LED display screen with sound absorption function

Abstract

The utility model discloses an LED display screen with a sound absorption function. The LED display screen comprises an LED display module, a perforated panel and a sound absorption material layer. The thickness of the perforated panel ranges from 1.2 mm to 2.0 mm, sound transmission holes are evenly distributed in the surface of the perforated panel, the hole diameter ranges from 0.3 mm to 2.0 mm, and the aperture ratio ranges from 5% to 35%. A plurality of light-emitting tubes are arranged on one face of the perforated panel, a plurality of LED display screen necessary devices such as driving chips are arranged on the other face of the perforated panel, sound transmission holes are formed between the light-emitting tubes and the chips, and a sound absorption material layer is arranged adjacent to the other face of the perforated panel. The thickness of the sound-absorbing material layer is 20-100 mm, and a plurality of holes are formed in the sound-absorbing material layer and used for enhancing the sound-absorbing effect. The sound absorption module further comprises a plurality of sound absorption cavities, the thickness of the cavities is 1 / 4 of the wavelength of sound waves entering the cavities, and therefore the absorption performance of low and medium frequency noise is improved.

Description

Technical Field

[0001] This utility model relates to the field of display screen technology, and in particular to an LED display screen with sound-absorbing function. Background Technology

[0002] With the continuous advancement of modern display technology, LED displays are increasingly widely used in conference rooms, theaters, multimedia exhibition halls, and other scenarios. Thanks to their superior image resolution, high brightness, and rich color performance, LED displays have become the dominant technology in the field of visual presentation. In recent years, researchers and manufacturers have invested considerable effort in improving the visual effects of LED displays, focusing on enhancing clarity, color accuracy, and response speed. However, as users' demand for high-quality integrated audio-visual experiences increases, simple visual optimization can no longer meet the requirements of certain specific scenarios. Especially in environments requiring high-quality audio-visual presentation, the importance of acoustic design is increasingly prominent. However, existing LED display technologies have paid relatively limited attention to acoustic performance, typically relying on independently installed sound-absorbing devices, such as sound-absorbing panels or sound-absorbing walls, to improve the acoustic effects of the environment.

[0003] However, existing technologies have significant shortcomings in integrating acoustic and display functions. First, separately installed sound-absorbing devices often occupy additional space, increasing installation complexity and potentially affecting the overall aesthetics of the space. This separate design cannot achieve an organic combination of sound absorption and display effects, leading to limitations in the user experience. Utility Model Content

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the present invention.

[0005] In view of the technical problems existing in the prior art, this application provides an LED display screen with sound absorption function, including

[0006] An LED display module includes an open panel and a sound-absorbing module. The open panel has a thickness of 1.2 mm to 2.0 mm and has sound-permeable holes evenly distributed on its surface, with an opening ratio of 5% to 35%. The sound-absorbing module is attached to the back of the open panel and has a plurality of pores.

[0007] As a preferred technical solution for an LED display screen with sound absorption function, the sound-permeable holes of the perforated panel are circular, the diameter of the sound-permeable holes is 0.3mm to 2.0mm, and they are evenly distributed on the entire surface of the perforated panel.

[0008] As a preferred technical solution for an LED display screen with sound absorption function, the perforated panel array is provided with a number of LED light-emitting pixels, the sound-transmitting holes and the LED light-emitting pixels are arranged alternately in sequence, and the intersection of the diagonals of the square formed by the centers of the four sound-transmitting holes is the center point of the LED light-emitting element.

[0009] As a preferred technical solution for an LED display screen with sound absorption function, the thickness of the sound absorption module is 20mm to 100mm.

[0010] As a preferred technical solution for an LED display screen with sound absorption function, the rear structure of the display screen also includes a system power supply, a frame-type cabinet, and a back cover, wherein the frame-type cabinet, the system power supply, and the back cover are sequentially arranged on the back of the display screen.

[0011] As a preferred technical solution for an LED display screen with sound absorption function, the sound absorption module is composed of several sound absorption groups, each of which includes a sound absorption material layer and a sound absorption cavity.

