CN113990278A - Double-layer thin film structure for low-frequency noise reduction - Google Patents
Double-layer thin film structure for low-frequency noise reduction Download PDFInfo
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- CN113990278A CN113990278A CN202111246353.6A CN202111246353A CN113990278A CN 113990278 A CN113990278 A CN 113990278A CN 202111246353 A CN202111246353 A CN 202111246353A CN 113990278 A CN113990278 A CN 113990278A
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- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
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Abstract
The invention relates to the field of noise reduction structures, in particular to a double-layer film structure for low-frequency noise reduction, which is cylindrical and is formed by gluing two layers of single films with the same structure in the same direction through a pure Polyimide (PI) film, wherein each single film comprises a pure Polyimide (PI) bottom film, ethylene vinyl acetate copolymer (EVA) rings uniformly arranged on the outer circumference of the pure Polyimide (PI) bottom film, a central cross vibrator attached to the central position of the pure Polyimide (PI) bottom film and two groups of cross aluminum alloy vibrators symmetrically arranged on the outer sides of four grooves of the central cross vibrator. The invention not only meets the requirements of the noise reduction structure on miniaturization and light weight, but also has good noise reduction performance, and can greatly improve the sound transmission loss bandwidth of the structure in the low-frequency range of less than 1600 Hz.
Description
Technical Field
The invention relates to the field of noise reduction structures, in particular to a double-layer thin film structure for low-frequency noise reduction.
Background
With the rapid development and industrial application of modern technologies, the noise problem generated by various devices is increasingly prominent, and noise pollution has become one of the main environmental pollutions. In the past two decades, the acoustics field has had huge development in the aspect of absorbing or suppressing sound wave propagation, wherein the technique of making an uproar falls in high frequency noise has matured relatively, but low frequency noise has the wavelength big, characteristics such as penetrability is strong, propagation distance is far away, adopt the tradition to fall to make an uproar material need bigger macroscopic size when making an uproar, this makes the cost of making an uproar increase, the space occupies the increase, and the noise reduction effect is poor, therefore tradition acoustics material has certain limitation in the aspect of low frequency sound insulation and sound absorption. Therefore, the pursuit of weight reduction and miniaturization of the structure on the basis of realizing effective control of low-frequency noise is one of the key problems to be solved in the field of sound insulation and noise reduction.
In recent years, the advent of acoustic metamaterials has provided an effective method for controlling low frequency noise. The film acoustic metamaterial is used as one kind of local resonance type acoustic metamaterial, the structure of the film acoustic metamaterial is that an elastic film is used as a carrier, the elastic film is fixed by a relatively rigid frame, a local vibrator is arranged on the tensioned elastic film, the local vibrator generates a negative dynamic mass to weaken elastic sound waves incident perpendicular to the plane of the film, the film acoustic metamaterial has sound transmission loss in a wide frequency range, and the sound insulation frequency band can be adjusted according to the magnitude of prestress of the film, the magnitude of additional mass, the mass position, the number of the additional mass and the like. Compared with the traditional acoustic metamaterial, the thin-film acoustic metamaterial has the characteristics of small size, large wavelength regulation, small size, light weight, excellent noise reduction performance and the like, and has a very wide application prospect in the field of low-frequency noise reduction. .
In 2000, scientists put forward the concept of localized resonance phononic crystals for the first time on Science, which was regarded as the earliest acoustic metamaterial. In the next two decades, researchers have improved the noise reduction performance of the structure by adding a mass block in the center of the film, multilayer overlapping the film, and the like. In 2019, ZHOU G et al designed four acoustic metamaterial models (ZHOU G, Wu G H, Tien X, et al, broadband low-frequency mean-type acoustic materials with multi-state anti-resonance [ J ] Applied Acoustics,2020,159:107078.) with different resonance distributions, effectively widened the acoustic attenuation band in the low-frequency region, and verified the low-frequency acoustic transmission loss performance of large-scale periodically-arranged acoustic metamaterial flat plate test pieces based on the models through simulation and experiments. The method promotes the engineering application research of the low-frequency bandwidth acoustic metamaterial to a certain extent.
