A thin plate radiation noise suppression device based on an electroacoustic non-linear energy sink

Abstract

The present invention relates to a thin plate radiation noise suppression device based on an electroacoustic non-linear energy sink, which comprises a sound cavity enclosed by an elastic plate and a plurality of total reflection wall surfaces. A thin film is installed on the total reflection wall surface opposite to the elastic plate in the sound cavity; a thin film back cavity is arranged outside the sound cavity, and the thin film back cavity covers the thin film. A loudspeaker is installed on the wall surface opposite to the wall surface where the thin film is located in the thin film back cavity. A loudspeaker back cavity is arranged outside the thin film back cavity, and the loudspeaker back cavity covers the loudspeaker. The loudspeaker is also connected with a feedback loop for controlling the excitation level of the loudspeaker, and the excitation input of the feedback loop is the sound pressure in the thin film back cavity. Compared with the prior art, the present invention adds an electroacoustic structure compared with the traditional thin film non-linear energy sink structure; through the optimized design of parameters such as the volume of the back cavity, the volume of the loudspeaker back cavity, and the feedback gain, the excitation lower threshold of the optimal target energy transfer phenomenon of the non-linear energy sink is reduced by 19 times.

Description

Technical Field

[0001] The present invention relates to the technical field of noise suppression, and in particular to a thin plate radiation noise suppression device based on an electro-acoustic non-linear energy well. Background Technique

[0002] Vibrations generated during the operation of the device form a sound cavity in a closed space, causing sound cavity noise, which will seriously affect the comfort and physical and mental health of people in the sound cavity.

[0003] Compared with traditional shock absorbers, non-linear energy wells can achieve energy attenuation in a relatively wide frequency range due to their non-linear stiffness.

[0004] The invention with the publication number CN112857553A discloses a noise reduction performance experimental device and method for a sound cavity coupled with a thin film non-linear energy well. The device includes a sound cavity, a loudspeaker and a microphone arranged in the sound cavity, an annular clamping plate, a thin film, a laser rangefinder and a host computer. A circular opening is provided on one side of the sound cavity, and an annular clamping plate is installed in the circular opening. The thin film is installed in the annular clamping plate and can move back and forth in the side wall of the sound cavity. The laser rangefinder is located outside the sound cavity to detect the displacement of the center point of the thin film; the loudspeaker, the microphone and the laser rangefinder are all connected to the host computer; the host computer obtains the sound pressure frequency response curve according to the sound cavity sound pressure, the displacement of the center point of the thin film and the external excitation force, and thereby judges the noise reduction performance of the sound cavity.

[0005] This solution only uses the non-linear energy well composed of a thin film for noise reduction, but the excitation lower threshold of the optimal target energy transfer phenomenon of the non-linear energy well is relatively fixed and difficult to optimize. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art, and to provide a thin plate radiation noise suppression device based on an electro-acoustic non-linear energy well, which is beneficial to optimizing the excitation lower threshold of the optimal target energy transfer phenomenon of the non-linear energy well.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A thin plate radiation noise suppression device based on an electro-acoustic non-linear energy well, including a sound cavity, the sound cavity is surrounded by an elastic plate and a plurality of fully reflecting wall surfaces, and a thin film is installed on the fully reflecting wall surface opposite to the elastic plate in the sound cavity;

[0009] A thin-film back cavity is provided outside the sound cavity. The thin-film back cavity covers the thin film. A loudspeaker is installed on the wall surface of the thin-film back cavity opposite to the wall surface where the thin film is located. A loudspeaker back cavity is provided outside the thin-film back cavity. The loudspeaker back cavity covers the loudspeaker. The loudspeaker is also connected to a feedback loop for controlling the excitation level of the loudspeaker. The excitation input of the feedback loop is the sound pressure in the thin-film back cavity.

[0010] Further, the feedback loop includes a back cavity microphone, a filter, a feedback gain setting component, and an amplifier connected in sequence. The back cavity microphone is located in the thin-film back cavity, and the amplifier is connected to the loudspeaker.

[0011] Further, by adjusting the feedback gain of the feedback loop, the volume of the thin-film back cavity, and the volume of the loudspeaker back cavity, the optimal parameters of the lower threshold of the effective excitation of the system target energy transfer are obtained.

