CN114913841A - Six-channel sound wave retro-reflector based on acoustic grating - Google Patents
Six-channel sound wave retro-reflector based on acoustic grating Download PDFInfo
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Abstract
The invention provides a six-channel sound wave retro-reflector based on an acoustic grating, wherein the upper surface and the lower surface of the six-channel sound wave retro-reflector based on the acoustic grating are respectively provided with a plurality of grooves which are periodically arranged and have the same rectangular cross section; all grooves have the same width, depth and period, and the arrangement of the width, the depth and the period satisfies that: when the incident sound waves are respectively incident at the incident angles of 0 degrees, theta, 180 degrees-theta, 180 degrees + theta and 360 degrees-theta, the incident sound waves are completely reflected by the retro-reflector, and the reflected sound waves are propagated along the direction opposite to the original incident path. According to the six-channel sound wave retro-reflector based on the acoustic grating, the geometrical parameters of the grooves in the acoustic grating are adjusted, so that incident sound waves in six channels can be completely reflected by the retro-reflector, the reflected sound waves are transmitted along the direction opposite to the original incident path, the problems of few channels and large sound loss of the existing sound wave retro-reflector are solved, and the six-channel sound wave retro-reflector is simple and compact in structure.
Description
Technical Field
The invention belongs to the field of acoustics, and particularly relates to a six-channel sound wave retro-reflector based on an acoustic grating.
Background
With the continuous development of acoustic technology, the precise regulation and control of sound field distribution and sound propagation path in space has become a research hotspot internationally. The acoustic wave retro-reflector is an acoustic device which totally reflects incident acoustic waves back to the original incident direction, and can support the retro-reflection of acoustic waves under a plurality of acoustic channels, and the retro-reflected acoustic waves can transmit contained acoustic information to an acoustic source end. The acoustic wave retro-reflector has attracted wide attention of numerous scholars due to the unique acoustic response characteristic, and has great application value in the fields of acoustic remote sensing, acoustic communication, target identification, nondestructive testing and the like.
In the current technical level, the acoustic wave retro-reflector can be mainly realized by using an acoustic wave reflector, an acoustic luneberg lens, an acoustic super-surface and the like. The sound wave reflector is the simplest sound wave retroreflector, but the sound wave reflector can only completely retroreflect a vertically incident sound wave, that is, the sound wave retroreflector only supports retroreflection of the sound wave in a single channel. The acoustic luneberg lens is also widely used in the design of the acoustic wave retro-reflector, for example, an acoustic luneberg lens with a gradient refractive index can be constructed by an archimedean spiral unit, but the acoustic wave retro-reflector based on the luneberg lens has the problem of too large volume, and the development of the acoustic device towards miniaturization and integration is severely restricted. The subwavelength scale acoustic super-surface provides an effective realization method for a simple, compact and planar sound wave retro-reflector, such as a sound wave retro-reflector constructed by two cascaded super-surfaces, a three-channel sound wave retro-reflector based on sound surface impedance regulation, a multifunctional sound wave reflector capable of realizing mirror reflection, quasi retro-reflection and three-channel retro-reflection, and the like. The acoustic grating is an acoustic artificial structure formed by periodically arranging sub-wavelength units, and the amplitude and the phase of diffracted waves can be effectively regulated and controlled by regulating unit parameters of the acoustic artificial structure. Based on the acoustic grating, a plurality of singular acoustic functions can be realized, such as abnormal reflection or refraction, perfect sound absorption, sound focusing, sound stealth, unidirectional sound propagation and the like, and the acoustic grating also provides a potential method for designing the sound wave retro-reflector.
According to research reports, the maximum number of channels supported by the existing acoustic wave retro-reflectors is three, acoustic wave retro-reflectors capable of realizing more channels are not reported, and a new generation of acoustic wave retro-reflectors supporting more channels have great significance for improving the acoustic communication efficiency. In addition, a period of the sound wave retro-reflector comprises a plurality of unit structures, the structural design is complex, the unit structures are of space coiling structures, and when sound waves are transmitted in a narrow acoustic channel, the retro-reflection efficiency of the sound waves is inevitably low due to high viscous sound loss.
