Noise reduction material structure for inhibiting main noise reduction of helicopter

Abstract

The invention belongs to the field of noise reduction in a helicopter cabin, and relates to a noise reduction material structure for inhibiting main noise reduction of a helicopter. The structure comprises six layers, namely a honeycomb plate, a first layer of acoustic transparent film, a first layer of porous medium, an elastic metal foil, a second layer of porous medium and a second layer of acoustic transparent film from top to bottom, sound waves are transmitted to the elastic metal foil from the cellular board and the first layer of porous medium in sequence and then enter the second layer of porous medium again, so that attenuation of sound energy is increased, and the acoustic film is used for improving the low-frequency reflection capacity of the elastic metal foil.

Description

Technical Field

[0001] The present invention belongs to the field of noise reduction in helicopter cabins and relates to a noise reduction material structure for suppressing the noise of the main reducer of a helicopter. Background Art

[0002] The noise environment in a helicopter cabin is harsh, seriously affecting the safety and comfort of crew members, and noise control in the cabin is required. The noise of the main reducer is a major component of the noise in the helicopter cabin, generally located in the medium and high frequency range of 500 - 2000 Hz, which is sensitive to the human ear. Currently, the main measures for controlling the noise of the main reducer include vibration damping, vibration absorption, and installing interior trim structures on the main reducer platform. For the interior trim structure, the current traditional aviation interior panel layering design is: honeycomb structure + porous sound-absorbing material, which is used to block the transmission of external noise into the cabin on the one hand and absorb the reverberant sound energy in the cabin on the other hand. It can achieve good noise reduction effects above 1000 Hz, but the noise reduction performance below 1000 Hz is not ideal. Improving the sound absorption coefficient of the interior trim structure below 1000 Hz to reduce the noise level in the helicopter cabin has become a key problem to be solved urgently.

[0003] Problems and disadvantages of the prior art: The sound absorption coefficient of traditional aviation interior materials usually reaches 0.9 only after 1000 Hz and cannot reach below 1000 Hz. If the sound absorption coefficient is forcibly increased, the weight and installation space need to be sacrificed, and lightweight design cannot be achieved. Summary of the Invention

[0004] Object of the Invention: To provide a design method for a noise reduction interior trim structure for suppressing the noise of the main reducer of a helicopter, which can adjust the sound absorption coefficient below 1000 Hz at a relatively small weight cost without changing the main structure of the interior trim, thereby suppressing the noise of the main reducer of the helicopter in the target frequency range, reducing the noise level in the helicopter cabin, and improving the comfort and safety of the helicopter.

[0005] Technical Solution:

[0006] Provide a noise reduction material structure for suppressing the noise of the main reducer of a helicopter, including 6 layers, which are, from top to bottom, a honeycomb panel, a first layer of acoustic transparent film, a first layer of porous medium, an elastic metal foil, a second layer of porous medium, and a second layer of acoustic transparent film;

[0007] Sound waves are transmitted from the honeycomb panel and the first layer of porous medium to the elastic metal foil in sequence, and then enter the second porous medium again, thereby increasing the attenuation of sound energy; the above two acoustic transparent films are mainly used to increase the low-frequency reflection ability of the elastic metal foil.

[0008] Further, both the first layer of porous medium and the second layer of porous medium are glass fiber cotton.

[0009] Further, the density of the honeycomb panel is 48 kg / m3 It has a thickness of 5 mm, serves as a sound insulation function, and is connected to the main reduction platform of the helicopter. Among them, the honeycomb material and its thickness can be selected according to actual needs.

[0010] Furthermore, both the first layer of porous medium and the thickness of the first layer of porous medium are 30 mm, and the density is 16 kg / m 3 It both absorbs sound and insulates sound. Among them, the porous material and its thickness can be selected according to actual needs.

[0011] Furthermore, the thickness of the elastic metal foil is 0.05 mm, which is used for the low-frequency reflection of sound energy. The material of the elastic metal foil can be selected according to actual needs, such as steel foil or aluminum foil, etc.

[0012] Furthermore, the thicknesses of both the first layer of acoustic transparent film and the second layer of acoustic transparent film are 1 mm, and the density is 170 kg / m 3 It is used to increase the low-frequency reflection ability of the elastic metal foil. The acoustic transparent film is in contact with the acoustic cavity inside the helicopter cabin. Among them, the material of the acoustic transparent film and its thickness can be selected according to actual needs.

