Patent Description:
Gas turbine engines may be employed to power various devices. For example, a gas turbine engine may be employed to propel or supply power to a mobile platform, such as an aircraft. The operation of the gas turbine engine to propel the aircraft may result in the generation of noise that is undesirable for passengers and crew while the aircraft is in flight. In addition, the gas turbine engine may run while the aircraft is on the ground to supply power to the aircraft. In these instances, noise generated by the gas turbine engine may be undesirable to one or more passengers or crew onboard the aircraft and service personnel outside.

Accordingly, it is desirable to provide systems for sound attenuation, for reducing the noise experienced by passengers, crew and service personnel, for example, during the operation of the gas turbine engine. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. <CIT> discloses an an acoustic insert comprising a sleeve and a number of wave-shaped passageways within the sleeve. A contour of the number of wave-shaped passageways is selected to provide a desired level of attenuation for a frequency of sound waves entering the sleeve.

According to various embodiments, provided is a sound attenuating cell according to claim <NUM>. The sound attenuating cell includes a first sound attenuating cavity defined between a first sidewall and a second sidewall. The first sidewall is opposite the second sidewall. The first sidewall includes a first undulating surface and the second sidewall includes a second undulating surface. A deflector is coupled to the first undulating surface. The deflector extends from the first undulating surface toward the second undulating surface. The first undulating surface is axially offset from the second undulating surface to define a tortuous path between the first sidewall and the second sidewall. The first sound attenuating cavity has a first end and a second end. The first end is opposite the second end, and an inlet and an outlet of the first sound attenuating cavity is defined at the first end. The sound attenuating cell includes a second sound attenuating cavity nested within the first sound attenuating cavity.

The deflector includes a first deflector end and a second deflector end. The first deflector end is coupled to the first undulating surface and the first deflector end defines a plurality of openings spaced apart about a periphery of the first deflector end. The deflector is cantilevered relative to the first undulating surface and the second deflector end extends toward the second undulating surface. The first undulating surface includes a plurality of first undulations, a plurality of first valleys and a plurality of first sloped surfaces that alternate to define the first undulating surface, and the deflector is coupled to at least one first valley of the plurality of first valleys of the first undulating surface. The sound attenuating cell includes a perforated facesheet coupled to the first end. The first sound attenuating cavity and the second sound attenuating cavity extend about a longitudinal axis of the sound attenuating cell. The second sound attenuating cavity has a third end and a fourth end, the third end opposite the fourth end, and a second inlet and a second outlet are defined at the third end. The sound attenuating cell includes a perforated backsheet coupled to at least a portion of the second end of the first sound attenuating cavity and the fourth end of the second sound attenuating cavity. The sound attenuating cell includes a plurality of walls that cooperate to surround the first sound attenuating cavity and the second sound attenuating cavity, with a base wall coupled to each of the plurality of walls, and the backsheet is coupled to the portion of the second end of the first sound attenuating cavity and the fourth end of the second sound attenuating cavity such that a chamber is defined between the backsheet and the base wall. The backsheet is coupled to the portion of the second end of the first sound attenuating cavity and the fourth end of the second sound attenuating cavity to extend along an axis that is transverse to the longitudinal axis of the sound attenuating cell to define the chamber. The first sound attenuating cavity and the second sound attenuating cavity are substantially symmetric about a longitudinal axis of the sound attenuating cell. The sound attenuating cell includes a third sound attenuating cavity nested within the second sound attenuating cavity. A length of the first sound attenuating cavity and the second sound attenuating cavity varies about a perimeter of the sound attenuating cell. The first sidewall of the first sound attenuating cavity defines a perimeter of the sound attenuating cell. The second end of the first sound attenuating cavity is closed, the second sound attenuating cavity has a third end and a fourth end, the third end opposite the fourth end and the fourth end is closed such that a second inlet and a second outlet of the second sound attenuating cavity is defined at the third end. The sound attenuating cell includes at least one partition that extends through at least the first sound attenuating cavity and the second sound attenuating cavity.

Also provided is a sound attenuating panel for a gas turbine engine. The sound attenuating panel includes at least one sound attenuating cell according to claim <NUM>. The at least one sound attenuating cell includes a perforated facesheet, a first sound attenuating cavity defined between a first sidewall and a second sidewall, with the first sidewall opposite the second sidewall. The first sidewall includes a first undulating surface and the second sidewall includes a second undulating surface. A deflector is coupled to the first undulating surface that extends from the first undulating surface toward the second undulating surface, and the first undulating surface is axially offset from the second undulating surface to define a tortuous path between the first sidewall and the second sidewall. The first sound attenuating cavity has a first end coupled to the facesheet and a second end, the first end is opposite the second end, and an inlet and an outlet are each defined at the facesheet. A second sound attenuating cavity is nested within an inner perimeter of the first sound attenuating cavity, and the second sound attenuating cavity having a second inlet and a second outlet defined at the facesheet.

The deflector is cantilevered relative to the first undulating surface. The deflector includes a first deflector end and a second deflector end. The first deflector end is coupled to the first undulating surface, and the first deflector end defines a plurality of openings spaced apart about a periphery of the first deflector end. The sound attenuating panel of Claim <NUM>, wherein the at least one sound attenuating cell includes a plurality of walls that cooperate to surround the first sound attenuating cavity and the second sound attenuating cavity, and a base wall is coupled to each of the plurality of walls opposite the facesheet. The sound attenuating panel includes a perforated backsheet coupled to a portion of the second end of the first sound attenuating cavity and an end of the second sound attenuating cavity to extend along an axis that is transverse to a longitudinal axis of the at least one sound attenuating cell to define a chamber between the backsheet and the base wall.

In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with any type of device that would benefit from sound attenuation and the use of the system for sound attenuation in a gas turbine engine described herein is merely one exemplary embodiment according to the present disclosure. In addition, while the system for sound attenuation is described herein as being used with a gas turbine engine onboard a mobile platform, such as a bus, motorcycle, train, motor vehicle, marine vessel, aircraft, rotorcraft and the like, the various teachings of the present disclosure can be used with a gas turbine engine on a stationary platform. Further, it should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the present disclosure. In addition, while the figures shown herein depict an example with certain arrangements of elements, additional intervening elements, devices, features, or components may be present in an actual embodiment. It should also be understood that the drawings are merely illustrative and may not be drawn to scale.

As used herein, the term "axial" refers to a direction that is generally parallel to or coincident with an axis of rotation, axis of symmetry, or centerline of a component or components. For example, in a cylinder or disc with a centerline and generally circular ends or opposing faces, the "axial" direction may refer to the direction that generally extends in parallel to the centerline between the opposite ends or faces. In certain instances, the term "axial" may be utilized with respect to components that are not cylindrical (or otherwise radially symmetric). For example, the "axial" direction for a rectangular housing containing a rotating shaft may be viewed as a direction that is generally parallel to or coincident with the rotational axis of the shaft. Furthermore, the term "radially" as used herein may refer to a direction or a relationship of components with respect to a line extending outward from a shared centerline, axis, or similar reference, for example in a plane of a cylinder or disc that is perpendicular to the centerline or axis. In certain instances, components may be viewed as "radially" aligned even though one or both of the components may not be cylindrical (or otherwise radially symmetric). Furthermore, the terms "axial" and "radial" (and any derivatives) may encompass directional relationships that are other than precisely aligned with (e.g., oblique to) the true axial and radial dimensions, provided the relationship is predominantly in the respective nominal axial or radial direction. As used herein, the term "substantially" denotes within <NUM>% to account for manufacturing tolerances. Also, as used herein, the term "about" denotes within <NUM>% to account for manufacturing tolerances.

With reference to <FIG>, a partial, cross-sectional view of an exemplary gas turbine engine <NUM> is shown with the remaining portion of the gas turbine engine <NUM> being axisymmetric about a longitudinal axis <NUM>, which also comprises an axis of rotation for the gas turbine engine <NUM>. In the depicted embodiment, the gas turbine engine <NUM> is an annular multi-spool turbofan gas turbine jet engine. As will be discussed herein, the gas turbine engine <NUM> includes a system for sound attenuation or a sound attenuation panel <NUM> that includes at least one sound attenuation cell <NUM>, which provides attenuation over a broad range of frequencies, such as a broad frequency range of about <NUM> hertz (Hz) to about <NUM>,<NUM> hertz (Hz). By providing attenuation over the broad range of frequencies, the sound attenuation panel <NUM> enables the reduction in sound over the broad range of frequencies without requiring separate systems for separate frequency bands. This reduces cost and complexity of the sound attenuation panel <NUM>. It should be noted that while the sound attenuation panel <NUM> is illustrated and described herein as being used with the gas turbine engine <NUM>, the sound attenuation panel <NUM> can be employed with various types of engines, including, but not limited to, gas turbine engines included with auxiliary power units, turbofan, turboprop, turboshaft, and turbojet engines, whether deployed onboard an aircraft, watercraft, or ground vehicle (e.g., a tank), included within industrial power generators, or utilized within another platform or application. In this example, the gas turbine engine <NUM> is employed within an aircraft <NUM>.