Therefore, it is important to design a multi-channel, high efficiency, simple and compact acoustic wave retro-reflector (e.g., a six-channel acoustic wave retro-reflector). The six-channel acoustic wave retro-reflector can enable incident acoustic waves in six channels to propagate along the direction opposite to the original incident path.
Reference documents:
[1]Y.Y.Fu,J.F.Li,Y.B.Xie,C.Shen,Y.D.Xu,H.Y.Chen,and S.A.Cummer.Compact acoustic retroreflector based on a mirrored Luneburg lens.Physical Review Materials,2018,2(10):105202.
[2]G.Y.Song,Q.Cheng,T.J.Cui,and Y.Jing.Acoustic planar surface retroreflector.Physical Review Materials,2018,2(6):065201.
[3]C.Shen,A.Díaz-Rubio,J.F.Li,and S.A.Cummer.A surface impedance-based three-channel acoustic metasurface retroreflector.Applied Physics Letters,2018,112(18):183503.
[4]Y.Y.Fu,Y.Y.Cao,and Y.D.Xu.Multifunctional reflection in acoustic metagratings with simplified design.Applied Physics Letters,2019,114(5):053502.
[5]A.L.Song,C.Y.Sun,Y.X.Xiang,and F.-Z.Xuan.Switchable acoustic metagrating for three-channel retroreflection and carpet cloaking.Applied Physics Express,2022,15(2):024002.
disclosure of Invention
The invention aims to provide a six-channel sound wave retro-reflector based on an acoustic grating, and aims to solve the problems of small number of channels, large sound loss and complex structure of the conventional sound wave retro-reflector.
In order to achieve the above object, the present invention provides a six-channel acoustic wave retro-reflector based on an acoustic grating, wherein the six-channel acoustic wave retro-reflector based on the acoustic grating is a flat substrate, and the upper surface and the lower surface of the substrate are respectively provided with a plurality of first grooves and second grooves which are periodically arranged along a first direction and have the same rectangular cross section; all the first grooves and the second grooves have the same width, depth and period of periodic arrangement; the widths, depths, and periods of the periodic arrangement of the first grooves and the second grooves are set so that the propagation directions of the incident sound waves and the reflected sound waves of the six-channel sound wave retro-reflector based on the acoustic grating satisfy: when incident sound waves are incident to the six-channel sound wave retro-reflector based on the acoustic grating at incidence angles of 0 degrees, theta, 180 degrees-theta, 180 degrees + theta, 360 degrees-theta respectively, and 20 degrees < theta <90 degrees, the incident sound waves are totally reflected by the retro-reflector, and the reflected sound waves are propagated along a direction opposite to an original incident path.
The widths, depths, and periods of the periodic arrangement of the first and second grooves are set so that the sound pressure field distribution of the reflected wave satisfies: when the incident sound wave is incident in each channel, the reflection coefficient of the diffraction wave of the order corresponding to the reflection direction opposite to the incident direction is maximum, and the reflection coefficients of the diffraction waves of the other orders are minimum.
The period a of the periodic arrangement of the first and second grooves is determined by using a formula of the x-direction wave number component of the nth order diffracted wave, and the period a of the periodic arrangement of the first and second grooves is: a is lambda/(2 sin theta), and lambda is the wavelength of sound waves in air; the width w of the first groove and the second groove takes any value in the range of 0< w < a.
When θ is 60 °, the period a of the periodic arrangement of the first and second grooves is 57.735mm, the width w of the first and second grooves is 28.8675mm, the depth h of the first and second grooves is 16mm, and the thickness of the acoustic grating is 36 mm.
The number of the first grooves and the number of the second grooves are any integer larger than 2.
The number of the first grooves and the number of the second grooves are both 12.
The acoustic impedance of the material of the acoustic grid-based six-channel acoustic wave back reflector is larger than 41500Pa s/m.
The material of the acoustic grating-based six-channel acoustic wave retro-reflector comprises one of a 3D printing material, a metal and an alloy.
The working frequency of the six-channel sound wave retro-reflector based on the acoustic grating can be in an audible frequency range of 20 Hz-20 kHz or an ultrasonic frequency range above 20 kHz.