[0012] As a preferred technical solution for an LED display screen with sound absorption function, the thickness of the sound-absorbing cavity is 1 / 4 of the wavelength of the sound wave entering the sound-absorbing cavity.

[0013] This invention combines sound absorption with LED display functionality, achieving an innovative design that maintains high-quality visual presentation while effectively absorbing noise. It is particularly suitable for venues with high acoustic and visual requirements, such as conference rooms and theaters. The scientifically laid-out sound-permeable holes on the perforated panel range in diameter from 0.3mm to 2.0mm, with an opening rate of 5% to 35%, ensuring smooth sound wave passage and absorption by the sound-absorbing module while maintaining uniform brightness and structural strength of the display screen. The cavity thickness within the sound-absorbing module is one-quarter of the sound wave wavelength, significantly improving the absorption of mid-to-low frequency noise, enabling the display screen to perform excellently in various complex acoustic environments. Furthermore, the rear structure design utilizes a combination of system power supply, frame-type cabinet, and back cover, ensuring structural stability of the display screen and effectively improving heat dissipation, extending the equipment's lifespan. The overall design is lightweight, easy to install and maintain, adaptable to various application scenarios, and possesses excellent practicality and multi-functionality. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Among them:

[0015] Figure 1 This is a schematic diagram of the overall structure of the device of this utility model;

[0016] Figure 2 This is a schematic diagram of the structure of the perforated panel of this utility model;

[0017] Figure 3 This is a schematic diagram of the structure of the LED display module of this utility model;

[0018] Reference numerals: 1. Opening panel; 11. Sound-permeable hole; 12. LED light-emitting pixel; 2. Sound-absorbing module sound-absorbing material layer; 21. Sound-absorbing material layer; 22. Sound-absorbing cavity; 3. System power supply; 4. Frame-type cabinet; 5. Back cover. Detailed Implementation

[0019] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings.

[0020] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0021] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0022] Secondly, this utility model is described in detail with reference to the schematic diagrams. When describing the embodiments of this utility model, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this utility model. In addition, actual manufacturing should include the three-dimensional spatial dimensions of length, width, and depth.

[0023] Example 1

[0024] Please refer to Figures 1 to 3As shown, an LED display screen with sound-absorbing function includes:

[0025] An LED display module comprises a perforated panel and a sound-absorbing module. The perforated panel has a thickness ranging from 1.2mm to 2.0mm and is made of high-strength materials to ensure structural stability and durability. Simultaneously, the surface of the perforated panel is uniformly distributed with sound-permeable holes, with an opening ratio set between 5% and 35%, to ensure that sound can effectively penetrate the panel without affecting the display effect. The shape of the sound-permeable holes can be circular, square, or other geometric shapes, and the specific shape can be optimized according to the application scenario and design requirements. The size and distribution density of the sound-permeable holes are precisely calculated to maximize the sound absorption effect while ensuring screen brightness uniformity and reducing the interference of environmental noise on sound quality.

[0026] The sound-absorbing module is tightly fitted to the back of the perforated panel. The module consists of multiple layers of sound-absorbing material, each with a different density and thickness to achieve broadband noise absorption. The sound-absorbing material layers can be made of polyester fiber, foam material, or nanofiber composite materials to ensure sound absorption performance and long-term durability. Several pores are also provided on the sound-absorbing material layers. These pores are precisely designed with specific pore sizes and arrangements to enhance sound absorption efficiency while reducing sound wave reflection, ensuring effective sound absorption. The shape and size of the pores are optimized according to the noise frequency range to ensure that the LED display maintains good sound absorption performance at different frequencies.

[0027] Furthermore, the sound-absorbing material layer not only absorbs environmental noise but also optimizes the heat dissipation performance of the LED display screen through its porous structure. This prevents the display screen from overheating due to prolonged operation and extends its lifespan. This structural design also ensures the display screen is lightweight, making it easy to install and maintain.

