Patent ID: 7621371

Claim:
A method for attenuating the jet noise of a turbofan engine comprising: a hollow nacelle having a longitudinal axis and including a front air intake section, provided with a leading edge, and a rear air outlet section comprising an outer annular surface and an inner annular surface which converge toward one another to form a trailing edge; a fan arranged in said nacelle opposite said front air intake section and designed to generate the cold stream of said turbofan engine; a generator arranged in said nacelle, downstream of said fan, and designed to generate the axial hot stream of said turbofan engine; and a cowl system surrounding said hot stream generator and including a rear section which comprises an outer annular surface and an inner annular surface which converge toward one another to form an outlet orifice for said hot stream, said cowl system defining with the nacelle a duct of annular cross section for said cold stream, and said duct being terminated by said rear air outlet section of the nacelle whose trailing edge forms the outlet orifice for said cold stream, which method involves producing notches designed to attenuate the jet noise of said turbofan engine at the periphery of the outlet orifice for at least one of said streams, wherein said notches ( 27 , 31 , 40 ) are produced so as to be blind, given that they cut into one of said convergent annular surfaces forming said outlet orifice without cutting into the other of said convergent annular surfaces.