[0012] Further, the size of the sound cavity is within the range of 0.9 - 1.1 m in length, 1.3 - 1.5 m in width, and 2.1 - 2.3 m in height. The radius of the thin film is within the range of 0.035 - 0.045 m. The value of the feedback gain of the feedback loop is within the range of -14 to -16. The volume of the thin-film back cavity is within the range of 0.120 - 0.130 m 3 range, and the volume of the loudspeaker back cavity is greater than 0.01 m 3 .

[0013] Further, a point of action of the plate excitation force is provided inside the elastic plate. The center point of the installation position of the thin film corresponds to the position of the point of action of the plate excitation force.

[0014] Further, the sound cavity is a hollow cuboid structure, and the sound cavity is enclosed by an elastic plate and five fully reflective wall surfaces.

[0015] Further, the thin-film back cavity is a hollow cuboid structure.

[0016] Further, the loudspeaker back cavity is a hollow cuboid structure.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] In the present invention, a back cavity is added to the elastic plate-sound cavity-thin film non-linear energy well multi-degree-of-freedom system. A loudspeaker is installed on the other side of the thin-film back cavity. The loudspeaker is connected to a loudspeaker back cavity at the back. At the same time, there is a feedback loop for controlling the excitation level of the loudspeaker. The excitation input of the loudspeaker is the sound pressure in the thin-film back cavity. At this time, the thin-film non-linear energy well is extended to an electro-acoustic non-linear energy well.

[0019] Compared with the traditional thin-film non-linear energy well structure, an electro-acoustic structure is added. Through the optimized design of parameters such as the back cavity volume, the back cavity volume of the speaker, and the feedback gain, the excitation lower threshold of the optimal target energy transfer phenomenon of the non-linear energy well is reduced by 19 times. Description of the Drawings

[0020] Figure 1 Schematic diagram of an elastic plate - three-dimensional acoustic cavity - thin-film non-linear energy well coupling system provided in an embodiment of the present invention;

[0021] Figure 2 Flowchart of a method for suppressing the radiation noise of a plate using a non-linear energy well provided in an embodiment of the present invention;

[0022] Figure 3 Sound pressure response diagram in the acoustic cavity with f = 75 - 85 Hz and F = 10 N - 450 N provided in an embodiment of the present invention;

[0023] Figure 4 Sound pressure response diagram in the acoustic cavity with f = 120 - 130 Hz and F = 250 N - 3000 N provided in an embodiment of the present invention;

[0024] Figure 5(a) is a sound pressure response diagram in the acoustic cavity with or without thin-film coupling under the excitation level of f = 75 - 85 Hz and F = 250 N provided in an embodiment of the present invention;

[0025] Figure 5(b) is a sound pressure response diagram in the acoustic cavity with or without thin-film coupling under the excitation level of f = 120 - 130 Hz and F = 1500 N provided in an embodiment of the present invention;

[0026] Figure 6 Displacement diagram of the center point of the thin film in the time domain response of the system under excitation with f = 80 Hz and F = 250 N provided in an embodiment of the present invention;

[0027] Figure 7 Displacement diagram of the center point of the thin film in the time domain response of the system under excitation with f = 125 Hz and F = 1500 N provided in an embodiment of the present invention;

[0028] Figure 8 Time domain response diagram of the system at the excitation level of 80 Hz, t = 4.6 - 4.8 s, and F = 250 N provided in an embodiment of the present invention;

[0029] Figure 9 Schematic diagram of an elastic plate - acoustic cavity - electro-acoustic non-linear energy well system provided in an embodiment of the present invention;

[0030] Figure 10(a) is a kind of V provided in an embodiment of the present invention ls = 0.005 m 3Lower F b Variation diagram of F with the back cavity volume V e and the feedback gain k;

[0031] Figure 10(b) is a diagram showing a V provided in an embodiment of the present invention ls = 0.01 m 3 Lower F b Variation diagram of F with the back cavity volume V e and the feedback gain k;

[0032] Figure 10(c) is a diagram showing a V provided in an embodiment of the present invention ls = 0.02 m 3 Lower F b Variation diagram of F with the back cavity volume V e and the feedback gain k;

[0033] Figure 10(d) is a diagram showing a V provided in an embodiment of the present invention ls = 0.03 m 3 Lower F b Variation diagram of F with the back cavity volume V e and the feedback gain k;

[0034] Figure 11 is a diagram showing a V provided in an embodiment of the present invention e = 0.025 m 3 Variation diagram of the optimal target energy transfer excitation interval of the system with the feedback gain;