[0013] Furthermore, the layers of this structure are bonded to each other through an adhesive.

[0014] Furthermore, the greater the stiffness of the elastic metal foil, the lower the sound wave reflection frequency, and the lower the sound absorption frequency of this structure.

[0015] Beneficial effects:

[0016] The present invention improves the sound absorption coefficient of the noise reduction material below 1000 Hz to a certain extent; by changing the stiffness of the elastic metal foil and adjusting the sound wave reflection frequency, the present invention can adjust the frequency of the sound absorption coefficient, that is, the present invention can select different elastic metal foils according to different target frequencies to improve the sound absorption coefficient within the target frequency band of the interior structure; when the sound absorption coefficients of the target frequencies are comparable, the present invention is lighter than the traditional design method of aviation interior noise reduction materials and can save installation space. Description of the drawings

[0017] Figure 1 It is a schematic diagram of a noise reduction material structure for suppressing the noise of the main reduction of a helicopter.

[0018] Figure 2 It is a comparison diagram of the calculation results between the present invention and the traditional aviation interior design method.

[0019] Figure 3 It is a simulation calculation result diagram of the present invention.

[0020] Figure 4 It is a comparison diagram of the designed thickness and weight of the present invention with the traditional design method. Specific implementation manners

[0021] To make the purpose, technical solutions, and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below in conjunction with the accompanying drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of the present application. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts fall within the scope of protection of the present application. The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0022] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "axial direction", "vertical", "upper", "lower", "upper end", "bottom end", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the scope of protection of the present invention.

[0023] The present invention provides a lightweight noise reduction material structure design for suppressing the noise of a helicopter main reducer, as Figure 1 shown. This structure is based on the traditional aircraft interior structure, with a layer of elastic metal foil (aluminum foil or steel foil) inserted inside the porous material, and a layer of acoustically transparent film added to both surfaces of the porous sound-absorbing material, increasing the sound reflection inside the interior structure. The sound energy is sequentially transmitted from the first layer of porous medium (the first layer of glass fiber cotton) to the elastic metal foil, and then enters the second layer of porous medium (the second layer of glass fiber cotton) again, thereby increasing the attenuation of the sound energy and improving the sound absorption coefficient in the target frequency range.

[0024] The composition of the interior layering design of the helicopter main reducer platform provided by the present invention is shown in Figure 1 , and includes: honeycomb panel 1, the first layer of acoustically transparent film 2, the first layer of glass fiber cotton 3, elastic metal foil 4, the second layer of glass fiber cotton 5, and the second layer of acoustically transparent film 6. Among them, the density of the honeycomb panel 1 is 48 kg / m 3 , the thickness is 5 mm, which mainly functions as sound insulation and is connected to the helicopter main reducer platform; the thicknesses of both the first layer of glass fiber cotton 3 and the second layer of glass fiber cotton 5 are 30 mm, and the densities are both 16 kg / m 3, which can both absorb sound and isolate sound; the elastic metal foil 4 has a thickness of 0.05 mm, and steel foil or aluminum foil can be selected according to needs, mainly used for the low-frequency reflection of sound energy; the thickness of the first acoustic transparent film 2 and the second acoustic transparent film 6 is both 1 mm, and the density is both 170 kg / m 3 , mainly used to increase the low-frequency reflection ability of the elastic metal foil, and the acoustic transparent film 6 is in contact with the sound cavity inside the helicopter cabin.

[0025] In the design of the present invention, the materials and thicknesses of the honeycomb material, porous material, acoustic transparent film, metal foil, etc. need to be selected according to the actual situation, and are not limited to a certain material and size.

[0026] The key points of the present invention are: 1. Insert a layer of elastic metal foil into the porous material to improve the low-frequency sound wave reflection ability of the aviation interior material below 1000 Hz, increase the attenuation of sound energy in the interior noise reduction structure, and thus improve the sound absorption coefficient of the interior structure; 2. Lightweight design and save installation space. When adding elastic metal steel foil and acoustic transparent film, the surface density of the interior structure is 1.93 kg / m 2 , only 0.73 kg / m more than the traditional aviation interior material layering design 2 , and the low-frequency sound absorption coefficient can be improved without sacrificing a large weight cost.