However, the following limitations still exist in the research on the thin film acoustic metamaterial: the existing acoustic metamaterial has weak links which limit the application and research of the existing acoustic metamaterial, such as a large and heavy structure, a rigid frame, rapid aging of a membrane material (rubber), unstable membrane tension, an additional heavy resonator, a complex structure and the like.
In the aspect of broadband design, the antiresonance mode of a plurality of thin-film acoustic metamaterials is usually discrete and is blocked by the resonance mode of the thin-film acoustic metamaterials, so that the antiresonance mode cannot exist continuously, which is the main reason for causing the acoustic transmission loss STL bandwidth to be narrow, and the noise reduction frequency is not low enough, and the broadband acoustic metamaterial has the defects in the aspect of widening the low-frequency sound insulation bandwidth due to the structural design of the thin-film acoustic metamaterials.
Therefore, structural design is carried out on the film acoustic metamaterial, and a light acoustic metamaterial unit with a plurality of oscillator resonances is obtained, so that the low-frequency sound insulation bandwidth is widened, the structural weight is reduced as far as possible under the condition of generating continuous multi-stage anti-resonance modes, and the urgent need of practical application is met.
Disclosure of Invention
In order to solve the problems, the invention provides a double-layer thin film structure for low-frequency noise reduction, which not only meets the requirements of miniaturization and light weight of a noise reduction structure, but also has good noise reduction performance, and can greatly improve the sound transmission loss bandwidth of the structure in a low-frequency range less than 1600 Hz.
In order to achieve the purpose, the invention adopts the technical scheme that:
the utility model provides a double-deck film structure for making an uproar falls in low frequency, this double-deck film structure is cylindrically, and two-layer single-deck homodromous that is the same by the structure glues through pure Polyimide (PI) membrane and constitutes, the single-deck membrane includes pure Polyimide (PI) basement membrane and evenly sets up at the outer circumference of pure Polyimide (PI) basement membrane ethylene vinyl acetate copolymer (EVA) ring, the central cross oscillator of central point on attached to pure Polyimide (PI) basement membrane and the two sets of cross aluminum alloy oscillator of symmetry setting in four recess outsides of central cross oscillator.
Further, the thicknesses of the pure Polyimide (PI) film and the pure Polyimide (PI) base film are both 0.2 mm.
Further, the ethylene vinyl acetate copolymer (EVA) rings have a thickness of 2mm, an outer diameter of 100mm, and a width of 5 mm.
Further, the central cross-shaped vibrator is made of Elast-blk-10, has the length and length of 36mm, the width of 4mm and the thickness of 2mm, and is positioned at the center of a pure Polyimide (PI) film.
Furthermore, the length and width of the cross-shaped aluminum alloy vibrator are 6mm, the width of the cross-shaped aluminum alloy vibrator is 2mm, the thickness of the cross-shaped aluminum alloy vibrator is 1.8mm, and the cross-shaped aluminum alloy vibrator is symmetrically arranged by taking the central point of the central cross as the center.
Further, the distance between the two single films was 15mm, and the two single films were connected by a pure Polyimide (PI) film.
Further, the cross-shaped aluminum alloy vibrator, the central cross-shaped vibrator and the ethylene vinyl acetate copolymer (EVA) ring are bonded with the pure Polyimide (PI) bottom film through glue.
