Patent Description:
Acoustic panels may be used in various applications to attenuate noise. An acoustic panel, for example, may be configured with a nacelle of an aircraft propulsion system to attenuate noise generated by a gas turbine engine. Such an acoustic panel typically includes a honeycomb core connected between a perforated face skin and a non-perforated back skin. The honeycomb core includes a plurality of resonating chambers.

The acoustic panel may be configured as a single degree of freedom (SDOF) acoustic panel, where each resonating chamber extends through the honeycomb core unobstructed between the face skin and the back skin. Alternatively, the acoustic panel may be configured as a double-degree of freedom (DDOF) acoustic panel, where each resonating chamber is divided by a septum into two fluidly coupled sub-chambers. While various types and configurations of double-degree of freedom acoustic panels are known in the art, there is still room in the art for improvement. There is a need in the art therefore for an improved double-degree of freedom acoustic panel.

<CIT> discloses an acoustic structure having multiple degrees of freedom for reducing noise generated from a source. <CIT> discloses an acoustic structure in which acoustic septa are located in the angled cells of a honeycomb. <CIT> discloses a structured panel with multi-panel structures that attenuates sound generated by a gas turbine engine for an aircraft propulsion system. <CIT> discloses structural panels with splice joint between adjacent core structures, for attenuating sound generated by an aircraft propulsion system. <CIT> discloses a noise reduction device for use in a bleed assembly of a gas turbine engine. <CIT> discloses an automotive sound insulating trim part for noise attenuation in a vehicle.

According to the present invention, an acoustic panel is provided as claimed in claim <NUM>. Some embodiments of the invention are as provided in the dependent claims.

<FIG> is a partial perspective schematic illustration of a structural, acoustic panel <NUM> for attenuating sound; e.g., noise. This acoustic panel <NUM> may be configured to attenuate noise generated by an aircraft propulsion system such as, for example, a turbofan propulsion system or a turbojet propulsion system. With such a configuration, the acoustic panel <NUM> may be configured with a nacelle of the propulsion system. The acoustic panel <NUM>, for example, may be configured as or otherwise included as part of an inner or outer barrel, a translating sleeve, a blocker door, etc. Alternatively, the acoustic panel <NUM> may be configured with another component / structure of the aircraft such as its fuselage or a wing. Furthermore, the acoustic panel <NUM> may be configured to also or alternatively attenuate aircraft related noise other than noise generated by the propulsion system. The acoustic panel <NUM> of the present disclosure, of course, may alternatively be configured for non-aircraft applications.

The acoustic panel <NUM> extends longitudinally along an x-axis. The acoustic panel <NUM> extends laterally along a y-axis. The acoustic panel <NUM> extends vertically along a z-axis. Note, the term "vertical" is used herein to describe a depthwise panel direction and is not limited to a gravitational up/down direction. Furthermore, for ease of illustration, the x-y plane is shown as a generally flat plane. However, in other embodiments, the x-y plane and, thus, the acoustic panel <NUM> may be curved and/or follow an undulating geometry. For example, the x-y plane and, thus, the acoustic panel <NUM> may be arcuate, cylindrical, conical, frustoconical, or tapered with or without radial undulations. In such embodiments, a solely vertical direction (e.g., z-axis direction) is defined relative to a position of interest on the x-y plane. For example, on a spherical x-y plane, the vertical direction (e.g., z-axis) direction is a radial direction.

The acoustic panel <NUM> includes a perforated first skin <NUM>, a solid, non-perforated second skin <NUM> and a structural cellular core <NUM>. Briefly, the cellular core <NUM> is arranged and extends vertically between the first skin <NUM> and the second skin <NUM>. The cellular core <NUM> is also connected to the first skin <NUM> and/or the second skin <NUM>. The cellular core <NUM>, for example, may be welded, brazed, fused, adhered or otherwise bonded to the first skin <NUM> and/or the second skin <NUM>. Alternatively, the cellular core <NUM> may be formed integral with the first skin <NUM> and/or the second skin <NUM> as a monolithic body using, for example, a molding process or an additive manufacturing process. The present disclosure, of course, is not limited to any particular manufacturing methods.

