Sound amplification device based on M-H metamaterial and sound propagation method using the same

Abstract

This application provides a sound amplification device based on M-H metamaterials and a sound propagation method utilizing them. The sound amplification device includes at least an upper shell, a lower shell, and a waveguide located between the upper and lower shells. The waveguide is made of Mie metamaterials. The waveguide includes an outer wall with multiple sound wave inlets. The upper shell, lower shell, and outer wall enclose and form a waveguide space. A through-hole is provided within the waveguide space, penetrating the waveguide and the upper shell, serving as the sound wave outlet in the sound amplification device. The waveguide includes multiple fan-shaped sections arranged circumferentially around the through-hole. A waveguide channel is formed between adjacent fan-shaped sections, connecting the sound wave outlet and the sound wave inlets. The control current of the sound source is determined by the size of the sound amplification device and the scattering distribution of the sound amplification device under different resonance modes. The sound energy level at the sound wave outlet is higher than that at the sound source, and the propagation direction has an angle. By determining the control current at the sound source that best matches the size of the sound amplification device, low-cost, high-precision, and widely applicable sound propagation control is achieved.

Description

Technical Field

[0001] This application relates to the field of loudspeaker technology, and more particularly to loudspeaker devices based on MH metamaterials and methods for sound propagation using the same. Background Technology

[0002] Sound propagation is ubiquitous in life. For example, electromagnetic speakers or dynamic speakers in mobile phones, computers, and stereos can be considered sound sources, propagating through a medium to reach a predetermined sound receiver. During the propagation of sound, there is a reduction in energy level, resulting in different levels of energy loss in the sound we hear, making it impossible to obtain clear sound content. Amplification equipment is usually used during sound propagation to adjust the direction and energy level of the sound.

[0003] In recent years, significant research progress has been made in the application of metamaterials in sound wave manipulation scenarios, and the development of novel acoustic components utilizing unconventional acoustic special effects has also attracted much attention.

[0004] However, due to the shortcomings of traditional metamaterials, such as high loss, complex structure, and limited specific properties, the design of acoustic metamaterials still faces many challenges. Effectively controlling large-wavelength low-frequency sound waves with micro-unit-scale structures is a particularly difficult problem in acoustic research. Furthermore, the structure of metamaterials directly affects the resonance effect. Traditional metamaterial structures have poor control over sound waves, and the placement of metamaterials is usually determined artificially based on experience or trial and error, failing to achieve precise control over the direction and energy of sound waves. Moreover, existing loudspeaker equipment is designed for specific application scenarios, meaning all parameters of the sound source are fixed, such as the current frequency and magnitude of an electromagnetic loudspeaker, and consequently, the sound frequency and energy level are also fixed. Therefore, if the amplification effect needs to be adjusted, only the size and position of the loudspeaker equipment can be adjusted, resulting in large loudspeaker equipment. Moreover, loudspeaker equipment for each scenario is customized, leading to high design and manufacturing costs and poor sound control. Summary of the Invention

[0005] In view of this, this application provides a sound amplification device based on MH metamaterial and a sound propagation method using it, which is used to adjust the current frequency at the sound source according to the size information of the sound amplification device, so that the sound amplification device with the same structure can be adapted to sound control in various scenarios, and achieve low-cost and highly adaptable adjustment of sound directionality and energy level.

[0006] Specifically, this application is implemented through the following technical solution:

[0007] The first aspect of this application provides a loudspeaker based on MH metamaterial, the loudspeaker comprising at least:

[0008] The upper shell, the lower shell, and the waveguide located between the upper shell and the lower shell, the waveguide being made of Mie metamaterial;

[0009] The waveguide includes an outer wall with multiple acoustic inlets on it, and the upper shell, lower shell, and outer wall surround to form a waveguide space.

[0010] The waveguide space is provided with a through hole that connects the waveguide and the upper shell, and the through hole is the sound wave outlet in the loudspeaker.

[0011] The waveguide includes multiple fan-shaped sections arranged circumferentially around the through-hole;

[0012] Each of the fan sections includes radial ribs and multiple circumferential ribs arranged on both sides of the radial ribs. The multiple circumferential ribs on the same side are arranged at intervals. Two sets of circumferential ribs facing each other on adjacent fan sections are arranged alternately. The free ends of the circumferential ribs of each radial rib are arranged at intervals relative to the adjacent radial ribs, so that a waveguide channel is formed between the adjacent fan sections, which runs through the acoustic wave outlet and the acoustic wave inlet.

[0013] The control current of the sound source is determined by the size of the amplification device and the scattering distribution of the amplification device under different resonance modes. The sound energy level at the sound wave outlet is greater than that at the sound source, and there is an angle between the propagation directions.

[0014] A second aspect of this application provides a sound propagation method based on the loudspeaker device provided in the first aspect, the method comprising:

[0015] Adjust the control current of the sound source according to the size of the amplification device;

[0016] The amplification device is placed in the sound propagation path, and the sound is output from the amplification device. There is an angle between the direction of the sound output from the amplification device and the direction of the sound input to the amplification device, and the energy value increases. The magnitude of the increase in the energy value is related to the control current value.