[0028] The sound-permeable holes in the perforated panel are designed to be circular, with a diameter ranging from 0.3mm to 2.0mm. This circular design not only ensures the smooth passage of sound waves but also minimizes the impact on the display effect. The circular aperture design also results in a more uniform stress distribution, further improving the panel's strength and resistance to deformation, effectively avoiding structural weakening caused by the perforations.

[0029] The acoustic perforations are scientifically and evenly distributed across the entire surface of the perforated panel. The distribution density is optimized based on specific needs and usage environments to ensure optimal sound transmission and absorption in various application scenarios. Specifically, the perforation ratio is controlled between 5% and 35%, meaning that acoustic perforations are distributed in a certain proportion of the panel surface to maintain good display quality and sound wave conduction. Too low a perforation ratio may restrict sound wave passage and reduce sound absorption, while too high a perforation ratio may affect the panel's structural stability and display brightness. Therefore, this range has been rigorously calculated to achieve the best balance between acoustic and visual performance.

[0030] The perforated panel has an array of LED light-emitting pixels arranged in an alternating pattern with the sound-permeable holes, ensuring that each light-emitting pixel is surrounded by multiple sound-permeable holes. Specifically, the centers of four sound-permeable holes form a square, and the intersection of the diagonals of this square is the center point of the LED light-emitting pixel. This layout not only ensures that sound can pass smoothly through the panel and be effectively absorbed by the sound-absorbing module, but also guarantees that the illumination area of ​​each LED light-emitting pixel is not interfered with by the sound-permeable holes, thus maintaining a high-quality display effect.

[0031] The thickness of the sound-absorbing material layer ranges from 20mm to 100mm, and can be adjusted according to the needs of the actual use environment, so as to ensure good sound absorption effect without affecting the overall thickness and ease of installation of the LED display screen, thereby achieving efficient noise control and excellent spatial adaptability.

[0032] The rear structure of the display screen also includes a system power supply, a frame-type cabinet, and a rear cover, which are arranged sequentially on the back of the display screen to ensure the structural stability of the display screen and the reliable operation of the power supply system. Specifically, the frame-type cabinet is made of lightweight, high-strength materials, possessing excellent load-bearing capacity and deformation resistance. It effectively supports the LED display modules and sound-absorbing modules, and provides protection and installation space for the power supply system and other electronic components inside the display screen. The system power supply integrated within the frame-type cabinet is optimized for efficient heat dissipation and energy conversion, ensuring stable power output for the display screen even during prolonged operation. The rear cover is securely fixed to the rear of the frame-type cabinet using bolts or clips, providing dustproof, waterproof, and impact-resistant functions, further enhancing the durability and safety of the display screen. Furthermore, the rationally designed rear structure not only effectively protects the internal electronic components but also facilitates installation and maintenance, thereby extending the lifespan of the display screen and improving its operational stability.

[0033] The sound-absorbing module consists of several sound-absorbing groups, each including a sound-absorbing material layer and a sound-absorbing cavity. The sound-absorbing material layer absorbs a portion of the sound wave energy, while the sound-absorbing cavity further enhances the sound absorption effect. Specifically, the thickness of the sound-absorbing cavity is precisely designed to be 1 / 4 of the wavelength of the sound wave entering the cavity, achieving a resonant absorption mechanism. This 1 / 4 wavelength design causes interference between the sound wave and the sound-absorbing material layer upon entering the cavity, significantly reducing the energy of reflected sound waves and improving the absorption efficiency for mid-to-low frequency noise. This structure effectively expands the sound absorption frequency range, enabling the display to maintain excellent sound absorption performance in various complex acoustic environments, especially excelling in handling low-frequency noise. Furthermore, the combined design of the sound-absorbing cavity and the sound-absorbing material layer, through an optimized multi-layer structure, further reduces sound wave reflection and transmission on the panel surface, improving the overall acoustic effect. This gives the display not only excellent display functionality but also strong environmental noise suppression capabilities, making it suitable for demanding environments such as theaters, conference rooms, and exhibition halls.

