224 results about "Acoustic metamaterials" patented technology

An acoustic metamaterial including cells to digitally process an incoming sound waveform, and to produce a corresponding response sound waveform as a function of a frequency and a phase of the incoming sound waveform, to produce a total response sound waveform that, when combined with the incoming sound waveform, modifies the incoming sound waveform.

An acoustic metamaterial layered composite for noise control may include a plurality of micro-perforated plates alternately and periodically arranged with a plurality of absorbent layers and optional air gaps. The plurality of micro-perforated plates may be in a form of a periodically arranged stack and include perforations extending therethrough. Each of the plurality of absorbent layers is formed of a poroelastic material. The metamaterial layered composite noise control device is designed using the metamaterial acoustics transformation approach for optimized noise control.

The invention relates to a sound-insulating, ventilating and heat transfer enhancing acoustic metamaterial structural unit, which comprises a frame, wherein a restraining body is arranged inside the frame, and at least one of the upper and lower surfaces of the frame is coated with a thin film; and at least one hole is formed in the restraining body and the thin film. In addition, the invention provides an acoustic metamaterial composite plate and an acoustic metamaterial composite structure comprising the acoustic metamaterial structural unit, as well as a frequency modulation method and an assembly method. The acoustic metamaterial structural unit has sound insulation capability superior to that of an ordinary perforated plate or micro-perforated plate within a broadband, can ensure that sufficient heat flow, air flow or liquid flow can pass through smoothly, and increases heat diffusion rate of fluid media on both sides of holes and accelerates heat convection efficiency through unit localized vibration generated by the structure under excitation of acoustic waves. The acoustic metamaterial structural unit and the array composite structure have the advantages of simple assembly technology and stable working performance.

Metamatenal members for absorbing sound and pressure, and modular systems built of metamaterial members are provided. The metamaterial member includes an outer mass. The outer mass can have a cavity formed therein in which a stem coupled to an inner mass is disposed, or the outer mass can be solid and contain an inner mass embedded therein. The inner mass can include an inner core and an outer shell. Multiple metamaterial members can be attached to form a modular system for absorption of sound and pressure.

The invention relates to an acoustic meta-material basic structure unit, and the structure unit comprises a boundary constraint frame. The interior of the boundary constraint frame is provided with an in-frame constraint body. At least one of the upper and lower surfaces of the boundary constraint frame is covered with a film. The invention also provides an acoustic meta-material plate comprising the acoustic meta-material basic structure unit, and an acoustic composite structure comprising the acoustic meta-material plate. In addition, the invention also provides a method for achieving working frequency adjustment sound insulation band of an acoustic meta-material through the change of the structural size and material parameters of the boundary constraint frame of the acoustic meta-material, the in-frame constraint body and the film. The unit is simple in assembly technology, is long in service life, restrains the vibration mode of the film, and enables the performance and stability of a sound insulating material to be improved.

A method for fabricating an acoustic metamaterial may include providing a planar pattern of springs arranged in columns and rows and separated from each other by interconnection nodes, providing a planar pattern of mass units separated from each other by a distance corresponding to a distance between the interconnection nodes, providing an array of vertically oriented springs separated from each other by the distance between the interconnection nodes, and aligning and joining the planar pattern of springs, the planar pattern of mass units and the array of vertically oriented springs to form a layer of unit cells.

The invention discloses a thin film acoustic metamaterial silencer and a designing method thereof. The thin film acoustic metamaterial silencer comprises a pipeline, wherein a frame installation hole communicated with the pipeline is formed in the side face of the pipeline, and a plurality of layers of silencer frames are installed in the frame installation hole. Each silencer frame is provided with a plurality of thin film installation holes. A thin film is arranged in each thin film installation hole and is in a tensioned state. A mass block is arranged at the center of each thin film. Each thin film and the corresponding mass block form a unit cell of the silencer. When the noise frequency in the pipeline is consistent with the working frequency of the silencer, fluid in the pipeline can not vibrate any more due to the vibration of the unit cells, so that the noise of the frequency is eliminated. In terms of pipeline noise, the thin film acoustic metamaterial silencer is good in noise reduction effect, small in size and high in working frequency. By combining a thin film acoustic metamaterial with traditional pipeline acoustics, a new idea is provided for solving the pipeline noise problem.

The invention discloses a polycell collaborative coupling acoustic meta-material design method. The method comprises a structure design method with insufficient localization rigidity and a structure design method with sufficient localization rigidity, wherein the structure design method with insufficient localization rigidity adopts a separating framework with localization rigidity lower than thinplate rigidity to separate local area resonance cells, so that strong coupling resonance behaviors of a single cell is generated, and a polycell combined structure with lumped coupling resonance effect is formed; the structure design method with sufficient localization rigidity adopts the separating framework with localization rigidity higher than thin plate rigidity, so that resonance of a single cell is not mutually affected within a design frequency band; and cells with gradient distribution of multiple thin plate widths, thin plate thicknesses or additionally mass block weight structure parameters define a polycell combined structure. The polycell collaborative structure can be applied to various transfer tools and various building decorations, and provides a brand-new denoising scheme for creating a low-noise environment.

