A surface liner member includes an external wall which is provided with multiple holes, a spacer structure, and tubes which are respectively associated with the holes in the external wall. The surface liner member is intended to be applied to a base surface in order to reduce, by acoustic absorption, an acoustic wave reflected on this base surface. The acoustic absorption efficiency is improved, particularly for frequencies below 500 Hz, by varying the shape of the holes in the external wall such that the ratio of the hole perimeter to the hole area varies. Such a surface liner member may be adapted to form a surface portion of an aircraft engine nacelle, or of a leading edge of an aircraft wing.

A surface liner member includes an external wall which is provided with multiple holes, a spacer structure, and tubes which are respectively associated with the holes in the external wall. The surface liner member is intended to be applied to a base surface in order to reduce, by acoustic absorption, an acoustic wave reflected on this base surface. The acoustic absorption efficiency is improved, particularly for frequencies below 500 Hz, by varying the shape of the holes in the external wall such that the ratio of the hole perimeter to the hole area varies. Such a surface liner member may be adapted to form a surface portion of an aircraft engine nacelle, or of a leading edge of an aircraft wing.

A fairing for a power generation machine, the fairing comprising: a first layer comprising a metallic material; a second layer comprising a composite; and a third layer positioned between the first layer and the second layer, the third layer being configured to attenuate acoustic waves over a predetermined frequency range.

A fairing for a power generation machine, the fairing comprising: a first layer comprising a metallic material; a second layer comprising a composite; and a third layer positioned between the first layer and the second layer, the third layer being configured to attenuate acoustic waves over a predetermined frequency range.

A vibration reduction device having an acoustic meta structure mounted to a vehicle body and configured to block a structure-borne noise transmitted through the vehicle body may include a plurality of unit structures arranged at a predetermined interval therebetween, wherein each of the unit structures includes frame mounted to the vehicle body and configured to separate a predetermined space into a predetermined number of separate sections formed by walls of the frame; and a vibrator formed at a corner portion of each of the separate sections and each of which has a natural frequency to block a vibration transmitted from the vehicle body through the frame.

Systems for magnetoacoustically transferring sound across an acoustic barrier include first and second acoustic resonators positioned on opposite sides of the barrier. Each of the first and second resonators includes an attached magnet. Via magnetic coupling between the magnets, an acoustic oscillation at the first resonator induces an oscillation of the same frequency at the second resonator. Thus sound waves absorbed at the first resonator are magnetically transferred across the barrier to the second resonator, from which they are emitted.

Systems for magnetoacoustically transferring sound across an acoustic barrier include first and second acoustic resonators positioned on opposite sides of the barrier. Each of the first and second resonators includes an attached magnet. Via magnetic coupling between the magnets, an acoustic oscillation at the first resonator induces an oscillation of the same frequency at the second resonator. Thus sound waves absorbed at the first resonator are magnetically transferred across the barrier to the second resonator, from which they are emitted.

A fan, and a silencer that silences a sound generated by the fan are provided, in which the silencer has a resonance characteristic, the silencer is disposed at a position connected to a sound field space of the sound generated by the fan, and a sum of an absorbance and a reflectivity of the silencer at a resonance frequency is 10% to 43% and a standardized half-width of the silencer is more than 0.05 and 0.25 or less.

An axial fan that includes a casing having an inner space that penetrates in one direction, and a rotor blade disposed in the inner space of the casing, and a silencer that is disposed at a position connected to the inner space of the axial fan are provided, in which the axial fan has a sound pressure distribution having a position at which a sound pressure is high and a position at which the sound pressure is low in a circumferential direction in the inner space during driving, and the silencer is disposed at the position of the axial fan in the circumferential direction at which the sound pressure is high and is not disposed at the position at which the sound pressure is low.

A structure is provided that includes a perforated first skin, a second skin and a core. The core includes a first sidewall, a second sidewall, a first baffle and a second baffle. The core forms a plurality of cavities vertically between the perforated first skin and the second skin. The first baffle is connected to the perforated first skin at a first baffle first end. The first baffle is connected to the second skin at a first baffle second end by a first moveable joint. The second baffle is connected to the perforated first skin at a second baffle first end. The second baffle is connected to the second skin at a second baffle second end. A first of the cavities extends laterally between the first sidewall and the second sidewall. The first cavity extends longitudinally between the first baffle and the second baffle.