A noise-attenuating covering configured for example for a pipe for guiding gases along a gas path. The covering includes a wall defining the gas path and at least one resonance cavity, the wall being pierced with holes for fluid communication between the gas path and the resonance cavity to attenuate noise. The holes have substantially identical diameters and, since the pipe is arranged to guide the gases in the downstream direction, a number of the openings per wall surface unit decreases continuously along the gas path in the downstream direction, such as to confer on the wall substantially constant acoustic resistance along the gas path, for which the noise attenuation is optimized along the gas path.