Abstract: Noise attenuation structures, such as acoustic liners for gas turbine engines, are provided. For example, an acoustic liner comprises a face sheet, a backing sheet spaced apart from the face sheet, and a plurality of cavities defined between the face and backing sheets. The cavities are defined by cavity walls. A plurality of backing sheet walls extends from the backing sheet toward the face sheet. The backing sheet walls extend adjacent the cavity walls, and the backing sheet is movable with respect to the face sheet such that the cavities have a variable depth. Other embodiments of noise attenuation structures also are provided.

Abstract: An apparatus for attenuating sound waves includes a first surface, a second surface opposite the first surface, and at least one opening defined by the second surface. The apparatus also includes a heat exchanger defining a plurality of cooling channels therein and including a plurality of fins. The plurality of cooling channels extend between the first surface and the second surface. The plurality of fins extend from the second surface. The apparatus further includes at least one cavity extending between the first surface and the second surface. The at least one cavity is in flow communication with the at least one opening. The at least one opening and the at least one cavity are configured to attenuate the sound waves. The apparatus also includes at least one passageway extending between the at least one opening and the at least one cavity and positioned between the plurality of cooling channels.

Abstract: An apparatus for attenuating sound waves in a gas turbine engine includes a surface at least partially defining a pathway for airflow and a plurality of fins extending from the surface. The plurality of fins are configured to dissipate heat into the airflow. Each fin of the plurality of fins includes a fin surface. The fin surface is configured to direct the sound waves between the plurality of fins such that the plurality of fins attenuate the sound waves. The plurality of fins are arranged such that spacing between adjacent fins of the plurality of fins facilitates sound attenuation.

Abstract: Noise attenuation structures, such as acoustic liners for gas turbine engines, are provided. For example, an acoustic liner comprises a face sheet, a backing sheet spaced apart from the face sheet, and a plurality of cavities defined between the face and backing sheets. The cavities are defined by cavity walls. A plurality of backing sheet walls extends from the backing sheet toward the face sheet. The backing sheet walls extend adjacent the cavity walls, and the backing sheet is movable with respect to the face sheet such that the cavities have a variable depth. Other embodiments of noise attenuation structures also are provided.

Abstract: An apparatus for attenuating sound waves includes a first surface, a second surface opposite the first surface, and at least one opening defined by the second surface. The apparatus also includes a heat exchanger defining a plurality of cooling channels therein and including a plurality of fins. The plurality of cooling channels extend between the first surface and the second surface. The plurality of fins extend from the second surface. The apparatus further includes at least one cavity extending between the first surface and the second surface. The at least one cavity is in flow communication with the at least one opening. The at least one opening and the at least one cavity are configured to attenuate the sound waves. The apparatus also includes at least one passageway extending between the at least one opening and the at least one cavity and positioned between the plurality of cooling channels.

Abstract: An apparatus for attenuating sound waves in a gas turbine engine includes a surface at least partially defining a pathway for airflow and a plurality of fins extending from the surface. The plurality of fins are configured to dissipate heat into the airflow. Each fin of the plurality of fins includes a fin surface. The fin surface is configured to direct the sound waves between the plurality of fins such that the plurality of fins attenuate the sound waves. The plurality of fins are arranged such that spacing between adjacent fins of the plurality of fins facilitates sound attenuation.