A multi-faceted open-hole interference tube for a directional microphone
Patent Information
- Application Number
- CN202522096316.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-29
- Publication Date
- 2026-09-04
- Estimated Expiration
- 2035-09-29
AI Technical Summary
然而，该方案存在以下缺陷：第一，受限于单/双排孔的线性布局，声波进入管腔的路径单一，导致不同频率的声压幅值分布不均，频响曲线出现明显的“峰”和“谷”，录音音色被染色，难以满足高保真拾音需求；第二，规则排列的通孔在管壁内侧形成若干对称反射面，极易激发轴向驻波，在特定频率产生尖锐共振，进一步加剧频响不平坦；第三，为抑制上述峰谷，生产线需对每一通孔或每一阻尼层进行人工调试，工艺复杂、一致性差、良品率低，不利于大批量制造；第四，圆形通孔对来自不同方向的声波衰减差异较大，导致指向性在三维空间内不对称，偏轴频率响应差异显著，实际使用中需频繁调整传声器角度，增加操作难度
采用本实用新型所述的多面开孔干涉管后，传声器在保持超心形指向性的同时，其频率响应曲线在主要工作频段内起伏得到抑制；由于圆周方向四组非连续渐变槽缝破坏了规则共振腔边界，管内轴向驻波被显著削弱，尖锐的共振峰被消除，三维空间指向性对称度提高；统一规格声阻材料一次性覆盖所有槽缝，生产线无需逐孔调试阻尼，单件组装时间缩短，批量生产一致性提高。
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Figure CN224721945U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electroacoustic transducer technology, specifically a multi-faceted perforated interference tube for directional microphones. Background Technology
[0002] With the ever-increasing demands for sound quality in broadcasting, stage performances, and film and television production, professional microphones not only need to maintain high sensitivity in complex acoustic environments but also must possess the ability to accurately separate the target sound source from background noise. Traditional cardioid microphones perform well in close-range sound pickup, but their ability to suppress lateral and rear noise is significantly insufficient in long-distance or high-noise environments, leading to decreased clarity of the target sound source and limiting recording quality. To obtain a narrower receiving beam, the industry commonly adds an acoustic interference tube to the front end of the condenser microphone capsule. By controlling the diffraction and interference path of sound waves, the microphone achieves a sharper superdirectivity in the axial direction than the traditional cardioid, thereby improving the signal-to-noise ratio for far-field sound pickup.
[0003] Existing interference tube structures typically involve creating single or double rows of circular through-holes in the metal or plastic tube wall, and covering the outside of these holes with acoustic damping materials such as damping silk, non-woven fabric, or foam plastic to create a gradient sound pressure difference. However, this approach has the following drawbacks: First, limited by the linear layout of the single / double rows of holes, the sound waves enter the tube cavity through a single path, resulting in uneven distribution of sound pressure amplitudes at different frequencies. This leads to obvious peaks and valleys in the frequency response curve, coloring the recorded sound and making it difficult to meet high-fidelity sound pickup requirements. Second, the regularly arranged through-holes form several symmetrical reflective surfaces on the inner side of the tube wall, which easily excite axial standing waves, producing sharp resonances at specific frequencies and further exacerbating the uneven frequency response. Third, to suppress these peaks and valleys, the production line requires manual adjustment of each through-hole or each damping layer, resulting in complex processes, poor consistency, and low yield, which is not conducive to mass production. Fourth, the circular through-holes attenuate sound waves from different directions significantly, leading to asymmetrical directivity in three-dimensional space and significant differences in off-axis frequency response. In actual use, the microphone angle needs to be frequently adjusted, increasing operational difficulty. The aforementioned problems have long hindered the widespread application of superdirectional microphones in high-quality, long-distance sound pickup applications. Utility Model Content
[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multi-faceted perforated interference tube for directional microphones, so as to simultaneously achieve precise control of microphone directivity and effective suppression of standing wave resonance, thereby meeting the professional requirements for high sensitivity, high signal-to-noise ratio and uncolored sound quality in long-distance sound pickup and high-noise environments.
