We do have some ups and downs with impact noises from our upstairs neighbors and the insulator rightfully said that cellulose would do very little for that kind of noise. He seems to be honest.

 

Welcome to the forums.

I'm not the pro here but an observation.....

Six inches of open wall between you and your neighbor ?
That doesn't sound right. If you intend to open the wall I'd look into what the firestop method is between units.

Roxul would be a good choice to be used there. ROXUL® | Fire and Soundproofing Insulation

 

Let me clarify. There is far more than 6 inches between my neighbor and I. However the open, unfilled cavity in wall measures about six inches. Thus, there is about 6 inches of open space that could be filled in.

 

A large open area between units like that does not make for a good firestop.

 

The cellulose will definitely help with sounds on the high end (although you say you don't have a problem with them now), but will do little for sounds on the low end. Low-frequency sounds travel through the structure, so the best way to deal with them is by using decoupling methods. And you are right, a decoupling option after a house has already been completed is costly, but since you only have to deal with the adjoining wall, and maybe the ceiling depending on what floor you live on, it may be worth the expense to eliminate the noise.