[0027] The present invention can improve the sound absorption coefficient of the interior to a certain extent in the frequency range of 1000 Hz, especially around 500 Hz; different properties of elastic metal foils can be inserted according to the target frequency to adjust the reflection frequency of sound waves, and thus adjust the frequency of the peak value of the sound absorption coefficient of the interior structure; meet the lightweight design requirements and can save installation space.

[0028] To verify the effectiveness of the present invention, simulation calculations were carried out, and the simulation results are as follows:

[0029] 1. When inserting steel foil, the comparison of the calculation results between the present invention and the traditional aviation interior design method is as Figure 2 shown;

[0030] 2. When inserting steel foil and aluminum foil into the glass fiber cotton respectively, the simulation calculation results of the present invention are as Figure 3 shown;

[0031] 3. When the sound absorption coefficients in the frequency range of 315 - 500 Hz are required to be the same, the comparison of the design thickness and weight between the present invention and the traditional design method is as Figure 4 shown;

[0032] Simulation calculations show that the present invention can, to a certain extent, improve the sound absorption coefficient of the noise reduction material below 1000 Hz. In particular, the average sound absorption coefficient within the range of 250 - 500 Hz is increased from 0.53 to 0.82. By changing the stiffness of the elastic metal foil and adjusting the reflection frequency of the sound wave, the present invention can adjust the frequency of the sound absorption coefficient, that is, the present invention can select different elastic metal foils according to different target frequencies to improve the sound absorption coefficient within the target frequency band of the interior structure. When the sound absorption coefficients of the target frequencies are equivalent, the present invention is lighter than the traditional design method of aviation interior noise reduction materials and can save nearly 50% of the installation space.

[0033] Other embodiments of the present disclosure will be readily apparent to those skilled in the art upon consideration of the specification and practice disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common general knowledge or conventional technical means in the technical field not disclosed herein. The specification and examples are only to be considered as exemplary, and the true scope and spirit of the present disclosure are pointed out by the following claims.

[0034] It should be understood that the present disclosure is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present disclosure is only limited by the appended claims.

Claims

1. A noise reduction material structure for suppressing the noise of a helicopter main reduction gear, characterized in that, It includes six layers, which are, from top to bottom, a honeycomb panel, a first acoustic transparent film, a first porous medium, an elastic metal foil, a second porous medium, and a second acoustic transparent film; Sound waves are transmitted from the honeycomb panel and the first porous medium to the elastic metal foil in sequence, and then enter the second porous medium again, thereby increasing the attenuation of sound energy; the above two acoustic transparent films are mainly used to increase the low-frequency reflection ability of the elastic metal foil.

2. The structure according to claim 1, characterized in that Both the first porous medium and the second porous medium are fiberglass wool.

3. The structure according to claim 2, wherein The density of the honeycomb panel is 48 kg / m 3 , with a thickness of 5 mm, which serves as a sound insulation function and is connected to the main reduction platform of the helicopter. Among them, the honeycomb material and its thickness can be selected according to actual requirements.

4. The structure according to claim 2, wherein, The first layer of porous medium and the thickness of the first layer of porous medium are both 30 mm, and the density is 16 kg / m 3 , which can both absorb sound and isolate sound. The porous material and its thickness can be selected according to actual needs.

5. The structure according to claim 2, characterized in that, The thickness of the elastic metal foil is 0.05 mm, which is used for the low-frequency reflection of sound energy. The material of the elastic metal foil can be selected according to actual needs, such as steel foil or aluminum foil, etc.

6. The structure according to claim 2, wherein The thickness of both the first acoustic transparent film and the second acoustic transparent film is 1 mm, and the density is 170 kg / m 3 , which is used to increase the low-frequency reflection ability of the elastic metal foil. The acoustic transparent film is in contact with the acoustic cavity inside the helicopter cabin, and the material and thickness of the acoustic transparent film can be selected according to actual needs.

7. The structure according to claim 1, wherein The layers of this structure are bonded to each other through an adhesive.

8. The structure according to claim 1, characterized in that, The greater the stiffness of the elastic metal foil, the lower the sound wave reflection frequency and the lower the sound absorption frequency of this structure.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1-8.

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