We did the wall between the living area/bedroom as well as the kitchen/bath. Can't really tell you yet if it made a difference because we are still building, but for the miniscule cost, if it reduces a little, then worth the effort.

I believe johns manville or owens corning makes a sound deading batts. I believe it's a little more dense than standard batts.

It's a minimal expense and it might help a little. However, you have to remember that sound travels well through dense materials and sound in one room will be transmitted through the sheetrock to the studs in the wall to the sheetrock on the other side.

Another consideration is what type of heating you have and whether you can change the amount of heat to individual rooms. Once you insulate an interior wall it will significantly reduce heat flow through the wall and you could end up with one part of the house warmer or cooler than the other part of the house, unless you have a way to compensate for that.

when we remodeled we put insulation in all interior walls. The noise reduction was significant and we also found that the rooms stayed warmer/cooler for longer. Heating and cooling bills were generally lower than before.

I did regular old fiberglass batts between wood panel living room wall that the TV sits infront of and plastered bedroom wall hoping to eliminate the tv sounds. Worked perfect!

Now the sound comes down the hallway and in through the door. Close the door and its quiet now. Before, the sound definetly came from the direction of the living room wall.

Difficult to deaden sounds - many different types of sounds as well - foot fall, voices, etc... - Using insulation batts btwn interior walls may have some effect - I would suggest if doing so, do yourself a favor & use mineral wool Roxul is a brand I believe made in Canada avail here & I found it to be same cost as pink insulation - this is what they use in sound studios & has been traditionally used as firestopping product for yrs -

The other suggestion is to use 5/8" sheetrock - which will help deaden better than the 1/2" - I used a j channel in my living room ceiling - attaches to the joists then applied sheetrock to that - which eliminates sound being transmitted to studs as described above.

HTH - good luck

bmmalone-
With all due respect, I don't understand how insulating interior walls saved on heating/cooling bills. When you pay for energy, the amount used is a result of how fast energy escapes the building envelope (floor, exterior walls, and roof). Insulating the interior walls does nothing to change heat loss through the exterior walls. Now if you have a wall between, say, your unheated garage and the rest of the house and you insulate that, you will, of course have a benefit. But just putting insulation between two interior spaces -- like two bedrooms which are at the same temperature -- has no thermodynamic consequences.

Insulation between walls will increase the STC; dense material, such as Roxul, will work better than lighter density materials. However, there's a much better improvement with the use of resilient channels,(not j clips). If it's just one crucial wall, you can also use Quietrock or Green Glue.