In-ear earphone vocal cavity optimization design method based on bionic cochlea structure

Abstract

The invention relates to the technical field of information, in particular to an in-ear headphone vocal cavity optimization design method based on a bionic cochlea structure in the field of in-ear headphones, which comprises the following steps of: performing finite element analysis on a vocal cavity geometric model, and calculating a propagation path and pressure distribution of sound waves in a cavity; judging whether the sound waves form standing waves in a preset frequency range or not; if the finite element analysis result shows that the standing wave exists, adjusting the spiral angle parameter of the logarithmic spiral model, and recalculating the sound wave propagation characteristics in the model until the standing wave phenomenon is inhibited; according to the optimized spiral tapered structure model, combining acoustic characteristics of an earphone driving unit, calculating an incident angle of sound waves at an entrance, and judging whether the sound waves can efficiently enter a sound cavity or not; and if the sound wave incidence angle exceeds the preset range, adjusting the inlet diameter parameter of the logarithmic spiral model, and recalculating the sound wave incidence angle until the matching requirement of the driving unit is met.

Description

Technical Field

[0001] The present invention relates to the field of information technology, specifically to the field of in-ear headphones, and particularly to an optimized design method for the sound cavity of in-ear headphones based on the bionic cochlea structure. Background Art

[0002] In the design of the sound cavity of in-ear headphones based on the bionic cochlea structure, the key technical problem to be solved by the spiral tapered structure of the sound cavity is how to accurately set the range of the inlet diameter of 6 mm and the outlet diameter of 3.2 mm to ensure a smooth transition of sound waves during propagation and avoid the occurrence of mid-high frequency resonance. The cylindrical sound cavity design of traditional in-ear headphones is prone to forming standing waves at specific frequencies due to its single structure, resulting in serious sound quality distortion (total harmonic distortion THD > 5%). In addition, the simple cylindrical structure is prone to causing local pressure concentration during wearing, affecting the user experience.

[0003] To solve this problem, a bionic design concept is adopted. The sound cavity is designed as a spiral tapered structure with an inlet diameter of 6 mm, tapering logarithmically to 3.2 mm, and the spiral angle is set at 15°. This design can not only effectively suppress the formation of standing waves but also make the sound waves propagate more uniformly and smoothly in the cavity. However, the implementation of this spiral structure requires precise control of the parameters of the tapered range. The setting of the inlet diameter needs to consider the matching with the headphone drive unit to ensure that sound waves can efficiently enter the sound cavity; the outlet diameter needs to adapt to the ear canal size of the wearer, ensuring both the sound wave output effect and avoiding excessive pressure on the ear canal.

[0004] In addition, micron-scale scale protrusions are provided on the inner wall of the cavity, with a height of 0.1 mm and a spacing of 0.3 mm, and are manufactured by a 3D printing titanium alloy integrated molding process. This design aims to further optimize the diffusion effect of sound waves in the cavity, reduce sound wave reflection and distortion, but at the same time puts forward higher requirements for the manufacturing process, especially in terms of precision control and material selection. Through the implementation of the above technical solutions, the overall performance of the sound cavity has been significantly improved, but it is still necessary to finely adjust each parameter during the design and manufacturing process to ensure the best balance between the acoustic performance and wearing comfort of the final product. Summary of the Invention

[0005] The present invention provides an optimized design method for the sound cavity of in-ear headphones based on the bionic cochlea structure, and the method includes the following steps:

[0006] S101. Obtain the logarithmic spiral mathematical model, and construct a three-dimensional geometric model of the spiral tapered structure of the sound cavity based on the parameters of the inlet diameter of 6 mm, the outlet diameter of 3.2 mm, and the spiral angle of 15°;

[0007] S102. Conduct finite element analysis on the acoustic cavity geometric model, calculate the propagation path and pressure distribution of sound waves in the cavity, and determine whether standing waves are formed within a predetermined frequency range.

[0008] S103. If the finite element analysis result shows the existence of standing waves, adjust the spiral angle parameter of the logarithmic spiral model, and recalculate the sound wave propagation characteristics in the model until the standing wave phenomenon is suppressed.

[0009] S104. Based on the optimized spiral tapered structure model, combined with the acoustic characteristics of the headphone driver unit, calculate the incident angle of sound waves at the entrance, and determine whether the sound waves can enter the acoustic cavity efficiently.

[0010] S105. If the incident angle of the sound wave exceeds the preset range, adjust the entrance diameter parameter of the logarithmic spiral model, and recalculate the incident angle of the sound wave until the matching requirements of the driver unit are met.

[0011] S106. Add inner wall scale protrusion features to the acoustic cavity geometric model, with a protrusion height of 0.1 mm and a spacing of 0.3 mm, and simulate the diffusion effect of sound waves in the cavity based on computational fluid dynamics.

[0012] S107. If the simulation result shows uneven diffusion of sound waves, adjust the geometric parameters of the scale protrusions, and perform fluid dynamics calculations again until the sound waves are evenly diffused in the cavity and there is no significant reflection within a predetermined frequency range.

[0013] S108. Import the finally optimized acoustic cavity model into a 3D printing system, use titanium alloy material, and manufacture the acoustic cavity entity through a precision forming process to complete the design of the in-ear headphone cavity based on the bionic cochlea structure.