[0034] Schematic diagram of an LED display module Figure 3 As shown: The surface is a PCB circuit board (perforated panel) with sound-through holes and LED display pixels (lamp tubes).

[0035] A combination of a cavity and a sound-absorbing material is called a sound-absorbing group. The enclosure of this patent is composed of one or more sound-absorbing groups.

[0036] The following example uses a cabinet with three sound-absorbing groups, i.e., three cavities and three different types of sound-absorbing materials:

[0037] Based on the fundamental theory of sound absorption, a PCB circuit board with sound-permeable holes on its surface can be considered as a micro-perforated board, and its transfer matrix [M] can be written as follows: Z s The acoustic impedance of a PCB circuit board with acoustic holes is calculated using the following formula:

[0038]

[0039] Where μ is the air viscosity coefficient; ρ is the air density; t is the PCB board thickness; p is the perforation rate of the micro-perforated board; d is the diameter of the sound-perforating hole; ω is the angular frequency of the sound wave, ω=2πf; k r and k m These are the acoustic impedance constant and acoustic mass constant, respectively; k is the micro-perforated plate constant.

[0040] transfer matrix of cavity

[0041] Let the thicknesses of the first cavity, the second cavity, and the third cavity be l1, l2, and l3, respectively. Then, the transfer matrix C of the first cavity, the second cavity, and the third cavity is...n for:

[0042]

[0043] Where c is the speed of sound in air.

[0044] Transfer matrix of sound-absorbing materials

[0045] Let the thicknesses of porous material 1, porous material 2, and porous material 3 be h1, h2, and h3, respectively. Then, what is the transfer matrix P of the porous material layers? n for:

[0046]

[0047] Where, k p Z represents the wave number of the sound wave in the sound-absorbing porous material. p The characteristic impedance of the sound-absorbing porous material.

[0048] Transfer matrix of composite structure

[0049] For the composite matrix of the enclosure schematic, the total transfer matrix can be obtained by multiplying the transfer matrices of the PCB circuit board, cavity, and sound-absorbing material in sequence.

[0050]

[0051] P1, P2, and P3 are the transfer matrices for the first, second, and third porous material layers from top to bottom, respectively; C1, C2, and C3 are the transfer matrices for the first, second, and third cavities from top to bottom, respectively.

[0052] The surface acoustic impedance of the composite structure is:

[0053] Z f =T 11 / T 21

[0054] The reflection coefficient β and the sound absorption coefficient α are respectively:

[0055]

[0056] α = 1 - |β| 2

[0057] Therefore, the sound absorption coefficient of the enclosure is related to the thickness of the cavity and the characteristics of the sound-absorbing material.

[0058] Influence of cavity thickness on transfer matrix

[0059] Because the transfer matrix C of the cavity n for:

[0060]

[0061] Among them l n Let k be the thickness of the cavity, ω = 2πf, and c be the speed of sound. Let k = ωc -1 Then sin(kl) n ) and cos(kl n The number () represents the phase change of sound wave propagation within the cavity. The thickness (l) of the cavity... n The thickness of the cavity affects the propagation time of sound waves, thus affecting the propagation phase. As the cavity thickness increases, the propagation path of sound waves within the cavity becomes longer, resulting in phase delay.

[0062] The sine and cosine terms in the matrix are: sin(kl) n ) and cos(kl n This reflects the reflection characteristics and transmission effects of sound waves propagating in the cavity. When kl n When increasing, cos(kl) n The value of ) oscillates between [-1, 1], and the reflection coefficient exhibits different extreme values ​​depending on the phase. The greater the thickness, the more pronounced the periodic variation. And sin(kl) n In ), when kl n When l = nπ, the sine function is zero, and the transmitted energy is minimum. As l... n As the cavity thickens, the propagation path of the sound wave increases, and the phase changes of the sine and cosine functions in the transfer matrix intensify. For thicker cavities, the sound wave undergoes multiple periods of phase change, leading to interference phenomena of multiple reflections and transmissions. This causes the system's reflection and transmission coefficients to fluctuate periodically with frequency and thickness.