According to the six-channel sound wave retro-reflector based on the acoustic grating, the geometrical parameters of the grooves in the acoustic grating are adjusted, so that incident sound waves in six channels can be completely reflected by the retro-reflector, the reflected sound waves are transmitted along the direction opposite to the original incident path, the problems of few channels and large sound loss of the existing sound wave retro-reflector are solved, the structure is simple and compact, the important requirements of a new generation of sound wave retro-reflectors on multiple channels, high efficiency and simple and compact characteristics can be met, and the six-channel sound wave retro-reflector based on the acoustic grating has wide application prospects in the fields of sound remote sensing, sound communication, target identification, nondestructive detection and the like.
Drawings
Figure 1 is a schematic diagram of the geometry of an acoustic grating-based six-channel acoustic wave retro-reflector designed according to one embodiment of this invention.
Fig. 2 is a schematic diagram of the cell structure of an acoustic grating of the six-channel acoustic wave retro-reflector shown in fig. 1.
Fig. 3 is a schematic diagram of the working principle of the acoustic grating-based six-channel acoustic wave retro-reflector of the present invention.
FIG. 4A is a sound pressure field profile of an incident wave when a planar acoustic wave with a frequency of 3430Hz is incident at an incident angle of 0 (channel 1), wherein white arrows indicate that the planar acoustic wave is incident at an incident angle of 0; FIG. 4B is a graph showing the sound pressure field distribution of the reflected wave when a planar acoustic wave with a frequency of 3430Hz is incident at an incident angle of 0 (channel 1), wherein black arrows indicate that the reflected acoustic wave is retro-reflected at a reflection angle of 0;
FIG. 5A is a sound pressure field profile of an incident wave when a planar acoustic wave with a frequency of 3430Hz is incident at an incident angle of 60 (channel 2), wherein white arrows indicate that the planar acoustic wave is incident at an incident angle of 60; FIG. 5B is a graph showing the sound pressure field distribution of the reflected wave when a planar sound wave with a frequency of 3430Hz is incident at an incident angle of 60 (channel 2), wherein black arrows indicate that the reflected sound wave is reflected back at a reflection angle of 60;
FIG. 6A is a sound pressure field profile of an incident wave when a planar acoustic wave with a frequency of 3430Hz is incident at an incident angle of 120 ° (channel 3), wherein white arrows indicate that the planar acoustic wave is incident at the incident angle of 120 °; FIG. 6B is a graph showing the sound pressure field distribution of the reflected wave when a planar sound wave with a frequency of 3430Hz is incident at an incident angle of 120 ° (channel 3), wherein black arrows indicate that the reflected sound wave is retro-reflected at a reflection angle of 120 °;
FIG. 7A is a sound pressure field profile of an incident wave when a planar acoustic wave with a frequency of 3430Hz is incident at an angle of incidence of 180 ° (channel 4), wherein white arrows indicate that the planar acoustic wave is incident at an angle of incidence of 180 °; FIG. 7B is a graph of the sound pressure field distribution of a reflected wave when a planar acoustic wave having a frequency of 3430Hz is incident at an incident angle of 180 (channel 4), wherein black arrows indicate that the reflected acoustic wave is retro-reflected at a reflection angle of 180;
FIG. 8A is a sound pressure field profile of an incident wave when a planar acoustic wave having a frequency of 3430Hz is incident at an incident angle of 240 ° (channel 5), wherein white arrows indicate that the planar acoustic wave is incident at an incident angle of 240 °; FIG. 8B is a graph of the sound pressure field distribution of a reflected wave when a planar acoustic wave having a frequency of 3430Hz is incident at an incident angle of 240 ° (channel 5), wherein black arrows indicate that the reflected acoustic wave is retro-reflected at a reflection angle of 240 °;
FIG. 9A is a sound pressure field profile of an incident wave when a planar acoustic wave with a frequency of 3430Hz is incident at an incident angle of 300 (channel 6), wherein white arrows indicate that the planar acoustic wave is incident at an incident angle of 300; FIG. 9B is a graph of the sound pressure field distribution of a reflected wave when a planar acoustic wave having a frequency of 3430Hz is incident at an incident angle of 300 (channel 6), wherein black arrows indicate that the reflected acoustic wave is retro-reflected at a reflection angle of 300;
fig. 10 is a far field directed diagram of reflected sound waves in six channels when a planar sound wave having a frequency of 3430Hz is incident on a six-channel sound wave retro-reflector at incident angles of 0 °, 60 °, 120 °, 180 °, 240 °, 300 °.