In this example, with reference back to <FIG>, the gas turbine engine <NUM> includes a fan section <NUM>, the compressor section <NUM>, a combustor section <NUM>, the turbine section <NUM>, and an exhaust section <NUM>. The fan section <NUM> includes a fan <NUM> that draws air into the gas turbine engine <NUM> and accelerates it. A fraction of the accelerated air exhausted from the fan <NUM> is directed through an outer (or first) bypass duct <NUM> and the remaining fraction of air exhausted from the fan <NUM> is directed into the compressor section <NUM>. The outer bypass duct <NUM> is generally defined between the inner bypass duct <NUM> and an outer casing <NUM>. In this example, the sound attenuation panel <NUM> is coupled to the outer bypass duct <NUM> to attenuate sound over the broad range of frequencies in the outer bypass duct <NUM>, however, the sound attenuation panel <NUM> may be employed throughout the gas turbine engine <NUM>, including, but not limited to, an inlet duct associated with the fan section <NUM>, access panels located within the outer bypass duct <NUM>, and a center body located within the exhaust section <NUM>. In the embodiment of <FIG>, the compressor section <NUM> includes an intermediate pressure compressor <NUM> and a high pressure compressor <NUM>. However, in other embodiments, the number of compressors in the compressor section <NUM> may vary. In the depicted embodiment, the intermediate pressure compressor <NUM> and the high pressure compressor <NUM> sequentially raise the pressure of the air and direct a majority of the high pressure air into the combustor section <NUM>. A fraction of the compressed air bypasses the combustor section <NUM> and is used to cool, among other components, turbine blades in the turbine section <NUM>.

In the embodiment of <FIG>, in the combustor section <NUM>, which includes a combustion chamber <NUM>, the high pressure air is mixed with fuel, which is combusted. The high-temperature combustion air is directed into the turbine section <NUM>. In this example, the turbine section <NUM> includes three turbines disposed in axial flow series, namely, a high pressure turbine <NUM>, an intermediate pressure turbine <NUM>, and a low pressure turbine <NUM>. However, it will be appreciated that the number of turbines, and/or the configurations thereof, may vary. In this embodiment, the high-temperature air from the combustor section <NUM> expands through and rotates each turbine <NUM>, <NUM>, and <NUM>. As the turbines <NUM>, <NUM>, and <NUM> rotate, each drives equipment in the gas turbine engine <NUM> via concentrically disposed shafts or spools. In one example, the high pressure turbine <NUM> drives the high pressure compressor <NUM> via a high pressure shaft <NUM>, the intermediate pressure turbine <NUM> drives the intermediate pressure compressor <NUM> via an intermediate pressure shaft <NUM>, and the low pressure turbine <NUM> drives the fan <NUM> via a low pressure shaft <NUM>.

With reference to <FIG>, a perspective view of the sound attenuation panel <NUM> is shown. As discussed, the sound attenuation panel <NUM> in this example is used in the gas turbine engine <NUM> to attenuate sound over the broad frequency range. The sound attenuation panel <NUM> includes a plurality of the sound attenuation cells <NUM>. It should be noted that the arrangement of the sound attenuation cells <NUM> to form the sound attenuation panel <NUM> shown in <FIG> is merely an example, as the sound attenuation cells <NUM> may be arranged in any configuration to form the sound attenuation panel <NUM>. In this regard, the sound attenuation cells <NUM> may be arranged to form any desired polygonal shape for the sound attenuation panel <NUM>, including, but not limited to, rectangular, square, triangular, trapezoid, etc. Moreover, the sound attenuation cells <NUM> may be arranged to form the sound attenuation panel <NUM> that has a shape configured for the particular use of the sound attenuation panel <NUM> within the gas turbine engine <NUM> such that the sound attenuation panel <NUM> may have a non-uniform or custom shape to fit the space available in the gas turbine engine <NUM>. In this example, the sound attenuation panel <NUM> is composed of <NUM> sound attenuation cells <NUM>, however, it should be understood that the sound attenuation panel <NUM> may comprise any number of sound attenuation cells <NUM>, including a single sound attenuation cell <NUM>.

In one example, the sound attenuation cells <NUM> are each additively manufactured to form the sound attenuation panel <NUM>. In this example, each of the sound attenuation cells <NUM> is composed of a metal or metal alloy, such as aluminum, titanium, Inconel® produced by American Special Metals Corporation of Miami, Florida, United States of America, or high strength plastics, including, but not limited to polyether ether ketone (PEEK) or polyetherimide; and is formed using additive manufacturing, including, but not limited to, direct metal laser sintering (DMLS) or fused deposition modeling (FDM). During the additive manufacture of the sound attenuation cells <NUM>, the sound attenuation panel <NUM> may be formed by additively manufacturing adjacent ones of the sound attenuation cells <NUM> together such that the sound attenuation panel <NUM> is composed of one or more integrally formed sound attenuation cells <NUM>. In other examples, the sound attenuation panel <NUM> may be formed by coupling discrete sound attenuation cells <NUM> together via welding, mechanical fasteners, brazing, etc..

With reference to <FIG>, one of the sound attenuation cells <NUM> is shown. As each of the sound attenuation cells <NUM> is the same, a single one of the sound attenuation cells <NUM> will be discussed in detail herein. In this example, each of the sound attenuation cells <NUM> includes a plurality of walls <NUM>, a base wall <NUM>, a facesheet <NUM>, a backsheet <NUM> and at least one or a plurality of sound attenuating cavities <NUM>. As discussed, generally, each of the sound attenuation cells <NUM> is integrally or monolithically formed so as to be one-piece via additive manufacturing.

The plurality of walls <NUM> cooperate to surround the plurality of sound attenuating cavities <NUM>. In one example, the plurality of walls <NUM> include six planar walls 204a-204f, which cooperate to define a hexagon. It should be noted that in other examples, the plurality of walls <NUM> may cooperate to define any suitable polygonal shape, including, but not limited to, cylindrical, rectangular, square, trapezoid, pentagon, etc. The walls 204a-204f are solid or non-perforated. The walls 204a-204f each extend from the facesheet <NUM> to the base wall <NUM>. In one example, the walls 204a-204f are each coupled to or integrally formed with the facesheet <NUM>, the base wall <NUM> and the plurality of sound attenuating cavities <NUM>.

The base wall <NUM> forms a second or bottom side of the sound attenuation cell <NUM>, while the facesheet <NUM> forms a first or top side of the sound attenuation cell <NUM>. The base wall <NUM> is hexagonal, and is coupled to or integrally formed with each of the walls 204a-204f so as to be opposite the facesheet <NUM>. The base wall <NUM> is also coupled to or integrally formed with a portion of the plurality of sound attenuating cavities <NUM> and the backsheet <NUM>. The base wall <NUM> is planar and is solid or non-perforated. In this example, each of the sound attenuation cells <NUM> has the base wall <NUM>, however, in other embodiments, the sound attenuation panel <NUM> may be formed such that a single base wall <NUM> extends over a plurality of the sound attenuation cells <NUM>. As will be discussed, in this example, the base wall <NUM> of each of the sound attenuation cells <NUM> cooperates with the backsheet <NUM> of each of the sound attenuation cells <NUM> to define a chamber <NUM> in each of the sound attenuation cells <NUM>. The base wall <NUM> extends parallel to the facesheet <NUM>.

With reference to <FIG>, the facesheet <NUM> is coupled to or integrally formed with each of the walls 204a-204f to enclose the sound attenuation cell <NUM>. The facesheet <NUM> is also coupled to or integrally formed with the plurality of sound attenuating cavities <NUM>. The facesheet <NUM> is planar, and is perforated with a plurality of perforations or openings 208a that enable fluid, such as air, to enter into the plurality of sound attenuating cavities <NUM> of the sound attenuation cell <NUM>. The facesheet <NUM> may include any predetermined number of openings 208a to fluidly couple the plurality of sound attenuating cavities <NUM> to the surrounding fluid. In this example, each of the sound attenuation cells <NUM> has the facesheet <NUM>, however, in other embodiments, the sound attenuation panel <NUM> may be formed such that a single facesheet <NUM> extends over a plurality of the sound attenuation cells <NUM>. The facesheet <NUM> defines both the inlet and the outlet for the sound attenuation cells <NUM>. In this regard, as the base wall <NUM> is solid or non-perforated, the base wall <NUM> does not define an outlet. Rather, fluid, such as air, enters the sound attenuation cells <NUM> via the facesheet <NUM>, and exits the sound attenuation cells <NUM> via the facesheet <NUM>.

