The HVAC (Heating, Ventilating and Air Conditioning) beneficiaries are in particular annoyed by the noise generated from the radiant unit and the air circulating ducts, since they are located inside the rooms and buildings. The comparatively experimental results highlight the relations between the air flow, pressure, power-charging and the sound level. The measurements are carried out at different fan's speeds, ranging the power-charge from 30100% while the duct air flow is slowly adjusted from full open to full closed, between 0-500 Pa. Third-octave band analysis of random noise of the handling units is realized in an anechoic room, using the measurement procedures that agrees the requirements of the ISO 3744: 2011 and ISO 5136: 2010 standards. For an accurate design of the HVAC system, the designer needs to know not only the sound power of the radiant unit, but also from all of the air paths, since the sound travels along with the conditioned air. The experimental methodology used in the paper is of real interest for the HVAC manufacturers, in order to rate the sound level of their products and to improve the noise attenuation.