Detailed Description
The six-channel acoustic wave retro-reflector of the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.
Figure 1 is a schematic diagram of the geometry of an acoustic grating-based six-channel acoustic wave retro-reflector designed according to one embodiment of this invention. As shown in fig. 1, the six-channel acoustic wave retro-reflector based on the acoustic grating is a flat plate-shaped substrate 1, and the upper surface and the lower surface of the substrate 1 are respectively provided with a plurality of first grooves 2 and second grooves 3 with the same rectangular cross section, which are periodically arranged along a first direction (i.e. the x direction in the figure). The first grooves 2 and the second grooves 3 correspond to each other one by one, and each pair of the first grooves 2 and the second grooves 3 are arranged opposite to each other. The first grooves 2 and the second grooves 3 each have a length extending in a second direction (i.e., z direction in the drawing) perpendicular to the first direction. In the present embodiment, the number of the first grooves 2 and the number of the second grooves 3 are 12, however, in other embodiments, the number of the first grooves 2 and the number of the second grooves 3 are any integer greater than 2, and the number of the first grooves 2 and the number of the second grooves 3 are independent of the operating frequency and the incident angle. The acoustic retroreflection effect can be achieved for acoustic waves incident at six angles of incidence in six channels.
The material of the six-channel acoustic wave counter reflector based on the acoustic grating is 3D printing material, metal, alloy and the like, wherein the acoustic impedance of the material is larger than 100 times that of air, and therefore the acoustic impedance of the material of the six-channel acoustic wave counter reflector based on the acoustic grating is required to be larger than 41500Pa · s/m.
Fig. 2 is a schematic diagram of the cell structure of an acoustic grating of the six-channel acoustic wave retro-reflector shown in fig. 1. Since the upper surface and the lower surface of the substrate 1 are respectively provided with a plurality of first grooves 2 and second grooves 3 of the same rectangular cross section which are periodically arranged in the first direction, each periodic structure in which the upper surface and the lower surface are respectively provided with one first groove 2 and one second groove 3 is an acoustic grating. As shown in fig. 2, each acoustic grating has the same structure, and all the first grooves 2 and the second grooves 3 have the same width, depth, and period of periodic arrangement, where the width of the first grooves 2 and the second grooves 3 is w, the depth of the first grooves 2 and the second grooves 3 is h, the period of periodic arrangement of the first grooves 2 and the second grooves 3 is a, and the thickness of the acoustic grating is t.
The widths, depths, and periods of the periodic arrangement of the first grooves 2 and the second grooves 3 are set so that the propagation directions of the incident sound wave and the reflected sound wave of the six-channel sound wave retro-reflector based on the acoustic grating satisfy specific conditions. That is, the sound pressure field distribution of the reflected wave can be controlled by adjusting the width, depth and periodic arrangement period of the first groove 2 and the second groove 3 (the sound pressure field distribution of the reflected wave is obtained by performing finite element numerical simulation experiments in the multi-physical field coupling analysis software Comsol), wherein the amplitude and phase of the reflected sound wave can be adjusted and controlled by changing the depth of the first groove 2 and the second groove 3, and then the propagation directions of the incident sound wave and the reflected sound wave of the six-channel sound wave retro-reflector based on the acoustic grating are obtained. The acoustic grating provided by the invention does not comprise narrow channels and resonant cavities, so that the viscous sound loss in the six-channel sound wave retro-reflector is very low, and finally, the very high sound wave retro-reflection efficiency can be realized.
FIG. 3 is a schematic diagram of the operation principle of the acoustic grating-based six-channel acoustic wave retro-reflector of the present invention, wherein the conditions required to be satisfied by the propagation directions of the incident acoustic wave and the reflected acoustic wave of the acoustic grating-based six-channel acoustic wave retro-reflector are given, and the solid arrows indicate the incident angle θ i The dotted arrow indicates the reflection angle θ r The reflected acoustic wave propagation direction.
As shown in fig. 3, when the plane sound waves in the six channels are incident to the six-channel sound wave retro-reflector based on the acoustic grating at the incident angles of 0 ° (channel 1), 60 ° (channel 2), 120 ° (channel 3), 180 ° (channel 4), 240 ° (channel 5), and 300 ° (channel 6), respectively, the incident sound waves can be totally reflected by the retro-reflector, and the reflected sound waves propagate in the direction opposite to the original incident path, so that the sound wave retro-reflection effect is achieved in the six channels.
