The element comprises a baseplate (1) above the panel (3) on which a capillary tube unit (2) is mounted. The capillary tubes are connected to manifolds. There can be direct contact between the panel and the baseplate or an acoustic cloth (4) can be inserted between them. The baseplate can be of sheet-metal and perforated, with stiffening and suspension profiled portions formed in it. The capillary tube unit can be accommodated in parallel grooves in an insulating plate, while being joined to the baseplate. Transverse grooves can also be formed in the insulating plate and in the same side as the lengthwise ones.
