In the mechanical insulation world, we are familiar with insulation being used for Sound Attenuation. The main purpose is to isolate sound to the equipment, machine, pipeline or enclosure.
Applications involving Acoustical Treatments present additional opportunities and challenges. Materials including insulation used on both the exterior and interior of the room must be carefully selected. Insulation used within these applications must allow the sound to be heard clearer and more distinct inside the room, contain it within that space, as well as minimize exterior noise.
When designing a Sound Studio or concerned about Acoustics in an enclosed area there are a number of factors to consider. This article specifically talks about various options for insulation materials as well as a summary of some of the most common products and their NRC Ratings & Flame & Smoke Test Data.
|
Product |
NRC Rating Tested to ASTM C 423 |
Flame Spread / Smoke Developed Tested to UL723, ASTM E 84 or CAN/ULC S102-M |
|
K Flex Duct® Liner Gray Rolls |
1” @ 0.50 |
25/50 less than 2” thick |
|
K Flex Insul-Sheet® Rubber Sheets/Rolls |
1” @ 0.35 |
25/50 Less than 1-1/2”thick |
|
Owens Corning Quiet R® Duct Liner Blanket or Board |
½” @ 0.50 1” @ 0.70 |
25/50 |
|
Owens Corning® 703 Board Plain |
1” @ 0.70 2” @ 1.00 |
25/50 |
|
Owens Corning® 705 Board Plain |
1” @ 0.65 2” @ 0.95 |
25/50 |
|
Owens Corning® Select Sound Blanket (1.5# density) |
1” @ 0.60 2” @ 0.80 |
25/50 |
|
Owens Corning® Select Sound Board |
1” @ 0.70 2” @ 1.00 |
25/50 |
|
Roxul AFB |
1” @ 0.70 2” @ 0.95 |
0/0 |
|
Roxul Fabrock LT |
1” @ 0.70 2” @ 1.00 |
5/5 UL723, ASTM E84 5/10 CAN/ULS S102-M |
Sound is made up of 2 physical properties, Loudness – Intensity which is measured in decibels (DB) and Tone – Frequency which is measured in (HZ). When selecting products you may also want to consider that sound will behave differently depending on the surface that it strikes. Dense surfaces will reflect sound back into the room as well as absorb some of it where porous surfaces will absorb sound well but will not isolate it.
Below are basic definitions for 2 common rating factors that are also important to consider when researching products to use.
NRC Ratings
NRC (Noise Reduction Coefficient) Ratings measure a product’s ability to absorb sound. Ratings are from 0 – 1 with 0 being perfectly reflective and 1 being perfectly absorptive. The test to get an NRC Rating averages sound at 4 middle frequencies 250, 500, 1000 & 2000 and round them to the nearest 5%. These middle frequencies are considered the speech frequencies so any product you select may perform differently to sound generated by music, musical instruments, equipment and other low frequency sounds.
STC Ratings
STC (Sound Transmission Class) measures an assembly’s ability to resist airborne sound transfer through frequencies 125-4000 HZ.
Whether your job is big or small, you’re best to contact your local GIC location for additional information, samples and to confirm availability on some of the products listed above. Most manufacturers will have minimum orders on certain products that may affect your choice. Selecting the right insulation for your application will have a definite impact on the sound quality in your space and allow you the ability to enjoy it for a longer period.
