The purpose of architectural acoustics is to create an environment where sounds are clearly heard by the intended listener and noise is isolated or absorbed. These are two ways of dealing with sound levels: sound insulation and sound absorption. Materials with a heavy mass (like concrete walls) work well with sound insulation, while porous lightweight materials work well with absorption. Sound insulation is usually more complicated than absorption.
STC (Sound Transmission Class) is a numerical rating system on how well a building partition reduces the amount of noise at a given frequency that passes through. The higher the STC, the better the performance of sound insulation.
STC What can be heard
25 Normal speech can be understood quite easily and distinctly through wall
35 Loud speech audible but not intelligible
40 Onset of “privacy”
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
An STC rating of 50 will satisfy most building code requirements. An 8” CarbonCast
panel with 4” of insulation will provide a STC rating of 52. This rating can be
increased if required by adding more mass to the wall.
The STC rating of a wall can be severely compromised through leaks and flanking. This may occur wherever there are penetrations, openings, windows, doors and gaps. Special attention needs to be paid during the design process to limit and correct these concerns. Because CarbonCast walls are produced in large widths and full height modules with caulking and insulation at the joints, there is much lower probability of leaks of flanking as compared to steel or wood structures.