In this embodiment, the six-channel acoustic wave retro-reflector will be described in detail by taking, as examples, an acoustic wave frequency f of 3430Hz and incident angles of 0 °, 60 °, 120 °, 180 °, 240 °, 300 ° (corresponding to six acoustic channels, respectively). The density of air is 1.21kg/m 3 The sound velocity in air is 343m/s, the corresponding sound wave number in air is 2 pi f/c, and the sound wave wavelength in air is λ 100 mm.
In other embodiments, the structure of the acoustic grating-based six-channel acoustic wave retro-reflector of the present invention can be used for other working conditions besides the above working frequency and incidence angle. The conditions required to be met by the propagation directions of the incident sound wave and the reflected sound wave of the six-channel sound wave retro-reflector based on the acoustic grating include: when incident sound waves are incident to the six-channel sound wave retro-reflector based on the acoustic grating at incidence angles of 0 degrees, theta, 180 degrees-theta, 180 degrees + theta, 360 degrees-theta respectively, and 20 degrees < theta <90 degrees, the incident sound waves are totally reflected by the retro-reflector, and the reflected sound waves are propagated along a direction opposite to an original incident path. The working frequency can be in the audible frequency range of 20 Hz-20 kHz or the ultrasonic frequency range above 20 kHz.
In the present embodiment, the period a of the periodic arrangement of the first grooves 2 and the second grooves 3 is determined by using the formula of the x-direction wave number component of the nth order diffracted wave, the widths w of the first grooves 2 and the second grooves 3 may be any value in the range of 0< w < a, and the depths h of the first grooves 2 and the second grooves 3 are determined by calculating the magnitude of the reflection coefficient, which is the ratio of the sound pressure amplitude of the diffracted wave to the sound pressure amplitude of the incident wave. In the multi-physical-field coupling analysis software Comsol, the reflection coefficients corresponding to different depths h are respectively calculated by using a geometric parameter scanning method, and when the reflection coefficient of the diffraction wave of the order corresponding to the reflection direction opposite to the incident direction is the maximum and the reflection coefficients of the diffraction waves of the other orders are the minimum, the corresponding depth value is the depth value h of the acoustic grating of the invention.
The following is a detailed description of the design method and the operation principle of the six-channel acoustic wave retro-reflector of the present invention.
When the incident angle is theta i When the plane acoustic wave is incident to the six-channel acoustic wave retro-reflector, the incident wave is reflected into a plurality of reflected waves with different diffraction orders.
Wherein the x-direction wave number component k of the nth order diffracted wave rx Comprises the following steps:
k rx ＝ksinθ i +2πn/a，
where k is the wave number of sound waves in air, θ i A is a period in which the first grooves 2 and the second grooves 3 are periodically arranged, and n is an order of the diffracted wave, which is an incident angle of the incident sound wave.
When the diffracted wave is transmissibleWhen propagating diffraction waves, | k needs to be satisfied rx |<k, the range of order n to obtain diffracted waves is: - (1+ sin θ) i )/|2sinθ i |<n<(1-sinθ i )/|2sinθ i |。
Due to-1<sinθ i <1, so the order n of the diffracted wave can take only three values of-1, 0 and + 1.
For the transmissible diffraction wave, the propagation direction thereof can be reflected by the angle theta r Is shown, and the angle of reflection theta r Satisfies the following conditions: theta r ＝sin -1 (sinθ i + n λ/a), where θ i In order to obtain an incident angle of the incident sound wave, a is a period in which the first grooves 2 and the second grooves 3 are periodically arranged, n is an order of the diffracted wave, and λ is a wavelength of the sound wave in the air.
For an untransmissible diffracted wave (i.e. an evanescent wave), which propagates along the surface of the retro-reflector and the acoustic energy is rapidly attenuated in the normal direction, it does not propagate into the far-field region.
In the present invention, the widths, depths, and periods of the periodic arrangement of the first and second grooves 2 and 3 are set so that the acoustic pressure field distribution of the reflected wave (i.e., the amplitude and phase of the reflected wave) satisfies: when the incident sound wave is incident in each channel, the reflection coefficient of the diffraction wave of the order corresponding to the reflection direction opposite to the incident direction is the largest, and the reflection coefficients of the diffraction waves of the other orders are the smallest. Therefore, the propagated diffraction waves except the retro-reflected waves can be perfectly restrained from being excited, and the high-efficiency sound wave retro-reflection effect can be realized in six channels.