[0035] Figure 12(a) is a diagram showing a V provided in an embodiment of the present invention e = 0.025 m 3 Lower F b Variation diagram of F with the speaker back cavity volume V ls and the feedback gain k;

[0036] Figure 12(b) is a diagram showing a V provided in an embodiment of the present invention e = 0.0625 m 3 Lower F b Variation diagram of F with the speaker back cavity volume V ls and the feedback gain k;

[0037] Figure 12(c) is a diagram showing a V provided in an embodiment of the present invention e = 0.125 m 3 Lower F b Variation diagram of F with the speaker back cavity volume V ls and the feedback gain k;

[0038] Figure 12(d) is a diagram showing a V provided in an embodiment of the present invention e = 0.1875 m 3 Lower Fb with the volume V of the speaker back cavity ls and the variation diagram of the feedback gain k;

[0039] Figure 12(e) shows a V provided in an embodiment of the present invention e = 0.125m 3 of F b with the volume V of the speaker back cavity ls and the variation diagram of the feedback gain k. Detailed implementation manners

[0040] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0043] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of the present invention.

[0044] It should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0045] In addition, terms such as "horizontal" and "vertical" do not require the components to be absolutely horizontal or hanging vertically, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0046] Embodiment 1

[0047] This embodiment provides a thin plate radiation noise suppression device based on an electro-acoustic non-linear energy well, including an acoustic cavity surrounded by an elastic plate and a plurality of total reflection wall surfaces, and a thin film is installed on the total reflection wall surface opposite to the elastic plate in the acoustic cavity;

[0048] A thin film back cavity is provided outside the acoustic cavity, the thin film back cavity covers the thin film, a loudspeaker is installed on the wall surface opposite to the wall surface where the thin film is located in the thin film back cavity, a loudspeaker back cavity is provided outside the thin film back cavity, the loudspeaker back cavity covers the loudspeaker, and the loudspeaker is also connected to a feedback loop for controlling the excitation level of the loudspeaker, and the excitation input of the feedback loop is the sound pressure in the thin film back cavity.

[0049] As an optional implementation manner, the feedback loop includes a back cavity microphone, a filter, a feedback gain setting component, and an amplifier connected in sequence. The back cavity microphone is located in the thin film back cavity, and the amplifier is connected to the loudspeaker.

[0050] As a preferred implementation manner, the size of the acoustic cavity is within the range of 0.9 - 1.1 m in length, 1.3 - 1.5 m in width, and 2.1 - 2.3 m in height, the thin film radius of the thin film is within the range of 0.035 - 0.045 m, the value of the feedback gain of the feedback loop is within the range of -14 to -16, the volume of the thin film back cavity is within the range of 0.120 - 0.130 m 3 range, and the volume of the loudspeaker back cavity is greater than 0.01 m 3 ; This setting can significantly reduce the excitation lower threshold of the optimal target energy transfer phenomenon of the non-linear energy well, and further improve the noise suppression performance.

[0051] As a preferred implementation manner, a point of action of the plate excitation force is provided in the elastic plate, and the center point of the installation position of the thin film corresponds to the position of the point of action of the plate excitation force.

[0052] In this embodiment, the acoustic cavity is a hollow cuboid structure surrounded by an elastic plate and five total reflection wall surfaces; both the thin film back cavity and the loudspeaker back cavity are hollow cuboid structures. As Figure 1 shown, one elastic plate and the thin film non-linear energy well are respectively installed on two opposite wall surfaces of the acoustic cavity. Let the lower left corner point of the coupling wall surface between the elastic plate and the acoustic cavity in the coupling system be the origin, and the point of action of the plate excitation force F acting on the elastic is (1 / 4L x , 1 / 4L y, 0), the position of the response point in the acoustic cavity is (1 / 4L x , 1 / 4L y , L z ), and the corresponding position of the center point of the film installation in the acoustic cavity is (1 / 4L x , 1 / 4L y , L z ).