[0005] To achieve the above objectives, a multi-faceted perforated interference tube for a directional microphone is designed. The interference tube is a hollow circular tube structure, installed in front of the microphone head. The end of the tube furthest from the microphone head faces the target sound source, while the end closest to the microphone head is used to mount the microphone head. Several slot groups are evenly distributed axially along the circumferential wall of the tube. Each slot group contains several parallel, circumferentially distributed through slots. The width of the slots in adjacent slot groups varies from farthest to farthest. The grooves decrease in width from the end furthest from the microphone head towards the end closest to the microphone head, making the grooves widest at the end furthest from the microphone head and narrowest at the end closest to the microphone head. The grooves and the circular tube form an irregularly shaped interference tube cavity, which is used to introduce ambient sound waves into the tube through a dispersed path. The sound waves then interfere with the non-axial sound waves entering from the end furthest from the microphone head at the diaphragm of the microphone head, thereby disrupting the standing wave conditions formed by the continuous smooth inner wall of the tube and suppressing the generation of high-energy standing waves and resonance peaks and valleys.
[0006] Preferably, the present invention further includes: an acoustic damping material layer covering the outer wall surface of the circular tube, the acoustic damping material layer simultaneously sealing all the outer openings of the slots, allowing external sound waves to enter the internal cavity of the circular tube through the acoustic damping material layer and the slots, the slots and the acoustic damping material layer together forming a sound wave entry channel.
[0007] Preferably, the present invention further includes: the acoustic damping material layer is an acoustic mesh with a constant flow resistance value, the acoustic mesh continuously covers the outer wall of the circular tube, and provides the same acoustic damping for all slots.
[0008] Preferably, the present invention further includes: the inside of the circular tube is provided with a continuous cavity, without an inner tube structure, and the slot and the end away from the microphone head are the only channels for sound waves to enter.
[0009] Preferably, the present invention further includes: the number of groove groups is three, and each groove group includes four grooves.
[0010] Preferably, the present invention further includes: structural ribs provided between adjacent slots in the same slot group.
[0011] Compared with the prior art, the advantages of this utility model are: By using the multi-faceted perforated interference tube described in this invention, the microphone maintains its supercardioid directivity while suppressing fluctuations in its frequency response curve within the main operating frequency band. Because the four sets of discontinuous, gradually changing slots in the circumferential direction disrupt the boundaries of the regular resonant cavity, the axial standing waves inside the tube are significantly weakened, sharp resonance peaks are eliminated, and the three-dimensional spatial directivity symmetry is improved. With uniform acoustic damping material covering all slots at once, the production line does not need to adjust the damping hole by hole, shortening the assembly time for single pieces and improving the consistency of batch production. Attached Figure Description
[0012] Figure 1 This is a front view of the utility model; Figure 2 This is the left view of this utility model; Figure 3 This is the right view of this utility model; Figure 4 This is a three-dimensional structural view of the present invention; Figure 5 This is a perspective view of the structure of this utility model from another angle; Figure 6 This is an exploded view of the structure of this utility model; In the diagram: 1. Circular tube, 11. End furthest from the microphone head, 12. End closest to the microphone head, 2. Slot group, 21. First slot group, 22. Second slot group, 23. Third slot group, 24. Structural rib, 3. Microphone head, 31. Diaphragm, 4. Acoustic damping material layer. Detailed Implementation
[0013] To make the purpose, principle and structure of this utility model clearer, the following description is provided in conjunction with the accompanying drawings and specific embodiments.