The first skin <NUM> is configured as a face, front and/or exterior skin of the acoustic panel <NUM>. The first skin <NUM>, for example, may be formed from a relatively thin sheet or layer of material that extends laterally and longitudinally along the x-y plane. This first skin material may include, but is not limited to, metal, polymer (e.g., thermoplastic or thermoset material), a fiber reinforced composite (e.g., fiber reinforcement such as, but not limited to, fiberglass, carbon fiber and/or aramid fibers within a polymer matrix), or a combination thereof. The first skin <NUM> has a vertical thickness <NUM>. This first skin vertical thickness <NUM> extends vertically between opposing side surfaces <NUM> and <NUM> of the first skin <NUM>. The first skin <NUM> includes a plurality of perforations <NUM>; e.g., apertures such as through-holes. Each of these first skin perforations <NUM> extends generally vertically through the first skin <NUM> between the first skin side surfaces <NUM> and <NUM>.

The second skin <NUM> is configured as a back and/or interior skin of the acoustic panel <NUM>. The second skin <NUM>, for example, may be formed from a relatively thin sheet or layer of (e.g., continuous, uninterrupted and/or non-porous) material that extends laterally and longitudinally along the x-y plane. This second skin material may include, but is not limited to, metal, polymer (e.g., thermoplastic or thermoset material), a fiber reinforced composite (e.g., fiber reinforcement such as, but not limited to, fiberglass, carbon fiber and/or aramid fibers within a polymer matrix), or a combination thereof. The second skin material may be the same as or different than the first skin material. The second skin <NUM> has a vertical thickness <NUM>. This second skin vertical thickness <NUM> extends vertically between opposing side surfaces <NUM> and <NUM> of the second skin <NUM>. The second skin vertical thickness <NUM> may be substantially equal to or different (e.g., greater or less) than the first skin vertical thickness <NUM>.

The cellular core <NUM> extends laterally and longitudinally along the x-y plane. The cellular core <NUM> has a vertical thickness <NUM>. This core vertical thickness <NUM> extends vertically between opposing sides <NUM> and <NUM> of the cellular core <NUM>. These core sides <NUM> and <NUM> are respectively abutted against the interior first skin side surface <NUM> and the interior second skin side surface <NUM>. The core vertical thickness <NUM> may be substantially greater than the first skin vertical thickness <NUM> and/or the second skin vertical thickness <NUM>. The core vertical thickness <NUM>, for example, may be at least ten to forty times (<NUM>-40x), or more, greater than the vertical thickness <NUM>, <NUM>; however, the acoustic panel <NUM> of the present disclosure is not limited to such an exemplary embodiment.

Referring to <FIG>, the cellular core <NUM> includes a plurality of corrugated structures <NUM> and a plurality of (e.g., planar) chamber sidewalls <NUM>. These cellular core components (e.g., <NUM> and <NUM>) are arranged together to provide the cellular core <NUM> with a plurality of internal (e.g., resonance) chambers <NUM> vertically between the first skin <NUM> and the second skin <NUM> (best seen in <FIG> and <FIG>). The internal chambers <NUM> of <FIG> are arranged in one or more linear chamber arrays 52A-C (generally referred to as "<NUM>"), where each chamber array <NUM> extends longitudinally along the x-axis. Each chamber array <NUM> includes a plurality of the internal chambers <NUM>. Each of the internal chambers <NUM> of <FIG> and <FIG> is respectively fluidly coupled with one or more of the first skin perforations <NUM>.

Referring to <FIG>, the sidewalls <NUM> may be arranged generally parallel with one another. The sidewalls <NUM> are spaced laterally from one another so as to respectively form the internal chambers <NUM> laterally between the sidewalls <NUM>. Each of the sidewalls <NUM> thereby respectively forms lateral peripheral sides of the internal chambers <NUM> in at least one of the chamber arrays <NUM>. Each intermediate sidewall <NUM> (e.g., a sidewall laterally disposed between two other sidewalls), for example, forms the lateral peripheral sides of the respective internal chambers <NUM> in a first of the chamber arrays <NUM> (e.g., 52A) as well as the lateral peripheral sides of the respective internal chambers <NUM> in a second of the chamber arrays <NUM> (e.g., 52B) that laterally neighbors (e.g., is immediately adjacent, next to) the first of the chamber arrays <NUM> (e.g., 52A). Each intermediate sidewall <NUM> is located laterally between the respective laterally neighboring pair of chamber arrays <NUM> (e.g., the first and second chamber arrays 52A and 52B). Each intermediate sidewall <NUM> may therefore fluidly separate the internal chambers <NUM> in the respective laterally neighboring pair of chamber arrays <NUM> (e.g., 52A and 52B) from one another.