The following discusses the propagation of the sound wave when the plane sound wave is incident from the upper side of the six-channel sound wave retro-reflector, corresponding to the incident angles of 60 ° (channel 2), 0 ° (channel 1) and 300 ° (channel 6), respectively.
When a plane acoustic wave having an incident angle of 60 ° (channel 2) is incident on the six-channel acoustic wave retroreflector (i.e., θ is 60 °), it is required that the order of a transmittable diffracted wave in which the reflected wave propagates in the reflection direction at the reflection angle of 60 ° be-1, and the transmittable diffracted waves of the remaining orders are suppressed from being excited. The wave number horizontal component of the-1 order diffracted wave is ksin60 °, and since the horizontal component is in the negative x-axis direction, the x-direction wave number component of the-1 order diffracted wave is-ksin 60 °, and thus the period a of the periodic arrangement of the first grooves 2 and the second grooves 3 is:
a＝λ/(2sin60°)＝57.735mm，
the width w of the first and second grooves 2, 3 is taken as: w is 0.5a 28.8675 mm.
It should be noted that, in other embodiments, when the six channels of the six-channel acoustic wave retro-reflector respectively correspond to incident acoustic waves with incident angles of 0 °, θ, 180 ° - θ, 180 °, 180 ° + θ, and 360 ° - θ, the period a of the periodic arrangement of the first grooves 2 and the second grooves 3 is a ═ λ/(2sin θ), and the widths of the first grooves 2 and the second grooves 3 are w (0< w < a).
When the depth h of the groove is changed from 0 to 0.5 lambda, the reflection coefficients of-1 order diffraction waves, 0 order diffraction waves and +1 order diffraction waves are calculated in sequence, and when the reflection coefficient of the-1 order diffraction waves is the largest and the reflection coefficients of the other orders diffraction waves are the smallest, the corresponding groove depth is the required value. For each order of transmissible diffraction waves, the reflection coefficient is the ratio of the sound pressure amplitude of the diffraction waves to the sound pressure amplitude of incident waves; for each order of diffraction wave (i.e. evanescent wave) which cannot propagate, the acoustic energy thereof is rapidly attenuated along the normal direction and cannot propagate into the far-field region, so that the reflection coefficient thereof does not need to be calculated.
In the present embodiment, the depth of the first groove 2 and the second groove 3 is taken as h 16mm, the corresponding reflected wave phase is 0.64 pi, and the thickness of the acoustic grating is taken as t 36mm, according to the reflection coefficient of the diffraction wave of each order.
When the plane acoustic wave having an incident angle of 0 ° (channel 1) is incident on the six-channel acoustic wave retro-reflector, only 0-order diffracted waves (specular reflected waves) are excited according to the diffracted wave order range, and thus the acoustic wave retro-reflection phenomenon can occur in the channel.
When a plane acoustic wave with an incident angle of 300 ° (channel 6) is incident on the six-channel acoustic wave retro-reflector, only +1 order diffracted waves (retro-reflected waves) are excited according to the diffracted wave order range and the geometrical symmetry of the acoustic grating, and thus the acoustic wave retro-reflection phenomenon may occur in the channel.
For the sound wave propagation condition when the planar sound wave is incident from the lower side of the six-channel sound wave retro-reflector, the corresponding incident angles are 120 degrees (channel 3), 180 degrees (channel 4) and 240 degrees (channel 5), and because the grooves on the upper surface and the lower surface of the acoustic grating are the same and have symmetry, the sound wave retro-reflection phenomenon can also occur in the three channels on the lower side.
Based on the analysis, the six-channel sound wave retro-reflector based on the acoustic grating can realize the retro-reflection effect on incident sound waves in six channels.
The above embodiment is a preferred embodiment of the present invention, and the geometric parameters of the groove for specific operating frequency and incident angle in practical application can be determined by the above method described in the present invention.
