Adding Green Glue Noiseproofing Compound vs. Just Adding Drywall to Wall:

Green Glue Noiseproofing Compound can easily be added to basic walls as a "retro-fit" soundproofing option.  Simply dispense 2 tubes of Green Glue per new sheet of drywall and screw onto the existing wall.  It's as easy as that, however clients always wonder, how well is this going to work?  

What is Green Glue Noiseproofing Compound?

Green Glue Noiseproofing Compound is a viscoelastic damping compound that is used between layers of drywall in walls, ceilings, and floors to drastically dampen vibrations. By damping these vibrations, Green Glue compound is able to reduce the amount of sound transferring from one side of the structure to the other. 

The Test:

We will discuss the results of three separate wall structures including Sound Transmission Class (STC Value) as well as the transmission loss at varying frequencies.  The first wall will be the original wall, this is your standard 2 x 4 wall with 5/8" drywall on both sides.  The 2nd wall we will call the Reference Wall in which we added a 2nd layer of drywall to both sides.  The 3rd wall we will call the Green Glue Wall in which we added a 2nd layer of drywall including Green Glue Noiseproofing Compound to both sides.

The tests we will discuss involve three separate walls listed below:
*All walls have Wood Studs and R-13 Fiberglass Batts

• Original Wall:             1 Layer of 5/8" Drywall (on Both Sides)
• Reference Wall:         2 Layers of 5/8" Drywall (on Both Sides)
• Green Glue:               5/8" Drywall / 2 Tubes of Green Glue / 5/8" Drywall (on Both Sides)

The Results:

STC Values:

• Original Wall:           STC 41
• Reference Wall:       STC 45
• Green Glue:             STC 55

Sound Transmission Class is an average performance over all audible frequencies so a lower STC Rated Wall can actually be more desirable depending on what level sound frequency we are trying to stop.  Because of this fact we cannot end our test here and say that the Green Glue wall wins because of its STC 55 (10 points higher than the reference wall).  We need to analyze the transmission loss across the frequencies to make sure the average is not skewed on one end of the spectrum.  Below is an image showing the two test wall structures along with their STC values.

Transmission Loss at Frequencies:

The chart shown below lists both wall tests for sound transmission loss.  The charts vertical side is Transmission Loss in Decibels.  The higher the number the better for blocking sound.  The charts horizontal side is the noise frequency, the lower the number the lower the frequency (bass).

• Up to 63 hz     Mostly inaudible to the human ear.  The 2 walls all perform within a few Db of each other.
• 80 to 125 hz    The Green Glue Wall outperforms the Reference Wall.

• 160 to 200 hz   Both walls perform similarly here with the Green Glue Wall edging it out slightly

• 250hz and Up   Green Glue Greatly Outperforms the Refernce Wall by at least 10 db per frequency.

From this chart you can see that for the most part adding Green Glue Noiseproofing Compound when installing an extra layer of drywall to both sides of your standard wall greatly helps sound transmission.  For very low frequencies both walls perform the same however from basically 80hz up, the Green Glue Wall excelled.

Conclusion:

The transmission loss chart and STC values clearly show that Green Glue Noiseproofing Compound "wins" the competition.  Green Glue offers a +14 STC point increase from the original wall and a +10 point increase over the reference wall.  The chart shows that the Green Glue wall performs better at almost every frequency.

Adding Green Glue Noiseproofing Compound greatly increases the transmission loss of a wall compared to just adding drywall.

*Note: All testing and charts were published by the Green Glue Company.  Testing was performed by an independent lab.