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1.
关于微穿孔板吸声体频带宽度极限的讨论   总被引:2,自引:1,他引:1       下载免费PDF全文
焦风雷  刘克  丁辉 《应用声学》2001,20(6):36-40
依据马大猷教授的微穿孔板吸声体准确理论,利用计算机辅助设计对于该结构频带宽度极限情况从理论上进行了讨论,把极限频宽和最大吸声系数的制约关系量化,并得到此情况下应用于低频或高频环境孔径的选用范围,以及此情况下板厚和穿孔率与传统观念不同的特点。以上分析结果以及所提供的结构参数为宽频带微穿孔板的具体设计提供有价值的参考。  相似文献   

2.
微穿孔板吸声结构是由微穿孔板与板后空腔组成的共振吸声结构,被认为是继多孔吸声材料之后发展起来的最有吸引力的吸声结构,其吸声特性与结构参数孔径d、板厚t、孔距b及空腔深度D有关,如何按需设计一个有效的微穿孔板吸声结构已成为目前研究的热点。本文从微穿孔板吸声结构和吸声特性混合设计的角度出发,使用面向对象的编程语言C++开发了微穿孔板吸声结构设计平台。与以往设计方法不同,本文开发的软件平台综合考虑了结构参数和吸声特性参数两方面的限制,根据实际应用要求平衡微穿孔板吸声结构的最大吸声系数与吸声带宽之间的制约关系,并以饱满的吸声曲线为目标,提供满足混合设计要求的优化结构参数。  相似文献   

3.
本文对一种新型声村一通气声村的声学特性进行了实验研究。首先,根据实验装置的实际结构给出了通气声村反射系数的理论计算公式,并使用不同孔径和穿孔率的穿孔板考察了通气声衬的特性参数随频率和气流速度的变化规律,理论与实验符合得较好,其结果表明:适当地选择声衬的几何参数和气流速度可以使通气声衬在共振频率处的吸声系数达到或接近于1.0。其次,本文对共振式声衬和通气声衬的特性进行了比较,对于大孔径穿孔板,前者的吸收频带较窄,而通过合理选择通气速度,则可以设计出高吸声系数和宽频带的通气声衬。最后,本文还对相同几何参数的穿孔板进行了吹气和吸气的对比实验。  相似文献   

4.
微穿孔板的实际极限   总被引:13,自引:3,他引:13  
马大猷 《声学学报》2006,31(6):481-484
对微穿孔板吸声器的构造和吸声特性进行了分析。曾认为低穿孔常数和孔径小可导致宽频带内的高吸声特性。为求得极限,从穿孔系数为1,孔径0.1 mm开始,因为负载声阻和吸声系数可接近1,高吸声系数的共振频率可达1000 Hz,高频率可在吸声范围之内。单片微穿孔板可否用于平常噪声控制,在宽频带内吸声较大?为了比较,半吸声带宽不适用,因为可能包括低吸声系数。建议用吸声系数0.5作为实际吸声底线,为比较微穿孔板的统一标准。更以吸声系数的频率曲线以进行详细比较。负载声阻为1(声阻等于空气特性阻抗)时,微穿孔板的吸声范围约为2.5倍频程,比常用的微穿孔板稍好。负载声阻大于1时,吸声的频率范围显著增加,有些适合宽频带高吸收的要求。将其实现可能是微穿孔板吸声器的重大发展。  相似文献   

5.
沈苏  Goran Pavi 《声学学报》2011,36(3):281-290
将微穿孔板吸声结构应用到外加旁支管路的管道声源特性测量方法中,分析和仿真了单层及双层微穿孔板及其后腔结构采用不同参数(板厚、微孔直径、穿孔率、后腔深度等)时改变管道负载声阻抗的作用和影响.研究结果表明:改变板厚、微孔直径、穿孔率、管道横截面积比等参数,可以有效地改变负载声阻;改变后腔深度及微穿孔板与主体管道之间距离,可...  相似文献   

