has sound insulation properties that are superior to normal concrete, achieving an STC rating of between 45 and 50 for (7.6 to 12.7 cm=3") thick wall panels respect fully, depending on the density and grade of mix. STC ratings of, up to 60 can be achieved with specialized construction, such as skin coats of on wall surfaces incorporated with small air spaces inside. STC ratings over 60 are not practical for normal construction.