25 gauge metal studs vs 20 & 16 gauge metal studs

When testing between a 25-gauge metal stud and a 20 or 16 gauge metal stud, tests show that there are measurable decreases in STC values as the stud becomes heavier and as the spacing between studs decreases. The testing results show that when comparing similar partitions, a 25-gauge metal stud wall was usually 4-5 STC points higher than 20- and 16-gauge stud walls. Also, by comparing similar partitions, the results show that there is a 3-4 STC point drop between walls when studs are installed 406 mm (16”) on center rather than 610 mm (24”) on center. There was really no significant difference in STC value between partitions with 16-gauge studs and 20-gauge studs. Based on the test results measurements, the walls in question in order to comply with the STC guideline for partitions between exam rooms referenced here, a double-stud partition would be required.  In other words, heavier gauge metal studs perform no better than wood because of the loss of STC values. 

 

Did You Know?

A large meal will temporarily make your hearing less sharp.

STC Ratings Simply Put

Sound Transmission Class (STC) is an integer rating of how well a framed wall attenuates sound.

• Doubling the mass of a wall assembly does not double the STC

• An empty framed wall (steel studs and a layer of gypsum wallboard on each side) has an STC of approximately 35dB

• Adding an additional layer of gypsum wallboard (from two sheets to four sheets) increases the STC by about 5–6 points

• Adding cavity insulation increases the STC approximately 4–6 dB

• Fiberglass batts increase the STC to 39; Cellulose insulation increases the STC to 44

• Batt insulation must fit tight without gaps

• Batt thickness provides better sound control than batt density. Compressing a batt reduces STC and thermal efficiency

• Stud assembly must span from deck to ceiling

• Structurally decoupling the gypsum wallboard panels from each other, like using a staggered stud assembly

or a double stud wall) can yield an STC as high as 63 or more

•Also materials such as United Plastics Corporation's dB-3PRO along with gypsum wallboard and insullation may also improve STC ratings (Refer to manufacturer specifications)

How Loud is TOO LOUD

Standards set by OSHA (Occupational Safety and Health Administration) indicate that continued exposure to noise over 85 dBA will eventually harm hearing. According to OSHA, the exposure time allowed is cut in half for every 5 decibel increase. For example, if a sound is 95 dBA, then 4 hours of exposure, over time, will cause hearing loss, and exposure to sounds at 115 dBA for just 15 minutes a day, over time, will cause hearing loss. Other groups, such as NIOSH (National Institute for Occupational Safety and Health) calculate safe exposure time by decreasing time in half for every 3 decibel increase. The NHCA (National Hearing Conservation Association) is an excellent resource for more information about occupational hearing conservation programs.

Will this really control sound?

Resilient channel is a specially-formed, metal device that, when used to hang drywall (instead of attaching the drywall directly to the wall studs or ceiling joists), significantly reduces the sound transmission of the wall or ceiling system. The channel material is secured to the studs and drywall is secured to the channel - providing a break in sound transmission through the wall.

Resilient channel for sound control is not effective if attached to sheet materials, such as drywall. It is also important to use the right length screws, so they do not penetrate into the wood framing.

Just a few screws into the wood can undermine the resilient connection and substantially lower the STC and IIC ratings.

Did you know?

Resilient Channel was not originally designed to provide improved sound attenuation, but rather to avoid cracks in drywall? 

More and more States are adopting ordinances for dealing with sound

Here is an example of what one state is doing:

Table 1 - State noise guidelines.

State Department of Health and County Liquor Commission Maximum Permissible Noise Limits
Zoning Districts:	Daytime (7:00 am to 10:00 pm)	Nighttime (10:00 pm to 7:00 am)
Residential, Conservation, Preservation, Public/Open Space	55 dBA	45 dBA
Multi-Family Dwellings, Apartments, Business, Commercial, Hotel, Resort	60 dBA	50 dBA
Agriculture, Country, Industrial	70 dBA	70 dBA
County Land Use Commission Special Ordinance for Outdoor Amphitheater
Nearest Apartment/Hotel/Business (approximately 2000 feet away)	68 dBA	Prohibited