The transmission of sound by ventilation ducts—A design guide

It has recently been shown that for situations in which two rooms are connected by a ventilation duct, the principal acoustic path from one room to the adjacent room is that via the duct cavity. As existing theories were found to be inadequate in predicting this path noise reduction, experiments have been carried out to determine the values of the unknown variables. These are described and a design guide for determining the overall noise reduction of the system has been produced.