With reference to <FIG>, the backsheet <NUM> is coupled to or integrally formed with a portion of the plurality of sound attenuating cavities <NUM> at an end of the portion of the plurality of sound attenuating cavities <NUM> opposite the facesheet <NUM>. The backsheet <NUM> is also coupled to or integrally formed with the base wall <NUM> and walls 204a and 204c-f (<FIG>). The backsheet <NUM> is perforated with a plurality of perforations or openings 210a that enable fluid, such as air, to enter into the chamber <NUM> of the sound attenuation cell <NUM>. The backsheet <NUM> may include any predetermined number of openings 210a to fluidly couple the plurality of sound attenuating cavities <NUM> to the chamber <NUM>. In this example, the backsheet <NUM> extends along an axis A, which is transverse or oblique to a longitudinal axis L of the sound attenuation cell <NUM>. The facesheet <NUM> and the base wall <NUM> are each orientated to extend along an axis that is substantially perpendicular to the longitudinal axis L. The backsheet <NUM> is generally formed to extend along the axis A, which is also transverse to an axis along which the facesheet <NUM> and an axis along which the base wall <NUM> extends. In other words, the backsheet <NUM> extends at an angle α defined between the backsheet <NUM> and the base wall <NUM>. The angle α is about <NUM> to about <NUM> degrees, and in one example, is about <NUM> degrees. By forming the backsheet <NUM> at the angle α and to extend transverse to the longitudinal axis L, the chamber <NUM> has a volume that varies along the sound attenuation cell <NUM>, which enables for attenuation of different frequency ranges by the sound attenuation cell <NUM>. The chamber <NUM> is defined as an empty space or void between the backsheet <NUM> and the base wall <NUM>. Since the chamber <NUM> does not contain any material and is an empty space or void, the chamber <NUM> provides a weight savings to each sound attenuation cell <NUM>. This weight savings benefit is multiplied by the number of sound attenuation cells <NUM> within the sound attenuation panel <NUM>, which may significantly reduce the weight associated with the sound attenuation panel <NUM>. In this example, the chamber <NUM> is pyramidal in shape, however, the chamber <NUM> may have any shape depending upon the orientation of the backsheet <NUM> to the base wall <NUM>. The volume of the chamber <NUM> increases from a first end 210b of the backsheet <NUM> to a second end 210c of the backsheet <NUM>. The first end 210b of the backsheet <NUM> is coupled to or integrally formed with the base wall <NUM>, and the second end 210c of the backsheet <NUM> is coupled to or integrally formed with the wall 204e (<FIG>).

In this example, with reference to <FIG>, the backsheet <NUM> is defined a distance D from a first side 206a of the base wall <NUM>. The first side 206a of the base wall <NUM> is opposite a second side 206b of the base wall <NUM>. The first side 206a is coupled to or integrally formed with the wall 204b, and the second side 206b is coupled to or integrally formed with the wall 204e. Generally, the distance D is slightly greater than a width W of the sound attenuation chamber 212a (<FIG>), or is about <NUM>% to about <NUM>% of the overall width W1 of the base wall <NUM>. This enables at least a portion of the sound attenuating cavities <NUM> to completely extend from the facesheet <NUM> to the base wall <NUM> (length L1, <FIG>) to realize the full height of the sound attenuation cell <NUM>. This provides sound attenuation at the lowest frequencies for this particular location of the sound attenuating cavities <NUM>, whereas the locations of the shorter portions of the sound attenuating cavities <NUM> (lengths L2-L6, <FIG>) provide sound attenuation for the higher frequencies. The constant change in lengths L1-L6 (<FIG>) in the sound attenuation cavities <NUM> provides the broadband sound attenuation in the sound attenuation cell <NUM>. Thus, the backsheet <NUM> is positioned the distance D from the first side 206a of the base wall <NUM> to enable a portion of one of the plurality of sound attenuating cavities <NUM> to attenuate sound at a different frequency than a remainder of the plurality of sound attenuating cavities <NUM>. As discussed, the distance D is predetermined such that the portion of one of the plurality of sound attenuating cavities <NUM> terminates at the base wall <NUM>, while a remainder of the plurality of sound attenuating cavities <NUM> terminate at the backsheet <NUM>. The varying of the lengths L1-L6 (<FIG>) of the plurality of sound attenuating cavities <NUM> and the termination locations enables the sound attenuation cell <NUM> to attenuate the broad range of frequencies.

With reference to <FIG>, the plurality of sound attenuating cavities <NUM> extend about the longitudinal axis L. In this example, the sound attenuation cells <NUM> each include three of the plurality of sound attenuating cavities <NUM>: a first sound attenuating cavity 212a, a second sound attenuating cavity 212b and a third sound attenuating cavity 212c. The second sound attenuating cavity 212b and the third sound attenuating cavity 212c are nested within an inner perimeter of the first sound attenuating cavity 212a. The third sound attenuating cavity 212c is nested within an inner perimeter of the second sound attenuating cavity 212b. Each of the sound attenuating cavities 212a-212c is concentric about the longitudinal axis L. Each of the sound attenuating cavities 212a-212c includes a first sidewall <NUM> opposite a second sidewall <NUM>. The second sidewall <NUM> is radially inward from the first sidewall <NUM> such that the first sidewall <NUM> defines a perimeter of the respective sound attenuating cavity 212a-212c. The first sound attenuating cavity 212a extends from a first end <NUM> coupled to or integrally formed with the facesheet <NUM> to a second end <NUM>. A portion 236a of the second end <NUM> proximate the wall 204b terminates at the base wall <NUM>, while a portion 236b of the second end <NUM> terminates at the backsheet <NUM>. Stated another way, the orientation of the backsheet <NUM> results in the first sound attenuating cavity 212a having a first length L1 proximate the first side 206a of the base wall <NUM>, and a second length L2 proximate the second side 206b of the base wall <NUM>. Thus, the length of the first sound attenuating cavity 212a varies about the perimeter of the sound attenuation cell <NUM> (<FIG>). In one example, the length of the first sound attenuating cavity 212a is reduced by about <NUM>% between the first length L1 and the second length L2.

The second sound attenuating cavity 212b extends from a third end <NUM> coupled to or integrally formed with the facesheet <NUM> to a fourth end <NUM>. A portion 240a of the fourth end <NUM> proximate the wall 204b terminates at the backsheet <NUM> proximate the first end 210b of the backsheet <NUM>, and a portion 240b of the fourth end <NUM> terminates proximate the second end 210c of the backsheet <NUM>. The orientation of the backsheet <NUM> results in the second sound attenuating cavity 212b having a third length L3 proximate the first side 206a of the base wall <NUM>, and a fourth length L4 proximate the second side 206b of the base wall <NUM>. Thus, the length of the second sound attenuating cavity 212b varies about the perimeter of the sound attenuation cell <NUM> (<FIG>). In one example, the length of the second sound attenuating cavity 212b is reduced by about <NUM>% between the third length L3 and the fourth length L4.

The third sound attenuating cavity 212c extends from a fifth end <NUM> coupled to or integrally formed with the facesheet <NUM> to a sixth end <NUM>. A portion 244a of the sixth end <NUM> proximate the wall 204b terminates at the backsheet <NUM> proximate the first end 210b of the backsheet <NUM>, and a portion 244b of the sixth end <NUM> terminates proximate the second end 210c of the backsheet <NUM>. The orientation of the backsheet <NUM> results in the third sound attenuating cavity 212c having a fifth length L5 proximate the first side 206a of the base wall <NUM>, and a sixth length L6 proximate the second side 206b of the base wall <NUM>. Thus, the length of the third sound attenuating cavity 212c varies about the perimeter of the sound attenuation cell <NUM> (<FIG>). In one example, the length of the third sound attenuating cavity 212c is reduced by about <NUM>% between the fifth length L5 and the sixth length L6. In this example, each of the lengths L1-L6 is different.

As discussed, each of the sound attenuating cavities 212a-212c is defined by extruding the first sidewall <NUM> and the second sidewall <NUM> about the longitudinal axis L. In this example, each of the sound attenuating cavities 212a-212c include the same first sidewall <NUM> and the same second sidewall <NUM>, but the lengths of the first sidewall <NUM> and the second sidewall <NUM> are varied due to the orientation of the backsheet <NUM> along the axis A. Each of the first sidewalls <NUM> includes a plurality of first undulations <NUM>, with each first undulation <NUM> separated by a respective first valley <NUM> of a plurality of first valleys <NUM>. A first sloped surface <NUM> of a plurality of first sloped surfaces <NUM> is defined to interconnect a respective adjacent first valley <NUM> with an adjacent first undulation <NUM>. The first undulation <NUM>, the first valley <NUM> and the first sloped surface <NUM> alternate or repeat along the first sidewall <NUM> from the respective end <NUM>, <NUM>, <NUM> to the respective end <NUM>, <NUM>, <NUM> to form a first undulating surface. Generally, from the respective end <NUM>, <NUM>, <NUM>, the first sidewall <NUM> includes one of the first sloped surfaces <NUM> coupled to or integrally formed with the facesheet <NUM>, transitions to one of the first undulations <NUM> and then to one of the first valleys <NUM>. This repeats until the first sidewall <NUM> terminates at the respective end <NUM>, <NUM>, <NUM>.