Referring to <FIG>, each of the sidewalls <NUM> extends vertically between and to the first skin <NUM> and the second skin <NUM>. Each of the sidewalls <NUM> may also be connected (e.g., bonded and/or otherwise attached) to the first skin <NUM> and/or the second skin <NUM>. Each of the sidewalls <NUM> is orientated substantially perpendicular to the first skin <NUM> and the second skin <NUM>. However, in other embodiments, one or more of the sidewalls <NUM> may be angularly offset from the first skin <NUM> and/or the second skin <NUM> by a non-ninety degree angle; e.g., an acute included angle.

Each corrugated structure <NUM> of <FIG> and <FIG> includes one or more first panels <NUM> (e.g., members, segments, etc.) and one or more second panels <NUM> (e.g., members, segments, etc.). These corrugated structure panels <NUM> and <NUM> are arranged together and are interconnected (e.g., in a zig-zag pattern) to provide a corrugated ribbon <NUM>; e.g., a longitudinally elongated corrugated panel, layer, body, etc. The first panels <NUM> of <FIG> are configured as baffles <NUM>; e.g., solid, non-porous segments of the corrugated ribbon <NUM>. The second panels <NUM> of <FIG> and <FIG> are configured as septums <NUM>; e.g., porous segments of the corrugated ribbon <NUM>. Each of these septums <NUM> includes at least one fluid passthrough region <NUM>. Such a fluid passthrough region <NUM> is configured to allow fluid (e.g., air carrying sound waves) to travel across the respective septum <NUM> as discussed below in further detail.

Referring to <FIG>, the baffles <NUM> and the septums <NUM> are arranged together into a longitudinally extending linear array to provide a respective corrugated ribbon <NUM>. The baffles <NUM> are interspersed with the septums <NUM>. Each baffle <NUM> (unless configured at a longitudinal end of the sidewall <NUM>), for example, is disposed and may extend longitudinally between and to a respective longitudinally neighboring pair of the septums <NUM>. Similarly, each septum <NUM> (unless configured at a longitudinal end of the sidewall <NUM>) is disposed and may extend longitudinally between and to a respective longitudinally neighboring pair of the baffles <NUM>.

The corrugated structure <NUM> includes one or more corrugations <NUM>. Each of these corrugations <NUM> includes a longitudinally neighboring pair of the elements <NUM> and <NUM>, <NUM> and <NUM>.

Referring to <FIG>, within the same corrugation <NUM>, each baffle <NUM> is connected to and may meet a respective septum <NUM> at a peak <NUM> adjacent the first skin <NUM>. Each baffle <NUM>, for example, extends to a first end <NUM> thereof. Each septum <NUM> extends to a first end <NUM> thereof. Each baffle first end <NUM> is (e.g., directly) connected to the first end <NUM> of the septum <NUM> in the same corrugation <NUM> at the first skin peak <NUM>. The baffle <NUM> is angularly offset from the respective septum <NUM> by an included angle <NUM>; e.g., an acute angle, a right angle or an obtuse angle. This first skin peak angle <NUM> of <FIG>, for example, may be between sixty degrees (<NUM>°) and one-hundred and twenty degrees (<NUM>°). The present disclosure, however, is not limited to such an exemplary first skin peak angle.

Each baffle <NUM> is connected to and may meet the septum <NUM> in a longitudinally neighboring corrugation <NUM> at a peak <NUM> adjacent the second skin <NUM>. Each baffle <NUM>, for example, extends to a second end <NUM> thereof. Each septum <NUM> extends to a second end <NUM> thereof. Each baffle second end <NUM> is (e.g., directly) connected to the second end <NUM> of the septum <NUM> in the longitudinally neighboring corrugation <NUM> at the second skin peak <NUM>. The baffle <NUM> is angularly offset from the respective septum <NUM> by an included angle <NUM>; e.g., an acute angle, a right angle or an obtuse angle. This second skin peak angle <NUM> may be equal to the first skin peak angle <NUM>. The second skin peak angle <NUM> of <FIG>, for example, may be between sixty degrees (<NUM>°) and one-hundred and twenty degrees (<NUM>°). The present disclosure, however, is not limited to such an exemplary second skin peak angle.

