A soundproofing coating with a cellular structure having several structures connected in a transverse direction, each formed by connecting a first longitudinal strip with a second longitudinal strip. Each structure has, successively in the longitudinal direction, 1) a first cavity, the cross-section of which narrows gradually in the thickness of the coating until it closes, 2) a first connection of two walls, respectively of the first strip and the second strip, in contact with each other over part of the thickness of the coating, which provides a passage between the first cavity and a second cavity that thus form a Helmholz resonator, 3) the second cavity, the cross-section of which gradually increases in the thickness of the coating and which is closed by a closing sheet, and 4) a second connection of two walls.