Each of the second sidewalls <NUM> includes a plurality of second undulations <NUM>, with each second undulation <NUM> separated by a respective second valley <NUM> of a plurality of second valleys <NUM>. A second sloped surface <NUM> of a plurality of second sloped surfaces <NUM> is defined to interconnect a respective adjacent second valley <NUM> with an adjacent second undulation <NUM>. The second undulation <NUM>, the second valley <NUM> and the second sloped surface <NUM> alternate or repeat along the second sidewall <NUM> from the respective end <NUM>, <NUM>, <NUM> to the respective end <NUM>, <NUM>, <NUM> to form a second undulating surface. Generally, from the respective end <NUM>, <NUM>, <NUM>, the second sidewall <NUM> includes one of the second valleys <NUM> coupled to or integrally formed with the facesheet <NUM>, transitions to one of the second sloped surfaces <NUM> and then to one of the second undulations <NUM>. This repeats until the second sidewall <NUM> terminates at the respective end <NUM>, <NUM>, <NUM>.

Thus, generally, the first sidewall <NUM> is out of phase with or is axially misaligned with the second sidewall <NUM> such that the plurality of first undulations <NUM> are axially misaligned with or offset from the plurality of second undulations <NUM>. The misalignment between the undulations <NUM>, <NUM> defines a tortuous path <NUM> between the first sidewall <NUM> and the second sidewall <NUM>. The tortuous path <NUM> causes the sound waves carried by the fluid F to continually be reflected into and between the first sidewall <NUM> and the second sidewall <NUM>. This causes friction losses and vibration, which dampen the sound by converting the sound energy into heat. In one example, with reference to <FIG>, the sound attenuation cell <NUM> is shown with a movement of the fluid F shown schematically within the cross-section of the sound attenuation cell <NUM>. As shown, the fluid F enters into the sound attenuating cavity <NUM> from the facesheet <NUM> and flows down each of the sound attenuating cavities 212a-212c. The fluid F is continually reflected into the first sidewall <NUM> and the second sidewall <NUM> due to deflectors <NUM>, the first undulating surface of the first sidewall <NUM> and the second undulating surface of the second sidewall <NUM>. The shape of the first sidewall <NUM> and the second sidewall <NUM> along with the deflectors <NUM> that define the tortuous path <NUM> causes the fluid F to be continuously reflected onto itself, which dampens the sound carried by the fluid F. Generally, the fluid F is deflected in various ways as it travels down the sound attenuating cavities 212a-212c from the facesheet <NUM>. Once the fluid F enters the chamber <NUM>, it may not enter perpendicular to the base wall <NUM>. Once inside the chamber <NUM>, the fluid F continues to reflect off the various walls 204a, 204c-204f and base wall <NUM> that define the chamber <NUM> and exits through any one of the perforations 210a associated with the backsheet <NUM>. This results in the fluid F traveling down the sound attenuation cavity 212a-212c, reflecting inside the chamber <NUM>, and exiting the chamber <NUM> via any combination of different sound attenuation cavities 212a-212c.

In one example, each of the valleys <NUM>, <NUM> includes a deflector <NUM> coupled to or integrally formed with the respective valley <NUM>, <NUM> that extends about a perimeter of the respective one of the sound attenuating cavities 212a-212c. With reference to <FIG>, a portion of the deflectors <NUM> is shown in greater detail. Each of the deflectors <NUM> is coupled to or integrally formed with the respective one of the valleys <NUM>, <NUM> to be cantilevered from a surface of the respective valley <NUM>, <NUM>. In this regard, each of the deflectors <NUM> includes a first deflector end <NUM> opposite a second deflector end <NUM>. The first deflector end <NUM> is coupled to or integrally formed with the respective one of the valleys <NUM>, <NUM>, and the second deflector end <NUM> extends outwardly from the respective valley <NUM>, <NUM> into the tortuous path <NUM> defined between the first sidewall <NUM> and the second sidewall <NUM>. Stated another way, the deflectors <NUM> coupled to or integrally formed with the first valleys <NUM> extend outwardly toward the second undulating surface of the second sidewall <NUM>, while the deflectors <NUM> coupled to or integrally formed with the second valleys <NUM> extend outwardly toward the first undulating surface of the first sidewall <NUM>. In this example, the first deflector end <NUM> includes a plurality of deflector openings 272a that are spaced apart about a periphery of the first deflector end <NUM>. The plurality of deflector openings 272a are substantially evenly spaced apart about the periphery of the first deflector end <NUM> and result in bridges 272b that couple the first deflector end <NUM> to the valley <NUM>, <NUM>. The plurality of deflector openings 272a also enable material, such as the metal or metal alloy used to form the sound attenuation cells <NUM>, to exit the sound attenuation cells <NUM> during the formation of the sound attenuating cavities 212a-212c. In addition, the deflector openings 272a also enable sound carried by the fluid F to pass through the deflector openings 272a, which assists in the attenuation of the sound. The deflectors <NUM> also provide support during the additive manufacture of the sound attenuating cell <NUM>. It should be noted that while the deflectors <NUM> are illustrated herein as being solid, in certain examples, as shown in <FIG>, the first sidewall <NUM> may terminate at the respective end <NUM>, <NUM>, <NUM> with a hollow deflector <NUM>'. The hollow deflector <NUM>' may provide a weight savings. In other examples, the first sidewall <NUM> may terminate at the respective end <NUM>, <NUM>, <NUM> with the solid deflector <NUM>.

It should be noted that in other embodiments, the sound attenuation cells <NUM> may be configured differently to attenuate sound over the broad range of frequencies. For example, with reference to <FIG>, a sound attenuation cell <NUM> is shown. As the sound attenuation cell <NUM> includes components that are the same or similar to components of the sound attenuation cell <NUM> discussed with regard to <FIG>, the same reference numerals will be used to denote the same or similar components. Further, while only one of the sound attenuation cell <NUM> is shown herein, it should be understood that one or more of the sound attenuation cells <NUM> may be coupled together or integrally formed into a sound attenuation panel <NUM> (<FIG>), similar to the sound attenuation panel <NUM> discussed with regard to <FIG>. In this example, the sound attenuation cell <NUM> includes the plurality of walls <NUM>, the base wall <NUM>, the facesheet <NUM>, the backsheet <NUM>, at least one or the plurality of sound attenuating cavities <NUM> and at least one or a plurality of partitions <NUM>. The sound attenuation cells <NUM> is integrally or monolithically formed to be one-piece from a metal or metal alloy, including, but not limited to aluminum, titanium, Inconel® produced by American Special Metals Corporation of Miami, Florida, United States of America, or high strength plastics including, but not limited to polyether ether ketone (PEEK) or polyetherimide; and is formed using additive manufacturing, including, but not limited to, direct metal laser sintering (DMLS) or fused deposition modeling (FDM).

The plurality of walls <NUM> cooperate to surround the plurality of sound attenuating cavities <NUM> and the plurality of partitions <NUM>. In one example, the plurality of walls <NUM> include the six planar walls 204a-204f, which cooperate to define the hexagon. It should be noted that in other examples, the plurality of walls <NUM> may cooperate to define any suitable polygonal shape, including, but not limited to, cylindrical, rectangular, square, trapezoid, pentagon, etc. The walls 204a-204f are each coupled to or integrally formed with the facesheet <NUM>, the base wall <NUM>, the plurality of sound attenuating cavities <NUM> and the plurality of partitions <NUM>. The base wall <NUM> forms a second or bottom side of the sound attenuation cell <NUM>, while the facesheet <NUM> forms a first or top side of the sound attenuation cell <NUM>. The base wall <NUM> is hexagonal, and is coupled to or integrally formed with each of the walls 204a-204f so as to be opposite the facesheet <NUM>. The base wall <NUM> is also coupled to or integrally formed with a portion of the plurality of sound attenuating cavities <NUM>, the backsheet <NUM> and the plurality of partitions <NUM>. The base wall <NUM> is planar and is solid or non-perforated. The base wall <NUM> of the sound attenuation cell <NUM> cooperates with the backsheet <NUM> to define the chamber <NUM> in the sound attenuation cell <NUM>.

