This investigation was performed to evaluate the effectiveness of detecting air leaks in typical constructions through the measurement of sound transmission. The sound transmission of various slits was measured. These were designed to simulate field constructions. Due to the fundamental difference between steady air-flow and sound propagation, it was concluded that the method fails, particularly in the case of foil-covered slits and slits coupled to damped cavities.
These problems can be overcome by compensating for the pressure drop over the flow meter in such a way that the pressure on the duct side of the grille remains the same before and after the positioning of the flow meter. This is a very well known technique. However in the field of air conditioning, devices using this principle are rare. The compensation of the pressure drop is performed by a fan and regulator which blows just enoughair through the flow meter to meet the pressure compensation before the grille.
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