CN112447161A - Breathable acoustic superabsorbent devices and barriers - Google Patents
Breathable acoustic superabsorbent devices and barriers Download PDFInfo
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- CN112447161A CN112447161A CN201910793952.6A CN201910793952A CN112447161A CN 112447161 A CN112447161 A CN 112447161A CN 201910793952 A CN201910793952 A CN 201910793952A CN 112447161 A CN112447161 A CN 112447161A
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- 230000004888 barrier function Effects 0.000 title description 2
- 239000012528 membrane Substances 0.000 claims abstract description 42
- 238000010521 absorption reaction Methods 0.000 claims abstract description 18
- 239000010408 film Substances 0.000 claims description 62
- 239000010409 thin film Substances 0.000 claims description 33
- 239000000463 material Substances 0.000 claims description 5
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- 230000000149 penetrating effect Effects 0.000 claims 1
- 239000006096 absorbing agent Substances 0.000 abstract description 42
- 230000002745 absorbent Effects 0.000 abstract description 2
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- G—PHYSICS
- 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
- G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
- E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
- E04B1/62—Insulation or other protection; Elements or use of specified material therefor
- E04B1/74—Heat, sound or noise insulation, absorption, or reflection; Other building methods affording favourable thermal or acoustical conditions, e.g. accumulating of heat within walls
- E04B1/82—Heat, sound or noise insulation, absorption, or reflection; Other building methods affording favourable thermal or acoustical conditions, e.g. accumulating of heat within walls specifically with respect to sound only
- E04B1/8227—Heat, sound or noise insulation, absorption, or reflection; Other building methods affording favourable thermal or acoustical conditions, e.g. accumulating of heat within walls specifically with respect to sound only screens ; Arrangements of sound-absorbing elements, e.g. baffles
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
- E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
- E04B1/62—Insulation or other protection; Elements or use of specified material therefor
- E04B1/74—Heat, sound or noise insulation, absorption, or reflection; Other building methods affording favourable thermal or acoustical conditions, e.g. accumulating of heat within walls
- E04B1/82—Heat, sound or noise insulation, absorption, or reflection; Other building methods affording favourable thermal or acoustical conditions, e.g. accumulating of heat within walls specifically with respect to sound only
- E04B1/84—Sound-absorbing elements
- E04B1/86—Sound-absorbing elements slab-shaped
-
- G—PHYSICS
- 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
- G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators
-
- G—PHYSICS
- 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
- G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators
- G10K11/04—Acoustic filters ; Acoustic resonators
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
- E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
- E04B1/62—Insulation or other protection; Elements or use of specified material therefor
- E04B1/74—Heat, sound or noise insulation, absorption, or reflection; Other building methods affording favourable thermal or acoustical conditions, e.g. accumulating of heat within walls
- E04B1/82—Heat, sound or noise insulation, absorption, or reflection; Other building methods affording favourable thermal or acoustical conditions, e.g. accumulating of heat within walls specifically with respect to sound only
- E04B1/84—Sound-absorbing elements
- E04B2001/8423—Tray or frame type panels or blocks, with or without acoustical filling
- E04B2001/8433—Tray or frame type panels or blocks, with or without acoustical filling with holes in their face
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- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Multimedia (AREA)
- Electromagnetism (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Soundproofing, Sound Blocking, And Sound Damping (AREA)
Abstract
The invention belongs to the technical field of shock absorption and noise reduction. The present invention provides an air permeable acoustic absorbent structure which overcomes the disadvantages of ultra sound absorbers (US 9,711,129B 2) using air impermeable weighted membrane resonators, using air permeable weighted membrane resonating cells and a small air chamber communicating with the air through small holes, allowing the air to communicate between the front and back of the structure, but still being able to absorb sound energy efficiently.
Description
Technical Field
The present disclosure relates to sound absorbers having the ability to breathe, vent and maintain a high absorption coefficient.