The invention has the following beneficial effects:
the noise reduction structure has the characteristics of light weight and miniaturization, can improve the acoustic transmission loss bandwidth of the structure to a great extent, particularly improves the STL bandwidth more than 30dB to a great extent compared with a reference model and a spider-web model, and has better low-frequency noise reduction effect. Specifically, the method comprises the following steps: compared with a cobweb model, the STL bandwidths of more than 10dB and more than 20dB in 1600Hz of the model disclosed by the invention are similar, and are greatly improved compared with a reference model. But in the aspect of STL bandwidth larger than 30dB, compared with a reference model, the model of the invention is improved by 401.7%, and compared with a spider-web model, the model is improved by 97.6%; at STL bandwidths greater than 40dB, the model of the invention was 1326.9% better than the reference model and 394.7% better than the spider model. In terms of STL peaks, the model of the present invention was 40.5% better than the reference model and 40.6% better than the spider web model. The model of the present invention is substantially comparable to the reference model in terms of structural weight. The two-film structure provided by the invention has the advantages that the noise reduction performance of the structure is improved to a great extent on the premise of keeping the structure light, and the performance is improved more obviously especially under the condition that the acoustic transmission is more than 30 dB.
Drawings
Fig. 1 is a schematic structural diagram of a double-layer thin film structure for low frequency noise reduction according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a single film in an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a cross-shaped aluminum alloy vibrator in an embodiment of the invention.
Fig. 4 is a schematic structural diagram of a central cross-shaped oscillator in the embodiment of the present invention.
FIG. 5 is a graph showing a comparison of STL curves for the model of the present invention with the reference model and the spider web model.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
As shown in fig. 1 to 4, an embodiment of the present invention provides a double-layer thin film structure for low frequency noise reduction, the double-layer thin film structure is cylindrical and is formed by adhering two single films with the same structure in the same direction through a Polyimide (PI) film with a pure thickness of 0.2mm, and the distance between the two single films is 15 mm; the single film comprises a pure Polyimide (PI) bottom film 1 with the thickness of 0.2mm, ethylene vinyl acetate copolymer (EVA) circular rings 2 uniformly arranged on the outer circumference of the pure Polyimide (PI) bottom film, a central cross-shaped vibrator 3 attached to the central position of the pure Polyimide (PI) bottom film, and two groups of cross-shaped aluminum alloy vibrators 4 symmetrically arranged on the outer sides of four grooves of the central cross-shaped vibrator; the ethylene vinyl acetate copolymer (EVA) ring has the thickness of 2mm, the outer diameter of 100mm and the width of 5 mm; the central cross-shaped vibrator is made of Elast-blk-10, has the longitudinal and transverse length of 36mm, the width of 4mm and the thickness of 2mm, and is positioned at the central position of a pure Polyimide (PI) film; the cross-shaped aluminum alloy oscillator is 6mm in length and length, 2mm in width and 1.8mm in thickness, and symmetrical arrangement is achieved by taking the central point of the central cross as the center.
The material parameters used in the model of the invention are shown in table 1.
TABLE 1 parameters of materials used in the model of the invention
In this embodiment, a 3D printing method is used to manufacture a frame and an oscillator made of EVA, a metal oscillator is manufactured by a machining method, a finished PI film is selected, and finally, a structural model of a reference and a structural model of the present invention are bonded and assembled, and the assembly is placed in an acoustic impedance tube for testing.
In the embodiment, an acoustic impedance tube is used for carrying out experiments on a designed acoustic metamaterial model according to GB/T27764-2011 Standard "transmission matrix method for measuring sound transmission loss in the acoustic impedance tube", and a measured value of sound transmission loss is given. In the experiment, a four-microphone method at a fixed position is adopted to measure the acoustic metamaterial test piece, and the experimental sampling frequency is 0.78125 Hz. The measurement frequency range is related to the distance between the microphones and the diameter of the impedance tube. The acoustic impedance tube used herein has a diameter of 100mm and a measurement frequency in the range of 80-1600 Hz.
In this embodiment, the sound insulation performance and efficiency of the structure are measured by using the weight of the structure and the STL Sound Transmission Loss (STL). Wherein STL may refer to the energy loss of acoustic energy through the structure, as shown in equation 1:
wherein, PinThe test amplitude was set to 1Pa, P for incident sound pressureoutIs in transmissionThe ratio of the sound pressure, the transmitted sound energy E tau, to the incident sound energy E0 is the sound energy transmission coefficient tau,<>and | | are the average and modulus of the parameter, respectively.
