Sound transmission through slotted concrete blocks with attached gypsum board Available to Purchase

Measurements of sound transmission loss through slotted concrete blocks with attached gypsum board showed that the cavity resonance of the blocks has an important beneficial effect. It counteracts the mass‐air‐mass resonance that occurs when gypsum board is added to the surface of a concrete block wall leaving an air space behind it. This significantly increases the sound transmission class rating relative to the same systems with normal‐weight nonslotted blocks. The effects of the two resonances could be seen at different frequencies when there was no sound‐absorbing material in the air space behind the gypsum board. When the air space was filled with sound‐absorbing material, however, both resonances moved together and could not be separated, but the transmission losses and sound transmission class for the composite wall were still significantly greater than those for wall systems using nonresonant blocks. Sound absorption measurements for the slotted blocks showed the need for one‐third octave band data in place of the octave band data often found in trade literature.