Each corrugation <NUM> at its first skin peak <NUM> vertically engages (e.g., contacts) and may be connected (e.g., bonded and/or otherwise attached) to the first skin <NUM>. Each baffle <NUM> is angularly offset from the first skin <NUM> by a first skin-baffle included angle <NUM>. This first skin-baffle included angle <NUM> may be an acute angle. The first skin-baffle included angle <NUM> of <FIG>, for example, may be between twenty degrees (<NUM>°) and seventy degrees (<NUM>°); e.g., exactly or about (e.g., +/- <NUM>°) forty-five degrees (<NUM>°). Similarly, each septum <NUM> is angularly offset from the first skin <NUM> by a first skin-septum included angle <NUM>. This first skin-septum included angle <NUM> may be an acute angle, and may be equal to (or different than) the first skin-baffle included angle <NUM>. The first skin-septum included angle <NUM> of <FIG>, for example, may be between twenty degrees (<NUM>°) and seventy degrees (<NUM>°); e.g., exactly or about (e.g., +/- <NUM>°) forty-five degrees (<NUM>°). The present disclosure, however, is not limited to such exemplary angles. In the embodiment of <FIG>, for example, the first skin-septum included angle <NUM> is different (e.g., greater) than the first skin-baffle included angle <NUM>. The first skin-septum included angle <NUM> of <FIG>, for example, may be between sixty-five degrees (<NUM>°) and ninety degrees (<NUM>°); e.g., exactly or about (e.g., +/- <NUM>°) ninety degrees (<NUM>°).

Referring to <FIG>, each corrugation <NUM> at one or each of its second skin peaks <NUM> vertically engages (e.g., contacts) and may be connected (e.g., bonded and/or otherwise attached) to the second skin <NUM>. Each baffle <NUM> is angularly offset from the second skin <NUM> by a second skin-baffle included angle <NUM>. This second skin-baffle included angle <NUM> may be an acute angle. The second skin-baffle included angle <NUM> of <FIG>, for example, may be between twenty degrees (<NUM>°) and seventy degrees (<NUM>°); e.g., exactly or about (e.g., +/- <NUM>°) forty-five degrees (<NUM>°). Similarly, each septum <NUM> is angularly offset from the second skin <NUM> by a second skin-septum included angle <NUM>. This second skin-septum included angle <NUM> may be an acute angle, and may be equal to (or different than) the second skin-baffle included angle <NUM>. The second skin-septum included angle <NUM> of <FIG>, for example, may be between twenty degrees (<NUM>°) and seventy degrees (<NUM>°); e.g., exactly or about (e.g., +/- <NUM>°) forty-five degrees (<NUM>°). The present disclosure, however, is not limited to such exemplary angles. In the embodiment of <FIG>, for example, the second skin-septum included angle <NUM> is different (e.g., greater) than the second skin-baffle included angle <NUM>. The second skin-septum included angle <NUM> of <FIG>, for example, may be between sixty-five degrees (<NUM>°) and ninety degrees (<NUM>°); e.g., exactly or about (e.g., +/- <NUM>°) ninety degrees (<NUM>°).

Referring to <FIG>, with the foregoing configuration, each corrugated structure <NUM> and each of its corrugations <NUM> extend vertically across the cellular core height <NUM> (see <FIG>) between the first skin <NUM> and the second skin <NUM>. Each corrugated structure <NUM> may thereby divide the one or more internal chambers <NUM> within a respective chamber array <NUM> into one or more first cavities 92A and one or more corresponding second cavities 92B. The first cavities 92A are located within the cellular core <NUM> on a first side (e.g., first skin side) of the respective corrugated structure <NUM>. The second cavities 92B are located within the cellular core <NUM> on a second side (e.g., second skin side) of the respective corrugated structure <NUM>.

