Racine Home Insulators, LLC is a leading contractor of sound proofing services. We sound proof and insulate exterior and interior walls (such as around bathrooms and  between units) and ceilings to greatly reduce sound transmission.  After years of experience and research we recommend dense packed cellulose for the best value when adding sound proofing to your home, rental property or business.  To better understand STC ratings please see the table at the bottom of this page.

If you have ever walked into a house that is not insulated you will immediately notice that noises from outside of the house are “louder” than in an insulated home. This is because the sound transmission coefficient (STC) is lower. Read about STC ratings on Wikipedia.  The STC is a calculation of the acoustic performance of a wall or ceiling and a higher number is better than a lower number.  While fiberglass insulation certainly improves the STC when compared to hollow wall cavities, dense packed cellulose offers more than twice the improvement and at a lower cost.

What about foam?

Adding Cellulose insulation to walls and ceilings is the most cost-effective and efficient way to minimize sound transmission between rooms or from the outside.  Having said that, the ideal construction method for sound proofing would be a staggered wall with foam insulation inside.  Staggering the studs creates an acoustical break for much of the sound flow (see the blue line).

Most customers are not willing to tear down their walls and build staggered ones as illustrated in this picture.  And while properly installed spray foam has a STC rating of 49, it can not be retrofit to existing walls and ceilings where the studs or joists are not visible.  In cases where the drywall or plaster has been removed, installing 3″ of foam costs double or triple that of cellulose or fiberglass.

STC Rating	What can be heard
25	Normal speech can be understood quite easily and distinctly through wall
30	Loud speech can be understood fairly well, normal speech heard but not understood
35	Loud speech audible but not intelligible
40	Onset of “privacy”
42	Loud speech audible as a murmur
45	Loud speech not audible; 90% of statistical population not annoyed
50	Very loud sounds such as musical instruments or a stereo can be faintly heard; 99% of population not annoyed.
60+	Superior soundproofing; most sounds inaudible