[0017] The sound amplification device based on MH metamaterial and the sound propagation method using it provided in this application, in the first aspect, within the adjustment range of the reasonable current frequency value of the sound source, that is, within the adjustment range of the current frequency value to ensure that the content is not distorted, the current frequency value of the sound source end is determined according to the size of the sound amplification device, that is, the control current matching it is determined according to the height, through hole diameter, height and other parameters of the sound amplification device, thereby realizing reverse matching. It achieves the ability to comprehensively adjust the sound propagation control according to the adjustment of the sound source end parameters, the structural design of the sound amplification device, the placement orientation of the sound amplification device when the size of the sound amplification device is fixed, thereby realizing low-cost, high-precision and wide-application scenario sound propagation control. On the other hand, when the loudspeaker is controlling the sound, it uses a labyrinthine waveguide channel propagation path and a structure that isolates different sectors from each other. Based on radial ribs and staggered circumferential ribs, multiple independent labyrinthine waveguide channels are formed, allowing sound from all directions to enter the loudspeaker, i.e., absorbing more sound. The labyrinthine propagation channels significantly increase the path length of sound propagation. Through the sidewalls of the labyrinthine channels composed of MH metamaterials, the equivalent refractive index of the sound is continuously improved. Finally, the through holes connect the waveguide and the upper shell, forming a Helmholtz resonant cavity with the waveguide space. At the monopole resonant frequency, the Mie resonant local sound energy is radiated to a specific angle in the Z direction, while suppressing scattering at a specific angle in the XY plane, thereby improving the directivity and sound pressure level of low-frequency sound waves. Attached Figure Description

[0018] Figure 1 A schematic diagram of the structure of the loudspeaker provided in this application;

[0019] Figure 2 A comparative experimental diagram illustrating the width of the waveguide channel, as shown in an exemplary embodiment of this application;

[0020] Figure 3 A comparative experimental diagram illustrating the diameter of a through hole, as shown in an exemplary embodiment of this application;

[0021] Figure 4 A comparative diagram of an experimental study on the thickness of the upper shell, illustrating an exemplary embodiment of this application;

[0022] Figure 5 A flowchart of the sound propagation method provided in this application;

[0023] Figure 6 A schematic diagram of an experimental apparatus for determining the placement orientation of a loudspeaker device, as shown in an exemplary embodiment of this application;

[0024] Figure 7 A diagram illustrating the directional characteristics of a loudspeaker device as shown in an exemplary embodiment of this application;

[0025] Figure 8The normalized directivity characteristics of a 200Hz low-frequency sound in polar coordinates are shown in an exemplary embodiment of this application.

[0026] Figure 9 This is a coordinate diagram of the sound field intensity distribution under 200Hz low-frequency sound, as shown in an exemplary embodiment of this application.

[0027] Figure 10 This is a real-world scene diagram illustrating the arrangement of a loudspeaker device as shown in an exemplary embodiment of this application. Detailed Implementation

[0028] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0029] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0030] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0031] The following specific embodiments are given to illustrate the technical solution of this application in detail.

[0032] Figure 1 A schematic diagram of the loudspeaker device provided in this application. Please refer to... Figure 1 This application provides a loudspeaker based on MH metamaterial, the loudspeaker comprising at least:

[0033] The upper shell, the lower shell, and the waveguide located between the upper shell and the lower shell, the waveguide being made of Mie metamaterial;

[0034] The waveguide includes an outer wall with multiple acoustic inlets on it, and the upper shell, lower shell, and outer wall surround to form a waveguide space.

[0035] The waveguide space is provided with a through hole that connects the waveguide and the upper shell, and the through hole is the sound wave outlet in the loudspeaker.

[0036] The waveguide includes multiple fan-shaped sections arranged circumferentially around the through-hole;

[0037] Each of the fan sections includes radial ribs and multiple circumferential ribs arranged on both sides of the radial ribs. The multiple circumferential ribs on the same side are arranged at intervals. Two sets of circumferential ribs facing each other on adjacent fan sections are arranged alternately. The free ends of the circumferential ribs of each radial rib are arranged at intervals relative to the adjacent radial ribs, so that a waveguide channel is formed between the adjacent fan sections, which runs through the acoustic wave outlet and the acoustic wave inlet.

[0038] The control current of the sound source is determined by the size of the amplification device and the scattering distribution of the amplification device under different resonance modes. The sound energy level at the sound wave outlet is greater than that at the sound source, and there is an angle between the propagation directions.

[0039] It should be noted that MH metamaterial is an acoustic metamaterial based on the principles of Mie and Helmholtz resonance. Furthermore, according to the sound amplification device provided in this application, within the range where the sound source content is not distorted, the resonant frequency is derived from the size parameters of the amplification device. This resonant frequency is then used as parameter information for the control current of the sound source. For common current-controlled loudspeakers such as electromagnetic loudspeakers or moving-coil loudspeakers, the resonant frequency can be directly used as the current frequency of the loudspeaker, thus obtaining a sound source with the same resonant frequency, achieving optimal sound propagation control based on the amplification device. Specifically, firstly, the structure of the amplification device is designed, and its corresponding size information is determined. After determination, based on experimental / simulation evaluation, the resonant frequency with the optimal directionality and sound pressure enhancement effect obtained from the size information is selected. Finally, the amplification device is installed at a designated location along the sound propagation path, achieving unidirectional sound control of low-frequency sound waves in the sound receiving direction. Through the superposition effect of Mie scattering and Helmholtz reverse amplification, the sound intensity in the Z direction is enhanced, while the sound intensity in the XY plane is suppressed.

[0040] Please continue to refer to Figure 1 As can be seen, compared with the Mie resonance principle metamaterial, the sound amplification device provided in this application has a through hole in the waveguide space that runs through the waveguide and the upper shell, and an opening of the same size is provided on the surface of the upper shell at the position corresponding to the through hole. This through hole allows the sound amplification device to control the sound waves in three-dimensional space.

