WEAKNESSES - WHAT YOU SHOULD KNOW
The STC rating is based on performance with frequencies from 125 to 4000 Hertz (the speech frequencies). The rating provides no evaluation of the barrier's ability to block low frequency noise, such as the bass in music or the noise of some mechanical equipment.
The STC rating is a lab test that does not take into consideration weak points, penetrations, or flanking paths. The field test however, does evaluate the entire assembly and includes all sound paths.
Note: Improving the STC rating of a wall will probably not affect the reverberation or reflections within the space. See our tutorial on the differences between STC and NRC.
Rules of Thumb
The difference between STC and NRC
STC Ratings for Various Wall Assemblies
STC Ratings for Masonry Walls
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