A method for manufacturing an alveolar core structure includes at least one cell including a secondary duct having a first end defining a sound wave inlet, and an opposite second end, the secondary duct comprising a sound wave outlet. The method also includes a fastening step in which adhesive tapes transverse to the longitudinal direction of said first plate are applied on a first longitudinal plate. The secondary duct in the form of a flattened element is fastened, on the first plate, by gluing at its sound wave inlet. A second plate is applied. A step of deploying the first and second plates so as to form the peripheral wall of the cells and so that the flattened element is deployed.

A noise and vibration attenuation panel for a structure within a propulsion system includes a first plurality of unit cells and a first plurality of mass elements disposed within the first plurality of unit cells. The first plurality of unit cells include a first periodic structure having a first unit cell, a second unit cell, a third unit cell, and a fourth unit cell, each of the first unit cell, the second unit cell, the third unit cell and the fourth unit cell including a central body interconnected via a plurality of lateral tubes extending from the central body, the first periodic structure forming a first lateral layer of unit cells. The noise attenuation panel can simultaneously control acoustic waves or energy (i.e., via noise attenuation flow paths) and vibration (i.e., via the mass elements).

Airborne acoustic absorbers include periodic arrays of Helmholtz resonators that are covered and/or partially filled with an acoustically absorptive material, such as a thermoplastic foam. The combined structures have much broader frequency ranges of high acoustic absorption than do structures having only Helmholtz resonators or acoustically absorbing foam.

Airborne acoustic absorbers include periodic arrays of Helmholtz resonators that are covered and/or partially filled with an acoustically absorptive material, such as a thermoplastic foam. The combined structures have much broader frequency ranges of high acoustic absorption than do structures having only Helmholtz resonators or acoustically absorbing foam.

Methods, systems, and apparatuses are disclosed for reducing sound level, by providing enclosures comprising enclosure walls having integral tunable resonator cavities, and reducing sound levels within the enclosure in response to detected sound levels outside of the enclosure.

Methods, systems, and apparatuses are disclosed for reducing sound level, by providing enclosures comprising enclosure walls having integral tunable resonator cavities, and reducing sound levels within the enclosure in response to detected sound levels outside of the enclosure.

An acoustic panel is provided that includes a perforated first skin, a second skin and a core. The core is connected to the perforated first skin and the second skin. The core includes a plurality of chambers and a plurality of septums respectively arranged with the chambers. The chambers include a first chamber that extends vertically between the perforated first skin and the second skin. The septums include a first septum that extends laterally across the first chamber. The first septum includes a first septum orifice. The first septum tapers laterally inward towards the first septum orifice as the first septum extends vertically towards the second skin.

An acoustic panel is provided that includes a perforated first skin, a second skin and a core. The core is connected to the perforated first skin and the second skin. The core includes a plurality of chambers and a plurality of septums respectively arranged with the chambers. The chambers include a first chamber that extends vertically between the perforated first skin and the second skin. The septums include a first septum that extends laterally across the first chamber. The first septum includes a first septum orifice. The first septum tapers laterally inward towards the first septum orifice as the first septum extends vertically towards the second skin.

A method of designing an acoustic liner includes identifying acoustic path lengths that will attenuate a frequency within a frequency range of interest, and selecting a liner configuration with a combination of acoustic paths that addresses the frequency range of interest. The selection may be made after a comparison of the response of different liner configurations.

A method for manufacturing acoustical elements, includes providing a first fibre component in a form of mineral wool and a second fibre component in a form of bicomponent fibres having a core with a thermoplastic outer layer, mixing the first fibre component and the second fibre component, for provision of a mixture, shaping the mixture into single layered tile shaped elements whereby the mixture is compressed with a compression ratio to a compressed state, and fixating the single layered tile shaped elements in the compressed state for obtaining the acoustical elements.