Seen all kinds of suggestions on sound deadening. ALL - never mention anything about electrical outlet boxes and can lights. I can't see how you could add 1/2" sawdust board or extra sheetrock for mass and not get failed by inspector over "fire issues" especially on a ceiling. I'd like to add 1" Poly-Iso foam to top floor ceiling B4 the 5/8" S Rock goes on but what do you do about can lights? Some can be extended down a little more than 1/2" but not much and not enough to cover 1-5/8". Same problem between 1st & 2nd floor. "Reslient Drywall Tracks" - How the heck could you use these unless you go to a hanging ceiling?
What am I not understanding? Any other ideas? Best thing I've seen is "sonoboard" vynil & fiberglass with a lead sheet between but they cost $50 for a 2x3' panel!

Look into rock wool instead of fiberglass. Good insulation and more fireproof than fiberglass.

The slight extra weight is the reason for lower transmission of sound.

You may have to look a bit for it in some areas.

Resilient clips are simply a method of fastening drywall to the clips, which in turn are fatsened to the structure. They allow a slight movement in the drywall, which asborbs some sound energy, and does not transmit most of the rest, as it would with the drywall firmly fastened to the ceiling joists.

However, if true sound absorbtion is to be achieved, every single path that sound may take must be blocked. Sound can even get through a keyhole in an otherwise sound-absorbent door. You would have to build boxes around the lighting fixtures, but with care that they still are able to ventilate heat properly. Electric boxes in walls should be sealed all around with either fiberglass or expanding foam.

Foams and rigid foam boards will do little to dampen sound. Fiberglass or rockwool will work much better. Instead of fiberglass insulation, use fiberglass sound-absorbing nsulation...it's more dense than thermal insulation and absorbs sound better.

True sound-proofing is nearly impossible to achieve. You are looking for assemblies with high NRC's...noise reduction coefficients...the higher the better. Some research into the various components of an assembly will give you that data.

Please excuse me, I should have said STC Sound Transmission Coefficient, not NRC...the higher the STC, the better the sound deadening. Ten points higher STC will double the effectiveness.

This message has been edited. Last edited by: Richard Hetzel,