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 (L) 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 (L), 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 . <EOS>