6.
王卫辰  冯军  马然 《声学学报》2021,46(5):721-729
微穿孔板几何参数的耦合性及其对整体吸声性能的影响,对于设计微穿孔板吸声体和优化其工作性能具有指导作用。根据微穿孔板吸声体基本理论,研究了穿孔率和穿孔直径双参数耦合作用下微穿孔板吸声体的整体吸声性能。穿孔率和穿孔直径之间的耦合性与其本身取值密切相关,而与板厚和板后腔深无明显关系;在穿孔率-穿孔直径参数域上,吸声体存在吸声系数为1.0的吸收峰,整体吸声性能随穿孔率或穿孔直径从小到大变化,呈现出先增强后减弱的变化趋势。该结论能够准确解释微穿孔板受粉尘污染后吸声性能的变化规律和演变路径。论文的工作为设计微穿孔板吸声体提供了一种新的理论依据和实施方法。   相似文献   

7.
微穿孔板吸声结构水下应用研究   总被引:2,自引:0,他引:2       下载免费PDF全文
王泽锋  胡永明  倪明  罗洪 《应用声学》2008,27(3):161-166
马大猷教授提出的微穿孔板吸声结构在空气噪声降低和隔离方面得到了广泛的应用,但未见水下应用的相关研究和报道。本文将空气中微穿孔板理论应用到水中,得到了水下微穿孔板吸声结构的吸声公式。通过理论分析,得出了微穿孔板结构直接应用于水中无法获得宽频吸收的结论。提出了通过匹配液将微穿孔板间接应用到水下的设想。设计了单层板和双层板吸声结构,并对它们的吸声特性进行了理论分析与仿真。结果表明,本文设计的微穿孔板吸声结构在水中能够获得优于空气中的宽频带吸声效果。实验测量了自制的微穿孔板吸声结构,吸声系数的测量值与理论曲线基本吻合,从而验证了理论分析的正确性。  相似文献   

8.
微穿孔板声阻抗的直接准确测量   总被引:5,自引:0,他引:5  
微穿孔板吸声结构的构造简单,适用范围广,吸收特性好并且可以比较准确地预计和设计。它的性能主要由微穿孔板的声阻和声质量决定。为了可靠地估计微穿孔板结构的性能,微穿孔板的准确特性是必要的。在本文中,作者提出直接测量微穿孔板声阻抗的简单方法(这方法也适用于一般穿孔板,或在一定范围内适用于一般吸声村料),由于直接了当地分别测出声阻和声抗,不必经过任何转换,所得结果可达到比一般方法更为准确的程度。应用这个方法,对微穿孔板的阻抗特性进行了测量,得到线性和非线性的现象。在本文中,将报告一些初步成果。  相似文献   

9.
一种微穿孔板消声器   总被引:3,自引:0,他引:3       下载免费PDF全文
本文根据马大猷教授提出的“微穿孔板吸声体精确理论”,在对微穿孔板消声器结构参数与吸声特性之间的相互影响进行了分析的基础上,设计了微穿孔板消声器并将其应用在新舟60飞机APU(辅助动力装置)降噪的实际工程中,并通过编写的噪音数据采集分析程序,对降噪效果进行了测试和分析,验证出微穿孔板消声器对消除飞机的APU的排气噪声具有良好的消声效果,平均降噪7.16dB。  相似文献   

10.
穿孔板的声学厚度修正   总被引:4,自引:0,他引:4  
康钟绪  季振林 《声学学报》2008,33(4):327-333
使用有限元法计算穿孔板的声学厚度修正系数,研究穿孔率、穿孔板厚度、孔径和穿孔排列形式对声学厚度的影响,获得了穿孔率低于40%的穿孔板的声学厚度修正系数.计算结果表明:穿孔板厚度、孔径和排列形式对声学厚度的影响不大;穿孔率对声学厚度影响很大.基于数值计算结果给出了声学厚度修正系数的近似表达式,利用由该表达式形成的穿孔声阻抗公式计算了穿孔管消声器的传递损失,计算结果与实验结果吻合良好,从而验证了应用该表达式预测穿孔管消声器消声性能的准确性.  相似文献   

11.
针对管道内低频噪声难以抑制的问题,本文基于亥姆霍兹共振腔(HR)阵列吸声板和穿孔管消声器组合,设计了一种复合式宽带消声器。首先利用有限元法仿真分析传统穿孔管消声器,发现中低频消声能力较差,通过嵌入HR阵列吸声板吸收中低频噪声。采用仿真与实验的方式研究吸声板的声学性能:在400-1000 Hz频段内的平均吸声系数达到了0.88。然后对复合式消声器进行数值模拟及3D打印阻抗管实验测试对比:复合式消声器在400-1718Hz频率范围内的平均传递损失为18.15 dB ,最终实现了管道内全频带噪声有效控制。  相似文献   