The facesheet <NUM> is coupled to or integrally formed with each of the walls 204a-204f and the plurality of partitions <NUM>. The facesheet <NUM> is also coupled to or integrally formed with the plurality of sound attenuating cavities <NUM>. While the facesheet <NUM> is shown partially broken away in <FIG>, it will be understood that the facesheet <NUM> extends over the entirety of the sound attenuation cell <NUM> to enclose the sound attenuation cell <NUM> and is coupled to each of the walls 204a-204f as shown in <FIG>. The facesheet <NUM> is planar, and is perforated with the plurality of perforations or openings 208a that enable fluid, such as air, to enter into the plurality of sound attenuating cavities <NUM> of the sound attenuation cell <NUM>. The facesheet <NUM> defines both the inlet and the outlet for the sound attenuation cell <NUM>.

The backsheet <NUM> is coupled to or integrally formed with a portion of the plurality of sound attenuating cavities <NUM> and the plurality of partitions <NUM> opposite the facesheet <NUM>. The backsheet <NUM> is also coupled to or integrally formed with the base wall <NUM> and walls 204a and 204c-f. The backsheet <NUM> is perforated with the plurality of perforations or openings 210a that enable fluid, such as air, to enter into the chamber <NUM> of the sound attenuation cell <NUM>. In this example, with reference to <FIG>, the backsheet <NUM> extends along the axis A, which is transverse or oblique to a longitudinal axis L10 of the sound attenuation cell <NUM>. The facesheet <NUM> and the base wall <NUM> are each orientated to extend along an axis that is substantially perpendicular to the longitudinal axis L10. The backsheet <NUM> extends at the angle α defined between the backsheet <NUM> and the base wall <NUM>. The first end 210b of the backsheet <NUM> is coupled to or integrally formed with the base wall <NUM>, and the second end 210c of the backsheet <NUM> is coupled to or integrally formed with the wall 204e. In this example, the backsheet <NUM> is defined the distance D from the first side 206a of the base wall <NUM>. The first side 206a is coupled to or integrally formed with the wall 204b, and the second side 206b is coupled to or integrally formed with the wall 204e.

The plurality of sound attenuating cavities <NUM> extend about the longitudinal axis L10. In this example, the sound attenuation cell <NUM> includes the first sound attenuating cavity 212a, the second sound attenuating cavity 212b and the third sound attenuating cavity 212c. The second sound attenuating cavity 212b and the third sound attenuating cavity 212c are nested within the inner perimeter of the first sound attenuating cavity 212a. The third sound attenuating cavity 212c is nested within the inner perimeter of the second sound attenuating cavity 212b. Each of the sound attenuating cavities 212a-212c is concentric about the longitudinal axis L10. Each of the sound attenuating cavities 212a-212c includes the first sidewall <NUM> opposite the second sidewall <NUM>. The first sound attenuating cavity 212a extends from the first end <NUM> coupled to or integrally formed with the facesheet <NUM> to the second end <NUM>. The second sound attenuating cavity 212b extends from the third end <NUM> coupled to or integrally formed with the facesheet <NUM> to the fourth end <NUM>. The third sound attenuating cavity 212c extends from the fifth end <NUM> coupled to or integrally formed with the facesheet <NUM> to the sixth end <NUM>. As discussed previously, the lengths L1-L6 (<FIG>) of the sound attenuating cavities 212a-212c vary about the perimeter of the sound attenuation cell <NUM>.

Each of the sound attenuating cavities 212a-212c is defined by extruding the first sidewall <NUM> and the second sidewall <NUM> about the longitudinal axis L10. In this example, each of the sound attenuating cavities 212a-212c include the same first sidewall <NUM> and the same second sidewall <NUM>, but the lengths of the first sidewall <NUM> and the second sidewall <NUM> are varied due to the orientation of the backsheet <NUM> along the axis A. Each of the first sidewalls <NUM> includes the plurality of first undulations <NUM>, with each first undulation <NUM> separated by the respective first valley <NUM> of the plurality of first valleys <NUM>. The first sloped surface <NUM> of the plurality of first sloped surfaces <NUM> is defined to interconnect the respective adjacent first valley <NUM> with the adjacent first undulation <NUM> to form the first undulating surface.

Each of the second sidewalls <NUM> includes the plurality of second undulations <NUM>, with each second undulation <NUM> separated by the respective second valley <NUM> of the plurality of second valleys <NUM>. The second sloped surface <NUM> of the plurality of second sloped surfaces <NUM> is defined to interconnect the respective adjacent second valley <NUM> with the adjacent second undulation <NUM> to form the second undulating surface. The first sidewall <NUM> is out of phase with or is axially misaligned with the second sidewall <NUM> such that the plurality of first undulations <NUM> are axially misaligned with or offset from the plurality of second undulations <NUM>. The misalignment between the undulations <NUM>, <NUM> defines the tortuous path <NUM> between the first sidewall <NUM> and the second sidewall <NUM>.

In one example, each of the valleys <NUM>, <NUM> includes the deflector <NUM> coupled to or integrally formed with the respective valley <NUM>, <NUM> that extends about the perimeter of the respective one of the sound attenuating cavities 212a-212c. Each of the deflectors <NUM> includes the first deflector end <NUM> opposite the second deflector end <NUM>. The first deflector end <NUM> is coupled to or integrally formed with the respective one of the valleys <NUM>, <NUM>, and the second deflector end <NUM> extends outwardly from the respective valley <NUM>, <NUM> into the tortuous path <NUM> defined between the first sidewall <NUM> and the second sidewall <NUM>. Stated another way, the deflectors <NUM> coupled to or integrally formed with the first valleys <NUM> extend outwardly toward the second undulating surface of the second sidewall <NUM>, while the deflectors <NUM> coupled to or integrally formed with the second valleys <NUM> extend outwardly toward the first undulating surface of the first sidewall <NUM>. In this example, the first deflector end <NUM> includes the plurality of deflector openings 272a that are spaced apart about the periphery of the first deflector end <NUM>. The bridges 272b couple the first deflector end <NUM> to the valley <NUM>, <NUM>. It should be noted that while the deflectors <NUM> are illustrated herein as being solid, in certain examples, the first sidewall <NUM> may terminate at the respective end <NUM>, <NUM>, <NUM> with a hollow deflector <NUM>'. The hollow deflector <NUM>' may provide a weight savings. In other examples, the first sidewall <NUM> may terminate at the respective end <NUM>, <NUM>, <NUM> with the solid deflector <NUM>.

With reference back to <FIG>, the plurality of partitions <NUM> provide additional structural support to the sound attenuating cavities 212a-212c, which may be desirable in instances where the sound attenuation cell <NUM> is employed in a high vibration environment. In this example, the sound attenuation cell <NUM> includes three partitions <NUM>: a first partition 304a, a second partition 304b and a third partition 304c. It should be understood, however, that the sound attenuation cell <NUM> may include any number of partitions <NUM>. The partitions 304a-304c are each coupled to or integrally formed with the sound attenuating cavities 212a-212c. The partition 304a is also coupled to or integrally formed with the wall 204b, the base wall <NUM>, the facesheet <NUM> and the backsheet <NUM> (<FIG>). The partition 304b is also coupled to or integrally formed with the wall 204d, the facesheet <NUM> and the backsheet <NUM>. The partition 304c is also coupled to or integrally formed with the wall 204f, the facesheet <NUM> and the backsheet <NUM>.

In this example, the partitions 304a-304c are evenly spaced about a perimeter of the sound attenuation cell <NUM>, however, the partitions 304a-304c may be positioned as needed. With additional reference to <FIG>, the partitions 304a-304c are each solid, and extend from the respective wall 204b, 204d, 204f to proximate the longitudinal axis L10. Thus, the partitions 304a-304c define a solid wall that extends from the outer perimeter of the sound attenuation cell <NUM> through each of the sound attenuating cavities 212a-212c toward a center 302a of the sound attenuation cell <NUM> to provide additional structural support to each of the sound attenuating cavities 212a-212c. In this example, an inner end <NUM> of each of the partitions 304a-304c terminates in third undulating surface 306a. The third undulating surface is a mirror image of the first sidewall <NUM> about the longitudinal axis L10. The inner end <NUM> of each of the partitions 304a-304c generally extends far enough into the sound attenuation cell <NUM> to provide structural support.

