Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C1/00—Fuselages; Constructional features common to fuselages, wings, stabilising surfaces or the like
  • B64C1/06—Frames; Stringers; Longerons ; Fuselage sections
  • B64C1/066—Interior liners
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C1/00—Fuselages; Constructional features common to fuselages, wings, stabilising surfaces or the like
  • B64C1/40—Sound or heat insulation, e.g. using insulation blankets

Definitions

• the present invention relates to a noise reduction treatment for an aircraft cabin, and more particularly to a lightweight acoustic absorption trim panel system to reduce aircraft interior noise levels.
• the most common sources are internally or externally mounted moving components, such as a transmission, engine or rotor system.
• Another source of cabin noise is airflow over various aircraft fuselage components. These components may generate vibrations in the aircraft that propagate through the airframe and radiate into the cabin.
• Noise may be a particular problem in rotary wing aircraft cabins since the rotor and transmission systems produce a significant amount of vibration directly into the airframe structure. This problem may be more pronounces in rotary wing aircraft than in fixed wing aircraft inasmuch as the dynamic components on a rotary wing aircraft are mounted directly above the cabin.
• Aircraft cabin interiors are generally designed to maintain aircraft interior noise below a certain level predetermined by competitive pressures in the marketplace.
• executive transport rotary wing aircraft typically provide a design average noise level limit with the environmental control system (fans, vent air and cooling/heating system) turned off of approximately 75 dB SH-4.
• the SIL4 (Speech Interference Level 4) noise measurement metric is the arithmetic average of the sound pressure levels in the 500, 1000, 2000 and 4000 Hz octave bands. It rates steady noise according to interference with conversation between two people.
• Various conventional acoustic absorption svstems have been provided to reduce noise levels within the cabin to below desired SIL4 values.
• One current method of damping includes mounting interior trim panels within the aircraft cabin. More specifically, the interior trim panel includes Kevlar skins, a layer of Nomex honeycomb core, a layer of polymer isolation/damping, another layer of Nomex honeycomb core and Kevlar skins.
• Such interior trim panel damping system offers minimal damping properties for the weight penalty incurred and may be relatively difficult and expensive to manufacture.
• An acoustic absorption trim panel includes a composite core, a decoupler layer, and a mass barrier layer.
• the composite core defines the outer aesthetic surface visible by a passenger within the aircraft cabin.
• the decoupler layer is a high loft decoupling material such as felted Nomex.
• the mass barrier layer is mounted to the composite core to at least partially surround the decoupler layer.
• the mass barrier layer is manufactured of vinyl which is mass loaded with barium sulfate powder.
• the acoustic absorption trim panel increases vibration damping to minimize the transfer of structurebome vibration into the cabin as noise; increases acoustic attenuation; increases acoustic absorption; increases vibration decoupling to minimize the transfer of structurebome vibration into the cabin as noise through incidental contact; and enhances thermal and burn through protection by the incorporation of low flammability and low moisture absorbing materials.
• the present invention therefore provide an effective, lightweight, acoustic absorption trim panel system that imparts not only damping but offers enhanced acoustic transmission loss properties, improved acoustic absorption, vibration isolation/decoupling and increased thermal/burn through protection.
• Figure 1 is a general perspective view an exemplary rotary wing aircraft embodiment for use with the present invention
• Figure 2 is a plan view of an airframe section for use with an acoustic absorption trim panel of the present invention
• Figure 3 is a plan view of an airframe section with a multitude of frame members with an interior skeleton structure attached thereto;
• Figure 4 is a plan view of an interior skeleton structure having acoustic absorption trim panel of the present invention attached thereto;
• Figure 5 is a sectional view of an acoustic absorption trim panel of the present invention.
• Figure 6A is a perspective view of a first layer of an acoustic absorption trim panel of Figure 5;
• Figure 6B is a perspective view of a first layer and a second layer of the acoustic absorption trim panel of Figure 5;
• Figure 6C is a perspective view of a first layer, a second layer and a third layer of the acoustic absorption trim panel of Figure 5;
• Figure 7A is a comparison of vibration resonance response between current interior panels and panels manufactured in accordance with the present invention.
• Figure 7B is a comparison of acoustic attenuation between a bare interior panel and panels manufactured in accordance with the present invention.
