A smoke-generating apparatus, such as a generator engine, a boiler or other, comprising a smoke exhaust duct, said smoke exhaust duct comprising, in the direction of travel of the smoke, a smoke duct section, a noise reduction device (1, 1', 1"), and a downstream smoke duct section, said noise reduction device (1. 1', 1") comprising a central tube provided, considering the direction of travel of the smoke, with an upstream extension connected to the upstream smoke duct section, and with a downstream extension connected to the downstream smoke duct section, said central tube comprising perforations and being surrounded by an external tube to define between each other a sound absorption chamber, said external tube being connected to said central tube, still considering the direction of travel of the smoke, by an upstream end wall, and by a downstream end wall, which delimit the length of said sound absorption chamber, said sound absorption chamber being partially filled with a sound absorbing material that fills its thickness between the central tube and the external tube, over a part of its length, characterized in that said central tube comprises (a) a solid upstream section, devoid or almost devoid of perforations, extending from said upstream end wall, to an intermediate area located between said upstream and downstream end walls, said solid upstream section being extended by (b) a downstream section provided with perforations, which extends from said intermediate area to said downstream end wall or approximately to said downstream end wall, and in that said sound absorbing material is delimited (i) by an upstream end edge, arranged downstream from said intermediate area, and (ii) by a downstream end edge, arranged in said sound absorption chamber near said downstream end wall, or against the latter, the space of said sound absorption chamber between said upstream end wall and said upstream end edge of said sound absorbing material, consisting of a cavity, an upstream part of which surrounds said solid upstream section of said central tube, and a downstream part (11a") of which surrounds a perforated upstream part (5b1) of said central tube. characterized in that said central tube comprises (a) a solid upstream section, devoid or almost devoid of perforations, extending from said upstream end wall, to an intermediate area located between said upstream and downstream end walls, said solid upstream section being extended by (b) a downstream section provided with perforations, which extends from said intermediate area to said downstream end wall or approximately to said downstream end wall, and in that said sound absorbing material is delimited (i) by an upstream end edge, arranged downstream from said intermediate area, and (ii) by a downstream end edge, arranged in said sound absorption chamber near said downstream end wall, or against the latter, the space of said sound absorption chamber between said upstream end wall and said upstream end edge of said sound absorbing material, consisting of a cavity, an upstream part of which surrounds said solid upstream section of said central tube, and a downstream part (11a") of which surrounds a perforated upstream part (5b1) of said central tube.