Each of the first cavities 92A of <FIG> is fluidly coupled with a respective one of the second cavities 92B through the respective at least one fluid passthrough region <NUM>. Each respective set of fluidly coupled cavities 92A and 92B collectively forms a respective one of the internal chambers <NUM> within the cellular core <NUM>. Each internal chamber <NUM> of <FIG> extends vertically between and to the first skin <NUM> and the second skin <NUM>. Each internal chamber <NUM> thereby extends diagonally (e.g., vertically and longitudinally) from the first skin <NUM>, along a respective longitudinally neighboring pair of the baffles <NUM> and through a respective septum <NUM> (via the at least one fluid passthrough region <NUM>), to the second skin <NUM>. Each internal chamber <NUM> of <FIG> extends longitudinally, along the each of the acoustic panel elements <NUM>, <NUM> and <NUM>, between and to the respective longitudinally neighboring pair of the baffles <NUM>. Each internal chamber <NUM> of <FIG> extends laterally, along the each of the corrugated structure elements <NUM> and <NUM>, between and to a respective laterally neighboring pair of the chamber sidewalls <NUM>.

Referring to <FIG>, the acoustic panel <NUM> is configured as a double-degree of freedom (DDOF) acoustic panel. Sound waves entering each internal chamber <NUM>, for example, may follow a plurality of trajectories 94A and 94B (generally referred to as "<NUM>"), which trajectories <NUM> are illustrated to schematically depict which cavities 92A and 92B are involved rather than specific sound wave paths. The sound waves, of course, may also follow one or more additional trajectories not shown in <FIG>. For example, one or more additional sound wave trajectories may exist due to interactions between the first cavity 92A and the second cavity 92B that produce additional reflections.

The first trajectory 94A extends away from the from the respective first skin perforations <NUM>, is reversed by the respective corrugated structure <NUM> (e.g., solid, non-porous portion(s) of the respective septum <NUM>), and extends back to the respective first skin perforations <NUM>. The second trajectory 94B extends away from the respective first skin perforations <NUM> and through the respective at least one fluid passthrough region <NUM>, is reversed by the second skin <NUM>, and extends back through the respective at least one fluid passthrough region <NUM> to the respective first skin perforations <NUM>. With such an arrangement, each internal chamber <NUM> may reverse phase of a plurality of frequencies of the sound waves using known acoustic reflection principles and subsequently direct the reverse phase sound waves out of the acoustic panel <NUM> through the first skin perforations <NUM> to destructively interfere with other incoming noise waves.

One or more or each of the cellular core elements (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and/or <NUM>) may be formed from a plurality of different materials and/or a plurality of different members; e.g., layers. The corrugated structure <NUM> of <FIG> is configured with a multi-layered body <NUM>. This multi-layered body <NUM> includes one or more structural, fluid barrier layers 98A and 98B (generally referred to as "<NUM>") (e.g., fluid non-passthrough layers, non-porous material layers) and at least one fluid passthrough layer <NUM> (e.g., porous material layer, perforated material layer, etc.). The passthrough layer <NUM> of <FIG> is configured (e.g., laid up) with the first barrier layer 98A and the second barrier layer 98B. More particularly, the passthrough layer <NUM> of <FIG> is disposed (e.g., sandwiched) between and attached (e.g., bonded) to the first barrier layer 98A and the second barrier layer 98B.

Each of the barrier layers <NUM> is formed (e.g., only) from fluid barrier (e.g., fluid non-passthrough) material which blocks fluid passage / fluid flow thereacross. Each barrier layer <NUM>, for example, may be configured from a sheet of solid, non-porous material; e.g., material without open cell pores. Examples of the barrier material include, but are not limited to, metal, polymer (e.g., thermoplastic or thermoset material), a fiber reinforced composite (e.g., fiber reinforcement such as, but not limited to, fiberglass, carbon fiber and/or aramid fibers within a polymer matrix), or a combination thereof.

Each passthrough layer <NUM> may be formed (e.g., only) from fluid passthrough material which provides for fluid passage / fluid flow thereacross. This passthrough material is porous material such as, but not limited to, material with open cell pores, material with interstices (e.g., mesh, or other woven or matted material), etc. The passthrough material may also or alternatively be material configured with one or more (e.g., micro) perforations. The passthrough material, more particularly, is configured with one or more apertures, which apertures form one or more discrete fluid paths and/or one or more interconnected networks of fluid paths through the passthrough material. For example, the passthrough material of <FIG> is open cell porous material 102A with a network of open cell pores 104A. The passthrough material of <FIG> is porous mesh material 102B with a network of interstices 104B formed between mesh elements <NUM>; e.g., threads, strands, members, etc. The passthrough material of <FIG> is porous or non-porous material 102B with one or more perforations 104C (e.g., through-holes) extending therethrough. Examples of the passthrough material include, but are not limited to, metal, polymer (e.g., thermoplastic or thermoset material), a fiber reinforced composite (e.g., fiber reinforcement such as, but not limited to, fiberglass, carbon fiber and/or aramid fibers within a polymer matrix), or a combination thereof, which materials may be porous or non-porous as described above.