• FIG. 1 schematically illustrates a rotary-wing aircraft 10 having a main rotor assembly 12.
• the aircraft 10 includes an airframe 14 having an extending tail 16 which mounts an anti-torque rotor 18.
• the main rotor assembly 12 is driven through a transmission (illustrated schematically at 20) by one or more engines 22.
• a particular helicopter configuration is illustrated m the disclosed embodiment, other machines such as turbo-props, tilt-rotor and tilt-wing aircraft will also benefit from the present invention.
• an airframe section 24 includes a multitude of frame members 26 . which support an outer skin 28.
• the airframe section 24 is the outer structure of the aircraft 10 and may include one or more window areas 30.
• the window areas 30 are typically located through the outer skin 28 between the multitude of frame members 26.
• the multitude of frame members 26 are typically arranged in a rectilinear pattern, however, any arrangement may be used with the present invention.
• the multitude of frame members 26 includes a multitude interior skeleton mounts 32 which support an interior skeleton structure 34 (Figure 3).
• the interior skeleton mounts 32 preferably include posts 36 to receive corresponding receivers 38 located in the interior skeleton structure 34 such that the interior skeleton structure 34 essentially "snaps" in place.
• the interior skeleton structure 34 is preferably manufactured of composite materials.
• the interior skeleton structure 34 provides support and attachment for a multitude of acoustic absorption trim panels 40 ( Figure 4) through fasteners such as quarter turn fasteners or the like.
• an acoustic absorption trim panel 40 includes a composite core 42, a decoupler layer 44, and a mass barrier layer 46.
• the composite core 42 defines the outer aesthetic surface S visible by a passenger within the aircraft cabin (also illustrated in Figure 4). Testing revealed that the weight, strength and acoustic attenuation differences between Fiberglass, Kevlar and Carbon Fiber did not greatly influence the choice of cores. Skin choice however became important when attempts were made to incorporate damping. Because stiffness of materials plays an important role in vibration resonance damping, the amount of imparted damping increased and the damping application weight decreased when applied to fiberglass core.
• the decoupler layer 44 is preferably a high loft decoupling material such as felted Nomex.
• the decoupler layer 44 is located adjacent the composite core 42.
• the decoupler layer 44 is preferably adhered to the composite core 42 ( Figure also illustrated in Figure 6B).
• the mass barrier layer 46 is mounted to the composite core 42 to at least partially surround the decoupler layer.
• the mass barrier layer 46 is preferably made from virgin (high grade) vinyl which is mass loaded with barium sulfate powder, or similar dense material to increase its mass, and has n thickness of approximately 1/16 tc IM inches.
• 1 WhIIc vinyl is the preferred material because of its limpness, high inherent damping and relatively high density, the mass barrier layer 46 can be made from a variety of alternate materials, such as silicone or rubber sheet material. The materials used are selected on the basis of limpness, lowest stiffness, high relative surface density, resistance to fire, low levels of toxic fume emission when exposed to flame, expense, etc.
• the mass barrier layer 46 includes an attachment area 48 which is adhered to the composite core 42 and a limp area 50 which is adjacent the decoupler layer 44 (also illustrated in Figure 6C).
• the limp area 50 is generally parallel to the composite core 42 to sandwich the decoupler layer 44 therebetween.
• the attachment area 48 provides a more rigid area which permits receives a fastener f therethrough to removably secure the acoustic absorption trim panels 40 to the interior skeleton structure 34 ( Figure 5).
• Figures 7 A and 7B the effect of a trim panel manufactured in accordance with the present invention is illustrated in graphic format.
• Figure 7A is a comparison of vibration resonance response between current interior panels and panels manufactured in accordance with the present invention.
• Figure 7B is a comparison of acoustic attenuation between a bare interior panel and a trim panel manufactured in accordance with the present invention.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Aviation & Aerospace Engineering (AREA)
• Laminated Bodies (AREA)
• Soundproofing, Sound Blocking, And Sound Damping (AREA)
• Vehicle Interior And Exterior Ornaments, Soundproofing, And Insulation (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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Family Cites Families (36)

• 2004
  • 2004-12-20 US US11/017,281 patent/US7246772B2/en not_active Expired - Lifetime
• 2005
  • 2005-12-12 EP EP05858650A patent/EP1836090A4/en not_active Withdrawn
  • 2005-12-12 CA CA002592338A patent/CA2592338A1/en not_active Abandoned
  • 2005-12-12 WO PCT/US2005/044916 patent/WO2007053159A2/en not_active Ceased
  • 2005-12-12 JP JP2007548276A patent/JP5021493B2/ja not_active Expired - Fee Related

Non-Patent Citations (2)

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