[0014] like Figures 1 to 6 As shown, the interference tube is composed of a single hollow circular tube 1. The circular tube 1 has an end 11 away from the microphone head and an end 12 near the microphone head. The end 11 away from the microphone head is open and faces the target sound source. The end 12 near the microphone head is used to install the microphone head 3, so that the microphone head diaphragm 31 is located on the central axis inside the cavity of the circular tube 1. Three sets of slot groups 2 are opened sequentially along the axial direction on the circumferential wall of the circular tube 1. From the end 11 away from the microphone head to the end 12 near the microphone head, they are the first slot group 21, the second slot group 22, and the third slot group 23. Each slot group 2 contains four straight slots that penetrate the tube wall. The slots in the same group are parallel to each other and are equidistantly distributed around the circumference of the circular tube 1. Structural ribs 24 are retained between adjacent slots to maintain the rigidity of the tube body.
[0015] All slots extend axially, and their width gradually decreases from the end 11 furthest from the microphone head to the end 12 closest to the microphone head, making the slots in the first slot group 21 the widest and the slots in the third slot group 23 the narrowest, thus forming three progressive sound entrances. Preferably, the slots within the same slot group 2 have the same width, while the widths differ between different slot groups 2.
[0016] The slots and the circular tube 1 form an irregularly shaped internal cavity of the interference tube. From a cross-sectional perspective, the cross-sections of the internal cavities of interference tubes in the prior art are mostly regular shapes, including circular cross-sections and circular cross-sections with a concave area of the same size on one side. Sound in the internal cavities of interference tubes in the prior art easily forms standing waves along smooth and continuous surfaces. However, the cross-section of the internal cavity of the interference tube in this application is irregular and constantly changing. This breaks the continuous circular cross-section of the prior art, which is destroyed into a discontinuous irregular structure by several slots set along the circumference. Moreover, the slots at different positions on the same interference tube have different widths and sizes. Therefore, the irregular structure of the internal cavity cross-section at different positions on the same interference tube is also inconsistent. This can eliminate all standing wave conditions to the greatest extent, eliminate unnecessary resonance effects, and record the upward-pointing sound waves that need to be recorded more realistically.
[0017] The outer wall of the circular tube 1 is entirely covered with a layer of acoustic damping material 4. The acoustic damping material 4 is an acoustic mesh with a constant flow resistance value, which is continuously glued to the outer surface of the circular tube 1. At the same time, it seals all the outer openings of the slots, so that external sound waves can only enter the inner cavity of the tube through the acoustic damping material 4 and the slots.
[0018] The inside of the circular tube 1 is a continuous cavity without any additional inner tube or partition. The slot and the end 11 away from the microphone head form the only channel for sound waves to enter.
[0019] During assembly, the acoustic mesh is first cut into rectangular strips and wrapped around the outer wall of the round tube 1 along the axial direction. The joints are overlapped and pressure is applied with a clamp to complete the curing. Then, the end 12 of the round tube 1 closest to the microphone head is inserted into the positioning step of the microphone head 3 shell so that the diaphragm 31 is aligned with the axis of the round tube. Adhesive is applied to the joint, and after curing at room temperature, a directional microphone head assembly with an interference tube is formed.
[0020] After being installed in the microphone housing, this component shows improved axial sensitivity and off-axis rejection ratio compared to the same model of interference-free microphone head, as measured at the reference frequency. The frequency response curve shows a reduced peak-to-valley difference in the main operating frequency range, meeting the needs of professional long-distance sound pickup.
[0021] In actual sound pickup, the end 11 of the interference tube furthest from the microphone head must face the target sound source. At this point, the tube's axis is the microphone's main pickup direction. Thanks to the shielding effect of the tube wall, most of the sound from the sides and rear is blocked, thus initially improving directivity. However, for traditional interference tubes with continuous smooth inner walls, some noise at a certain angle to the axis still enters the tube from the end 11 furthest from the microphone head and reflects multiple times along the smooth inner wall. Energy accumulates continuously, eventually forming high-energy standing waves within the tube, resulting in sharp resonance peaks and valleys at specific frequencies. These standing waves, acting on the diaphragm 31 of the microphone head 3, are superimposed on the target sound source signal, causing timbre coloration and a decrease in signal-to-noise ratio.