Referring to <FIG>, one or more or each of the cellular core elements <NUM>, <NUM> and <NUM> may be formed from the stack of layers <NUM> and <NUM>; e.g., see the baffles <NUM> in <FIG>. Within these elements <NUM>, <NUM> and <NUM>, one or each of the barrier layers <NUM> is uninterrupted; e.g. not include any apertures. The passthrough layer <NUM> is (e.g., completely) covered / overlapped by at least one of the barrier layers <NUM>. The passthrough layer <NUM> of <FIG>, for example, may be embedded / sandwiched between the barrier layers <NUM>. The material of each barrier layer <NUM> may thereby block, cover, obstruct the apertures within the passthrough material of the passthrough layer <NUM>. Of course, one or more or each of the cellular core elements <NUM>, <NUM> and <NUM> may be configured without one of the barrier layers <NUM> and/or without the passthrough layer <NUM> as shown, for example, in <FIG>. With the foregoing configurations of <FIG>, an entirety of each face (e.g., baffle face <NUM>, <NUM>; see <FIG>) of the respective cellular core elements <NUM>, <NUM>, <NUM> is formed by an uninterrupted portion of a respective one of the barrier layers <NUM> and its barrier material.

Referring to <FIG>, each of the septums <NUM> is also formed from the stack of layers <NUM> and <NUM>. However, by contrast to the baffles <NUM> of <FIG> (see also <FIG>), each barrier layer <NUM> is configured with at least one interruption 112A, 112B (generally referred to as "<NUM>"); e.g., an aperture such as a window, an opening, a perforation, etc. Each interruption <NUM> of <FIG>, for example, is configured as an aperture (e.g., a window or opening). The interruption 112A in the first barrier layer 98A is aligned with the interruption 112B in the second barrier layer 98B. The interruptions <NUM> also have common cross-sectional geometries (e.g., shapes and sizes); however, the present disclosure is not limited thereto. Each of these interruptions <NUM> exposes (e.g., uncovers, makes visible, etc.) a respective portion <NUM> of the passthrough layer <NUM> and its passthrough material. This exposed passthrough portion <NUM> forms the fluid passthrough region <NUM> in the respective septum <NUM>.

Referring to <FIG>, the septum <NUM> has a septum length <NUM> and a septum width <NUM>. The fluid passthrough region <NUM> (and the respective portion of the passthrough layer <NUM> and its passthrough material) has a passthrough region length <NUM> and a passthrough region width <NUM>. The passthrough region length <NUM> of <FIG> is less than the septum length <NUM>. The passthrough region width <NUM> of <FIG> is less than the septum width <NUM>. The fluid passthrough region <NUM> of <FIG> is also positioned intermediately (e.g., centered) in the respective septum <NUM>. The fluid passthrough region <NUM> of <FIG> (see also <FIG>) is thereby surrounded by a (e.g., annular, border) fluid barrier region <NUM> of the respective septum <NUM>.

Referring to <FIG>, the barrier region <NUM> may be (e.g., completely) formed by the stack of the layers 98A, <NUM> and 98B. A (e.g., annular, border) portion of the passthrough layer <NUM> and its passthrough material, for example, may be embedded / sandwiched between respective (e.g., annular, border) portions of the barrier layers <NUM>. These portions of the barrier layers <NUM> also respectively form peripheral borders of the interruptions <NUM>. A length and/or a width of the passthrough layer <NUM> within the respective septum <NUM> of <FIG> are respectively equal to the septum length <NUM> and/or the septum width <NUM> (and each barrier layer). However, in other embodiments, a portion of the barrier region <NUM> may also (or alternatively) be formed by a stack of the layers 98A and 98B as shown, for example, in <FIG>. A length <NUM> and/or a width <NUM> of the passthrough layer <NUM> within the respective septum <NUM> of <FIG>, for example, are respectively less than the septum length <NUM> and/or the septum width <NUM>. In still other embodiments, referring to <FIG>, the respective septum <NUM> may omit one of the barrier layers <NUM>. With the foregoing configurations of <FIG>, <FIG> and <FIG>, each face <NUM> of the respective septum <NUM> is partially formed by the respective barrier portion and its barrier material and the respective passthrough portion and its passthrough material.