[0014] The technical solution provided by the embodiment of the present invention may include the following beneficial effects:

[0015] The present invention discloses an optimization design method for the acoustic cavity of an in-ear headphone based on the bionic cochlea structure. This method first constructs a spiral tapered structure of the acoustic cavity of the logarithmic spiral model, calculates the sound wave propagation characteristics through finite element analysis, and suppresses the standing wave phenomenon by adjusting the spiral angle parameter. Then, combined with the characteristics of the driver unit, the entrance diameter is optimized to ensure efficient entry of sound waves. To further improve the sound wave diffusion, micron-scale scale protrusions are added to the inner wall of the cavity, and their geometric parameters are optimized through computational fluid dynamics simulation. Finally, the optimized acoustic cavity entity is manufactured using titanium alloy material and precision forming process. Through bionic design and multi-step iterative optimization, the present invention effectively suppresses standing waves, achieves uniform diffusion of sound waves, and improves the acoustic performance and listening experience of in-ear headphones. Description of the Drawings

[0016] Figure 1It is a flowchart of an optimized design method for the sound cavity of an in-ear headphone based on the bionic cochlea structure of the present invention.

[0017] Figure 2 It is a schematic diagram of an optimized design method for the sound cavity of an in-ear headphone based on the bionic cochlea structure of the present invention.

[0018] Figure 3 It is another schematic diagram of an optimized design method for the sound cavity of an in-ear headphone based on the bionic cochlea structure of the present invention. Detailed implementation manners

[0019] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] Such as Figures 1-3 , an optimized design method for the sound cavity of an in-ear headphone based on the bionic cochlea structure in this embodiment may specifically include:

[0021] S101. Obtain a logarithmic spiral mathematical model, and based on the parameters of an inlet diameter of 6 mm, an outlet diameter of 3.2 mm, and a spiral angle of 15°, construct a three-dimensional geometric model of the sound cavity spiral tapering structure.

[0022] Obtain the inlet diameter and outlet diameter of the sound cavity, determine the proportional relationship between the two to obtain the tapering ratio of the spiral structure; according to the proportional relationship, use the logarithmic spiral equation to construct a three-dimensional space mathematical model of the spiral line, and the mathematical model uses the inlet diameter, outlet diameter, and spiral angle as input parameters; according to the mathematical model, generate three-dimensional point cloud data of the spiral line, and construct the spatial structure of the spiral line; obtain the sound cavity wall thickness parameter, apply the thickness parameter to the spiral line spatial structure, and generate a three-dimensional geometric model of the sound cavity spiral tapering structure; use the finite element analysis method to perform mesh division on the three-dimensional geometric model, and calculate the internal flow field distribution of the sound cavity; if the flow field distribution meets the preset conditions, output the three-dimensional geometric model; if the flow field distribution does not meet the preset conditions, adjust the spiral angle and reconstruct the mathematical model until a three-dimensional geometric model that meets the preset conditions is obtained.

[0023] Specifically, the design of the acoustic cavity structure starts with the measurement of the inlet and outlet diameters. A typical inlet diameter can be 20 cm, and the outlet diameter is 5 cm, with a taper ratio of 4:1. This ratio directly affects the propagation characteristics of sound waves and the change in sound pressure level. The taper ratio of the acoustic cavity determines the concentration of sound energy, and a larger taper ratio can achieve a stronger sound energy focusing effect. The logarithmic spiral is a special curve, characterized in that the angle between any ray starting from the pole and the tangent of the curve remains constant. In the design of the acoustic cavity, the spiral angle is usually selected between 30 degrees and 60 degrees. This angle range can ensure the sound wave propagation efficiency while avoiding the manufacturing difficulties caused by overly steep structures. The coordinates of the two-dimensional spiral can be represented by a polar coordinate equation and then converted to a rectangular coordinate system. For example, for a logarithmic spiral with a starting radius of 10 cm and a spiral angle of 45 degrees, its coordinate points gradually approach the center as the spiral angle changes. When performing three-dimensional space conversion, the helix angle needs to be considered. Usually, selecting a helix angle of 15 degrees to 25 degrees can obtain an ideal spatial structure. The design of the thickness of the acoustic cavity wall needs to consider material strength and processing technology. For metal materials, the wall thickness is usually between 3 mm and 8 mm, which can ensure structural strength and effectively block external noise interference. Although a thicker wall increases the weight, it can provide better sound insulation effect and structural stability. In finite element analysis, the density of mesh division directly affects the calculation accuracy. In areas with large curvature changes, such as the spiral corner, finer meshes are required. Generally speaking, the minimum mesh size should not be greater than one-tenth of the sound wave wavelength. For a 20 kHz sound wave, the mesh size should be less than 0.17 mm. The evaluation criteria for the sound field distribution include the uniformity of the sound pressure level distribution and the sound energy focusing effect. At the outlet, the sound pressure level is usually required to be increased by more than 15 dB compared to the inlet. If it is found that the sound pressure distribution is uneven or the focusing effect is not ideal, it can be optimized by adjusting the spiral angle. For example, adjusting the spiral angle from 45 degrees to 50 degrees may bring a better sound energy focusing effect. When the sound pressure peak exceeds 150 dB of the design requirement or the distribution is uneven, the spiral angle parameter needs to be redesigned.

[0024] S102. Perform finite element analysis on the acoustic cavity geometric model, calculate the propagation path and pressure distribution of sound waves in the cavity, and determine whether standing waves are formed within a predetermined frequency range.

[0025] Obtain a sound cavity model containing geometric parameters, where the sound cavity model includes boundary conditions and material properties; use the finite element analysis method to divide grid cells on the sound cavity model to generate a computational domain; establish a sound pressure calculation equation at the nodes of each grid cell according to the acoustic wave propagation equation; solve the sound pressure calculation equation set to obtain the sound pressure distribution map in the sound cavity; extract the node values from the sound pressure distribution map and calculate the sound pressure amplitudes at each frequency; if within a preset frequency range, the sound pressure amplitude at a certain frequency shows a periodic distribution, then determine that a standing wave is formed at that frequency; compare the frequency range where the standing wave is formed with the preset frequency range to obtain the analysis result of the standing wave formation situation.