[0022] This invention features three sets of slot groups 2 on the circumferential wall of a hollow circular tube 1. Each set of slot groups 2 includes four slots penetrating the tube wall. Adjacent slot groups 2 maintain an axial distance and are reinforced by structural ribs 24 within the same group to maintain the rigidity of the tube body. The slots extend axially, with their width gradually increasing from the end 11 furthest from the microphone head to the end 12 closest to the microphone head, forming a progressive sound inlet. The outer wall of the circular tube 1 is entirely covered with a layer of acoustic resistive material 4 with constant flow resistance, sealing the openings on the outer side of the slots. External sound waves can enter from the end 11 furthest from the microphone head, as well as through the acoustic damping material layer 4 and the slots into the tube cavity. Because the slots are distributed circumferentially with gradually varying widths, sound waves of different directions and frequencies are divided into multiple weak amplitude paths. These paths encounter axial sound waves entering from the end 11 furthest from the microphone head in front of the diaphragm 31, creating a phase difference and causing destructive interference. This disrupts the standing wave formation conditions and eliminates or weakens high-energy resonance peaks and valleys. Since the target sound wave is on the same axis as the diaphragm 31 and there is no deflection angle between the incident angle and the axis, it will not interfere with or cancel out the sound waves entering from the slots, thus maintaining high-quality, clear recording of the target sound wave. Therefore, the target sound source signal received by the diaphragm 31 remains pure, and the microphone achieves a flat frequency response and stable supercardioid directivity.
[0023] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in this utility model, based on the technical solution and concept of this utility model, should be included within the protection scope of this utility model.
Claims
1. A multi-faceted perforated interference tube for a directional microphone, wherein the interference tube is a hollow circular tube structure, installed in front of the microphone head, with one end of the tube away from the microphone head facing the target sound source, and the other end of the tube closer to the microphone head for mounting the microphone head, characterized in that... Several groove groups are evenly distributed along the axial direction on the circumferential wall of the circular tube. Each groove group contains several through grooves that are evenly distributed around the circumferential wall of the circular tube and are parallel to each other. The width of the slots in adjacent slot groups decreases from the end furthest from the microphone head to the end closest to the microphone head, making the slots furthest from the microphone head end the widest and the slots closest to the microphone head end the narrowest. The slot and the circular tube form an irregularly shaped interference tube cavity, which is used to introduce ambient sound waves into the tube through a dispersed path, and interfere with non-axial sound waves entering from the end away from the microphone head at the diaphragm of the microphone head, thereby disrupting the standing wave conditions formed by the continuous smooth inner wall of the tube and suppressing the generation of high-energy standing waves and resonance peaks and valleys.
2. The multi-faceted perforated interference tube for a directional microphone as described in claim 1, characterized in that, The outer wall of the circular tube is covered with a layer of acoustic damping material, which simultaneously seals all the outer openings of the slots, allowing external sound waves to enter the internal cavity of the circular tube through the acoustic damping material layer and the slots. The slots and the acoustic damping material layer together form a sound wave entry channel.
3. A multi-faceted perforated interference tube for a directional microphone as described in claim 2, characterized in that, The acoustic damping material layer is an acoustic mesh with a constant flow resistance value. The acoustic mesh continuously covers the outer wall of the circular tube and provides the same acoustic damping for all slots.
4. A multi-faceted perforated interference tube for a directional microphone as described in claim 1, characterized in that, The circular tube has a continuous cavity inside and no inner tube structure. The slot and the end away from the microphone head are the only channels for sound waves to enter.
5. A multi-faceted perforated interference tube for a directional microphone as described in claim 1, characterized in that, The number of slot groups is three, and each slot group includes four slots.
6. A multi-faceted perforated interference tube for a directional microphone as described in claim 1, characterized in that, Structural reinforcement bars are provided between adjacent slots within the same slot group.