It should be noted that in other embodiments, the sound attenuation cells <NUM> may be configured differently to attenuate sound over the broad range of frequencies. For example, with reference to <FIG>, a sound attenuation cell <NUM> is shown. As the sound attenuation cell <NUM> includes components that are the same or similar to components of the sound attenuation cell <NUM> discussed with regard to <FIG>, the same reference numerals will be used to denote the same or similar components. Further, while only one of the sound attenuation cell <NUM> is shown herein, it should be understood that one or more of the sound attenuation cells <NUM> may be coupled together or integrally formed into a sound attenuation panel <NUM> (<FIG>), similar to the sound attenuation panel <NUM> discussed with regard to <FIG>. In this example, the sound attenuation cell <NUM> includes a wall <NUM>, the base wall <NUM>, the facesheet <NUM>, the backsheet <NUM>, at least one or a plurality of sound attenuating cavities <NUM>. The sound attenuation cell <NUM> is integrally or monolithically formed to be one-piece from a metal or metal alloy, including, but not limited to such as aluminum, titanium, Inconel® produced by American Special Metals Corporation of Miami, Florida, United States of America, or high strength plastics including, but not limited to polyether ether ketone (PEEK) or polyetherimide; and is formed using additive manufacturing, including, but not limited to, direct metal laser sintering (DMLS) or fused deposition modeling (FDM). It should be noted that while the base wall <NUM>, the facesheet <NUM> and the backsheet <NUM> are circular in the example of <FIG> instead of hexagonal in the example of <FIG>, the base wall <NUM>, the facesheet <NUM> and the backsheet <NUM> are the same between the sound attenuation cell <NUM> and the sound attenuation cell <NUM> except for the shape.

The wall <NUM> surrounds the plurality of sound attenuating cavities <NUM>. In one example, the wall <NUM> is cylindrical to define a cylinder. The wall <NUM> is solid or non-perforated. The wall <NUM> extends from the facesheet <NUM> to the base wall <NUM>. In one example, the wall <NUM> is coupled to or integrally formed with the facesheet <NUM> and the base wall <NUM>. The base wall <NUM> forms a second or bottom side of the sound attenuation cell <NUM>, while the facesheet <NUM> forms a first or top side of the sound attenuation cell <NUM>. The base wall <NUM> is circular, and is coupled to or integrally formed with the wall <NUM> so as to be opposite the facesheet <NUM>. The base wall <NUM> is also coupled to or integrally formed with a portion of the plurality of sound attenuating cavities <NUM> and the backsheet <NUM>. The base wall <NUM> is planar and is solid or non-perforated. The base wall <NUM> of the sound attenuation cell <NUM> cooperates with the backsheet <NUM> to define the chamber <NUM> in the sound attenuation cell <NUM>.

The facesheet <NUM> is coupled to or integrally formed with the wall <NUM>. The facesheet <NUM> is also coupled to or integrally formed with the plurality of sound attenuating cavities <NUM>. While the facesheet <NUM> is shown partially broken away in <FIG>, it will be understood that the facesheet <NUM> extends over the entirety of the sound attenuation cell <NUM> to be coupled to the entirety of the wall <NUM> to enclose the sound attenuation cell <NUM> similar to that shown in <FIG>. The facesheet <NUM> is planar, and is perforated with the plurality of perforations or openings 208a that enable fluid, such as air, to enter into the plurality of sound attenuating cavities <NUM> of the sound attenuation cell <NUM>. The facesheet <NUM> defines both the inlet and the outlet for the sound attenuation cell <NUM>.

With reference to <FIG>, the backsheet <NUM> is coupled to or integrally formed with a portion of the plurality of sound attenuating cavities <NUM> at an end of the portion of the plurality of sound attenuating cavities <NUM> opposite the facesheet <NUM>. In <FIG>, the base wall <NUM> is removed for clarity. The backsheet <NUM> is also coupled to or integrally formed with the base wall <NUM> and the wall <NUM>. The backsheet <NUM> is perforated with the plurality of perforations or openings 210a that enable fluid, such as air, to enter into the chamber <NUM> of the sound attenuation cell <NUM>. The backsheet <NUM> may include any predetermined number of openings 210a to fluidly couple the plurality of sound attenuating cavities <NUM> to the chamber <NUM>. In this example, with reference to <FIG>, the backsheet <NUM> extends along the axis A, which is transverse or oblique to a longitudinal axis L20 of the sound attenuation cell <NUM>. The facesheet <NUM> and the base wall <NUM> are each orientated to extend along an axis that is substantially perpendicular to the longitudinal axis L20. The backsheet <NUM> extends at the angle α defined between the backsheet <NUM> and the base wall <NUM>. The volume of the chamber <NUM> increases from the first end 210b of the backsheet <NUM> to the second end 210c of the backsheet <NUM>.

In this example, the backsheet <NUM> is defined the distance D from the first side 206a of the base wall <NUM>. The first side 206a of the base wall <NUM> is opposite a second side 206b of the base wall <NUM>. The backsheet <NUM> is positioned the distance D from the first side 206a of the base wall <NUM> to enable a portion of one of the plurality of sound attenuating cavities <NUM> to attenuate sound at a different frequency than a remainder of the plurality of sound attenuating cavities <NUM>. In this regard, the distance D is predetermined such that the portion of one of the plurality of sound attenuating cavities <NUM> terminates at the base wall <NUM>, while a remainder of the plurality of sound attenuating cavities <NUM> terminate at the backsheet <NUM>. The varying of the lengths of the plurality of sound attenuating cavities <NUM> and the termination locations enables the sound attenuation cell <NUM> to attenuate the broad range of frequencies.

With continued reference to <FIG>, the plurality of sound attenuating cavities <NUM> extend about the longitudinal axis L20. In this example, the sound attenuation cell <NUM> includes three of the plurality of sound attenuating cavities <NUM>: a first sound attenuating cavity 412a, a second sound attenuating cavity 412b and a third sound attenuating cavity 412c. The second sound attenuating cavity 412b and the third sound attenuating cavity 412c are nested within an inner perimeter of the first sound attenuating cavity 412a. The third sound attenuating cavity 412c is nested within an inner perimeter of the second sound attenuating cavity 412b. Each of the sound attenuating cavities 412a-412c is concentric about the longitudinal axis L20. Each of the sound attenuating cavities 412a-412c includes a first sidewall <NUM> opposite a second sidewall <NUM>. The second sidewall <NUM> is radially inward from the first sidewall <NUM> such that the first sidewall <NUM> defines a perimeter of the respective sound attenuating cavity 412a-412c. The first sound attenuating cavity 412a extends from a first end <NUM> coupled to or integrally formed with the facesheet <NUM> to a second end <NUM>. A portion 436a of the second end <NUM> proximate the first side 206a of the base wall <NUM> terminates at the base wall <NUM>, while a portion 436b of the second end <NUM> terminates at the backsheet <NUM>. Stated another way, the orientation of the backsheet <NUM> results in the first sound attenuating cavity 412a having a first length L21 proximate the first side 206a of the base wall <NUM>, and a second length L22 proximate the second side 206b of the base wall <NUM>. Thus, the length of the first sound attenuating cavity 412a varies about the perimeter of the sound attenuation cell <NUM>. In one example, the length of the first sound attenuating cavity 412a is reduced by about <NUM>% between the first length L21 and the second length L22.

The second sound attenuating cavity 412b extends from a third end <NUM> coupled to or integrally formed with the facesheet <NUM> to a fourth end <NUM>. A portion 440a of the fourth end <NUM> proximate the first side 206a of the base wall <NUM> terminates at the backsheet <NUM> proximate the first end 210b of the backsheet <NUM>, and a portion 440b of the fourth end <NUM> terminates proximate the second end 210c of the backsheet <NUM>. The orientation of the backsheet <NUM> results in the second sound attenuating cavity 412b having a third length L23 proximate the first side 206a of the base wall <NUM>, and a fourth length L24 proximate the second side 206b of the base wall <NUM>. Thus, the length of the second sound attenuating cavity 412b varies about the perimeter of the sound attenuation cell <NUM>. In one example, the length of the second sound attenuating cavity 412b is reduced by about <NUM>% between the third length L23 and the fourth length L24.

The third sound attenuating cavity 412c extends from a fifth end <NUM> coupled to or integrally formed with the facesheet <NUM> to a sixth end <NUM>. A portion 444a of the sixth end <NUM> proximate the first side 206a of the base wall <NUM> terminates at the backsheet <NUM> proximate the first end 210b of the backsheet <NUM>, and a portion 444b of the sixth end <NUM> terminates proximate the second end 210c of the backsheet <NUM>. The orientation of the backsheet <NUM> results in the third sound attenuating cavity 412c having a fifth length L25 proximate the first side 206a of the base wall <NUM>, and a sixth length L26 proximate the second side 206b of the base wall <NUM>. Thus, the length of the third sound attenuating cavity 412c varies about the perimeter of the sound attenuation cell <NUM>. In one example, the length of the third sound attenuating cavity 412c is reduced by about <NUM>% between the fifth length L25 and the sixth length L26. In this example, each of the lengths L21-L26 is different.