Background
The Hybrid Membrane resonance Absorber (Hybrid Membrane Resonator) of the disclosed technology forms an Acoustic super-absorption (Acoustic super Absorber) device as shown in fig. 1A, comprising an air-impermeable elastic Membrane 101 to which a weight plate 102 is attached, the boundary of the Membrane fixing and sealing the opening of a sealed cavity 104 formed by a solid structure 103. The film with the weight plate is fixed on the frame edge of the opening to form a weighted Membrane Resonator (weighted Membrane Resonator). Fluids such as air and water are not able to pass through the membrane and the solid structure. The hybrid thin film resonant sound absorber manufactured using the disclosed technology has a thin film that is air-tight and air-tight inside the cavity. However, in many practical applications, the ambient temperature varies widely, from-40 degrees in the winter to more than 70 degrees in the summer when the sun is directly shining. The change of the outside air temperature can change the pressure of the sealed air in the cavity, so that the pressure balance at the two sides of the film is broken, and the pretension change of the film and the drift of the sound absorption frequency are caused. If the membrane of the hybrid membrane resonance absorber is permeable to air and the air in the chamber is in direct communication with the ambient atmosphere, the pressure balance across the membrane and the original pre-tension of the membrane can be maintained regardless of changes in ambient temperature. Furthermore, if a large area noise absorbing wall (fig. 1B) consisting of a two-dimensional array of air-permeable hybrid thin film resonant absorber devices of the disclosed technology is used, the wall is completely air-impermeable. Other prior art devices that are fully absorbent may provide good ventilation capacity (fig. 1C), but they require large side structures around the ventilation channel. The structure includes a ventilation channel 105, weighted film resonators 106, 107 forming part of the side walls of the channel, and enclosing back cavities 108, 109. The back cavity becomes a large side structure surrounding the ventilation channel. Therefore, a significant portion of the surface of the sound-absorbing wall formed by the two-dimensional array of such devices is a rigid plate, which absorbs sound less than the breathable hybrid film resonance absorber device, so that such a sound-absorbing wall, although it is breathable, only partially absorbs sound perfectly, and does not achieve complete sound absorption as a whole.
We first identified breathable films that might be used on breathable hybrid film resonance absorbers. Fig. 2A shows the theoretical acoustic transmission spectrum of the transmission spectrum of a gas-impermeable elastic film (curve 201), a perforated rigid plate with many small holes (curve 202), and an elastic perforated film (curve 203). Curve 201 has several resonances and antiresonances, as does a typical bulk film resonator that is gas impermeable. Curve 202 has no other resonance features than acoustic leakage through the air passages of the perforated plate apertures. Curve 203 shows the characteristics of an elastic membrane having resonance and antiresonance, and the characteristics of sound leakage due to air passage. The existing literature and published techniques prove that Perforated rigid plates are not suitable for breathable hybrid thin film resonance absorbers, and therefore the only remaining candidate for breathable hybrid thin film resonance absorbers with breathable films is Elastic Perforated films (Elastic Perforated Membranes). On the other hand, if the permeability is too high (too many pores and/or too large pores), the acoustic leakage benefit masks the resonance and anti-resonance effects of the elastic structure of the elastic perforated film, which determine the acoustic impedance of the elastic perforated film.
Disclosure of Invention
The hybrid thin film resonant absorber is constructed using a breathable thin film as a breathable acoustic super-absorber. Micropores on the elastic film provide air permeability for the device, and the small holes on the back plate of the hybrid film resonance sound absorber enable the front and the back of the device to be ventilated simultaneously. Two breathable films are used, one of which is stretched to prestress it, but the voids of the film are therefore stretched and the breathability is too great. This problem is solved by a second non-stretched film to reduce sound leakage. If desired, several layers of unstretched film may be added to reduce sound leakage. (if the stretched membrane already has good noise leakage reducing effect, only one membrane may be used.) the two layers are rigidly connected by a mass or a small piece, and the vibration of the two layers is synchronized. The mode of vibration in which the membrane and the vented chamber are coupled determines the frequency of sound absorption, which can be adjusted by the volume of the chamber and the tension of the elastic membrane.
Drawings
FIG. 1A is a schematic representation of a conventional hybrid thin film resonant absorber.
FIG. 1B is a hybrid thin film resonant absorber sound absorbing wall.