[0041] like Figure 1 The loudspeaker has a hollow cylindrical structure with a hollow cylinder in the middle. Figure 1Between the upper and lower shells is a waveguide made of Mie metamaterial. As an optional embodiment, during the experiment, the Mie metamaterial in the waveguide can be made of epoxy resin and printed using 3D printing technology.

[0042] Furthermore, the waveguide incorporates multiple waveguide channels. Sound waves emitted from the external sound source propagate to the cylindrical outer surface of the waveguide and enter each isolated waveguide channel through multiple incoherent sound inlets located at different positions on the outer surface of the waveguide and parallel to each other in space. Each waveguide channel has a maze-like pathway configuration. Sound entering the waveguide channel is reflected by the channel's sidewalls and exits from the sound wave outlet. The outlets of all waveguide channels are located at different positions on the sidewalls of the through-holes in the waveguide and are connected to the through-holes. Therefore, sound waves scattered from various directions enter through the inlets, are reflected by the intermediate waveguide channels, and then radiate out from the through-hole at the center of the amplification device, achieving enhancement of the sound pressure level in the direction of the through-hole and directional propagation control.

[0043] Under the same resonance mode, the control current exhibits a nonlinear inverse relationship with the thickness of the upper shell, the length of the waveguide channel, and the height of the amplifier, respectively, while the control current shows a nonlinear direct relationship with the diameter of the through-hole. The resonance modes include at least monopole, dipole, or multipole resonance modes. Under different resonance modes, the relationship between the control current and the thickness of the upper shell, the length of the waveguide channel, and the height of the amplifier shows the same trend, but the rates of change differ. In some resonance modes, the control current and the aforementioned dimensions exhibit a weak correlation. Therefore, by selecting a resonance mode with a strong correlation and obtaining the aforementioned quantitative change relationship experimentally, and then calculating the current frequency and other control current information of the amplifier based on the dimensions of the amplifier, the accuracy of sound propagation control is improved.

[0044] Specifically, the loudspeaker includes multiple fan-shaped sections arranged circumferentially around the through-hole, such as... Figure 1 As shown in section a, each of the fan-shaped sections includes radial ribs b and multiple circumferential ribs c arranged on both sides of the radial ribs, formed by... Figure 1As can be seen from the top view, the radial ribs of the loudspeaker have two endpoints in the radial direction. The first endpoint is located on the inner wall of the through hole. There are multiple radial ribs, and the first spacing between the first endpoints of adjacent radial ribs is the same. The second endpoint is located on the outer wall of the waveguide, and the second spacing between the second endpoints of adjacent radial ribs is the same, and the second spacing is greater than the first spacing. Each pair of adjacent radial ribs forms an independent fan section. The fan section is formed by circumferential ribs as sidewalls, forming a waveguide channel for sound propagation. For a radial rib, it serves as a shared radial rib for two adjacent fan sections. Its two sides are respectively provided with circumferential ribs for the two adjacent fan sections. Multiple circumferential ribs on one side are equally spaced. Except for the circumferential ribs forming the sidewall of the through hole and the circumferential ribs forming the outer wall of the waveguide, which are set in the same position, the other circumferential ribs on both sides of the same radial rib are arranged crosswise. From the outside to the inside, the circumferential ribs of the left fan section, the right fan section, the left fan section, and so on are provided in a repeated cycle. Within each sector, each circumferential rib originates from a radial rib on one side and extends towards the radial rib on the opposite side, but there is still a third spacing between them. The radial ribs originating from adjacent circumferential ribs are different. That is to say, the circumferential ribs originating from the radial ribs on both sides are spaced apart, but the third spacing within the same sector can be the same or different. The third spacing within different sectors can be the same or different.

[0045] Preferably, the dimensional relationships of the components within the waveguide include at least the following: the first spacing between the free ends of the circumferential ribs and adjacent radial ribs is less than the length of the circumferential ribs; the first spacing between the circumferential ribs in the same sector is equal; the interval between the free ends of the circumferential ribs furthest from the through-hole in each sector and adjacent radial ribs serves as the acoustic wave inlet; the interval between the free ends of the circumferential ribs closest to the through-hole in each sector and adjacent radial ribs serves as the acoustic wave outlet. The waveguide is a hollow cylindrical structure with a central through-hole. The heights of the acoustic wave inlet and outlet are the same as those of the waveguide, and the heights of the radial ribs and circumferential ribs are the same as those of the waveguide. The radial ribs isolate adjacent waveguide channels. Each sector includes one waveguide channel, each sector has the same area, and each waveguide channel has the same channel width.

[0046] The fan section is a three-dimensional structure. From the three-dimensional view, the height of the fan section is the same as the height of the amplifier. The circumferential ribs are arc-shaped, starting from the side opposite to the radial rib within the fan section and extending towards the side opposite to another radial rib. The arc length of each radial rib is less than the arc length of the fan section at its location. Each radial rib has the same thickness. Within the same fan section, the distance between the endpoint of each radial rib and the distance between the side opposite to the starting side of the radial rib are the same. The height of each radial rib is the same as the height of the amplifier. Vertically, any cross-section of the amplifier parallel to the upper and lower shells has the same shape, and each interface is annular. The upper and lower shells are parallel and of the same size. The projections of multiple radial ribs onto the cross-section divide the annulus into multiple annular sectors. Within each sector, two radial ribs are arranged alternately with two sets of circumferential ribs, and the arc length of each circumferential rib is less than the arc length of the sector at the location of the circumferential rib. This forms a labyrinthine channel of equal width at each location for propagating the sound source. The wall thickness of the circumferential ribs is much smaller than the radius of the cylindrical waveguide.