The invention provides a Helmholtz cavity acoustic metamaterial with a thin film structure. According to the structure of the metamaterial, the thin film structure is added in the cylindrical Helmholtz cavity. The cylindrical cavity structure is made of aluminium, and the thin film is made of silicone rubber. For the structure, within the frequency range of 500Hz or below, a transmission coefficient curve can generate a plurality of peak values, and the frequency width range corresponding to the peak values can reach 30Hz. By changing the geometrical parameters of the structure, the noise-control acoustic metamaterial structure within the needed low frequency range can be obtained. The cylindrical cavity structure and the thin film structure have good coupling property, and enable the single sharp transmission coefficient curve peak value generated by the traditional Helmholtz cavity to be converted into a plurality of peak values, and the frequency width corresponding to the plurality of peak values is relatively large. The acoustic metamaterial adopting the structure is easy to prepare, the cost of the material is low, and an effective practical application is provided for the noise control within the low frequency range.

An embedded acoustic metamaterial lenses allows for ultrasonic beam-forming and high resolution identification of acoustic sources for structural health monitoring. The lenses design provides an alternative to conventional phased-array technology enabling the formation of steerable and collimated (or focused) ultrasonic beams by exploiting a single transducer. The ultrasonic beam can be steered by simply tuning the frequency of the excitation. Also, the embedded lens can be designed to achieve sub-wavelength resolution to clustered acoustic sources which is a typical scenario encountered in incipient structural damage.

The invention relates to the field of acoustic panel absorber and discloses a composite sound absorption structure based on combination of a micro-perforated board with an acoustic metamaterial. The composite sound absorption structure comprises a cover plate, side plates, a bottom plate, thin-film units, separation racks and mass blocks. The cover plate and the bottom plate are opposite to each other at an interval; and the side plates are connected with the cover plate and the bottom plate tightly to form a sound absorption back cavity. A plurality of micro sound absorbing holes and a plurality of unit holes are formed in the cover plate; one thin-film unit and one separation racks are arranged in each unit hole; and the thin-film units are fixed at the separation racks. The separation racks separate the unit holes into a plurality of cells. Each mass block is attached to the thin-film unit of one cell in each unit hole. Therefore, the sound absorption bandwidth can be broadened on the premise that the complexity of the sound absorption structure of the micro-perforated board is not increased; and thus the sound absorption effect can be enhanced.

A metamaterial comprising, a plurality of acoustic vector field sensors, each configured to sense an acoustic vector field of a fluid within a fluid-filled space in response to fluid waves, and producing an electrical signal corresponding to the sensed acoustic vector field; a processor configured to perform a time and space transform on the electrical signal; and at least one phased array transducer, configured to emit fluid waves according to a produced acoustic vector field pattern dependent on a result of the time and space transform, a within a portion of the fluid.

The invention, which relates to the field of metamaterial sound insulation, discloses a lightweight honeycomb type low-frequency sound insulation metamaterial structure which comprises an upper frame,a lower frame, elastic thin films arranged between the two frames, a mass blocks attached to the films and a homogeneous thin plate covering the outer sides of the frames. Each frame is composed of aplurality of regularly arranged hexagonal honeycomb units, and the honeycomb units of the upper frame and the lower frame are in one-to-one correspondence in position. The mass blocks are attached tothe elastic thin films of all honeycomb units, the mass blocks can be all identical or different in type and are arranged in a combined mode according to a certain rule, wherein the shapes of the mass blocks comprise a circular ring shape, a cylindrical shape and a circular truncated cone shape. The used honeycomb type acoustic metamaterial is superior to a traditional sound insulation material and has very excellent sound insulation performance in a low-frequency band; the overall quality of a structure can be controlled effectively by selecting a light frame material, so that the purposes of light weight and low-frequency sound insulation are achieved. The lightweight honeycomb type low-frequency sound insulation metamaterial structure has very broad application prospects in the fieldsof automobiles, buildings and the like.

The invention belongs to the field of vibration and noise control, and discloses a high-stiffness and high-damping local resonance unit for constructing an acoustic metamaterial structure. The high-stiffness and high-damping local resonance unit comprises an oscillator elastic element 1, an oscillator rigid element 2, an oscillator elastic element 3, a support and protection structure 4 and an oscillator unit 5. The oscillator elastic element 1 is firmly connected with one end of the oscillator rigid element 2; the other end of the oscillator rigid element 2 is firmly connected with the oscillator elastic element 3; and after being connected, the vibrator elastic element 1, the vibrator rigid element 2 and the vibrator elastic element 3 are closely placed together in the support and protection structure 4 to form the vibrator unit 5. The oscillator unit 5 can simultaneously give consideration to the performance of high rigidity and high damping, can generate multiple coupling action resonance modes in a low frequency band, can effectively broaden the low-frequency resonance frequency band by designing the oscillator unit 5 or changing the installation state or the combination modethereof, and the high-stiffness and high-damping local resonance unit has an important application prospect in terms of vibration and noise reduction of modern equipment.