Simulation result
A specific finite element numerical simulation experiment is carried out in a Comsol coupling analysis software to verify the effect of the six-channel acoustic wave retro-reflector, wherein the six-channel acoustic wave retro-reflector is placed in an air background medium in the simulation experiment, and the density of air is rho 1.21kg/m 3 The speed of sound in air is 343m/s, all boundaries of the retro-reflector are set as the hard acoustic boundary conditions, and the frequency of the incident sound wave is 3430 Hz.
Fig. 4A, 5A, 6A, 7A, 8A, and 9A are sound pressure field patterns of incident waves when the six-channel acoustic wave retro-reflector is irradiated with acoustic waves having incident angles of 0 °, 60 °, 120 °, 180 °, 240 °, and 300 °, respectively (white arrows indicate the propagation direction of the incident acoustic waves), fig. 4B, 5B, 6B, 7B, 8B, and 9B are sound pressure field patterns of reflected waves corresponding to the incident angles (black arrows indicate the propagation direction of the reflected acoustic waves). The sound pressure field distribution diagram of the reflected waves clearly shows that when the plane sound waves in the six channels are incident to the six-channel sound wave retro-reflector, the incident waves can be completely reflected back to the initial incident direction by the retro-reflector, and the reflected sound waves propagate along the direction opposite to the original incident path, so that the sound wave retro-reflection effect is realized in the six channels. Since the acoustic grating only comprises the periodically arranged grooves, the viscous acoustic loss is small, and the retro-reflection efficiency of the acoustic waves in six channels is close to 100%.
When the propagation direction of the incident acoustic wave is perpendicular to the six-channel acoustic wave retro-reflector, fig. 4B and 7B show the acoustic pressure field profiles of the reflected wave at the incident angles of 0 ° and 180 °, some excited surface waves exist in the surface region of the six-channel acoustic wave retro-reflector, but the energy of the surface waves is rapidly attenuated in the normal direction and does not propagate into the far-field region.
Fig. 10 is a far field directed diagram of reflected sound waves in six channels when a planar sound wave having a frequency of 3430Hz is incident on a six-channel sound wave retro-reflector at incident angles of 0 °, 60 °, 120 °, 180 °, 240 °, 300 °. According to the sound pressure field distribution of the reflected wave, sound energy values under different angles in a far-field region are extracted under a cylindrical coordinate system, and a distribution diagram of the relation between the sound energy values and the angles is drawn, namely a far-field directional diagram of the reflected sound wave. The far-field directional diagram of the reflected sound waves shows that the incident sound waves in the six channels are all completely reflected back to the original incident direction by the retro-reflector 1, and the reflection angles are respectively 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees.
The sound pressure field distribution diagram and the far field direction diagram of the reflected wave in the six channels prove that the six-channel sound wave retro-reflector based on the acoustic grating can achieve an efficient sound wave retro-reflection effect in the six channels.
According to the six-channel sound wave retro-reflector based on the acoustic grating, the geometrical parameters of the grooves in the acoustic grating are adjusted, so that incident sound waves in six channels can be completely reflected by the retro-reflector, the reflected sound waves are transmitted along the direction opposite to the original incident path, the problems of few channels and large sound loss of the existing sound wave retro-reflector are solved, the structure is simple and compact, the important requirements of a new generation of sound wave retro-reflectors on multiple channels, high efficiency and simple and compact characteristics can be met, and the six-channel sound wave retro-reflector based on the acoustic grating has wide application prospects in the fields of sound remote sensing, sound communication, target identification, nondestructive detection and the like.
The upper surface and the lower surface of the six-channel sound wave retroreflector based on the acoustic grating respectively comprise the grooves with the same rectangular cross section, the grooves are arranged periodically, the width and the depth of the grooves in the acoustic grating and the period of the periodic arrangement are adjusted to perfectly inhibit the propagated diffraction waves except the retroreflected waves from being excited, so that the incident sound waves in the six channels can be completely reflected by the retroreflector, the reflected sound waves are propagated along the direction opposite to the original incident path, and the retroreflection purpose of the six-channel sound waves is achieved. The planar sound waves incident at the incidence angles of 0 ° (channel 1), 60 ° (channel 2), 120 ° (channel 3), 180 ° (channel 4), 240 ° (channel 5), and 300 ° (channel 6) in the six channels are completely reflected back to the original incident direction by the six-channel sound wave retro-reflector, and the reflected sound waves all propagate along the direction opposite to the original incident path. The six-channel sound wave retro-reflector is flat based on the design scheme of the acoustic grating, the structure is simple and compact, and very high sound wave retro-reflection efficiency can be obtained due to low viscous sound loss. The six-channel sound wave retro-reflector has the advantages of multiple channels, high efficiency, simplicity, compactness and the like, and simulation experiments prove that the six-channel sound wave retro-reflector can achieve a high-efficiency sound wave retro-reflection effect in six channels.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: several modifications and embellishments (such as the shape of the profile of the recess) could be made without departing from the principle and function of the invention, and these should also be considered as the scope of protection of the invention.