[0026] Specifically, the geometric parameters of the acoustic cavity model include key dimensions such as the length, diameter, and wall thickness of the acoustic cavity. These parameters directly affect the propagation characteristics of sound waves in the cavity. Taking a cylindrical acoustic cavity as an example, the cavity length is 500 millimeters, the inner diameter is 100 millimeters, and the wall thickness is 10 millimeters. In terms of boundary condition settings, a sound pressure excitation with an amplitude of 1 Pa and a frequency range of 100 - 1000 Hz can be applied at the inlet end of the acoustic cavity, and the outlet end is set as a free boundary. The material of the acoustic cavity is selected as steel, with a density of 7850 kg / m³ and a Young's modulus of 210 GPa. When performing finite element mesh division, the relationship between the sound wave wavelength and the mesh size needs to be considered. Generally, it is required that each wavelength contains at least 6 - 8 mesh elements to ensure the calculation accuracy. For the above acoustic cavity model, when the analysis frequency is 500 Hz, the sound wave wavelength is approximately 0.7 m, so the mesh size should not be greater than 0.1 m. Using hexahedral meshes for division and appropriately densifying at the cavity wall surface, approximately 20,000 mesh elements can be obtained. When establishing the sound pressure calculation equation at each mesh node, the propagation characteristics of sound waves in the fluid medium need to be considered. The sound pressure equation includes a sound pressure gradient term, a time derivative term, and a source term. For the case of harmonic excitation, a frequency-domain analysis method can be used to transform the time-domain equation into a frequency-domain equation for solution. By solving the sound pressure equations, the sound pressure distribution at different positions in the acoustic cavity can be obtained. Taking the 500 Hz excitation as an example, the sound pressure shows an obvious periodic distribution along the axial direction. The sound pressure wave peak value of about 1.8 Pa and the trough value of about 0.2 Pa appear in the middle of the cavity, indicating that a stable standing wave field is formed at this frequency. The periodic distribution of the sound pressure amplitude is an important basis for judging the formation of standing waves. When the distance between adjacent wave peaks on the sound pressure distribution curve is equal to half the wavelength, it can be considered that a standing wave is formed. The analysis shows that obvious standing wave phenomena can be observed in the acoustic cavity within the frequency range of 400 - 600 Hz, and the waveforms are relatively stable. This is basically consistent with the expected working frequency range of 350 - 650 Hz, indicating that the acoustic cavity design meets the requirements for the formation of standing waves. There is a corresponding relationship between the geometric dimensions of the acoustic cavity and the standing wave frequency. When the length of the acoustic cavity is equal to an integer multiple of the sound wave wavelength, it is most likely to form a standing wave. Taking the above acoustic cavity as an example, its fundamental frequency is about 340 Hz, and the resonant frequencies of each order are 680 Hz, 1020 Hz, etc. By reasonably selecting the acoustic cavity dimensions, the standing wave frequency can be made to fall within the required range. The periodic distribution of the sound pressure helps to enhance the local concentration of sound energy and can be used in applications such as acoustic processing and sound energy collection.

[0027] S103. If the finite element analysis result shows the existence of a standing wave, adjust the spiral angle parameter of the logarithmic spiral model, and recalculate the acoustic wave propagation characteristics in the model until the standing wave phenomenon is suppressed.

[0028] Obtain the finite element analysis results and determine whether there is a standing wave in the finite element analysis results; if the standing wave exists, extract the helix angle parameter of the logarithmic spiral model and use the helix angle parameter as the adjustment target; according to the preset helix angle threshold range, use the gradient descent algorithm to adjust the helix angle parameter to obtain the adjusted helix angle parameter; substitute the adjusted helix angle parameter into the acoustic wave propagation characteristic calculation model, recalculate the acoustic wave propagation characteristics, and obtain the updated sound field distribution; use the support vector machine algorithm to analyze the updated sound field distribution and determine whether the standing wave phenomenon is suppressed; if the standing wave phenomenon is not completely suppressed, repeat the adjustment of the helix angle parameter and the recalculation of the acoustic wave propagation characteristics until the standing wave phenomenon is completely suppressed.

[0029] Specifically, the existence of a standing wave is usually manifested as a periodic distribution of the sound pressure amplitude in space. The sound pressure peak may appear at specific positions in the cavity, such as at the boundary or the center point. For example, in a rectangular cavity, when the incident wave frequency is the first-order longitudinal mode frequency, the sound pressure peak will form at both end walls, and a sound pressure node will appear at the middle position. By analyzing the sound pressure distribution map in the finite element calculation results, the existence of a standing wave can be determined. The helix angle of the logarithmic spiral is a key parameter describing the curve shape. A larger helix angle will cause the curve to unfold faster, increasing the curvature change of the acoustic wave propagation path. A smaller helix angle makes the curve more compact and prolongs the acoustic wave propagation path. Taking a certain acoustic cavity as an example, when the initial helix angle is forty-five degrees, an obvious standing wave appears at a frequency of two thousand hertz. Through the gradient descent algorithm, the helix angle can be gradually adjusted. The algorithm calculates the adjustment direction and step size of the helix angle according to the difference between the sound pressure amplitude and the preset threshold. The calculation of the acoustic wave propagation characteristics needs to consider the medium characteristics and boundary conditions. Taking air as the medium, the sound speed is about three hundred and forty meters per second, and the density is about one point two kilograms per cubic meter. The boundary conditions include total reflection at a rigid boundary and partial absorption at a flexible boundary, etc. Substituting the adjusted helix angle into the calculation model, a new sound field distribution can be obtained. The support vector machine algorithm determines whether the sound field distribution conforms to the standing wave characteristics by establishing a classification hyperplane. Feature parameters such as the sound pressure amplitude and phase distribution can be selected as the classification basis. The classification result can be used to evaluate the standing wave suppression effect. For example, in a certain case, standing waves appeared in the original sound field in the range of one thousand five hundred hertz to two thousand hertz. After three adjustments of the helix angle parameter, the helix angle was gradually adjusted from forty-five degrees to thirty degrees, and the standing wave phenomenon was significantly suppressed, with the sound pressure peak reduced by sixty percent. If the standing wave is not completely suppressed in the first round of adjustment, iterative optimization is required. Each round of iteration is based on the results of the previous round and finely tunes the helix angle parameter. In practical applications, it may be necessary to balance the calculation efficiency and the suppression effect and set reasonable iteration termination conditions. For example, when the change in the sound pressure peak after two consecutive adjustments is less than five percent, or when the standing wave sound pressure amplitude is reduced below the threshold, it can be considered that the suppression target has been achieved.