In some embodiments, referring to <FIG>, each septum face <NUM> has a face area, which is defined by the septum length <NUM> and the septum width <NUM>. Each fluid passthrough region <NUM> and each associated interruption <NUM> has a cross-sectional area when viewed, for example, in a plane parallel with the respective septum face <NUM>. The cross-sectional area is defined by the length <NUM> and the width <NUM> of the element <NUM>, <NUM>. The cross-sectional area of <FIG> is at least one half (<NUM>/<NUM>) of the face area; e.g., greater than seventy-five percent (<NUM>%) of the face area, but less than one-hundred percent (<NUM>%) of the face area. However, in other embodiments, the cross-sectional area may be less than one half (<NUM>/<NUM>) of the face area as shown, for example, in <FIG>. In such embodiments, each barrier material layer <NUM> may include one or more additional interruptions <NUM> in order to provide the respective septum <NUM> with one or more additional fluid passthrough regions <NUM>; e.g., exposed portions of passthrough material.

Each of the fluid passthrough regions <NUM> described above is formed by at least one layer of the passthrough material. In addition to providing a path for fluid travel across the septums <NUM>, the passthrough material may also provide acoustic linearity as compared, for example, to a septum without the passthrough material; e.g., a septum formed with open perforations. The passthrough material may also or alternatively provide the septum <NUM> with a higher acoustic impedance as compared, for example, to a septum without the passthrough material. Inclusion of the passthrough material, of course, may also or alternative provide the acoustic panel <NUM> with one or more other acoustic and/or structural properties.

Referring to <FIG>, each corrugated structure <NUM> has an aspect ratio. This aspect ratio may be determined by dividing a vertical height <NUM> of the respective corrugated structure <NUM> by a longitudinal length <NUM> of a corrugation <NUM> in the respective corrugated structure <NUM>. The aspect ratio may be <NUM>:<NUM> (see <FIG>), greater than <NUM>:<NUM> (e.g., see <FIG>) or less than <NUM>:<NUM> (e.g., see <FIG>).

The cellular core <NUM> and one or more of its elements (e.g., <NUM>, <NUM>) may be formed using various formation techniques. For example, the barrier and the passthrough materials may be cut and laid up to provide a multilayered sheet of material. This multilayered sheet of material may subsequently be manipulated (e.g., folded, cut, etc.) to form the cellular core <NUM>. The multilayered sheet of material, for example, may be folded (e.g., using origami and/or kirigami techniques) into a three-dimensional body that includes / forms one, some or all of the cellular core elements (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>). Other suitable formation techniques include, but are not limited to, compression molding, injection molding, stamping, machining and additive manufacturing.

Claim 1:
An acoustic panel (<NUM>), comprising:
a perforated first skin (<NUM>);
a second skin (<NUM>);
a corrugated structure (<NUM>) between and connected to the perforated first skin and the second skin, the corrugated structure including a plurality of baffles (<NUM>), a plurality of septums (<NUM>), first material and second material; and
a chamber (<NUM>) extending from the perforated first skin, along a first of the plurality of baffles and a second of the plurality of baffles, to the second skin;
wherein a first of the plurality of septums divides the chamber into a first cavity and a second cavity;
wherein the plurality of baffles (<NUM>) and the plurality of septums (<NUM>) are arranged together into a longitudinally extending linear array to provide a respective corrugated ribbon (<NUM>), wherein the baffles (<NUM>) are interspersed with the septums (<NUM>); and
wherein the first material comprises non-porous material, and the second material comprises porous material;
the acoustic panel being characterised in that:
the corrugated structure includes a layer of the first material and a layer of the second material, and the layer of the second material is attached to the layer of the first material;
each of the first and second of the plurality of baffles is formed by an uninterrupted portion of the first material;
the first of the plurality of septums is formed by a portion of the second material that is exposed through an interruption in the first material so that the second cavity is fluidly coupled with the first cavity through one or more apertures the first septum.