[0053] Next, the effect of the thin plate radiation noise suppression device based on the electro-acoustic non-linear energy sink in this embodiment is verified, and the specific description is as follows:

[0054] 1. Model Introduction

[0055] Compared with traditional shock absorbers, non-linear energy sinks can achieve energy attenuation in a wide frequency range due to their non-linear stiffness. When the main system vibrates freely, internal resonance will occur in the main system, and there will be strong interactions between internal resonance modes, and the modes will be strongly coupled. When a certain mode of the main system has a certain initial energy, due to the effect of internal resonance, the energy will be transferred between several different modes. Under certain conditions, modal localization occurs in the system, and the vibration energy is locally concentrated in several modes. The use of the complex variable averaging method to simplify the study of the target energy transfer phenomenon on the non-linear energy sink shows that this phenomenon is caused by the transient resonance capture of the system resonance. For the regular acoustic cavity-elastic plate structure coupling system, a numerical analysis method for this system is established, and a multi-modal analytical model of the system is established by using methods such as the modal superposition method.

[0056] 2. Dynamic Model of the Coupling of the Elastic Plate-Acoustic Cavity-Thin Film Non-Linear Energy Sink Multi-Degree-of-Freedom System

[0057] As Figure 2 shown, a thin film is selected as the non-linear energy sink, and the non-linear stiffness of the thin film material adds non-linear stiffness conditions to the acoustic cavity-thin film coupling system. Using the thin film simplified model, the thin film material follows the simplified Kelvin-Voigt continuity theorem, and the Rayleigh-Ritz method is used to simplify the thin film equation, and the single-degree-of-freedom dynamic equation of the thin film is obtained as:

[0058]

[0059] In the formula, m m is the mass of the thin film, k 1 and k 3 represent the linear stiffness and non-linear stiffness of the thin film respectively, η is the viscous parameter, and the coordinates of the center point of the thin film in the three-dimensional acoustic cavity are (x m , y m , z m ), then the nth-order modal vibration shape of the acoustic medium at the center point position of the thin film in the acoustic cavity is ψ n(x m , y m , z m ).

[0060] When the thin film is installed on the surface of the acoustic cavity, there is a coupling relationship between the thin film and the acoustic medium in the acoustic cavity. Adding the damping term of air and being subjected to the external force F p (t), the dynamic equation of the acoustic medium in the acoustic cavity can be obtained:

[0061]

[0062] where m air is the mass of the acoustic cavity, c a and k a are the damping and stiffness of the acoustic cavity respectively.

[0063] When the elastic plate is coupled with the acoustic cavity, the plate is the boundary enclosing the acoustic cavity. When the plate is subjected to a harmonic excitation, the coupled equations of the acoustic medium and the elastic plate in the acoustic cavity with only the plate excitation force are obtained as:

[0064]

[0065] c is the coupling coefficient, F(t) is the modal vector force, m p is the mass of the elastic plate, k p and c p are the modal stiffness and modal damping of the elastic plate respectively, and the relationship between m a and m air is m a = m air / ρ 0 2 c 0 2 .

[0066] Combining them, the dynamic equation of the elastic plate - three - dimensional regular acoustic cavity - thin film coupling system is obtained as:

[0067]

[0068] where x represents the normal vibration displacement of the elastic plate, with the unit of m, p represents the acoustic pressure of the acoustic medium in the acoustic cavity, with the unit of Pa, q represents the normal vibration displacement of the center point of the thin film, with the unit of m, F(t) represents the excitation force acting on the elastic plate, and F p (t) represents the sound source excitation acting on the acoustic cavity, with the unit of N.

[0069] When the single - order modal coupling model is extended to multi - order modes, using the modal superposition principle, in the case of the coupling of n multi - order acoustic cavity modes and m multi - order elastic plate modes, when the sound source excitation is 0, under the condition that the excitation frequency is f, the dynamic equations of the coupling of multi - order acoustic cavity modes and multi - order elastic plate modes are:

[0070]

[0071] The thin-film system equation is added to the sound cavity coupled elastic plate equations, and finally a multi-degree-of-freedom equation set of the thin-film non-linear energy well coupling multi-order sound cavity modes and multi-order elastic plate modes can be obtained, where Ψ n (x m ,y m ,z m ) is the n-th order sound cavity mode at the center position of the thin film in the sound cavity:

[0072]

[0073] After being arranged in matrix form, it is:

[0074]

[0075] Among them, (x f ,y f ,z 0 ) is the position of the point excitation on the elastic plate, and q is the magnitude of the sound source excitation.

