Acoustic panel for a nacelle of an aircraft propulsion unit, and related manufacturing methods

An acoustic panel with resonators for a nacelle of an aircraft propulsion unit, the acoustic panel comprising a plurality of adjoining acoustic cells which form a cellular core, each acoustic cell being enclosed by a peripheral wall, and each acoustic cell extending along a longitudinal main axis corresponding to an axis of propagation of sound waves, from a front end up to a rear end of the acoustic cell,

• wherein at least one acoustic cell among the plurality of acoustic cells includes a first obstacle extending from a first side of the peripheral wall and a second obstacle extending from an opposing second side of the peripheral wall, the first and second obstacles extending transversely with respect to the longitudinal main axis of the at least one acoustic cell, the first and second obstacles each having a respective free end edge which delimits a passage with a portion of the peripheral wall opposing the respective free end edge to increase a length of a path traveled by the sound waves through the at least one acoustic cell,
• wherein the first obstacle and the second obstacle are spaced from each other along the longitudinal main axis, wherein the passage defined by the free end edge of the first obstacle and the passage defined by the free end edge of the second obstacle are radially shifted away from each other so as to form a baffle to increase the length of the path traveled by the sound waves through the at least one acoustic cell,
• wherein at least one of the first and second obstacles comprises a central portion which extends transversely with respect to the longitudinal main axis of the at least one acoustic cell and two lateral portions, each lateral portion extending in an oblique direction with respect to the longitudinal main axis of the at least one acoustic cell, each oblique direction being between 30° and 60° with respect to the longitudinal main axis.