FIG. 1C is a prior art hybrid membrane resonant sound absorber ventilation and sound insulation.
FIG. 2A is a transmission coefficient spectrum of an air-impermeable film, a perforated rigid plate, and a perforated film.
Figure 2B is a side cross-sectional view of a two-layer air-permeable weighted film resonator.
Figure 2C is a photomicrograph of a two-layer air-permeable weighted film resonator.
Fig. 3A is an experimental transmission and reflection curve for an air-impermeable weighted film resonator.
Fig. 3B is a plot of the real and imaginary parts of the sample surface impedance as set forth in the plot of fig. 3A.
FIG. 3C is a graph of the acoustic reflection of the breathable hybrid film resonant absorber for back cavities of 40mm and 50mm depth.
FIG. 3D is a graph of real and imaginary acoustic impedance curves extracted from FIG. 3C for two sample surfaces. FIG. 3E is a plot of the real and imaginary acoustic impedances of two sample surfaces near the full absorption frequency extracted from FIG. 3D.
FIG. 4A is a reflection spectrum of a breathable hybrid film resonant absorber with several holes in the cavity back panel.
Fig. 4B is a surface impedance curve corresponding to the sample in fig. 4A.
Fig. 4C is a transmission spectrum corresponding to the sample in fig. 4A.
Fig. 4D shows the reflection spectrum of the breathable hybrid film resonator absorber with six holes on the back panel after cavity volume fine tuning optimization, wherein 431 is the reflection spectrum incident on the front side (the resonator side of the breathable weight film resonator) and 432 is the reflection spectrum incident on the back side (the cavity back panel). The inset is a photograph of the sample, with the small photograph in the lower right hand corner showing the back of the perforation.
FIG. 4E is a Willis coefficient for the sample in FIG. 4D, where 433 is the real part and 434 is the imaginary part.
Detailed Description
The invention adopts nylon cloth as the elastic perforated membrane, but the nylon cloth is not the only material, and other similar materials can be used for achieving the same purpose. A two-layer film structure is shown in FIG. 2B, which is used to construct an Air Permeable weighted Membrane Resonator (Air Permeable Membrane Resonator). One of the elastic perforated films 204 is stretched slightly so that it can still have sufficient density to maintain small air gaps so that the penetration rate is not too high to cause substantial leakage of sound; the other layer of elastic perforated film 205 is then stretched sufficiently to provide the necessary pre-tension. The two membranes are connected by a small rigid plate 206 to couple their vibrations to each other. The membrane is secured at its edges to a substantially rigid frame 207 to form a gas permeable, weighted membrane resonator. The resonator has both good gas permeability and elasticity. Stretching the less permeable membrane controls the air permeability so that the membrane retains its original permeability. Another sufficiently stretched film provides elasticity without having to worry about the perforation rate of the film being too great to mask the resonance and anti-resonance characteristics of the air permeable weighted film resonator. Figure 2C is a photomicrograph of an air-permeable, weighted film resonator. The air-permeable weighted film resonator is mounted at one end of a cavity having a cross-sectional area of 30mm x 30mm, the length of the cavity being adjustable between 20mm and 50 mm. The ideal cavity wall is hard and thick enough to have extremely high sound insulation efficiency.
The experimental setup used for reflection and transmission measurements in the present invention is the same as used before in terms of working principle. The side length of the internal square section of the impedance tube is 5 cm, so the cut-off frequency of the system is about twice of the frequency used in the previous work, and reaches more than 3000 Hz.