[0047] It should be noted that the waveguide has a hollow cylindrical structure running through it at its center; furthermore, the sound inlet of the waveguide channel is located at the outermost circumferential rib of the fan section, and the sound outlet of the waveguide channel is located at the sidewall of the through hole. The sound wave enters from the sound inlet, passes through the waveguide channel formed by the staggered circumferential ribs within a fan section, and exits from the through hole; adjacent waveguide channels are isolated from each other by radial ribs, and the height of the sound inlet and sound outlet of the waveguide channel is the same as the height of the waveguide; the width of the sound inlet and sound outlet of the waveguide channel is the same, and the width of the waveguide channel is the same as the width of the sound inlet; the thickness of the circumferential rib is less than the thickness of the waveguide space.

[0048] As described above, the waveguide channels formed by the staggered circumferential ribs within the sector guide the sound to propagate within them. This effectively enhances the propagation path length and phase control of low-frequency sound waves, thereby improving directivity and sound pressure level. Furthermore, the radial ribs isolate adjacent waveguide channels, preventing sound wave interference between different channels and ensuring independent control of each channel. The thickness of the circumferential ribs is less than the thickness of the waveguide space, which also reduces material usage and damping loss, further improving the energy utilization and enhancement effect of sound wave propagation.

[0049] Furthermore, from a structural perspective, traditional Mie resonant metamaterials are typically based on the Mie scattering principle, relying on the geometric dimensions of periodic or quasi-periodic structures to match the wavelength of sound waves to generate local resonance. They primarily control sound wave scattering in a two-dimensional plane, with typical structures being solid units or closed cavities without through-holes. These traditional Mie metamaterials lack open sound wave channels in three-dimensional space, limiting the three-dimensional propagation control of sound waves. In contrast, the amplification device provided in this application, based on traditional Mie metamaterials, introduces through-holes at the center of the upper and lower shells, forming a continuous sound wave entrance. Combined with waveguides, this constitutes a labyrinthine waveguide channel. The staggered circumferential ribs between the through-holes and the fan-shaped sections form channels connecting the interior and exterior, allowing sound waves to propagate and interfere in three-dimensional space (Z direction and XY plane).

[0050] Furthermore, in the amplification device provided in this application, the waveguide space (enclosed by the upper shell, lower shell, and waveguide) forms a Helmholtz resonant cavity, optimizing the monopole resonant frequency f≈580 Hz, and the through-hole diameter... =4mm is much smaller than the wavelength (62 cm) at the resonant frequency, which can effectively ensure subwavelength resonance; in addition, the through hole connects to the labyrinth-type waveguide channel, so that the sound wave propagates along the labyrinth path composed of radial and circumferential ribs in the waveguide space after entering, generating phase interference and low effective sound velocity, supporting sound intensity enhancement in the Z direction and sound wave suppression at a specific angle in the XY plane.

[0051] In summary, the openings provided at the center of the upper shell of the amplification device provided in this application, corresponding to the through holes that penetrate the waveguide, enable the amplification device to break through the two-dimensional limitation. Compared with the limitations of traditional Mie metamaterials in controlling low-frequency sound waves in a fixed plane, this allows low-frequency sound waves to propagate, interfere, and reconstruct in three-dimensional space, achieving flexible sound field directivity in three-dimensional space. In the three-dimensional space provided in this application, the cylindrical outer surface of the loudspeaker device has multiple waveguide channel entrances. Each sound entrance is located at a different position on the same outer surface. Therefore, sound waves from all directions can enter different channels through the sound entrances. The exits of the waveguide channels are located on the sidewalls of the cylindrical through-holes, i.e., at different positions on the same outer surface. Each channel is isolated from the others and does not interfere with them. The diameter of the channel is smaller than the diameter of the loudspeaker device, thereby adjusting the sound waves from all directions to propagate out from the relatively small diameter through-holes, improving the directional control effect. On the other hand, within each channel, the width at each position of the channel is the same as the width of the entrance opening, ensuring that the sound waves can propagate along the path in the narrow channel. Since the width is smaller than the diameter of the through-hole and the propagation distance of the sound waves, the sound waves repeatedly strike the sidewalls of the channel within the channel, increasing the intensity of the sound waves.

[0052] As an optional embodiment, the parameters of each structure in the loudspeaker provided in this application satisfy the following design: the radius of the upper shell and the lower shell is R=5cm; the thickness of the circumferential ribs... The thickness of the upper and lower shells With the thickness of the circumferential rib Same; width of waveguide channel The height of the waveguide =2cm; Diameter of the through hole =4mm.

[0053] Specifically, in this application, to investigate the correlation between the width of the waveguide channel, the resonant frequency, and the scattering characteristics under the same structural radius, the thickness of the circumferential ribs in the waveguide space is designed to be... The number of space folds is =8 times, for the width of the waveguide channel respectively = , = , = The scattering characteristics of the loudspeaker were simulated and analyzed. Figure 2 This is a comparative experimental diagram illustrating the width of waveguide channels in an exemplary embodiment of this application. The widths of the three waveguide channels are as follows: = , = , = The curves showing the ratio of forward and backward scattering to upward and downward scattering of the MH metamaterial unit under plane wave incident conditions as a function of frequency; among which, Figure 2 Figure (a) shows the ratio of forward and backward scattering of MH metamaterial units with three different waveguide channel widths as a function of frequency under plane wave incidence. Figure 2 Figure (b) shows the ratio of vertical to horizontal scattering as a function of frequency for amplifiers with three different waveguide channel widths under plane wave incidence. The width of the waveguide channel is directly proportional to the resonant frequency and inversely proportional to the wavelength of the sound wave. In monopole resonance mode, it is directly proportional to the ratio of vertical to horizontal scattering. The wider the waveguide channel, the higher the resonant frequency of the unit under the same resonant mode. This means that for the same unit size, the narrower the waveguide channel, the larger the wavelength of the sound wave that can be controlled under the same control effect.

