ICF As A Sound Barrier

STC Rating
Sound Transmission Class rating is a single number quantifier used to rate walls, doors, and other partitions for their effectiveness in preventing sound transmission. Basically, a high STC rating indicates a more efficient sound absorption characteristic. That said, the typical wood frame wall has an STC (sound transmission class) rating of 33. ICF walls consistently achieve STC ratings of 55.

STC ratings, however, can be misleading because they are based on a logarithmic scale. An STC rating of 50 is not one better than 49. An STC rating of 50 should be deemed twice as effective as an STC rating of 49.

Furthermore, the actual behavior of two partitions with the same STC rating can be dramatically different, as the STC is weighted in favor of the part of the sound spectrum that represents the human voice. In practice, one of the most annoying transmitted sounds between dwelling units tends to be the bass in music, a part of the sound spectrum far removed from the voice range. This in mind, an ICF wall with an STC rating of 50 will perform better than a wood frame wall with insulation and drywall, having an STC rating of 50. Same STC rating, but still the ICF wall is more effective in stopping the transmission of annoying sound.