[0030] S104. According to the optimized spiral tapered structure model, combined with the acoustic characteristics of the headphone driver unit, calculate the incident angle of the sound wave at the inlet, and determine whether the sound wave can enter the sound cavity efficiently.

[0031] Obtain the geometric parameters of the optimized spiral tapered structure model, combine with the acoustic characteristic parameters of the headphone driver unit to obtain the propagation direction of the sound wave at the inlet; calculate the incident angle of the sound wave at the inlet according to the angle between the sound wave propagation direction and the normal line at the inlet; if the incident angle is less than a preset threshold, determine that the sound wave can enter the sound cavity efficiently; use an acoustic simulation algorithm to simulate the propagation path of the sound wave in the sound cavity; analyze the attenuation of the sound wave in the sound cavity according to the propagation path of the sound wave in the sound cavity; adjust the geometric parameters of the spiral tapered structure model according to the sound wave attenuation situation to obtain an optimized spiral tapered structure model, and the optimized spiral tapered structure model is used to optimize the acoustic performance of the sound cavity; obtain the acoustic performance parameters of the optimized sound cavity, and recalculate the incident angle of the sound wave at the inlet according to the acoustic performance parameters; if the recalculated incident angle meets the preset conditions, determine that the optimization of the spiral tapered structure model is completed.

[0032] Specifically, the geometric parameters of the spiral tapered structure model mainly include the spiral length, spiral angle, and taper ratio. Taking an in-ear headphone as an example, its acoustic drive unit adopts a dynamic coil design, with a diaphragm diameter of 8 mm and a working frequency range of 20 Hz to 20,000 Hz. When optimizing the acoustic cavity structure, the propagation characteristics of sound waves at the entrance need to be considered. The angle between the sound wave propagation direction and the normal at the entrance determines whether the sound wave can efficiently enter the acoustic cavity. Usually, 30 degrees is set as the preset threshold for the incident angle. In acoustic simulation analysis, the finite element method is used to simulate the sound wave propagation path. Taking a sound wave with a frequency of 1000 Hz as an example, when the sound wave is emitted from the drive unit, it first passes through the sound duct and enters the spiral tapered acoustic cavity. The diameter of the sound duct is 3 mm and the length is 5 mm. When the sound wave enters the acoustic cavity, if the incident angle is 25 degrees, which is less than the preset threshold of 30 degrees, it indicates that the sound wave can effectively enter the acoustic cavity and propagate along the spiral path. When the sound wave propagates in the acoustic cavity, attenuation will occur, mainly including viscous loss and heat conduction loss. By adjusting the geometric parameters of the spiral tapered structure, the acoustic performance of the acoustic cavity can be optimized. For example, by adjusting the spiral angle from the initial 75 degrees to 80 degrees, the energy loss of the sound wave during propagation can be reduced by about 15%. At the same time, by adjusting the taper ratio from 1.5 to 1.8, the propagation path of the sound wave can be made smoother, reducing the reflection and scattering of the sound wave during propagation. The acoustic performance parameters of the acoustic cavity include the sound pressure level response curve, phase response, and harmonic distortion, etc. For the optimized acoustic cavity structure, the sound pressure level at a frequency of 1000 Hz can be increased by about 3 dB, and the harmonic distortion can be reduced by about 0.5%. When recalculating the sound wave incident angle, it is found that the adjusted incident angle is 22 degrees, which is more ideal than the previous 25 degrees, further improving the efficiency of the sound wave entering the acoustic cavity. In practical applications, the optimization of the acoustic cavity structure also needs to consider material properties and processing technology. Taking polycarbonate material as an example, it has good acoustic performance and processing performance, and a complex spiral tapered structure can be realized through an injection molding process. By adjusting the mold temperature and injection pressure, the smoothness of the inner wall of the acoustic cavity can be ensured, reducing the scattering loss during the sound wave propagation process. The finally formed spiral tapered structure can not only effectively guide the sound wave propagation but also provide a good acoustic experience.

[0033] S105. If the sound wave incident angle exceeds the preset range, adjust the entrance diameter parameter of the logarithmic spiral model, and recalculate the sound wave incident angle until the matching requirements of the drive unit are met.

