Abstract: The noise damping device for piston motors in aircrafts, which allows the simultaneous cooling of the exhaust gases, offers a square cross section and a variable configuration according to the direction of the exhaust. The exterior sheets (3,4) converge towards the exhausts direction into a slot-like output aperture (7), while the lateral sheets (5,6) diverge in the same direction so that the profile of the exterior sheets diverges and that of the lateral sheets converges. Perforated sheets (8,9) are placed in parallel to and at a distance from the internal surfaces of the exterior converging sheets (3,4) and comprise edges (8a, 9a) forming cooling chambers (10,11) which are open towards the outlet aperture (7). The diverging lateral sheets (5,6) can also be fitted with holes which open into lateral supplementary cooling chambers, which chambers are open towards the side of the outlet aperture.