[0063] Therefore, when l n When the values ​​are small, the values ​​of the sine and cosine functions are smaller, resulting in less reflection in the system and better sound absorption.

[0064] When l n When the sine and cosine functions are increased, the periodic changes may lead to larger phase changes, making sound waves more easily reflected and reducing the sound absorption effect.

[0065] Therefore, the cavity thickness and the sound absorption coefficient are usually negatively correlated; that is, the sound absorption effect weakens as the cavity thickness increases. This is because a thicker cavity causes more sound waves to be reflected rather than absorbed by the porous material.

[0066] However, if the cavity is too thin, it won't provide enough path length to absorb long-wavelength low-frequency sound waves. Therefore, a cavity that is too thin will result in very poor low-frequency absorption, with more low-frequency sound waves being reflected back. To effectively absorb low-frequency sound waves, the cavity thickness can be set to one-quarter of the wavelength, or approximately λ / 4. Due to the design limitations of the enclosure, we can use three cavities to absorb low-frequency, mid-frequency, and high-frequency sound waves respectively, decreasing their thickness sequentially. For example, to absorb 200Hz low-frequency noise, whose wavelength is approximately 1.72 meters, the cavity thickness can be set to 0.43 meters for optimal absorption. For mid-frequency noise (500Hz to 1000Hz), whose wavelength ranges from 0.686 meters to 0.343 meters, the cavity thickness should be reduced accordingly. For example, for 500Hz sound waves, the cavity thickness can be set to approximately 0.17 meters to ensure effective absorption of mid-frequency noise. In the absorption of high-frequency noise (above 1000Hz), the wavelength of sound waves is shorter, so the cavity thickness can be further reduced. For example, for a 1000Hz sound wave, the wavelength is about 0.343 meters, and the cavity thickness can be set to about 0.086 meters.

[0067] Influence of porous materials on transfer matrix

[0068] The transfer matrix of porous materials is:

[0069]

[0070] Where, k p It is the wave number Z in the material. p It is the characteristic impedance of porous materials.

[0071]

[0072] The higher the frequency, the higher the wavenumber of the sound.

[0073] Characteristic impedance Z of porous materials p It is directly related to the transmission and reflection intensity of sound waves in the matrix.

[0074] When Z p As Z increases, the material's resistance to sound waves increases, resulting in more reflections of the sound waves as they pass through the material. p When decreasing,

[0075] The material's resistance to sound waves is reduced, making it easier for sound waves to enter the material and be absorbed.

[0076] Because of the final sound absorption coefficient

[0077]

[0078] Where ρc is the characteristic impedance of air, it can be seen that when Zf The closer the absorption coefficient α is to the air characteristic impedance ρc, the larger the sound absorption coefficient α is.

[0079] because

[0080] Z f =T 11 / T 21

[0081] Therefore, when the characteristic impedance Z of the material p The closer to Z f The closer the material's characteristic impedance ρc is to that of air, the better the sound absorption effect. In sound absorption design, the characteristic impedance Z of the material is utilized. p The sound absorption effect at different frequency bands is optimized by matching the characteristic impedance ρc of melamine foam with that of air. Melamine foam performs well in the high-frequency range because its characteristic impedance Z... p With an impedance closer to air impedance ρc, reflection is reduced and the sound absorption coefficient is increased. In the mid-frequency range, the structure of polyester fiber sound-absorbing cotton allows sound waves to undergo multiple scattering and reflections within the material, thereby lengthening the sound wave path and increasing the chance of absorption, despite its impedance Z. p Although not perfectly matched, the structure and moderate material thickness still allow for effective absorption of mid-frequency sounds. In the low-frequency range, the high density and thickness of the fiberglass material allow it to gradually attenuate low-frequency sound waves by reducing sound wave penetration and increasing absorption paths, thus compensating for the impedance mismatch.

