Abstract: A multi-duct diffusion exhaust device for a turbomachine. The exhaust device including an annular inlet, an outer casing shaped symmetrically overall with respect to an axis, one or more internal partitions defining several roughly concentric ducts for an exhaust stream to flow through, and an absorbent coating capable of absorbing some of the acoustic energy generated by the flow. The absorbent coating being provided on at least one of a surface of one internal partition and an interior surface of the outer casing. The absorbent coating having a thickness that is tailored along a length of the exhaust device to optimize the flow in the ducts by maintaining progressive diffusion and avoiding detachment near stationary surfaces.