Claims (9)
1. The six-channel acoustic wave retro-reflector based on the acoustic grating is characterized in that the six-channel acoustic wave retro-reflector based on the acoustic grating is a flat substrate, and a plurality of first grooves and second grooves which are periodically arranged along a first direction and have the same rectangular cross section are respectively formed in the upper surface and the lower surface of the substrate; all the first grooves and the second grooves have the same width, depth and periodically arranged period; the widths, depths, and periods of the periodic arrangement of the first and second grooves are set so that the propagation directions of the incident sound wave and the reflected sound wave of the acoustic-grating-based six-channel acoustic wave retro-reflector satisfy: when incident sound waves are incident to the six-channel sound wave retro-reflector based on the acoustic grating at incidence angles of 0 degrees, theta, 180 degrees-theta, 180 degrees + theta, 360 degrees-theta respectively, and 20 degrees < theta <90 degrees, the incident sound waves are totally reflected by the retro-reflector, and the reflected sound waves are propagated along a direction opposite to an original incident path.
2. The acoustic grating-based six-channel acoustic wave retro-reflector of claim 1, wherein the widths, depths, and periods of the periodic arrangement of the first and second grooves are set such that the acoustic pressure field distribution of the reflected wave satisfies: when the incident sound wave is incident in each channel, the reflection coefficient of the diffraction wave of the order corresponding to the reflection direction opposite to the incident direction is maximum, and the reflection coefficients of the diffraction waves of the other orders are minimum.
3. The acoustic grating-based six-channel acoustic wave retro-reflector as claimed in claim 2, wherein a period a of the periodic arrangement of the first and second grooves is determined using a formula of an x-direction wave number component of an nth order diffracted wave, and the period a of the periodic arrangement of the first and second grooves is: a is lambda/(2 sin theta), and lambda is the wavelength of sound waves in air; the width w of the first groove and the second groove takes any value in the range of 0< w < a.
4. The six-channel acoustic wave retro-reflector based on an acoustic grating as claimed in claim 3, wherein when θ is 60 °, the period a of the periodic arrangement of the first and second grooves is 57.735mm, the width w of the first and second grooves is 28.8675mm, the depth h of the first and second grooves is 16mm, and the thickness of the acoustic grating is 36 mm.
5. The acoustic grating-based six-channel acoustic wave retro-reflector of claim 1, wherein the number of the first grooves and the number of the second grooves are any integer greater than 2.
6. The acoustic grating-based six-channel acoustic wave retro-reflector of claim 5, wherein the number of the first and second grooves is 12.
7. The acoustic grating-based six-channel acoustic wave retro-reflector as claimed in claim 1, wherein the acoustic impedance of the material of the acoustic grating-based six-channel acoustic wave retro-reflector is greater than 41500Pa · s/m.
8. The acoustic grating-based six-channel acoustic wave retro-reflector as claimed in claim 7, wherein the material of the acoustic grating-based six-channel acoustic wave retro-reflector comprises one of a 3D printed material, a metal, and an alloy.
9. The acoustic grating-based six-channel acoustic wave retro-reflector as claimed in claim 1, wherein the operating frequency of the acoustic grating-based six-channel acoustic wave retro-reflector is in an audible frequency range of 20Hz to 20kHz or an ultrasonic frequency range above 20 kHz.
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| WO2024196866A1 (en) * | 2023-03-17 | 2024-09-26 | Microsoft Technology Licensing, Llc | Acoustic sensing and communication using a metasurface |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2024196866A1 (en) * | 2023-03-17 | 2024-09-26 | Microsoft Technology Licensing, Llc | Acoustic sensing and communication using a metasurface |
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