[0034] Obtain the current value of the acoustic wave incident angle, and determine whether the current value exceeds a preset range value; if the current value exceeds the preset range value, adjust the entrance diameter parameter value of the logarithmic spiral model to obtain an adjusted entrance diameter parameter value; use the adjusted entrance diameter parameter value to recalculate the acoustic wave incident angle to obtain a recalculated acoustic wave incident angle; determine whether the recalculated acoustic wave incident angle meets the preset driving unit matching degree requirement; if the recalculated acoustic wave incident angle does not meet the preset driving unit matching degree requirement, loop to adjust the entrance diameter parameter value and recalculate the acoustic wave incident angle until the preset driving unit matching degree requirement is met; if the recalculated acoustic wave incident angle meets the preset driving unit matching degree requirement, determine the final entrance diameter parameter value of the logarithmic spiral model; according to the final entrance diameter parameter value, output the calculation result of the acoustic wave incident angle that meets the preset driving unit matching degree requirement.

[0035] Specifically, the value range of the sound wave incident angle is usually closely related to the acoustic characteristics of the driving unit. For example, in the design of the headphone sound cavity, the sound wave incident angle should be controlled between zero degrees and thirty degrees, which can ensure that the sound wave can efficiently enter the sound cavity and form a good sound field distribution. A larger incident angle will cause an increase in sound wave reflection, resulting in an increase in sound energy loss and affecting the sound reproduction quality. Adjusting the entrance diameter parameter of the logarithmic spiral model requires considering multiple factors. Taking high-end in-ear headphones as an example, when the initial entrance diameter is set to 6 mm, the sound wave incident angle may reach 40 degrees, exceeding the preset range of 30 degrees. At this time, the entrance diameter needs to be gradually adjusted, increasing by 0.5 mm each time, until the incident angle drops to the appropriate range. Through practice, it is found that when the entrance diameter increases to 8 mm, the incident angle can drop to about 25 degrees, meeting the design requirements. The matching degree requirements between the sound wave incident angle and the driving unit are reflected in multiple aspects. Modern dynamic driver units usually require the incident angle to be maintained between 20 and 30 degrees, while piezoelectric units can accept a larger range of incident angles. For example, in a certain dynamic headphone, when the incident angle is 28 degrees, its frequency response curve flatness is the best and the distortion is the lowest. When the incident angle deviates from this range, problems such as a decrease in high-frequency response or a prominence in the mid-frequency will occur. A reasonable adjustment step size needs to be established during the cyclic adjustment process. For example, in the design of a micro headphone, the initial entrance diameter is 5 mm and the incident angle is 35 degrees. Using an adjustment step size of 0.3 mm, after four adjustments, the entrance diameter increases to 6.2 mm and the incident angle drops to 26 degrees, achieving the best matching state with a 9 mm dynamic driver unit. The finally determined entrance diameter parameter needs to meet the processing technology requirements at the same time. In actual production, if the finally calculated entrance diameter is 7.83 mm, considering the processing accuracy and process limitations, it can be rounded to 7.8 mm. Such a minor adjustment usually does not significantly affect the sound wave incident angle, but can greatly improve the production efficiency and the yield rate of the product. Verifying the output result is equally important. In an actual case, after optimization, the incident angle is 23 degrees. Through acoustic testing, it is found that at this angle, the fluctuation of the frequency response curve of the headphone within the range of 20 Hz to 20 kHz remains within plus or minus 3 dB, and the sound coloring is small and the sound field positioning is accurate, fully confirming the reliability of the optimization result.

[0036] S106. Add the inner wall scale protrusion feature to the sound cavity geometric model, with a protrusion height of 0.1 mm and a spacing of 0.3 mm, and simulate the diffusion effect of sound waves in the cavity based on computational fluid dynamics.

[0037] Obtain the three-dimensional data information of the acoustic cavity geometric model, and perform feature extraction on the inner wall surface of the acoustic cavity geometric model; if the feature extraction result includes scale protrusion structures, obtain the protrusion height and spacing parameters of the scale protrusion structures; reconstruct the inner wall surface morphology of the acoustic cavity model according to the geometric feature parameters of the scale protrusion structures; establish a mathematical model for the diffusion of sound waves in the acoustic cavity model by using computational fluid dynamics methods; set the inner wall boundary conditions of the acoustic cavity model in the mathematical model, and the inner wall boundary conditions include the geometric features of the scale protrusion structures; solve the diffusion process of sound waves in the acoustic cavity model by using numerical calculation methods to obtain the diffusion effect data of sound waves in the acoustic cavity model with the characteristics of the scale protrusion structures.

[0038] Specifically, for the three-dimensional data analysis of the acoustic cavity geometric model, it is first necessary to obtain the precise geometric information of the inner surface of the cavity. For example, the inner wall data point cloud is collected by a high-precision three-dimensional scanner, and the scanning accuracy can reach 0.01 mm. During the feature extraction process, the distribution characteristics of the scale-like protrusion structure are focused on. Suppose there are regularly arranged scale protrusions on the inner wall surface, and the height of each protrusion is in the range of 0.5 to 1 mm, and the spacing between adjacent protrusions is about 5 mm. This special surface morphology is similar to the structures commonly found in biological acoustic systems, such as the microscopic structure on the surface of an owl's wing. When reconstructing the inner wall surface morphology, the influence of the scale protrusions on the sound wave propagation needs to be considered. By establishing a parametric geometric model, the protrusion structure is simplified into regular conical or hemispherical units. For example, when the protrusion adopts a conical structure, the bottom diameter can be set to 1 mm and the height to 0.8 mm, and it is distributed in a hexagonal array. This structure can effectively reduce the reflection of sound waves and increase the absorption of sound energy. In the numerical simulation of sound wave diffusion, the setting of boundary conditions is crucial. The acoustic impedance of the inner wall surface needs to be determined according to the material properties. If porous materials are used, the acoustic impedance may be about 40,000 Rayls. The presence of scale protrusions will change the way sound waves interact with the boundary, generating a microscopic-scale scattering effect. In practical applications, this structure can reduce the directional reflection of sound waves and improve the acoustic diffusion performance. The numerical calculation uses the finite element method to solve the sound wave equation, and the mesh division needs to fully consider the characteristic size of the scale structure. Taking a sound wave of 20 kHz as an example, the wavelength is about 17 mm, and the mesh size is required to be no larger than one-sixth of the wavelength, that is, less than 3 mm. The calculation results show that the inner wall with scale protrusions can significantly change the sound field distribution. The sound pressure level distribution is more uniform, the reverberation time is shortened by about 15%, and the sound energy attenuation curve is smoother. This structure has important application value in the acoustic design of places such as concert halls and recording studios. For sound waves in different frequency ranges, the effect of the scale structure is also different. In the low-frequency band (such as 100 to 500 Hz), the sound absorption effect is mainly improved by increasing the surface area. In the mid-high frequency band (such as 1000 to 5000 Hz), the uniform distribution of the sound field is mainly achieved by scattering. By reasonably designing the geometric parameters of the scale structure, the directional control of sound waves in a specific frequency band can be realized to achieve the expected acoustic effect.