[0054] Figure 3 This is a comparative experimental diagram illustrating the diameter of a through hole, as shown in an exemplary embodiment of this application. The thickness of the circumferential rib is... The width of the waveguide channel is The height of the loudspeaker upper shell thickness The spatial folding number is N=8 times, and the diameters of the through holes are respectively . Figure 3 (a) shows the ratio of forward and backward scattering as a function of frequency under plane wave incidence. Figure 3 (b) shows the ratio of upscattering to downscattering as a function of frequency under plane wave incident conditions. The smaller the diameter of the aperture, the lower the resonant frequency under the same resonant mode. In monopole resonant mode, the ratio of upscattering to downscattering of the loudspeaker increases with the diameter of the aperture at the resonant frequency, while the ratio of upscattering to downscattering decreases with the diameter of the aperture.

[0055] Figure 4 This is a comparative experimental diagram illustrating the thickness of the upper shell, as shown in an exemplary embodiment of this application. The thickness of the circumferential rib is... The width of the waveguide channel is waveguide height Diameter of the through hole The number of spatial folds is N=8, and the thickness of the upper shell is respectively... . Figure 4 (a) shows the ratio of vertical to horizontal scattering as a function of frequency. Figure 4 (b) The figure shows the ratio of forward and backward scattering as a function of frequency. The greater the thickness of the upper shell, the lower the resonant frequency of the amplifier under the same resonant mode. In the monopole resonant mode, the ratio of forward and backward scattering of the amplifier decreases at the resonant frequency with the increase of the upper shell thickness, while the ratio of upward and downward scattering decreases with the increase of the upper shell height.

[0056] Furthermore, after the sound amplification device is designed, in order to determine the optimal control current parameters, such as the frequency of the control current, within the adjustable range of the sound source, the method provided by this invention also includes calculating the control current based on the size of the sound amplification device. For common loudspeakers, the frequency of the control current is directly equal to the frequency of the emitted sound. To optimize the sound control effect of the sound amplification device, the frequency of the sound emitted by the loudspeaker is directly equal to the resonant frequency. Then, the resonant frequency is calculated based on the size parameters, and the frequency value of the control current is derived from this. The sound source provided by this invention is a low-frequency sound wave, with a frequency between 70Hz and 600Hz. The calculation of the resonant frequency value will be explained in detail later and will not be elaborated upon here.

[0057] The method provided by this invention, on the one hand, achieves Z-plane sound modulation by integrating multiple independent labyrinthine waveguide channels of a loudspeaker and setting through holes in the upper shell and waveguides. The waveguide, constructed of MH metamaterial, resonates within the waveguide channels, achieving highly efficient sound modulation. The modulated sound exhibits enhanced directivity in the direction of the through holes, and the sound energy level (i.e., sound pressure level) is significantly enhanced. On the other hand, the structure of the loudspeaker provides a tool for sound modulation. The effectiveness of sound modulation still depends on the matching degree between the size of the loudspeaker and the sound emitted from the sound source. This invention can directly calculate the corresponding resonant frequency based on the size information, and then adjust the control current so that the frequency value of the sound emitted by the loudspeaker is the same as the resonant frequency, achieving optimal sound modulation effect. Therefore, for different loudspeakers, the already designed and manufactured loudspeaker can be fixedly adapted to different loudspeakers based on its fixed size parameters. By adjusting other variable parameters, such as the control current, the sound propagation effect can be modulated, achieving low-cost and highly adaptable sound propagation modulation. Ultimately, the low-frequency sound waves emitted by the original electromagnetic transducer were enhanced in the Z direction and the radiation at a specific angle in the XY plane was suppressed by the amplification device, thereby improving the directivity and sound pressure level of the low-frequency sound waves.

[0058] Corresponding to the aforementioned embodiments of the loudspeaker based on MH metamaterials, this application also provides a sound propagation method based on the loudspeaker described in the above embodiments. Please refer to... Figure 5 The method includes:

[0059] S501. Adjust the control current of the sound source according to the size of the amplification device.

[0060] As an optional embodiment, adjusting the control current of the sound source according to the size of the amplifier includes: determining the thickness of the upper shell of the amplifier, the length of the waveguide channel, the height of the amplifier, and the diameter of the through hole; calculating the ratio between the square of the through hole diameter and the thickness of the upper shell; calculating the sum of the ratio and the derivative of the through hole diameter; calculating a first product of the sum and the height of the amplifier; determining the resonant frequency based on the square root of the first product and the product of the length of the waveguide channel; and adjusting the control current of the sound source to the optimal control current according to the resonant frequency.

[0061] S502. The amplification device is placed in the sound propagation path, and the sound is output from the amplification device. There is an angle between the direction of the sound output from the amplification device and the direction of the sound input to the amplification device, and the energy value increases. The magnitude of the increase in the energy value is related to the control current value.

[0062] The placement location is the relative position of the loudspeaker to the sound source. As an optional embodiment, there may be only one loudspeaker or multiple loudspeakers. The number of loudspeakers is determined by the limitation of the frequency of the sound source control current, the effect of sound propagation control, and the size of the loudspeakers. Preferably, there may be multiple loudspeakers, placed in the same circular position centered on the sound source.