12.
管束穿孔板的管腔耦合共振吸声机理研究   总被引:1,自引:0,他引:1  
苏玉  梅中建  吕亚东  程晓斌 《声学学报》2021,46(6):1202-1211
为了揭示管束穿孔板共振吸声结构的吸声机理,利用热黏性条件下基于有限元算法的管束穿孔板仿真模型,研究了平面声波正入射条件下,管束穿孔板内部声场分布特征,并利用阻抗管对吸声系数的理论仿真结果进行了试验验证.结果表明,管束穿孔板在低频主要靠腔体共振吸声,在高频主要靠管共振吸声,管束穿孔板整体呈现出较为明显的管腔耦合共振吸声特征。管束穿孔板共振时管中声强和质点法向振速较大,高频次吸声峰频点处管中和腔中均有驻波形成,频率越高驻波数量越多.管束穿孔板的耦合共振受到管长、腔深、穿孔率和管内径等参数变化的影响,管长对高频耦合共振的影响最大,管长增大使高频主吸声峰频点移向低频,并使相邻主吸声峰之间的间距减小.   相似文献   

13.
针对普通薄膜型降噪结构的吸声性能较差和吸声带宽较窄的问题,本文设计了一种微穿孔的介电弹性体薄膜吸声结构。该结构由穿孔的介电弹性体薄膜与背腔组合而成,目的是拓宽介电弹性体薄膜低频率段的吸声带宽。针对微穿孔的介电弹性体薄膜吸声结构,从试验角度分析穿孔薄膜初始厚度、穿孔孔径及穿孔间距对结构吸声性能的影响。分析结果可知:通过适当增加薄膜的初始厚度,薄膜的整体吸声性能得到有效提升,最大可将319Hz吸声频带的吸声系数从0.2提升至0.7;减小薄膜的穿孔孔径能够有效拓宽穿孔薄膜的吸声频带,可使吸声系数0.4以上的吸声带宽由304Hz拓宽至432Hz;适当控制穿孔间距能够达到更好的吸声效果。  相似文献   

14.
吴勇 《声学学报》2021,46(5):712-720
推导出穿孔管消声器声学长度修正以及共振频率的理论公式。证明了在均匀分布情况下,多小孔向膨胀腔声辐射与单个小孔向膨胀腔声辐射的声学长度修正系数是一致的。对于小孔向主管道的声辐射,根据理论公式研究了穿孔率、周向均布数以及亥姆赫兹数对声学长度修正的影响,有限元计算得出在直径比小于0.4的情况下声学长度修正系数理论公式与仿真计算结果吻合良好。并利用理论公式的性质以及仿真结果获得了实用的拟合公式,提升了穿孔管消声器在高频时共振频率的计算精度。   相似文献   

15.
This paper studies the basic characteristics of sound fields in urban squares surrounded by reflecting building fa?ades and the effectiveness of architectural changes and urban design options. A radiosity model and an image source model are developed, and a parametric study is carried out in hypothetical squares. The results show that the reverberation time (RT) is rather even in a square, whereas the early decay time (EDT) is very low in the near field, and then becomes close to RT after a rapid increase. Compared to diffuse boundaries, with geometrical boundaries the RT and EDT are significantly longer and the sound pressure level (SPL) attenuation with distance is generally smaller unless the height/side ratio is high. With a boundary diffusion coefficient of 0.2, the sound field is already close to that resulting from purely diffusely reflecting boundaries. The SPL in far field is typically 6-9 dB lower if the square side is doubled; 8 dB lower if the height of building fa?ades is decreased from 50 m to 6 m (diffuse boundaries); 5 dB (diffuse boundaries) or 2 dB (geometrical boundaries) lower if the length/width ratio is increased from 1 to 4; and 10-12 dB lower if the boundary absorption coefficient is increased from 0.1 to 0.9.  相似文献   