[0076] 3. Frequency-domain response analysis

[0077] According to the dynamic model of the elastic plate-sound cavity-thin film non-linear energy well multi-degree-of-freedom system coupling, modal selection is carried out for the elastic plate-regular sound cavity coupling system, and the Runge-Kutta method of the fourth and fifth orders is used for numerical analysis of the coupling system. The first 2 modes in the sound cavity are selected to study the cascade resonance capture characteristics of the thin film non-linear energy well. The first and second modes of the sound cavity are selected for analysis, and the modal frequencies are 79.55 Hz and 125.00 Hz respectively; the fourth, eighth, ninth, and twelfth modes of the elastic plate are selected for analysis, and the modal frequencies are 40.52 Hz, 68.91 Hz, 80.00 Hz, and 99.67 Hz respectively.

[0078] The excitation ranges are taken as f = 75 - 85 Hz and f = 120 - 130 Hz respectively, and separate analyses are carried out at intervals of Δf = 0.2 Hz. In the excitation amplitude selection of f = 75 - 85 Hz, F = 10 N, 25 N, 50 N, 100 N, 250 N, 350 N, 450 N are selected, and in the excitation amplitude range of f = 120 - 130 Hz, F = 250 N, 500 N, 1000 N, 1500 N, 2000 N, 3000 N are selected. The sound pressure response of the main system is shown in Figure 3 and Figure 4 as shown.

[0079] When the excitation amplitude is 50N < F < 350N near the first-order modal frequency of the acoustic cavity and the sound pressure reaches above 130 dB under the condition that there is no coupling of the thin-film non-linear energy well in the acoustic cavity; and when the excitation amplitude is 1000N < F < 2500N near the second-order modal frequency of the acoustic cavity and the sound pressure reaches above 140 dB under the condition that there is no coupling of the thin-film non-linear energy well in the acoustic cavity, with or without thin-film coupling, the sound pressure frequency response diagrams in the acoustic cavity are shown in Figure 5. It can be seen from Figure 5 that near the two modal frequencies of the acoustic cavity, within a bandwidth of about 2 Hz, response platforms are generated, effectively suppressing the response peaks caused by the modal resonance of the acoustic cavity. Although the excitation force ranges for the non-linear energy well to generate target energy transfer are different at the two modal frequencies, the noise energy in different frequency bands has been attenuated, indicating that the thin-film non-linear energy well has the ability of cascaded resonance capture.

[0080] 4. Time-domain response analysis

[0081] Perform time-domain response analysis on the system and apply a harmonic excitation force to the elastic plate. When the system is subjected to medium-level excitation, that is, when f = 80 Hz, F = 250N and f = 125 Hz, F = 1500N, the time-domain diagrams of the sound pressure response of the acoustic cavity and the vibration displacement response of the thin film are as follows near the two modal frequencies Figure 6 and 7 shown. Although the excitation acting on the elastic plate is a continuous and stable harmonic excitation, periodic strong modulation response phenomena can be seen at the center of the acoustic cavity and the thin film. At this time, the phase of the sound pressure change in the acoustic cavity is misaligned with the phase of the vibration displacement of the center point of the thin film. As the sound pressure level in the acoustic cavity increases, the vibration response level of the thin film also gradually increases; however, the response speed lags behind the sound pressure response. After reaching the peak value, it vibrates continuously with a large amplitude, and the energy in the acoustic cavity is unidirectionally transferred to the thin film and dissipated by damping. When the energy in the acoustic cavity decays to a certain level below, it cannot support the large-amplitude vibration of the thin film, and the vibration displacement of the center point of the thin film decreases, and then the whole response change process is repeated as the sound pressure response increases.

[0082] Select Figure 6 the excitation frequency near the first-order modal frequency of the acoustic cavity in

[0083] 5. Analysis of the influence of the electro-acoustic structure on the optimal target energy transfer interval of the system

[0084] In the multi - degree - of - freedom system of elastic plate - acoustic cavity - thin - film non - linear energy sink, a back cavity is added, and a loudspeaker and a feedback loop are added to the back cavity. As shown in Figure 9 Figure Figure 9 , a loudspeaker is installed on the other side of the thin - film back cavity. The back of the loudspeaker is connected to a second back cavity. At the same time, there is a feedback loop for controlling the excitation level of the loudspeaker. The excitation input of the loudspeaker is the sound pressure in the thin - film back cavity. At this time, the thin - film non - linear energy sink is extended to an electro - acoustic non - linear energy sink.