By way of comparison, the measurement results of the prior hybrid thin film resonant acoustic absorber devices based on the disclosed technology are first presented. The weighted membrane resonator of the hybrid membrane resonance absorber device was composed of a 60 mm diameter, 0.02 mm thick PVC membrane with a 6 mm diameter, 130 mg heavy rigid sheet bonded in the middle. Curve 301 in FIG. 3A is the transmission spectrum of a bulk film resonator having first and second resonance modes forming two transmission peaks at 310Hz and 810Hz and an anti-resonance mode therebetween forming a transmission valley at 460 Hz. The diameter of the back cavity of the hybrid film resonance sound absorber device is 60 mm, and the length of the back cavity of the hybrid film resonance sound absorber device is 30 mm. The experimental reflectance spectrum of the device is shown as curve 302 in figure 3A. A reflective valley at 368Hz can be clearly seen with a minimum value of 0.3. The frequency of which is between the first resonant frequency and the first anti-resonant frequency exhibited by the transmission spectrum of the weighted thin film resonator, as is typical of the hybrid thin film resonant acoustic absorber devices of the disclosed technology. Normalized surface impedance extracted from reflectance spectra using a formulaZ Re As shown in fig. 3B. It is the typical hybrid film resonance absorber impedanceThe spectrum of the light beam is measured,Z Re the real part 311 of (A) decreases from above 80 to near zero, andZ Re crosses the neutral line 313 around 370 Hz. When both cross the neutral line at almost the same frequency, the reflection is minimized. If the cavity volume is adjusted to fine tuneZ Re The real and imaginary parts of the impedance can be made to cross the zero line at the same frequency, thus achieving perfect absorption with the reflection infinitely close to zero.
Figure 3C shows experimental acoustic reflection spectra of a hybrid thin film resonant absorber containing an air-permeable weighted thin film resonator composed of a double layer nylon cloth weighted thin film resonator, as shown in figure 3C. Curve 321 is the reflection spectrum of a gas permeable hybrid thin film resonant acoustic absorber with a cavity length of 40 mm. Curve 322 is the reflection spectrum of a breathable hybrid film resonance absorber with a cavity length of 50 mm. The static pressure inside and outside the cavity of the breathable hybrid film resonance sound absorber (breathable hybrid film resonance sound absorber) is always balanced. The well-sealed cavity in the conventional hybrid thin film resonant absorber now becomes a leaky cavity because of the air-permeable weighted thin film resonator. Even so, the reflection valley around 900Hz can be clearly seen. After careful fine tuning of the volume of the cavity, the minimum can be as low as 4%, which means only 1.6 × 10-3Is reflected and the remainder is totally absorbed. This is a dramatic example, indicating that impedance matching is the determining condition for perfect absorption, and can be achieved with a hybrid thin film resonant absorber with either a gas-tight chamber or a leaky chamber.
FIG. 3D shows an impedance spectrum extracted from the reflection spectrum of the sample of the gas-permeable hybrid thin film resonant absorber of FIG. 3CZ Re . Where curve 331 is the real impedance component of a sample having a 40mm long cavity and curve 332 is the corresponding imaginary component. Curve 333 is the real impedance part of a sample with a 50mm long cavity and curve 334 is the corresponding imaginary part. The impedance spectrum shows quite different characteristics from the conventional sealed hybrid thin film resonant absorber in fig. 3B. First, the impedance of the device when non-resonant is significantly lower than that of a sealed hybrid thin film resonant absorber due to the microchannels in the elastic film of the air-permeable weighted thin film resonator. Actual peak impedanceAbout 20, while conventional hybrid film resonant absorbers exceed 80. The imaginary part also starts with a small value of 4. Second, the impedance peak caused by the first antiresonance at around 500Hz for the sealed hybrid film resonance absorber does not appear in the breathable hybrid film resonance absorber. This is probably because the antiresonance strength of the air-permeable weighted membrane resonator is greatly weakened by the leakage of sound from the microchannels in the elastic membrane. In the case of the air-permeable hybrid film resonator absorber, the reason for the small impedance is not the strong resonance of the air-permeable weighted film resonator, but rather the air permeability of the air-permeable weighted film resonator. When the air permeable weighted film resonator resonates at around 900Hz,Z Re the imaginary part and the real part of (c) cross the zero line 335 at the same time, thus creating a deep acoustic reflection valley.
Fig. 3E shows details of the impedance spectrum of an air-permeable weighted thin film resonator sample with different cavity lengths passing through neutral line 335 near the reflection valley 850Hz to reveal details of the fine tuning of the impedance matching condition by varying the cavity volume. Instead of what the formula in equation (1) predicts, now changing the cavity product will change not only the imaginary part but also the real part of the impedance. Equation (1) is suitable for sealing hybrid film resonance absorbers, but is overly simplified due to the more complex conditions that are brought about by the leakage cavity. However, by simple adjustment and trial, the impedance can be fine-tuned and a near perfect match with air is achieved, and perfect absorption is obtained.