As discussed, each of the sound attenuating cavities 412a-412c is defined by revolving the first sidewall <NUM> and the second sidewall <NUM> about the longitudinal axis L20. In this example, each of the sound attenuating cavities 412a-412c include the same first sidewall <NUM> and the same second sidewall <NUM>, but the lengths of the first sidewall <NUM> and the second sidewall <NUM> are varied due to the orientation of the backsheet <NUM> along the axis A. Each of the first sidewalls <NUM> includes a plurality of first undulations <NUM>, with each first undulation <NUM> separated by a respective first valley <NUM> of a plurality of first valleys <NUM>. A first ramp surface <NUM> of a plurality of first ramp surfaces <NUM> is defined to interconnect a respective adjacent first valley <NUM> with an adjacent first undulation <NUM>. The first undulation <NUM>, the first valley <NUM> and the first ramp surface <NUM> alternate or repeat along the first sidewall <NUM> from the respective end <NUM>, <NUM>, <NUM> to the respective end <NUM>, <NUM>, <NUM> to form a first undulating surface. Generally, from the respective end <NUM>, <NUM>, <NUM>, the first sidewall <NUM> includes one of the first ramp surfaces <NUM> coupled to or integrally formed with the facesheet <NUM>, transitions to one of the first undulations <NUM> and then to one of the first valleys <NUM>. This repeats until the first sidewall <NUM> terminates at the respective end <NUM>, <NUM>, <NUM>.

Each of the second sidewalls <NUM> includes a plurality of second undulations <NUM>, with each second undulation <NUM> separated by a respective second valley <NUM> of a plurality of second valleys <NUM>. A second ramp surface <NUM> of a plurality of second ramp surfaces <NUM> is defined to interconnect a respective adjacent second valley <NUM> with an adjacent second undulation <NUM>. The second undulation <NUM>, the second valley <NUM> and the second ramp surface <NUM> alternate or repeat along the second sidewall <NUM> from the respective end <NUM>, <NUM>, <NUM> to the respective end <NUM>, <NUM>, <NUM> to form a second undulating surface. Generally, from the respective end <NUM>, <NUM>, <NUM>, the second sidewall <NUM> includes one of the second valleys <NUM> coupled to or integrally formed with the facesheet <NUM>, transitions to one of the second ramp surfaces <NUM> and then to one of the second undulations <NUM>. This repeats until the second sidewall <NUM> terminates at the respective end <NUM>, <NUM>, <NUM>.

Thus, generally, the first sidewall <NUM> is out of phase with or is axially misaligned with the second sidewall <NUM> such that the plurality of first undulations <NUM> are axially misaligned with or offset from the plurality of second undulations <NUM>. The misalignment between the undulations <NUM>, <NUM> defines a tortuous path <NUM> between the first sidewall <NUM> and the second sidewall <NUM>. The tortuous path <NUM> causes the sound waves carried by the fluid F to continually be reflected into and between the first sidewall <NUM> and the second sidewall <NUM>. This causes friction losses and vibration, which dampen the sound by converting the sound energy into heat.

In one example, each of the valleys <NUM>, <NUM> includes the deflector <NUM> coupled to or integrally formed with the respective valley <NUM>, <NUM> that extends about a perimeter of the respective one of the sound attenuating cavities 412a-412c. Each of the deflectors <NUM> includes the first deflector end <NUM> opposite the second deflector end <NUM>. The first deflector end <NUM> is coupled to or integrally formed with the respective one of the valleys <NUM>, <NUM>, and the second deflector end <NUM> extends outwardly from the respective valley <NUM>, <NUM> into the tortuous path <NUM> defined between the first sidewall <NUM> and the second sidewall <NUM>. The first deflector end <NUM> includes the plurality of deflector openings 272a that are spaced apart about the periphery of the first deflector end <NUM>. The bridges 272b couple the first deflector end <NUM> to the valley <NUM>, <NUM>. It should be noted that the sound attenuation cell <NUM> may also include partitions, similar to the partitions <NUM> discussed with regard to <FIG> and <FIG>, if desired. In addition, it should be noted that while the deflectors <NUM> are illustrated herein as being solid, in certain examples, as shown in <FIG>, the first sidewall <NUM> may terminate at the respective end <NUM>, <NUM>, <NUM> with a hollow deflector <NUM>'. The hollow deflector <NUM>' may provide a weight savings. In other examples, the first sidewall <NUM> may terminate at the respective end <NUM>, <NUM>, <NUM> with the solid deflector <NUM>.

It should be noted that in other embodiments, the sound attenuation panel <NUM> may be configured differently to attenuate sound over the broad range of frequencies. For example, with reference to <FIG>, a sound attenuation panel <NUM> is shown. As the sound attenuation panel <NUM> includes components that are the same or similar to components of the sound attenuation panel <NUM> discussed with regard to <FIG>, the same reference numerals will be used to denote the same or similar components. The sound attenuation panel <NUM> includes a plurality of the sound attenuation cells <NUM>. It should be noted that the arrangement of the sound attenuation cells <NUM> to form the sound attenuation panel <NUM> shown in <FIG> is merely an example, as the sound attenuation cells <NUM> may be arranged in any configuration to form the sound attenuation panel <NUM>. In this regard, the sound attenuation cells <NUM> may be arranged to form any desired polygonal shape for the sound attenuation panel <NUM>, including, but not limited to, rectangular, square, triangular, trapezoid, etc. Moreover, the sound attenuation cells <NUM> may be arranged to form the sound attenuation panel <NUM> that has a shape configured for the particular use of the sound attenuation panel <NUM> within the gas turbine engine <NUM> (<FIG>) such that the sound attenuation panel <NUM> may have a non-uniform or custom shape to fit the space available in the gas turbine engine <NUM>. In this example, the sound attenuation panel <NUM> is composed of <NUM> sound attenuation cells <NUM>, however, it should be understood that the sound attenuation panel <NUM> may comprise any number of sound attenuation cells <NUM>, including a single sound attenuation cell <NUM>.

In one example, the sound attenuation cells <NUM> are each additively manufactured to form the sound attenuation panel <NUM>. In this example, each of the sound attenuation cells <NUM> is composed of a metal or metal alloy, such as aluminum, titanium, Inconel® produced by American Special Metals Corporation of Miami, Florida, United States of America, or high strength plastics including, but not limited to polyether ether ketone (PEEK) or polyetherimide; and is formed using additive manufacturing, including, but not limited to, direct metal laser sintering (DMLS) or fused deposition modeling (FDM). During the additive manufacture of the sound attenuation cells <NUM>, the sound attenuation panel <NUM> may be formed by additively manufacturing adjacent ones of the sound attenuation cells <NUM> together such that the sound attenuation panel <NUM> is composed of one or more integrally formed sound attenuation cells <NUM>. In other examples, the sound attenuation panel <NUM> may be formed by coupling discrete sound attenuation cells <NUM> together via welding, mechanical fasteners, etc..

With reference to <FIG>, one of the sound attenuation cells <NUM> is shown. As each of the sound attenuation cells <NUM> is the same, a single one of the sound attenuation cells <NUM> will be discussed in detail herein. In this example, each of the sound attenuation cells <NUM> includes the facesheet <NUM> and at least one or a plurality of sound attenuating cavities <NUM>. As discussed, generally, each of the sound attenuation cells <NUM> is integrally or monolithically formed so as to be one-piece via additive manufacturing.

With reference back to <FIG>, the facesheet <NUM> is coupled to or integrally formed with the plurality of sound attenuating cavities <NUM> to enclose an end of the plurality of sound attenuating cavities <NUM>. The facesheet <NUM> is planar, and is perforated with the plurality of perforations or openings 208a that enable fluid, such as air, to enter into the plurality of sound attenuating cavities <NUM> of the sound attenuation cell <NUM>. In this example, each of the sound attenuation cells <NUM> has the facesheet <NUM>, however, in other embodiments, the sound attenuation panel <NUM> may be formed such that a single facesheet <NUM> extends over a plurality of the sound attenuation cells <NUM>. The facesheet <NUM> defines the inlet and the outlet for the sound attenuation cells <NUM>. In this regard, the plurality of sound attenuating cavities <NUM> not define an outlet, but rather are closed along an end of the plurality of sound attenuating cavities <NUM> opposite the facesheet <NUM>. Fluid, such as air, enters the sound attenuation cells <NUM> via the facesheet <NUM>, and exits the sound attenuation cells <NUM> via the facesheet <NUM>.