[0085] Combined with the coupling equation of the elastic plate - acoustic medium in the acoustic cavity - thin - film non - linear energy sink, the coupling equation of the elastic plate - acoustic cavity - electro - acoustic non - linear energy sink can be obtained:

[0086]

[0087] In order to explore the influence of multi - parameter changes in the non - linear energy sink system with electro - acoustic structure on the target energy transfer characteristics of the system, the optimal parameters for reducing the lower threshold F b of the effective excitation of the system target energy transfer are selected. The three key parameters of the volume V e of the thin - film back cavity, the volume V ls of the loudspeaker back cavity, and the feedback gain k of the electro - acoustic structure are analyzed. The value ranges of the parameters are V e = 0.025m 3 , 0.0625m 3 , 0.125m 3 , 0.175m 3 , 0.25m 3 , V ls = 0.005m 3 , 0.01m 3 , 0.02m 3 , 0.03m 3 , k = - 15, - 10, - 5, 0, 5, 10, 15.

[0088] In this embodiment, the size of the acoustic cavity is within the range of 1m in length, 1.4m in width, and 2.2m in height, and the radius of the thin - film is 0.04m.

[0089] When the volume V ls of the loudspeaker back cavity is different, the variation of the lower threshold F b of the effective interval of target energy transfer with the back - cavity volume V e and the feedback gain k is as shown in Figures 10(a) - 10(d) Figure Figures 10(a) - 10(d) . When the volume V e of the back cavity is different, the variation of the lower threshold F b of the effective interval of target energy transfer with the volume V ls of the loudspeaker back cavity and the feedback gain k is as shown in Figures 12(a) - 12(e) Figure Figures 12(a) - 12(e) , where the missing data part indicates that there is no target energy transfer phenomenon under this condition.

[0090] It can be seen from Figures 10(a) - 10(d) that under the condition of a fixed volume of the back cavity of the speaker, the curve trend of F b with respect to V e and k is relatively consistent. When the volume V e of the back cavity is small, as the gain k increases, F b first increases and then decreases. At this time, the effective excitation threshold interval of the system target energy transfer in the case of V ls = 0.02 m 3 is as shown in Figure 11 ; when the volume V e of the back cavity is large, as the gain k increases, F b shows a gradually increasing trend; when the volume of the back cavity of the speaker is small, as shown in Fig. 10(a), there is a system target energy transfer phenomenon within the investigated range; when the volume of the back cavity of the speaker is large, as shown in Fig. 10(d), when V e and k are small, there is no system target energy transfer phenomenon. The maximum value of F b first increases and then decreases as V ls increases. The minimum value of F b occurs when the feedback gain is small and the volume V e of the back cavity is around 0.01 m 3 .

[0091] It can be seen from Figures 12(a) - 12(e) that under the condition of a fixed volume of the back cavity, the curve trend of F b with respect to V ls and k is quite different. When the volume of the back cavity is small, as shown in Fig. 12(a), F b is in a relatively large range. At this time, as the feedback gain k increases, F b first increases and then decreases, reaching the maximum value when k = 0. As V ls increases, the change of F b is small, showing a trend of first increasing and then decreasing.

[0092] When the volume of the back cavity is at a medium level, as shown in Figs. 12(b) and 12(c), the overall threshold of F b decreases as V e decreases. When V ls is small, F b is not sensitive to the change of feedback k; the change with k is small. When V ls is large, as k increases, F b shows a trend of first increasing and then decreasing. When V e = 0.125 m 3 , V ls > 0.02 m3 When k = -15, F b reaches a minimum value of F b = 1 N.

[0093] When the volume of the back cavity is large, as shown in Figs. 12(d) and 12(e), it can be seen that at this time F b hardly changes with the feedback gain k and the back cavity V of the speaker ls and remains at the level of F b = 19 N. The lower threshold F of the optimal target energy transfer interval of the system b is affected by the back cavity volume V e , the back cavity volume V of the speaker ls and the electro-acoustic structure feedback gain k. The minimum value of F b appears in the range where the electro-acoustic structure feedback gain k selected in the study is small, the back cavity volume V of the speaker ls is large, and the back cavity volume V e is at a medium level.