[0082] In this specific implementation, melamine foam, polyester fiber, and glass fiber are selected as the three sound-absorbing materials, and they are placed in sequence from front to back to absorb high-frequency, mid-frequency, and low-frequency sound-absorbing materials, respectively. As shown in the formula above, the higher the characteristic impedance, the smaller the frequency range absorbed. Material 1, melamine foam, placed at the front, effectively absorbs high-frequency noise (mainly handling frequencies above 1000Hz) and reduces reflection; Material 2, polyester fiber sound-absorbing cotton, handles frequencies between high and low frequencies (approximately 500Hz to 1000Hz); Material 3, glass fiber, placed last, better absorbs low-frequency sound waves (mainly handling frequencies between 200Hz and 500Hz). Through this reasonable combination of materials, the overall acoustic performance of the enclosure is significantly improved, especially in noise control across various frequency ranges.

[0083] Example 2

[0084] The LED display module has passed the rigorous testing of the Tsinghua University Environmental Testing Center and obtained a test report. According to the test results, the weighted sound absorption coefficient (WBC) of the display module reached 0.85 (L), and the noise reduction coefficient (NRC) was 0.95. These indicators demonstrate the product's excellent acoustic performance. The weighted sound absorption coefficient is a comprehensive parameter describing the sound absorption efficiency of a material at multiple frequencies, while the noise reduction coefficient (NRC) is a standard indicator measuring the overall sound absorption effect of a material. These two high values ​​indicate that the LED display can effectively absorb and reduce environmental noise, improving the quality of the acoustic environment.

[0085] According to the GB / T16731-2023 standard "Classification of Sound Absorption Performance of Building Sound Absorption Products", the sound absorption performance of this display module's sound absorption structure was rated as Grade B and Grade 1, respectively. This rating indicates that the product not only meets the high requirements of national standards but also performs excellently in terms of acoustic regulation. The Grade B and Grade 1 ratings are based on the average performance of the sound absorption coefficient and noise reduction coefficient across various frequency bands, demonstrating that the product provides effective acoustic improvement in a variety of usage environments.

[0086] This high-performance sound-absorbing LED display is designed for spaces requiring improved acoustic environments, such as conference rooms, theaters, recording studios, and public exhibition areas. It not only provides high-quality visual displays but also significantly enhances acoustic comfort through its sound-absorbing properties. This gives it a unique competitive advantage in the market, especially in applications with specific acoustic performance requirements.

[0087] The embodiments are only used to illustrate the technical solutions of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this utility model without departing from the spirit and scope of the technical solutions of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. An LED display screen with sound-absorbing function, characterized in that, include An LED display module includes an open panel and a sound-absorbing module. The open panel has a thickness of 1.2 mm to 2.0 mm and has sound-permeable holes evenly distributed on its surface, with an opening ratio of 5% to 35%. The sound-absorbing module is attached to the back of the open panel and has a plurality of pores.

2. The LED display screen with sound-absorbing function according to claim 1, characterized in that, The sound-permeable holes of the perforated panel are circular, with a diameter of 0.3 mm to 2.0 mm, and are evenly distributed across the entire surface of the perforated panel.

3. The LED display screen with sound-absorbing function according to claim 2, characterized in that, The perforated panel array is provided with a number of LED light-emitting pixels. The sound-permeable holes and the LED light-emitting pixels are arranged alternately in sequence. The intersection of the diagonals of the square formed by the centers of the four sound-permeable holes is the center point of the LED light-emitting element.

4. The LED display screen with sound-absorbing function according to claim 1, characterized in that, The thickness of the sound-absorbing module is 20mm to 100mm.

5. The LED display screen with sound-absorbing function according to claim 1, characterized in that, The rear structure of the display screen also includes a system power supply, a frame-type cabinet, and a rear cover, which are sequentially arranged on the back of the display screen.

6. The LED display screen with sound-absorbing function according to claim 1, characterized in that, The sound-absorbing module consists of several sound-absorbing groups, each of which includes a sound-absorbing material layer and a sound-absorbing cavity.

7. The LED display screen with sound-absorbing function according to claim 6, characterized in that, The thickness of the sound-absorbing cavity is 1 / 4 of the wavelength of the sound wave entering the sound-absorbing cavity.

Images