The results of the specific tests are shown in table 2 and fig. 5.
TABLE 2 summary of three model parameters and calculation results
From the STL curve data, the first STL bandwidth of the inventive model greater than 30dB was between 407Hz to 652Hz with an STL peak at 535Hz of 65.37 dB. As shown in FIG. 5, the frequency bands with STL value greater than 30dB in 1600Hz are 407-.
In comparison, the first STL bandwidth of the reference model larger than 30dB is between 365Hz and 458Hz, the STL peak value at 415Hz is 46.54dB, the frequency band with the STL value larger than 30dB is 365-458Hz and 916-938Hz within 1600Hz, and the total bandwidth of the total STL value larger than 30dB is 115 Hz; the first STL bandwidth of the spider-web model larger than 30dB is between 625Hz and 851Hz, the STL peak value at 755Hz is 46.51dB, the frequency bands with the STL value larger than 30dB in 1600Hz have 625 plus 851Hz and 1105 plus 1171Hz, and the total bandwidth of the total STL value larger than 30dB is 292 Hz.
Compared with the spider web model, the STL bandwidths of more than 10dB and more than 20dB in 1600Hz are similar in the model of the invention. However, in the aspect of STL bandwidth larger than 30dB, the model of the invention is greatly improved compared with a reference model and a spider web model, and particularly, the STL bandwidth larger than 40dB is improved more obviously. In addition, the STL peak value of the model of the invention is improved by 40.5 percent and 40.6 percent relative to the reference model and the spider web model respectively, but the weight of the on-film matrix is basically equivalent to that of the reference model. Therefore, the model greatly improves the noise reduction performance in the low-frequency range of the structure on the basis of realizing the lightweight structure.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (7)
1. A double-layer film structure for low-frequency noise reduction is characterized in that: this double-deck film structure is cylindrically, glues through pure Polyimide (PI) membrane by the two-layer monofilm syntropy that the structure is the same and constitutes, the monofilm includes pure Polyimide (PI) basement membrane and evenly sets up at the outer circumference of pure Polyimide (PI) basement membrane ethylene vinyl acetate copolymer (EVA) ring, the central cross oscillator of central point on attached to pure Polyimide (PI) basement membrane and the symmetry sets up two sets of cross aluminum alloy vibrators in the four recess outsides of central cross oscillator.
2. A double-layered thin film structure for low frequency noise reduction as defined in claim 1, wherein: the thicknesses of the pure Polyimide (PI) film and the pure Polyimide (PI) bottom film are both 0.2 mm.
3. A double-layered thin film structure for low frequency noise reduction as defined in claim 1, wherein: the ethylene vinyl acetate copolymer (EVA) ring has a thickness of 2mm, an outer diameter of 100mm and a width of 5 mm.
4. A double-layered thin film structure for low frequency noise reduction as defined in claim 1, wherein: the central cross-shaped vibrator is made of Elast-blk-10, has the longitudinal and transverse lengths of 36mm, the width of 4mm and the thickness of 2mm, and is positioned at the central position of a pure Polyimide (PI) film.
5. A double-layered thin film structure for low frequency noise reduction as defined in claim 1, wherein: the cross-shaped aluminum alloy oscillator is 6mm in length and length, 2mm in width and 1.8mm in thickness, and symmetrical arrangement is achieved by taking the central point of the central cross as the center.
6. A double-layered thin film structure for low frequency noise reduction as defined in claim 1, wherein: the spacing between the two single films was 15mm and the two single films were connected by a pure polyimide (P I) film.
7. A double-layered thin film structure for low frequency noise reduction as defined in claim 1, wherein: the cross-shaped aluminum alloy vibrator, the central cross-shaped vibrator and the ethylene vinyl acetate copolymer (EVA) ring are bonded with a pure Polyimide (PI) bottom film through glue.
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