A passive and active acoustic reduction method comprising the following steps: • producing a plurality of acoustic reduction elements, each comprising a microphone and a loudspeaker, by carrying out the following steps for each element: • placing the microphone in a box produced in a passive acoustically absorbent material or including a passive acoustically absorbent material in the vicinity of the surface of a main side of the box; • placing the loudspeaker in this box, beside the microphone, also in the vicinity of the surface of the main side and in such a manner that the main emission direction of the loudspeaker is substantially perpendicular to the main side; • disposing n acoustic reduction elements side by side to constitute an acoustic reduction bar or electro-acoustic bar; • disposing m electro-acoustic bars side by side, substantially parallel to one another and separated by gaps and directing the main side of the box towards the side opposite the main side of the adjacent bar, so that the loudspeakers emit into the gap between two bars, thus constituting an open-work acoustic barrier combining a passive noise-reduction effect and an active noise-reduction effect; the method being characterized in that it comprises the steps of: • introducing an acoustically absorbent material on the side of the box opposite the main side to adjust the acoustic impedance of the box and prevent the appearance of standing waves between the main side of one bar and the side opposite the main side of the adjacent bar; • for each acoustic reduction element, measuring the transfer function between the microphone and the loudspeaker; • for each acoustic reduction element, computing a feedback control electronic filter from the transfer function between the microphone and the loudspeaker, the transfer function being linearized by the presence of acoustically absorbent material introduced onto the side of the box opposite the main side, the electronic filter acting, within each acoustic reduction element, to enable electro-acoustic looping of the loudspeaker to the microphone by amplifying the feedback in order to obtain a real-time acoustic absorption effect for a predetermined range of frequencies. • producing a plurality of acoustic reduction elements, each comprising a microphone and a loudspeaker, by carrying out the following steps for each element: • placing the microphone in a box produced in a passive acoustically absorbent material or including a passive acoustically absorbent material in the vicinity of the surface of a main side of the box; • placing the loudspeaker in this box, beside the microphone, also in the vicinity of the surface of the main side and in such a manner that the main emission direction of the loudspeaker is substantially perpendicular to the main side; • disposing n acoustic reduction elements side by side to constitute an acoustic reduction bar or electro-acoustic bar; • disposing m electro-acoustic bars side by side, substantially parallel to one another and separated by gaps and directing the main side of the box towards the side opposite the main side of the adjacent bar, so that the loudspeakers emit into the gap between two bars, thus constituting an open-work acoustic barrier combining a passive noise-reduction effect and an active noise-reduction effect; • introducing an acoustically absorbent material on the side of the box opposite the main side to adjust the acoustic impedance of the box and prevent the appearance of standing waves between the main side of one bar and the side opposite the main side of the adjacent bar; • for each acoustic reduction element, measuring the transfer function between the microphone and the loudspeaker; • for each acoustic reduction element, computing a feedback control electronic filter from the transfer function between the microphone and the loudspeaker, the transfer function being linearized by the presence of acoustically absorbent material introduced onto the side of the box opposite the main side, the electronic filter acting, within each acoustic reduction element, to enable electro-acoustic looping of the loudspeaker to the microphone by amplifying the feedback in order to obtain a real-time acoustic absorption effect for a predetermined range of frequencies.