A phonemic crystal is made of a first solid medium having a first density and a substantially periodic array of structures disposed in the first medium, the structures being made of a second solid medium having a second density different from the first density. The first medium has a speed of propagation of longitudinal sound waves and a speed of propagation of transverse sound waves, the speed of propagation of longitudinal sound waves being approximately that of a fluid, and the speed of the propagation of transverse sound waves being smaller than the speed of propagation of longitudinal sound waves.

The invention relates to an active acoustic metamaterial based on local resonance. According to the metamaterial, a hard sheet metal material is used as a substrate plate; a plurality of magnetic massblock units are embedded in the substrate plate; each magnetic mass block unit is composed of a magnetic mass block and a circular thin film fixed to the magnetic mass block, the magnetic mass blockunits are periodically arranged on the substrate plate in a lattice form, an electromagnet with adjustable current magnitude and positive and negative currents is further arranged above each magneticmass block unit, the vertical distance between each electromagnet and the corresponding magnetic mass block is 2-3 cm, and the electromagnets are used for applying adjustable reverse restoring force to the magnetic mass block units. According to the acoustic metamaterial provided by the invention, the electromagnets with adjustable current are introduced, and the intrinsic frequency of the thin film type acoustic metamaterial unit is actively adjusted, so that the sound insulation peak frequency is adjusted, the metamaterial has negative mass density, the sound insulation quantity far higher than the mass law can be realized, and the low-frequency line spectrum sound insulation is realized.

The invention relates to a silencer comprising an inlet pipe, an outlet pipe, a hollow expansion cavity formed between the inlet pipe and the outlet pipe, and a perforated acoustic metamateiral bafflearranged vertically or obliquely at the internal cross section of the hollow expansion cavity. The a perforated acoustic metamateiral baffle includes a frame; a constraint body in rigid connection with the frame is arranged inside the frame; a thin film covers the surface of the frame; and through holes are formed in the constraint body and the thin film. In addition, the invention also relates to an improved silencer; and occurrence of standing wave damping valley of the traditional resistant silencer is avoided and the good low-frequency noise elimination effect is realized. In addition, according to another embodiment, the invention also relates to an improved silencer, so that a problem of the direct contact between the sound absorption material and the fluid is solved. And accordingto another embodiment, the invention also relates to a silencer for improving the heat transfer efficiency of the fluid medium at the two sides of the hole by using vibration of a perforated acousticmetamateiral baffle. Besides, the invention also provides a method for frequency modulation and preparation of a perforated acoustic metamateiral baffle and a method of assembling the silencer. The silencer has characteristics of compact structure, simple process, stable performance, and long service life.

The invention discloses an acoustic supermaterial structure of an adjustable double-layer thin film plate based on repulsion force of a permanent magnet, and belongs to the field of low frequency anechoic devices. The structure includes a plurality of single cellular structures which are arranged in an array mode, each single cellular structure comprises an upper layer supporting plate structure and a lower layer supporting plate structure, the upper layer supporting plate structure and the lower layer supporting plate structure are fixed through adjustable screw rods, the upper layer supporting plate structure and the lower layer supporting plate structure are both provided with a thin film, and repulsive permanent magnets as bearing loads are arranged at the centers of the thin films. According to the double-layer thin film plate supermaterial, the film prestressing force is changed through the magnetic action of permanent magnet, and the range of adjustable sound insulation band iswidened compared with a film plate structure of an ordinary mass block. By adjusting the distance between the two layers of plates, the magnetic force can be adjusted indirectly, thus, the film tension can be adjusted, the adjustment mode is simple and easy to be achieved, and the structure can play the role of adjustable low frequency silencing in a certain frequency range.

The invention discloses an ultra-open type efficient ventilation sound absorption unit. The unit comprises a first shunt tube resonant cavity and a second shunt tube resonant cavity which are arrangedsymmetrically front and back side by side, wherein each shunt tube resonant cavity is composed of an inner frame and an outer frame; each shunt tube resonant cavity is integrally concentric-square-shaped; cover plates are arranged on the left sides and right sides of the first shunt tube resonant cavity and the second shunt tube resonant cavity, so that sound absorption channels are formed amongthe inner frames and the outer frames; and horizontal sound absorption narrow slits are further formed in the first shunt tube resonant cavity and the second shunt tube resonant cavity. The inventionalso discloses an ultra-open type efficient ventilation sound absorber. Each sound absorption unit forms a rigid loss oscillator similar to a spring, the sound absorber is installed in an open air flow channel, and efficient low-frequency absorption (more than 95%) and ventilation (wind speed ratio is larger than 80%) can be achieved, so that the existing technical bottleneck that the flow channelneeds to be completely sealed by an acoustic metamaterial to achieve perfect sound absorption but the ventilation cannot be realized is overcome, and the sound absorption unit and the sound absorberare particularly suitable for the noise control of fluid-filled environment such as an air conditioner, an exhaust hoods and a flow passage.