[0094] In summary, based on the analysis of the three parameters of the thin film back cavity volume V e , the back cavity volume V of the speaker ls and the electro-acoustic structure feedback gain k, it is concluded that when V e < 0.125 m 3 or V ls > 0.02 m 3 , the lower threshold F of the excitation force b is relatively stable and at a low level, around 19 N; when V e > 0.02 m 3 and V ls < 0.125 m 3 , F b varies relatively violently with the feedback gain. In this range, the smaller k and V e , the smaller F b . However, if V e is too small, there will be no target energy transfer phenomenon in the system. In this study, when k = -15, V e = 0.125 m 3 , and V ls > 0.01 m 3 , F b can drop from 19 N to 1 N.

[0095] 6. Advantages of the design method for suppressing the radiation noise of the non-linear energy trap plate

[0096] The broadband low-frequency noise generated by the coupling of an elastic plate and an acoustic cavity can be suppressed by utilizing the cascaded resonance capture characteristics of a thin-film non-linear energy sink. A multi-degree-of-freedom dynamic theory model of the coupling system of the multi-order modes of the elastic plate - the multi-order modes of the acoustic cavity - the thin-film non-linear energy sink is established. By analyzing the coupling coefficients between different orders of modes of the elastic plate - acoustic cavity, the order with the greatest contribution to the system coupling is selected to construct a dynamic model, and the sound energy suppression effect of a single non-linear energy sink at the frequencies of multiple modes of the acoustic cavity is analyzed, demonstrating that the thin-film non-linear energy sink can perform cascaded resonance capture on the energy of the acoustic cavity system in the low-frequency range.

[0097] A structural improvement design method for applying a thin-film non-linear energy sink to the suppression of thin-plate radiation noise is proposed. Compared with the traditional thin-film non-linear energy sink structure, an electro-acoustic structure is added. Through the optimized design of parameters such as the volume of the back cavity, the volume of the speaker back cavity, and the feedback gain, the excitation threshold of the optimal target energy transfer phenomenon of the non-linear energy sink is reduced by 19 times.

[0098] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention through logical analysis, reasoning, or limited experiments based on the concept of the present invention on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. A thin plate radiation noise suppression device based on an electro-acoustic non-linear energy sink, comprising a sound cavity, characterized in that, the sound cavity is enclosed by an elastic plate and a plurality of fully reflecting wall surfaces, and a thin film is installed on the fully reflecting wall surface opposite to the elastic plate in the sound cavity; a thin film back cavity is provided outside the sound cavity, the thin film back cavity covers the thin film, a loudspeaker is installed on the wall surface opposite to the wall surface where the thin film is located in the thin film back cavity, a loudspeaker back cavity is provided outside the thin film back cavity, the loudspeaker back cavity covers the loudspeaker, and the loudspeaker is also connected to a feedback loop for controlling the excitation level of the loudspeaker, and the excitation input of the feedback loop is the sound pressure in the thin film back cavity; the feedback loop includes a back cavity microphone, a filter, a feedback gain setting component and an amplifier connected in sequence, the back cavity microphone is located in the thin film back cavity, and the amplifier is connected to the loudspeaker; by adjusting the feedback gain of the feedback loop, the volume of the thin film back cavity and the volume of the loudspeaker back cavity, the optimal parameters of the effective excitation lower threshold of the system target energy transfer are obtained; The size of the sound cavity is within the range of 0.9 - 1.1 m in length, 1.3 - 1.5 m in width, and 2.1 - 2.3 m in height. The film radius of the film is within the range of 0.035 - 0.045 m. The value of the feedback gain of the feedback loop is within the range of - 14 to - 16. The volume of the film back cavity is within the range of 0.120 - 0.130 m 3 3. The volume of the speaker back cavity is greater than 0.01 m 3 .

2. A thin plate radiation noise suppression device based on an electro-acoustic non-linear energy sink according to claim 1, characterized in that, a point of action of a plate excitation force is provided in the elastic plate, and the center point of the installation position of the thin film corresponds to the position of the point of action of the plate excitation force.

3. A thin plate radiation noise suppression device based on an electro-acoustic non-linear energy sink according to claim 1, characterized in that, the sound cavity is a hollow cuboid structure, and the sound cavity is enclosed by an elastic plate and five fully reflecting wall surfaces.

4. A thin plate radiation noise suppression device based on an electro-acoustic non-linear energy sink according to claim 1, characterized in that, the thin film back cavity is a hollow cuboid structure.

5. A thin plate radiation noise suppression device based on an electro-acoustic non-linear energy sink according to claim 1, characterized in that, the loudspeaker back cavity is a hollow cuboid structure.

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