[0063] The step of placing the amplification device along the sound propagation path includes: conducting a single-variable experiment on the amplification device to obtain the correlation between the sound propagation performance of the amplification device and the installation orientation of the amplification device; determining the sound receiving orientation; and determining the placement position of the amplification device along the sound propagation path based on the receiving orientation and the correlation, wherein there is an angle between the line connecting the receiving orientation and the sound outlet of the amplification device and the local sound propagation path from the sound source to the amplification device; and the energy level of the sound at the receiving point is higher than the energy level of the sound at the emitting point.

[0064] Specifically, orientation includes direction and location. A single-variable experiment is conducted on the loudspeaker, including a single-variable comparative experiment on the directional characteristics of the loudspeaker. The single variables include at least the orientation of the loudspeaker relative to the sound source and the distance of the loudspeaker relative to the sound source. Directivity parameters are calculated based on the sound intensity ratios of different dimensions under the single variable. The test results are evaluated based on the directional parameters, and the relationship between the change in sound source energy level and the orientation and distance of the loudspeaker are determined based on the evaluation results. Sound propagation performance is evaluated using the directional parameters.

[0065] Based on the above experiments, a quantitative evaluation index for the experimental results was calculated using the directivity parameter. The directivity parameter refers to a quantitative index for evaluating sound intensity at a specific direction or distance. In the azimuth-based single-variable experiment, the directivity parameter was calculated based on the ratio of the sound intensity in that specific direction to the omnidirectional sound intensity. In the distance-based single-variable experiment, the directivity parameter was calculated based on the ratio of the sound intensity of the sound source in the far field to the sound intensity emitted by an omnidirectional sound source of the same intensity in a two-dimensional context. Specifically, in the azimuth-based single-variable experiment, the directivity parameter was calculated based on the ratio of the sound intensity in that specific direction to the omnidirectional sound intensity.

[0066] ;

[0067] in, For directional parameters; The sound intensity in the direction to be evaluated; This is the omnidirectional sound intensity.

[0068] It should be noted that during the experiment, it is necessary to measure the directional sound intensity in each direction to optimize the sound energy level adjustment effect in the target direction. Therefore, the directional sound intensity to be evaluated... The sound pressure in the direction to be evaluated is obtained by measuring the sound pressure in that direction of the loudspeaker. Using the formula The sound intensity in the direction to be evaluated is calculated, where, air density, Speed ​​of sound; all-directional sound intensity Sound pressure was recorded at multiple uniformly distributed, equally spaced measurement points around the sound source. Calculate the sound intensity at each point Then take the average value. The omnidirectional sound intensity is calculated; further, the directivity parameter... Then, according to the formula given above The directivity parameter, expressed in decibels, is calculated. This parameter reflects the degree of sound intensity enhancement of the loudspeaker in the direction being evaluated. Experimental results are collected for multiple different directions being evaluated, and the relationship between the direction and the directivity parameter is fitted.

[0069] In the univariate distance experiment, the directional parameter is The unit is decibels (dB), where I1 is the sound intensity of the sound source in the far field, and I2 is the sound intensity emitted by an omnidirectional sound source of the same intensity in a two-dimensional case. This directivity parameter reflects the degree of sound intensity enhancement of the amplification device at different distances from the sound source. Experimental results were collected at multiple different distances, and the relationship between distance and the directivity parameter was fitted.

[0070] The following experiment investigates the relationship between the orientation and directional characteristics of a loudspeaker. In each experiment, a low-frequency transducer emits low-frequency sound waves with a source frequency of 70-600 Hz. The experiment includes the following steps:

[0071] Step 1: Set up two control experiments with and without amplification devices.

[0072] Specifically, two sets of control experiments were set up, one with a sound source and the other with a sound amplification device. One set included both a sound source and a sound amplification device, while the other set included only a sound source. The control current of the sound source and the surrounding environment were kept consistent in both sets of control experiments to analyze the enhanced directivity of the sound amplification device to the low-frequency sound waves emitted by the sound source.

[0073] Step 2: Select multiple directional sampling points on a circle centered on the sound source according to the preset angle interval.

[0074] In this step, the distribution characteristics of the sound field in different directions are comprehensively captured by sampling points evenly distributed in the horizontal plane to evaluate the directivity of the amplification device. For example, with the sound source as the center, multiple directional sampling points are selected evenly and at equal intervals (e.g., 1 meter) along a circle at a fixed distance (e.g., 1 meter) and at preset angle intervals (e.g., 10°). (For example, with the direction from the sound source as 0°, there are 36 directional sampling points along the left and right ends of the circle within a 360° range in the horizontal direction, and each directional sampling point represents an azimuth angle.) It should be noted that the preset angle interval must be small enough to ensure resolution, and the sampling points should be evenly distributed to eliminate the influence of distance variables.

[0075] Step 3: Place the two control experiments at the same distance from the sound source on the same horizontal plane.

[0076] The purpose of this step is to ensure that the sound pressure level measurements of the two control experiments are conducted under the same spatial conditions so that the effects of having or not having amplification devices can be directly compared.

[0077] Figure 6 This is a schematic diagram of an apparatus for determining the orientation experiment, as shown in an exemplary embodiment of this application. The sound level meter is placed at one of the 36 directional sampling points selected in step 2, at a fixed distance of 1m from the sound source, and at a height aligned with the center of the sound source. The two sets of control experimental apparatus are kept in the same horizontal plane. In this way, in subsequent steps, the platform can be rotated at preset angle intervals to continuously measure the sound pressure level at the 36 directional sampling points in the horizontal direction, thereby conducting experiments on the directional characteristics of the loudspeaker.