16.
An experimental investigation of the onset of detonation   总被引:2,自引:0,他引:2  
An experimental configuration is devised in the present investigation whereby the condition at the final phase of the deflagration to detonation transition (DDT) process can be generated reproducibly by reflecting a CJ detonation from a perforated plate. The detonation products are transmitted downstream through the plate, generating a turbulent reaction front that mixes with the unburned mixture and that drives a precursor shock ahead of it at a strength of about M = 3. The gasdynamic condition that is generated downstream of the perforated plate closely corresponds to that just prior to the onset of detonation in the DDT process. The turbulence parameters can be controlled by varying the geometry of the perforated plate; thus, the condition leading to the onset of detonation can be experimentally investigated. A one-dimensional theoretical analysis of the steady wave processes was first performed, and the experimental results show good agreement, indicating that the present experimental condition can be theoretically described. Two different detonation tube geometries (one with a square cross-section of 300 mm by 300 mm and the other with a circular cross-section of 150 mm) are used to demonstrate the independence of the tube diameter at the critical condition for DDT. Perforated plates with different hole diameters (d = 8, 15, and 25 mm) were tested, and the hole spacing to hole diameter ratio was maintained at 0.5. Different hydrogen–air mixtures were tested at normal temperature and pressure. For the plate with 8 mm holes, the onset of detonation is never observed. For the plate with 15 mm holes, successful initiation of a detonation is achieved for 0.8 < < 1.75 in both detonation tubes. For the plate with 25 mm holes, detonation initiation is observed for 0.7 < < 2.1 in the square detonation tube and for 0.8 < < 1.6 in the smaller circular detonation tube.  相似文献   

17.
Developing efficient sound absorption materials is a relevant topic for large scale structures such as gymnasiums, shopping malls, airports and stations. This study employs artificial neural network (ANN) algorithm to estimate the sound absorption coefficients of different perforated wooden panels with various setting combinations including perforation percentage, backing material and thickness. The training data sets are built by carrying out a series of experimental measurements in the reverberation room to evaluate the sound absorption characteristics of perforated wooden panels. A multiple linear regression (MLR) model is also developed for making comparisons with ANN. The analytical results indicate that the ANN exhibits satisfactory reliability of a correlation between estimation and truly measured absorption coefficients of approximately 0.85. However, MLR cannot be applied to nonlinear cases. ANN is a useful and reliable tool for estimating sound absorption coefficients estimation.  相似文献   

18.
Yang Kang 《中国物理 B》2022,31(10):104701-104701
Acoustic characteristics of the detonation sound wave generated by a pulse detonation engine with an annular nozzle, including peak sound pressure, directivity, and A duration, are experimentally investigated while utilizing gasoline as fuel and oxygen-enriched air as oxidizer. Three annular nozzle geometries are evaluated by varying the ratio of inner cone diameter to detonation tube exit diameter from 0.36 to 0.68. The experimental results show that the annular nozzles have a significant effect on the acoustic characteristics of the detonation sound wave. The annular nozzles can amplify the peak sound pressure of the detonation sound wave at 90° while reducing it at 0° and 30°. The directivity angle of the detonation sound wave is changed by annular nozzles from 30° to 90°. The A duration of the detonation sound wave at 90° is also increased by the annular nozzles. These changes indicate that the annular nozzles have an important influence on the acoustic energy distribution of the detonation sound wave, which amplify the acoustic energy in a direction perpendicular to the tube axis and weaken it along the direction of the tube axis.  相似文献   

19.
Recently, a linear compressor has been actively developed to improve the energy efficiency of home appliances, such as refrigerators. Unlike a reciprocating compressor, the suction part of a linear compressor is periodically moving. Therefore, the suction valve and the muffler constituting the suction part are periodically moving. However, up to now, there has been no research into the characteristics of the sound propagation in a periodically moving acoustic system. Thus, in this study, characteristics of sound propagation in a periodically moving acoustic system were investigated for the first time. Among a variety of acoustic filters used in a suction muffler, the change in the orifice impedance has been observed because this change is considered to be easily affected by periodically moving. Due to difficulty in measuring the orifice impedance in a periodically moving acoustic system, the change in the orifice impedance was predicted from the change in the input impedance of the suction muffler that included orifice. The experiments were carried out while changing the diameter and the pattern of orifice as well as length of the duct. As a result of experiments, the impedance of periodically moving orifice was changed depending on diameter, pattern of orifice and frequency band. Therefore, if periodically moving orifice was used to design a suction muffler in linear compressor or acoustic system, the change in the orifice impedance should be taken into consideration.  相似文献   

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