Noise attenuating device (100, 100a) in order to equip the end of an air conduit with a gas stream running through it, wherein the device comprises: - a deflector (2, 3, 4), which is suitable to intersect the axis (xx) of the stream at the end of the conduit, - wherein the deflector is formed from: * resonator cavities (31, 31a), which are provided with necks (34, 34a), * wherein these cavities (31, 31a) are covered with a layer of absorbent foam (4, 4a), and * wherein the necks (34, 34a) of the cavities (31, 31a) traverse the layer of absorbent foam (4, 4a), wherein the noise attenuating device (100, 100a) comprises an open (13, 13a) body (1, 1a), which is provided with a connector for the conduit and with an inlet/outlet opening, characterized in that the body (1, 1a) is provided with a cut-out at the point of intersection of the stream out of the conduit and into the opening, wherein this cut-out is closed by a cover which is combined with the body in order to form the deflector, by including: - a frame (3, 3a, which is provided with partitions (33, 33a) and is fixed in the cover and which, together with the cover, delimits resonator cavities (31, 31a), with: * a sheet (32, 32a) which carries tubular elements (34, 34a) which form the necks of the resonator cavities (31, 31a), * wherein the sheet (32, 32a) is covered by a layer of absorbent foam and is traversed by the tubular elements (34, 34a). - a deflector (2, 3, 4), which is suitable to intersect the axis (xx) of the stream at the end of the conduit, - wherein the deflector is formed from: * resonator cavities (31, 31a), which are provided with necks (34, 34a), * wherein these cavities (31, 31a) are covered with a layer of absorbent foam (4, 4a), and * wherein the necks (34, 34a) of the cavities (31, 31a) traverse the layer of absorbent foam (4, 4a), wherein the noise attenuating device (100, 100a) comprises an open (13, 13a) body (1, 1a), which is provided with a connector for the conduit and with an inlet/outlet opening, characterized in that the body (1, 1a) is provided with a cut-out at the point of intersection of the stream out of the conduit and into the opening, wherein this cut-out is closed by a cover which is combined with the body in order to form the deflector, by including: - a frame (3, 3a, which is provided with partitions (33, 33a) and is fixed in the cover and which, together with the cover, delimits resonator cavities (31, 31a), with: * a sheet (32, 32a) which carries tubular elements (34, 34a) which form the necks of the resonator cavities (31, 31a), * wherein the sheet (32, 32a) is covered by a layer of absorbent foam and is traversed by the tubular elements (34, 34a). * resonator cavities (31, 31a), which are provided with necks (34, 34a), * wherein these cavities (31, 31a) are covered with a layer of absorbent foam (4, 4a), and * wherein the necks (34, 34a) of the cavities (31, 31a) traverse the layer of absorbent foam (4, 4a), wherein the noise attenuating device (100, 100a) comprises an open (13, 13a) body (1, 1a), which is provided with a connector for the conduit and with an inlet/outlet opening, characterized in that the body (1, 1a) is provided with a cut-out at the point of intersection of the stream out of the conduit and into the opening, wherein this cut-out is closed by a cover which is combined with the body in order to form the deflector, by including: - a frame (3, 3a, which is provided with partitions (33, 33a) and is fixed in the cover and which, together with the cover, delimits resonator cavities (31, 31a), with: - a frame (3, 3a, which is provided with partitions (33, 33a) and is fixed in the cover and which, together with the cover, delimits resonator cavities (31, 31a), with: * a sheet (32, 32a) which carries tubular elements (34, 34a) which form the necks of the resonator cavities (31, 31a), * wherein the sheet (32, 32a) is covered by a layer of absorbent foam and is traversed by the tubular elements (34, 34a).