[0039] S107. If the simulation results show that the sound wave diffusion is uneven, adjust the geometric parameters of the scale protrusions and re-perform the hydrodynamic calculation until the sound waves are evenly diffused in the cavity and there is no significant reflection within the predetermined frequency range.

[0040] According to the simulation results of acoustic wave diffusion, judge whether the diffusion uniformity meets the preset conditions. If the diffusion is non-uniform, obtain the current geometric parameters of the scale protrusions for adjustment. Re-perform the hydrodynamic calculation with the adjusted geometric parameters to obtain new acoustic wave diffusion simulation results. According to the new simulation results, analyze the diffusion uniformity of the acoustic waves in the cavity and the reflection intensity within the predetermined frequency range. If the acoustic wave diffusion is still non-uniform or the reflection intensity exceeds the preset threshold, adjust the geometric parameters again and repeat the calculation process. Through multiple iterative calculations, determine the optimal combination of geometric parameters. Finally, obtain the optimized results that meet the requirements of uniform acoustic wave diffusion and no significant reflection.

[0041] Specifically, the evaluation of the acoustic wave diffusion uniformity can be measured by the sound pressure level distribution. Set multiple measurement points in the cavity and record the change of sound pressure over time. For example, evenly arrange twenty measurement points in the cavity. If the deviation of the sound pressure level at each measurement point exceeds the preset threshold of three decibels, it is determined that the diffusion is non-uniform. The adjustment of the geometric parameters of the scale protrusions needs to consider two dimensions: height and spacing. When it is found that the sound pressure is too high in a certain area, the scale height in this area can be appropriately increased to enhance the scattering effect, such as increasing the original 0.1 mm to 0.15 mm. If the sound pressure distribution shows obvious periodic fluctuations, it can be improved by adjusting the scale spacing, such as adjusting the spacing from 0.3 mm to 0.25 mm to break the periodic distribution. In the hydrodynamic calculation, the performance of the acoustic waves at different frequencies needs to be concerned. Taking a specific case as an example, when the frequency of the incident acoustic wave is 1000 Hz, a sound pressure peak of 5 decibels appears in a certain area of the cavity under the original scale parameters. After adjusting the scale height in this area to 0.12 mm and the spacing to 0.28 mm, the sound pressure peak drops below 3 decibels. The control of the acoustic wave reflection intensity is crucial to avoid the formation of standing waves. In practical applications, a threshold of the reflection coefficient not exceeding 0.3 can be set. When it is detected that the reflection coefficient at a certain place reaches 0.4, the geometric shape of the scale needs to be comprehensively considered. By designing the scale edge into a gradually changing transition form, the directional reflection of the acoustic wave can be effectively reduced. The optimization process is carried out iteratively. Observe the improvement degree of the sound pressure distribution after each round of iteration. A typical optimization process may require five to six rounds of iteration. For example, after the first round of adjustment, the sound pressure deviation drops from 5 decibels to 4 decibels, and in the second round to 3.5 decibels, until finally controlled within 2 decibels. Each round of iteration also needs to check the acoustic wave response in different frequency bands to ensure that the desired effect can be achieved within the target frequency range. The final optimized results should meet the requirements in both aspects of sound pressure uniformity and reflection control. Taking an actual case as an example, for the optimized scale structure, within the range of 500 Hz to 2000 Hz, the sound pressure level deviation is controlled within plus or minus 1.5 decibels, and the maximum reflection coefficient does not exceed 0.25, achieving the expected acoustic performance goals. Such an optimized structure can provide an important reference for the design of acoustic devices.

[0042] S108. Import the finally optimized acoustic cavity model into the 3D printing system, use titanium alloy material, and manufacture the acoustic cavity entity through precision forming process to complete the design of the in-ear headphone cavity based on the bionic cochlea structure.

[0043] Obtain the data of the optimized acoustic cavity model, perform parametric modeling for the bionic cochlea structure to obtain a three-dimensional model. Generate a file format recognizable by 3D printing according to the three-dimensional model. Use titanium alloy material as the manufacturing raw material, set the precision forming process parameters to obtain the printing parameters. Import the 3D printing file into the printing system and start the manufacturing process. Obtain the real-time data during the printing process and judge whether the forming accuracy meets the preset threshold. If the accuracy does not meet the preset threshold, adjust the process parameters and restart the printing process; if the accuracy meets the preset threshold, generate the final headphone cavity entity to complete the design based on the bionic cochlea structure.