With reference to <FIG>, the plurality of sound attenuating cavities <NUM> are symmetric about a longitudinal axis L30. In this example, the sound attenuation cells <NUM> each include three of the plurality of sound attenuating cavities <NUM>: a first sound attenuating cavity 512a, a second sound attenuating cavity 512b and a third sound attenuating cavity 512c. The second sound attenuating cavity 512b and the third sound attenuating cavity 512c are nested within an inner perimeter of the first sound attenuating cavity 512a. The third sound attenuating cavity 512c is nested within an inner perimeter of the second sound attenuating cavity 512b. Each of the sound attenuating cavities 512a-512c is concentric about the longitudinal axis L30. Each of the sound attenuating cavities 512a-512c includes a first sidewall <NUM> opposite a second sidewall <NUM>. The second sidewall <NUM> is radially inward from the first sidewall <NUM> such that the first sidewall <NUM> defines a perimeter of the respective sound attenuating cavity 512a-512c. For the first sound attenuating cavity 512a, the first sidewall <NUM> defines the perimeter of the sound attenuation cell <NUM>. The first sound attenuating cavity 512a extends from a first end <NUM> coupled to or integrally formed with the facesheet <NUM> to a second end <NUM>. The second end <NUM> is closed, such that the fluid is inhibited from exiting the sound attenuating cavity 512a at the second end <NUM>. The second sound attenuating cavity 512b extends from a third end <NUM> coupled to or integrally formed with the facesheet <NUM> to a fourth end <NUM>. The fourth end <NUM> is closed, such that the fluid is inhibited from exiting the sound attenuating cavity 512a at the fourth end <NUM>. The third sound attenuating cavity 512c extends from a fifth end <NUM> coupled to or integrally formed with the facesheet <NUM> to a sixth end <NUM>. The sixth end <NUM> is closed, such that the fluid is inhibited from exiting the sound attenuating cavity 512a at the sixth end <NUM>. Thus, in this example, each of the sound attenuating cavities 512a-512c extend for the same length L31.

Each of the sound attenuating cavities 512a-512c is defined by extruding the first sidewall <NUM> and the second sidewall <NUM> about the longitudinal axis L30. In this example, each of the sound attenuating cavities 512a-512c include the same first sidewall <NUM> and the same second sidewall <NUM>. Each of the first sidewalls <NUM> includes the plurality of first undulations <NUM>, with each first undulation <NUM> separated by the respective first valley <NUM> of the plurality of first valleys <NUM>. The first sloped surface <NUM> of the plurality of first sloped surfaces <NUM> is defined to interconnect the respective adjacent first valley <NUM> with an adjacent first undulation <NUM> to form the first undulating surface. Generally, from the respective end <NUM>, <NUM>, <NUM>, the first sidewall <NUM> includes one of the first sloped surfaces <NUM> coupled to or integrally formed with the facesheet <NUM>, transitions to one of the first undulations <NUM> and then to one of the first valleys <NUM>. This repeats until the first sidewall <NUM> terminates at the respective end <NUM>, <NUM>, <NUM>.

Each of the second sidewalls <NUM> includes the plurality of second undulations <NUM>, with each second undulation <NUM> separated by the respective second valley <NUM> of the plurality of second valleys <NUM>. The second sloped surface <NUM> of the plurality of second sloped surfaces <NUM> is defined to interconnect a respective adjacent second valley <NUM> with the adjacent second undulation <NUM> to form the second undulating surface. Generally, from the respective end <NUM>, <NUM>, <NUM>, the second sidewall <NUM> includes one of the second valleys <NUM> coupled to or integrally formed with the facesheet <NUM>, transitions to one of the second sloped surfaces <NUM> and then to one of the second undulations <NUM>. This repeats until the second sidewall <NUM> terminates at the respective end <NUM>, <NUM>, <NUM>. Thus, generally, the first sidewall <NUM> is out of phase with or is axially misaligned with the second sidewall <NUM> such that the plurality of first undulations <NUM> are axially misaligned with or offset from the plurality of second undulations <NUM>. The misalignment between the undulations <NUM>, <NUM> defines the tortuous path <NUM> between the first sidewall <NUM> and the second sidewall <NUM>.

Each of the valleys <NUM>, <NUM> includes the deflector <NUM> coupled to or integrally formed with the respective valley <NUM>, <NUM> that extends about a perimeter of the respective one of the sound attenuating cavities 512a-512c. Each of the deflectors <NUM> includes the first deflector end <NUM> opposite the second deflector end <NUM>. The first deflector end <NUM> is coupled to or integrally formed with the respective one of the valleys <NUM>, <NUM>, and the second deflector end <NUM> extends outwardly from the respective valley <NUM>, <NUM> into the tortuous path <NUM> defined between the first sidewall <NUM> and the second sidewall <NUM>. In this example, the first deflector end <NUM> includes the plurality of deflector openings 272a that are spaced apart about the periphery of the first deflector end <NUM>. The bridges 272b that couple the first deflector end <NUM> to the valley <NUM>, <NUM>. It should be noted that while the deflectors <NUM> are illustrated herein as being solid, in certain examples, as shown in <FIG>, the first sidewall <NUM> may terminate at the respective end <NUM>, <NUM>, <NUM> with a hollow deflector <NUM>'. The hollow deflector <NUM>' may provide a weight savings. In other examples, the first sidewall <NUM> may terminate at the respective end <NUM>, <NUM>, <NUM> with the solid deflector <NUM>.

Generally, once installed in the gas turbine engine <NUM>, each of the sound attenuation cells <NUM>, <NUM>, <NUM>, <NUM> receive sound through the facesheet <NUM>, which is directed into the respective sound attenuating cavities <NUM>, <NUM>, <NUM>. Depending on where the sound enters the facesheet <NUM>, the sound either travels down the sound attenuating cavity <NUM>, <NUM> to the respective end <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or travels down the sound attenuating cavity <NUM>, <NUM> to the backsheet <NUM> and into the chamber <NUM>. Once the sound has passed one-way through the sound attenuating cavity <NUM>, <NUM>, <NUM>, the sound is deflected back towards the facesheet <NUM>. The shape of the first undulating surface formed by the first sidewall <NUM>, <NUM> and the second undulating surface formed by the second sidewall <NUM>, <NUM> causes the sound to be continually turned on itself by the multiple deflectors <NUM> that line the tortuous path <NUM>, <NUM>. This continual turning of the sound or the fluid F carrying the sound on itself causes large pressure loss, which in turn, causes the sound to be suppressed. The varying lengths of the sound attenuating cavities <NUM>, <NUM> caused by the backsheet <NUM> allows the sound attenuation over the broad frequency range, and the backsheet <NUM> also assists in breaking up the sound waves.

Thus, the sound attenuation cells <NUM>, <NUM>, <NUM>, <NUM> provide for the attenuation of sound at the broad range of frequencies, which reduces cost and complexity associated with sound suppression in a gas turbine engine <NUM> (<FIG>). Generally, each sound attenuating cavity <NUM>, <NUM>, <NUM> of the sound attenuation cells <NUM>, <NUM>, <NUM>, <NUM> forms a one-way valve, which permits the fluid F, such as air, to enter and exit at the same end with the sound being attenuated as the fluid travels down and back through the one-way valve. The sound attenuation cells <NUM>, <NUM>, <NUM>, <NUM> may be coupled together or integrally formed together, via additive manufacturing, including, but not limited to DMLS or FMS, to form sound attenuating panels, such as the sound attenuation panels <NUM>, <NUM>, <NUM>, <NUM>, which may be of a custom size and shape for placement within the gas turbine engine <NUM> (<FIG>). In addition, the use of a metal or metal alloy for the sound attenuation cells <NUM>, <NUM>, <NUM>, <NUM> enables the attenuation of the broad range of frequencies with non-foam based sound attenuating panels, which enables the sound attenuation cells <NUM>, <NUM>, <NUM>, <NUM> to be employed in a variety of environments that are not conducive to the use of a foam-based structure. The sound attenuation cells <NUM>, <NUM>, <NUM>, <NUM> also enable the attenuation of the broad range of frequencies with a reduced weight due to the nested structure of the sound attenuating cavities <NUM>, <NUM>, <NUM>. In addition, the chamber <NUM> also reduces an overall weight of the sound attenuation cells <NUM>, <NUM>, <NUM> by providing the empty or void space, and also reduces material costs associated with the sound attenuation cells <NUM>, <NUM>, <NUM>.

Claim 1:
A sound attenuating cell, comprising:
a first sound attenuating cavity (212a, 412a, 512a) defined between a first sidewall (<NUM>, <NUM>, <NUM>) and a second sidewall (<NUM>, <NUM>, <NUM>), the first sidewall opposite the second sidewall, the first sidewall including a first undulating surface and the second sidewall including a second undulating surface, with a deflector (<NUM>, <NUM>') coupled to the first undulating surface, the deflector extending from the first undulating surface toward the second undulating surface, wherein the sound attenuating cell has a longitudinal axis (L10) and wherein the first undulating surface is axially misaligned with or offset from the second undulating surface to define a tortuous path (<NUM>) between the first sidewall and the second sidewall, the first sound attenuating cavity having a first end and a second end, the first end opposite the second end, with an inlet and an outlet of the first sound attenuating cavity defined at the first end; and
a second sound attenuating cavity (212b, 412b, 512b) nested within the inner perimeter of the first sound attenuating cavity.