FIELD: acoustics.
SUBSTANCE: invention relates to noise absorbing panels. Acoustic structure comprises a honeycomb structure with a plurality of walls extending between first and second edges, the walls forming a plurality of cells. Each of the cells has a cross-sectional area measured perpendicular to the walls, an acoustic barrier located at the second edge of the honeycomb structure or within at least one of the cells to form an acoustic resonator. Depth of the acoustic resonator is equal to the distance between the first edge of the honeycomb structure and the acoustic barrier. Frusto-conical waveguide is located in said acoustic resonator. Waveguide comprises a sound-permeable wall that includes an input edge defining the input of the waveguide and an output edge defining the outlet of the waveguide, the inlet of the waveguide being closer to the first edge of the honeycomb structure than the outlet of the waveguide. Sound-permeable wall is a mesh fabric with an open structure or a perforated plastic film.
EFFECT: widening the range of absorbed sound frequencies without increasing the thickness or weight of the acoustic structure of the nacelle.
20 cl, 5 dwg