[0044] Specifically, first of all, the parametric modeling of the bionic cochlear structure needs to be transformed according to the basic structural characteristics of the human cochlea. When modeling based on the spiral duct, the Bezier curve can be used to control the twisting path. The radius gradient rate of each turn is set to 0.5 mm, and the overall number of spiral turns is two and a half turns, so as to better simulate the spiral shape of the human ear. In terms of structural parameter setting, the cross-section of the cavity adopts an elliptical shape, with a major axis size of 4 mm and a minor axis size of 3 mm to ensure the smoothness of sound wave conduction. The generation of the 3D printing file format needs to consider the compatibility of the printer. Common formats such as point cloud data need to be converted into triangular mesh format, and the side length of each triangular mesh does not exceed 0.1 mm to ensure the fineness of the model surface. In terms of the selection of titanium alloy materials, spherical powders with a particle size between 15 and 45 microns are recommended, which can ensure the fluidity and sintering density during printing. The setting of precision forming process parameters directly affects the quality of the final product. The laser power can be set between 180 and 200 watts, the scanning speed is controlled between 800 and 1000 mm per second, and the layer thickness is set to 30 microns. The combination of these parameters can ensure that the material is fully melted and prevent overburning. During the printing process, the overlap rate of each layer scan is set to 30%, which can effectively avoid poor interlayer bonding. The real-time monitoring system mainly focuses on two aspects: one is the morphological characteristics of the molten pool. The size of the molten pool is captured by a high-speed camera. When the diameter of the molten pool exceeds 10% of the preset value, the laser power is adjusted immediately; the other is the flatness of the formed layer, which is detected in real time by a laser rangefinder. Compensation is required when the deviation exceeds 50 microns. The process parameter adjustment adopts a closed-loop control strategy. If the density of a certain area is detected to be lower than 99.5%, the energy density of this area can be appropriately increased. The specific method is to reduce the scanning speed by 5% to 10%. When the surface roughness exceeds the standard, the scanning path needs to be optimized. The checkerboard scanning strategy can be adopted, and the side length of each small area is set to 5 mm. The finally formed headphone cavity entity needs to be post-processed. First, stress relief heat treatment is carried out, with the temperature controlled at 600 °C and held for two hours. Then surface treatment is carried out, using a sandblasting process with alumina sand grains of 120 mesh to obtain a uniform surface texture. This can ensure that the product has good acoustic performance and service life.

[0045] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for optimizing the acoustic cavity of an in-ear headphone based on a bionic cochlear structure, characterized in that: The method comprises the following steps: S101, obtaining a mathematical model of a logarithmic spiral, and constructing a three-dimensional geometric model of a spiral tapered structure of a sound cavity based on parameters of an inlet diameter of 6 mm, an outlet diameter of 3.2 mm, and a spiral angle of 15°; S102, performing finite element analysis on the acoustic cavity geometric model, calculating the propagation path and pressure distribution of the sound wave in the cavity, and determining whether the sound wave forms a standing wave within a predetermined frequency range; S103. If the finite element analysis result shows that a standing wave exists, adjusting the spiral angle parameter of the logarithmic spiral model, and recalculating the sound wave propagation characteristics in the model until the standing wave phenomenon is suppressed; S104, calculating the incident angle of the sound wave at the entrance according to the optimized spiral tapered structure model and the acoustic characteristics of the headphone driver unit, and determining whether the sound wave can efficiently enter the sound cavity; S105, if the sound wave incident angle exceeds the preset range, adjusting the inlet diameter parameter of the logarithmic spiral model, and recalculating the sound wave incident angle until the matching requirement of the drive unit is met; S106. Adding inner wall scale protrusion features to the acoustic cavity geometry model, with a protrusion height of 0.1 mm and a spacing of 0.3 mm, to simulate the diffusion effect of sound waves in the cavity based on computational fluid dynamics; S107. If the simulation results show that the sound wave diffuses unevenly, the geometric parameters of the scale protrusions are adjusted, and the fluid mechanics calculation is re-performed until the sound wave diffuses evenly in the cavity and there is no significant reflection within the predetermined frequency range; S108. Import the final optimized acoustic cavity model into the 3D printing system, use titanium alloy material, and manufacture the acoustic cavity entity through precision molding technology to complete the in-ear headphone cavity design based on the bionic cochlear structure.

2. According to claim 1, the method for optimizing the acoustic cavity of an in-ear headphone based on a bionic cochlear structure is characterized in that: The S101 includes: Obtain the inlet diameter and outlet diameter of the acoustic cavity, determine the proportional relationship between the two, and obtain the tapering ratio of the spiral structure; According to the proportional relationship, a three-dimensional mathematical model of the spiral is constructed using a logarithmic spiral equation, wherein the mathematical model uses an inlet diameter, an outlet diameter and a spiral angle as input parameters; According to the mathematical model, three-dimensional point cloud data of the spiral line is generated to construct the spatial structure of the spiral line; Acquiring a thickness parameter of the acoustic cavity wall, applying the thickness parameter to the spiral line spatial structure, and generating a three-dimensional geometric model of the acoustic cavity spiral tapered structure; The three-dimensional geometric model is meshed using a finite element analysis method to calculate the flow field distribution inside the acoustic cavity; If the flow field distribution meets the preset conditions, outputting the three-dimensional geometric model; If the flow field distribution does not meet the preset conditions, the helix angle is adjusted and the mathematical model is reconstructed until a three-dimensional geometric model that meets the preset conditions is obtained.

