[EN 12792:2003, 6]:treatment of the internal or external walls of the ducts so as to reduce the transmission of acoustic energy along the length and through the duct and/or the thermal energy across the walls.

[AIVC, Air infiltration and ventilation glossary, 1992]:a method of detecting cracks in a building where leakage may occur. A steady source of high-pitched sound is placed within the building and a microphone is used outside the building as a detector. … Continue reading →