[0078] Step 4: Rotate the sound source and the amplification device to detect the sound pressure level value at each sampling point.

[0079] In this step, the sound source and amplification device are fixed on a rotating platform, which is then rotated to rotate the sound source and amplification device. The sound pressure level values ​​at various sampling points are then measured in both experiments with and without the amplification device. It should be noted that in the experiment without the amplification device, a cylinder of the same size is placed at the location where the amplification device is set, serving as a supplementary control.

[0080] Furthermore, the amplification device is placed horizontally and vertically on the turntable, and the turntable is rotated in the manner described above, thereby quantifying the directional enhancement effect of the amplification device in the XY plane and the Z direction.

[0081] Figure 7 This is an example illustration of an experimental test result of the directional characteristics of a loudspeaker device. Figure 7(a) and (b) show the sound field intensity distribution of the sound source in the XY plane and Z direction, respectively, with and without an amplifier. After the amplifier is placed, a significant increase in sound field intensity is observed in the Z direction of the sound source within an angle range of 150° to 165°. Therefore, the amplifier can control the sound source, causing the sound waves to propagate in a concentrated direction, thus enhancing the directivity and sound pressure level of the low-frequency sound waves emitted by the sound source.

[0082] The following experiment investigates the relationship between the distance and directional characteristics of a loudspeaker. The experiment includes the following steps:

[0083] Step 1: Set up two sets of experiments with and without amplification devices. One set includes both a sound source and amplification device, while the other set includes only a sound source. In this step, two control experiments are set up: one set includes both a sound source and amplification device, while the other set includes only a sound source.

[0084] It should be noted that, in another embodiment, a control experiment can be set up. In this control experiment, cylinders of the same size as the amplification device are set around the sound source. The experimental results obtained are analyzed together with the experimental results of the two sets of experiments with and without the amplification device to further verify the enhancement effect of the amplification device on the directional characteristics of the sound source.

[0085] Step 2: Select multiple distance sampling points in the circumference and Z-axis direction of the vertical plane centered on the sound source according to the preset distance interval; wherein, the preset distance interval is an integer multiple of 1 / 4 wavelength of the test sound source frequency value.

[0086] In this step, multiple distance sampling points are selected on the circumference of the vertical plane where the sound source is located. For example, in the experiment provided in this embodiment, the sound source frequency is 200 Hz, and the wavelength of the sound source is 1.7 meters. One-quarter of the wavelength of the sound wave is 0.425 meters. Therefore, the distances between the multiple distance sampling points selected in this embodiment and the sound source are 0.425 meters, 0.85 meters and 1.29 meters respectively.

[0087] Multiple distance sampling points are selected along the Z-axis of the sound source based on a preset distance. For example, distance sampling points are set at positions of 0m, 1m, 5m, 10m and 20m along the Z-axis of the sound source. These distance sampling points are used to systematically measure the acoustic response at different Z-axis positions. Combined with the aforementioned sound pressure level data in various directions of the detection horizontal plane, this facilitates subsequent analysis of the spatial distribution of the sound field.

[0088] Step 3: In the experiment involving the sound source and the amplification device, the amplification device is set up at multiple distance sampling points in sequence.

[0089] Specifically, in the experiment involving the sound source and the amplification device, the amplification device was set up on the circumference of a circle in the vertical plane where the sound source was located at multiple sampling points, with distances from the sound source being 0.425 meters, 0.85 meters, and 1.29 meters respectively.

[0090] Step 4: Detect the sound pressure level at a preset distance along the axis of the sound source.

[0091] In this step, the amplification device is set up at multiple sampling points at different distances, and the sound pressure level at that point is calculated using a sound level meter at a distance of 1m along the direction of the sound source axis.

[0092] Figure 8 The normalized directivity characteristics of a 200Hz low-frequency sound in polar coordinates are shown in an exemplary embodiment of this application. Figure 9 The sound field intensity diagram for a 200Hz low-frequency sound shown in an exemplary embodiment of this application is also referenced. Figure 8 and Figure 9 It can be seen that placing the amplification device at the location obtained by combining the target orientation and the target distance can maximize the gain of the sound source propagation target location.

[0093] Determining the sound receiving direction involves at least analyzing the scenario requirements and the experimental objectives needed by the operator to determine the specific spatial location of the sound receiving direction. The specific spatial location of the receiving direction can be described by coordinates or azimuth angles; this application does not limit this. There can be one or more receiving directions. The direction and distance relative to the sound source are calculated based on the receiving direction. Based on the geometric relationship between the direction, distance, and the directivity parameter obtained from the experimental fitting, the optimal direction and optimal distance are calculated as the target direction and target distance. The amplification device is then positioned at the target direction and target distance.

[0094] As an optional embodiment, one or more loudspeaker devices can be installed. Figure 10 The illustration shows an actual scenario of a loudspeaker setup in an exemplary embodiment of this application. A door frame with an outer side length of 2.5m and an inner side length of 0.52m is nested within the sound wave outlet of an electromagnetic transducer serving as the sound source. The electromagnetic transducer fits precisely at the center of the inner side of the door frame. Loudspeakers are placed at 45° intervals inside the door frame. After placing the loudspeakers around the sound source based on the determined placement, the sound source emits sound according to the adjusted control current. By combining the acoustic control characteristics of the loudspeakers, the propagation direction and intensity of the sound waves are optimized to enhance low-frequency sound waves and maximize the sound field intensity, thereby meeting the sound propagation requirements in specific application scenarios.