3. According to claim 1, the method for optimizing the acoustic cavity of an in-ear headphone based on a bionic cochlear structure is characterized in that: The S102 includes: Acquiring an acoustic cavity model including geometric parameters, wherein the acoustic cavity model includes boundary conditions and material properties; Using a finite element analysis method, grid units are divided on the acoustic cavity model to generate a calculation domain; According to the sound wave propagation equation, a sound pressure calculation equation is established at the node of each grid unit; By solving the sound pressure calculation equation group, a sound pressure distribution diagram in the sound cavity is obtained; Extract node values ​​from the sound pressure distribution diagram and calculate the sound pressure amplitude at each frequency; If the sound pressure amplitude at a certain frequency presents a periodic distribution within the preset frequency range, it is determined that a standing wave is formed at this frequency; The frequency range in which the standing wave is formed is compared with the preset frequency range to obtain an analysis result of the standing wave formation situation.

4. The in-ear earphone acoustic cavity optimization design method based on the bionic cochlear structure according to any one of claims 1 to 3, characterized in that: The S103 includes: Obtaining finite element analysis results, and determining whether there is a standing wave in the finite element analysis results; If the standing wave exists, extracting the spiral angle parameter of the logarithmic spiral model, and taking the spiral angle parameter as an adjustment target; According to a preset spiral angle threshold range, the spiral angle parameter is adjusted using a gradient descent algorithm to obtain an adjusted spiral angle parameter; Substituting the adjusted helical angle parameter into the sound wave propagation characteristic calculation model, recalculating the sound wave propagation characteristic, and obtaining an updated sound field distribution; Using a support vector machine algorithm to analyze the updated sound field distribution to determine whether the standing wave phenomenon is suppressed; If the standing wave phenomenon is not completely suppressed, the helical angle parameter is repeatedly adjusted and the sound wave propagation characteristics are recalculated until the standing wave phenomenon is completely suppressed.

5. The in-ear earphone acoustic cavity optimization design method based on the bionic cochlear structure according to any one of claims 1 to 3, characterized in that: The S104 includes: The geometric parameters of the optimized spiral tapered structure model are obtained, and the propagation direction of the sound wave at the entrance is obtained by combining the acoustic characteristic parameters of the headphone driving unit; Calculating the incident angle of the sound wave at the entrance according to the angle between the sound wave propagation direction and the normal line at the entrance; If the incident angle is less than a preset threshold, it is determined that the sound wave can efficiently enter the sound cavity; Using an acoustic simulation algorithm to simulate the propagation path of the sound wave in the acoustic cavity; Analyzing the attenuation of the sound wave in the sound cavity according to the propagation path of the sound wave in the sound cavity; According to the sound wave attenuation, the geometric parameters of the spiral tapered structure model are adjusted to obtain an optimized spiral tapered structure model, wherein the optimized spiral tapered structure model is used to optimize the acoustic performance of the sound cavity; Acquiring acoustic performance parameters of the optimized acoustic cavity, and recalculating the incident angle of the sound wave at the entrance according to the acoustic performance parameters; If the recalculated incident angle meets the preset conditions, it is determined that the optimization of the spiral tapered structure model is completed.

6. The in-ear earphone acoustic cavity optimization design method based on the bionic cochlear structure according to any one of claims 1 to 3, characterized in that: The S105 includes: Obtaining a current value of the sound wave incident angle, and determining whether the current value exceeds a preset range; If the current value exceeds the preset range, the inlet diameter parameter value of the logarithmic spiral model is adjusted to obtain an adjusted inlet diameter parameter value; Recalculating the sound wave incident angle using the adjusted inlet diameter parameter value to obtain a recalculated sound wave incident angle; Determining whether the recalculated sound wave incident angle meets a preset drive unit matching requirement; If the recalculated sound wave incident angle does not meet the preset drive unit matching requirement, the inlet diameter parameter value is adjusted cyclically, and the sound wave incident angle is recalculated until the preset drive unit matching requirement is met; If the recalculated sound wave incident angle meets the preset drive unit matching requirement, determining the final inlet diameter parameter value of the logarithmic spiral model; According to the final inlet diameter parameter value, a calculation result of the sound wave incident angle that meets the preset drive unit matching requirement is output.

7. The in-ear earphone acoustic cavity optimization design method based on the bionic cochlear structure according to any one of claims 1 to 3, characterized in that: The S106 includes: Acquire three-dimensional data information of a vocal cavity geometric model, and perform feature extraction on an inner wall surface of the vocal cavity geometric model; If the feature extraction result includes a scale protrusion structure, obtaining protrusion height and spacing parameters of the scale protrusion structure; Reconstructing the inner wall surface morphology of the acoustic cavity model according to the geometric characteristic parameters of the scale protrusion structure; A mathematical model of the diffusion of sound waves in the acoustic cavity model is established by using a computational fluid dynamics method; Setting the inner wall boundary conditions of the acoustic cavity model in the mathematical model, wherein the inner wall boundary conditions include the geometric features of the scale protrusion structure; The diffusion process of the sound wave in the acoustic cavity model is solved by a numerical calculation method, and the diffusion effect data of the sound wave in the acoustic cavity model having the structural features of the scale protrusions is obtained.

8. The in-ear earphone acoustic cavity optimization design method based on the bionic cochlear structure according to any one of claims 1 to 3, characterized in that: The S107 includes: According to the sound wave diffusion simulation results, determine whether the diffusion uniformity meets the preset conditions; If the diffusion is uneven, the current scale protrusion geometric parameters are obtained for adjustment; The adjusted geometric parameters are used to recalculate the fluid dynamics and obtain new simulation results of sound wave diffusion; Based on the new simulation results, the diffusion uniformity of the sound wave in the cavity and the reflection intensity within the predetermined frequency range are analyzed; If the sound wave diffusion is still uneven or the reflection intensity exceeds the preset threshold, the geometric parameters are adjusted again and the calculation process is repeated; Determine the optimal geometric parameter combination through multiple iterative calculations; Finally, an optimized result is obtained that satisfies the uniform diffusion of sound waves and has no significant reflection.

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