And a plurality of holes with the diameter of 3 mm are drilled on the back plate of the back cavity. Air can pass through such devices, for example, first through the air-permeable, weighted film resonator, and then through the holes in the back cavity back plate. Starting with an optimally dimensioned gas-permeable hybrid film resonance absorber (cavity length 40mm, reflection spectrum see fig. 3C), the number of open holes increased from 1 to 13. FIG. 4A shows experimental reflectance spectra for samples with different numbers of holes, where curve 401 is the reflectance spectrum for a sample with one hole in the back plate, and curves 402, 403, 404, 405, and 406 are the reflectance spectra for samples with two, six, seven, nine, and thirteen holes in the back plate, respectively. As the number of holes increases, the sample gradually deviates from the perfectly absorbing state and the reflection valleys become shallower. While the transmittance increases with the number of holes (see fig. 4C). Where curve 411 is the transmission spectrum of a sample having a hole in the back plate and curves 412, 413, 414, 415, 416 are the transmission spectra of samples having two, six, seven, nine, thirteen holes in the back plate, respectively. The total absorption of the sample with one hole in the back plate was 0.989, the total absorption of the sample with two holes in the back plate was 0.996, and the total absorption of the sample with three holes in the back plate was 0.942. It can be seen that, if a breathable total sound absorbing wall is to be constructed, a sample having one or two holes in the back plate is suitable.
Fig. 4B shows normalized surface impedance spectra for the sample for the condition corresponding to fig. 4A. Where curves 421, 422 are the real and imaginary impedance parts, respectively, for one hole sample, curves 423, 424 are the real and imaginary impedance parts, respectively, for six hole samples, and curves 425, 426 are the real and imaginary impedance parts, respectively, for nine hole samples. As can be seen, the real part of the impedance of the sample can still reach 0 value until the working condition of six holes. After adding some clay filler to the sample chamber with six holes to reduce its volume, when the sound wave is incident from the side of the membrane, the measured reflection spectrum is curve 431 in fig. 4D, and it can be seen that the reflection valley of the sample is again deepened until less than 2%. And the reflection spectrum measured when the sound wave is incident from the back plate side is curve 432 in fig. 4D. It can be seen that the reflectance spectra of the two faces of the sample differ most when curve 431 reaches its minimum, and therefore can be used as a Willis asymmetric effector device. Curves 433 and 434 shown in fig. 4E are the real and imaginary parts, respectively, of the Willis coefficient lines of the sample, which exhibit a pronounced resonance characteristic near 1000Hz, with a maximum of 0.5. The transmission of the device is up to 0.4. if multiple devices are used in series to enhance the asymmetric effect, the device of the present invention is significantly more advantageous than prior devices with much less transmission.
Experiments show that the airtight cavity is not a necessary condition for realizing perfect absorption of the hybrid film resonance sound absorber device, more importantly, the impedance matching between various hybrid film resonance sound absorber devices and air can be realized, and the impedance matching can be realized by adjusting the volume of the back cavity. These hybrid thin film resonant absorber devices include dense film weighted thin film resonators plus leaky back cavities, air permeable weighted thin film resonators plus non-leaky back cavities (the remainder of the back cavity is air-tight except for the air permeable weighted thin film resonators), and air permeable weighted thin film resonators plus leaky back cavities, such as devices that open a hole in the back plate of the back cavity.
It is contemplated that various other changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the subject matter, may be made by those skilled in the art without departing from the spirit of the invention and the scope of protection as defined in the appended claims.
Claims (14)
1. A sound absorbing metamaterial comprising an acoustic impedance matching surface configured to minimize reflection of incident sound waves, the surface comprising: an elastic or flexible breathable film; a volume of space bounded completely by a substantially rigid shell structure and a plane defined by an opening in the shell structure; and a substantially rigid weight mounted on said membrane, whereby said membrane and said weight establish a plurality of eigenfrequencies of resonance, wherein the boundaries of said membrane are tightly fixed with the boundaries of said opening in said shell structure.