[0095] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A sound amplification device based on MH metamaterial, characterized in that, The amplification device includes at least: The upper shell, the lower shell, and the waveguide located between the upper shell and the lower shell, the waveguide being made of Mie metamaterial; The waveguide includes an outer wall with multiple acoustic inlets on the outer wall, and the upper shell, lower shell and outer wall surround to form a waveguide space. The waveguide space is provided with a through hole that connects the waveguide and the upper shell, and the through hole is the sound wave outlet in the loudspeaker. The waveguide includes multiple fan-shaped sections arranged circumferentially around the through-hole; Each of the fan sections includes radial ribs and multiple circumferential ribs arranged on both sides of the radial ribs. The multiple circumferential ribs on the same side are arranged at intervals. Two sets of circumferential ribs facing each other on adjacent fan sections are arranged alternately. The free ends of the circumferential ribs of each radial rib are arranged at intervals relative to the adjacent radial ribs, so that a waveguide channel is formed between the adjacent fan sections, which runs through the acoustic wave outlet and the acoustic wave inlet. The control current of the sound source is determined by the size of the amplification device and the scattering distribution of the amplification device in different resonance modes. The sound energy level at the sound wave outlet is larger than that at the sound source, and there is an angle between the propagation directions. In the monopole resonance mode, the forward and backward scattering ratio of the amplification device decreases with the increase of the upper shell thickness and increases with the increase of the diameter of the through hole at the resonance frequency. The vertical scattering ratio decreases with the increase of the upper shell height and decreases with the increase of the diameter of the through hole. Under the same unit size, the narrower the width of the waveguide channel, the larger the controlled sound wave wavelength.

2. The loudspeaker device according to claim 1, characterized in that, Under the same resonance mode, the control current is inversely proportional to the thickness of the upper shell, the length of the waveguide channel, and the height of the amplification device, respectively, and the control current is directly proportional to the diameter of the through hole.

3. The loudspeaker device according to claim 1, characterized in that, The first distance between the free end of the circumferential rib and the adjacent radial rib is less than the length of the circumferential rib; the first distance between each circumferential rib in the same sector is equal; the interval between the free end of the circumferential rib farthest from the through hole on each sector and the adjacent radial rib serves as the sound wave inlet; the interval between the free end of the circumferential rib closest to the through hole on each sector and the adjacent radial rib serves as the sound wave outlet.

4. The loudspeaker according to claim 1, characterized in that, The waveguide is a hollow cylindrical structure with a central penetration. The heights of the acoustic inlet and the acoustic outlet are the same as those of the waveguide, as are the heights of the radial ribs and the circumferential ribs.

5. The loudspeaker according to claim 1, characterized in that, The radial ribs isolate adjacent waveguide channels, each sector includes one waveguide channel, each sector has the same area, and each waveguide channel has the same channel width.

6. A method for sound propagation using a loudspeaker as described in any one of claims 1-5, characterized in that, The method includes: Adjust the control current of the sound source according to the size of the amplification device; The amplification device is placed in the sound propagation path, and the sound is output from the amplification device. There is an angle between the direction of the sound output from the amplification device and the direction of the sound input to the amplification device, and the energy value increases. The magnitude of the increase in the energy value is related to the control current value.

7. The method according to claim 6, wherein adjusting the control current of the sound source according to the size of the loudspeaker includes: Determine the thickness of the upper shell of the loudspeaker, the length of the waveguide channel, the height of the loudspeaker, and the diameter of the through hole; Calculate the ratio between the square of the diameter of the through hole and the thickness of the upper shell; Calculate the sum of the ratio and the derivative of the through-hole diameter; Calculate the first product of the sum and the height of the loudspeaker; The resonant frequency is determined by multiplying the square root of the first product with the length of the waveguide channel. The control current of the sound source is adjusted to the optimal control current based on the resonant frequency and the optimal control current at the sound source.

8. The method according to claim 6, wherein placing the amplification device in the sound propagation path comprises: A single-variable experiment was conducted on the loudspeaker to obtain the correlation between the sound propagation performance of the loudspeaker and the installation orientation of the loudspeaker. The receiving direction of the sound is determined, and the placement position of the amplification device on the sound propagation path is determined according to the receiving direction and the correlation relationship, wherein there is an angle between the line connecting the receiving direction and the sound outlet of the amplification device and the local sound propagation path from the sound source to the amplification device; the energy level of the sound at the receiving point is higher than the energy level of the sound at the emitting point.

9. The method according to claim 8, wherein the single-variable test on the loudspeaker includes: A single-variable comparative experiment was conducted on the directional characteristics of the loudspeaker. The single variable included at least the orientation of the loudspeaker relative to the sound source and the distance of the loudspeaker relative to the sound source. Calculate the directivity parameter based on the ratio of sound intensity in different dimensions under a single variable; The test results are evaluated based on the directivity parameters, and the relationship between the changes in the sound source energy level and the orientation and distance of the amplification device is determined based on the evaluation results.

10. The method according to claim 9, wherein calculating the directivity parameter based on the sound intensity ratio of different dimensions under a single variable includes: In univariate azimuth tests, the directivity parameter is calculated based on the ratio of sound intensity in a specific direction to sound intensity in all directions. In the single-variable distance experiment, the directivity parameter is calculated based on the ratio of the sound intensity of the sound source in the far field to the sound intensity emitted by an omnidirectional sound source of the same intensity in the two-dimensional case.

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