2. The sound absorbing metamaterial according to claim 1, wherein:
the eigenfrequency is selected such that the metamaterial causes incident acoustic waves to produce minimal reflections of acoustic energy.
3. The sound absorbing metamaterial according to claim 1, wherein the sound absorbing metamaterial provides an effective mass density irregularity of a thin film type acoustic metamaterial in an anti-resonance state that, in combination with the reflective surface and the fluid space between the thin film and the solid surface, matches an impedance of air at a predetermined frequency, thereby substantially attenuating reflected sound waves and allowing substantial absorption of incident sound waves.
4. The sound absorbing metamaterial according to claim 1, wherein:
the substantially rigid weights have a transverse dimension less than a transverse dimension of the elastic or flexible breathable film.
5. The sound absorbing metamaterial according to claim 1, wherein the membrane is pre-stressed in-plane by a predetermined amount.
6. The sound absorbing metamaterial according to claim 1, wherein:
the inner surface of the shell and the space comprise a material having acoustic absorption properties.
7. A sound absorbing metamaterial includes
An acoustic impedance matching surface configured to minimize reflection of incident acoustic waves, the surface comprising: an elastic or flexible breathable film; a volume of space bounded completely by a substantially rigid shell structure and a plane defined by an opening in the shell structure; and a substantially rigid weight mounted on said membrane, whereby said membrane and said weight establish a plurality of eigenfrequencies of resonance, wherein the boundaries of said membrane are tightly fixed with the boundaries of said opening in said shell structure.
8. The sound absorbing metamaterial according to claim 7, wherein:
the eigenfrequency is selected such that the metamaterial causes incident acoustic waves to produce minimal reflections of acoustic energy.
9. The sound absorbing metamaterial according to claim 7, wherein the sound absorbing metamaterial provides an effective mass density irregularity of a thin film type acoustic metamaterial in an anti-resonance state that, in combination with the reflective surface and the fluid space between the thin film and the solid surface, matches an impedance of air at a predetermined frequency, thereby substantially attenuating reflected sound waves and allowing substantial absorption of incident sound waves.
10. The sound absorbing metamaterial according to claim 7, wherein:
the substantially rigid weights have a transverse dimension less than a transverse dimension of the elastic or flexible breathable film.
11. The sound absorbing metamaterial according to claim 7, wherein the membrane is pre-stressed in-plane by a predetermined amount.
12. The sound absorbing metamaterial according to claim 7, wherein:
the inner surface of the shell and the space comprise a material having acoustic absorption properties.
13. The sound absorbing metamaterial according to claim 7, wherein:
the shell is provided with a plurality of holes penetrating through the shell, so that the space is connected with the space outside the shell without obstruction.
14. A plurality of the acoustic impedance matching surfaces of claims 1-6 or 7-13 formed into a two-dimensional large area surface to form a large area acoustic impedance matched acoustic wave absorbing wall or panel.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112942159A (en) * | 2021-04-04 | 2021-06-11 | 宋豪澎 | Silencing device arranged in urban near traffic track area |
| CN115424602A (en) * | 2022-07-31 | 2022-12-02 | 苏州声学产业技术研究院有限公司 | Rigidity-adjustable sound insulation board made of metamaterial |
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| CN105118496A (en) * | 2015-09-11 | 2015-12-02 | 黄礼范 | Acoustic meta-material basic structure unit, composite structure thereof, and assembly method |
| CN105393300A (en) * | 2013-07-18 | 2016-03-09 | 香港科技大学 | Extraordinary acoustic absorption induced by hybrid resonance and electrical energy generation from sound by hybrid resonant metasurface |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112942159A (en) * | 2021-04-04 | 2021-06-11 | 宋豪澎 | Silencing device arranged in urban near traffic track area |
| CN115424602A (en) * | 2022-07-31 | 2022-12-02 | 苏州声学产业技术研究院有限公司 | Rigidity-adjustable sound insulation board made of metamaterial |
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| CN112447161B (en) | 2024-09-13 |
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