Software for Acoustic Design

We present the СATEС software, which implements the solution to the problems of computational acoustics. The software is based on the use of the superelement method and finite element modeling algorithms, in-cluding hydrodynamic noise. The paper presents the main possibilities of software for solving acoustic design problems. .

Acoustic design sensitivity analysis of structural sound radiation

This paper presents an acoustic design sensitivity(ADS)analysis on sound radiation of structures by using the boundary element method(BEM).We calculated the velocity distribution of the thin plate by analytical method and the surface sound pressure by Rayleigh integral,and expressed the sound radiation power of the structure in a positive definite quadratic form of the Hermitian with an impedance matrix.The ADS analysis of the plate was thus translated into the analysis of structure dynamic sensitivity and impedance matrix sensitivity.Finally,taking a simple supported thin plate as a simulation example,we investigated the relationships among the sound power,excitation frequency and thickness of the plate.The sound radiation power of the plate has a sharp rise in the vicinity of the plate natural frequency.The method proposed is verified to be able to predict the sound radiation of a thin plate with arbitrary boundary conditions and provide a theoretical basis for structural low noise design which is important to engineering design.

Acoustic design and research on the auditorium of Shanghai Grand Theatre

Shanghai Grand Theatre is a great modern theatre with the largest formula, the highest investment, the most advanced technique and excellent acoustic quality in China. This article mainly introduced Shanghai Grand Theatre's characteristics of formula, technical requirements of acoustic design of Auditorium, characteristics of figure design, reverberation control, acoustic simulation research, acoustic performance and subjective evaluation.

Acoustic design of Beijing Theater

Beijing Theater, with a capacity of 1,000 seats, is a multipurpose theater mainly for dramatic performances. To meet the acoustic criteria of different kinds of performances, adjustable sound absorption structures are installed in the hall. Special consideration has been given to the sound diffusion for gratifying natural sound effect of mustic performance. In addition, a movable orchestra shell and a lifting orchestra pit have also been employed. In this paper, the authors discuss the acoustic design of the Theater and the success achieved to testify the necessity and possibility of multi-purpose utilization in acoustics in an auditorium .

Acoustic design of the Gymnasium and Natatorium of Chinese National Olympic Sports Center

The proper control over the reverberation times is of vital importance to acoustic design of large-sized gymnasium. In the projects discussed in this paper gratifying reverberation times have been obtained by employing space absorbers suspended under the exposed space frame and strong absorbing structures mounted on the side walls. Some suggestions concerning acoustic design of large-sized gymnasia and natatoria are made on the basis of the practical experience gained from the projects.

Optimization Design for the Sandwich Piezoelectric Transmitters in Acoustic Logging

An optimized transducer prototype with a sandwich structure vibrated longitudinally is proposed for a transmitter in acoustic logging, especially in acoustic logging while drilling, 5y taking account of drilling environments with high temperature and pressure, as well as strong collar drilling vibration during the drilling process. Aimed to improve the transmitting performance, numerical and experimental studies for the transducer optimization are conducted. The impact of location and length of the piezoelectric stack on resonance characteristics arid effective electromeehanical coupling coefficient is calculated and analyzed. Admittance and transmitting performance of the proposed transducer are measured in laboratory experiments, and the results are compared with simulated ones. It is shown that the newly proposed transducer has higher transmitting performance with lower resonance frequencies. This work provides theoretical and experimental bases for transducer designing and acoustic wave measurements in acoustic logging, especially in acoustic logging while drilling.

Design of an Acoustic Levitator for Three-Dimensional Manipulation of Numerous Particles

We present a design of an acoustic levitator consisting of three pairs of opposite transducer arrays.Three orthogonal standing waves create a large number of acoustic traps at which the particles are levitated in mid-air.By changing the phase difference of transducer arrays,three-dimensional manipulation of particles is successfully realized.Moreover,the relationship between the translation of particles and the phase difference is experimentally investigated,and the result is in agreement with the theoretical calculation.This design can expand the application of acoustic levitation in many fields,such as biomedicine,ultrasonic motor and new materials processing.

Toward Estimating the Variance in Acoustic Surveys Based on Sampling Design

This paper develops a sampling method to estimate the integral of a function of the area with a strategy to cover the area with parallel lines of observation. This sampling strategy is special in that lines very close to each other are selected much more seldom than under a uniformly random design for the positions of the parallel lines. It is also special in that the positions of some of the lines are deterministic. Two different variance estimators are derived and investigated by sampling different man made signal functions. They show different properties in that the estimator that estimate the biggest variance gives an error interval that, in some situations, may be more than ten times the error interval computed from the other estimator. It is also obvious that the second estimator underestimates the variance. The author has not succeeded to derive an expression for the expectation of this estimator. This work is motivated towards finding the variance of acoustic abundance estimates.

Design of elliptical underwater acoustic cloak with truss-latticed pentamode materials

Pentamode acoustic cloak is promising for underwater sound control due to its solid nature and broadband efficiency,however its realization is only limited to simple cylindrical shape.In this work,we established a set of techniques for the microstructure design of elliptical pentamode acoustic cloak based on truss lattice model,including the inverse design of unit cell and algorithms for latticed cloak assembly.The designed cloak was numerically validated by the well wave concealing performance.The work proves that more general pentamode acoustic wave devices beyond simple cylindrical geometry are theoretically feasible,and sheds light on more practical design for waterborne sound manipulation.

Meta-silencer with designable timbre

Timbre,as one of the essential elements of sound,plays an important role in determining sound properties,whereas its manipulation has been remaining challenging for passive mechanical systems due to the intrinsic dispersion nature of resonances.Here,we present a meta-silencer supporting intensive mode density as well as highly tunable intrinsic loss and offering a fresh pathway for designable timbre in broadband.Strong global coupling is induced by intensive mode density and delicately modulated with the guidance of the theoretical model,which efficiently suppresses the resonance dispersion and provides desirable frequency-selective wave-manipulation capacity for timbre tuning.As proof-of-concept demonstrations for our design concepts,we propose three meta-silencers with the designing targets of high-efficiency broadband sound attenuation,efficiency-controlled sound attenuation and designable timbre,respectively.The proposed meta-silencers all operate in a broadband frequency range from 500 to 3200 Hz and feature deep-subwavelength sizes around 50 mm.Our work opens up a fundamental avenue to manipulate the timbre with passive resonances-controlled acoustic metamaterials and may inspire the development of novel multifunctional devices in noise-control engineering,impedance engineering,and architectural acoustics.

柴油机油底壳穿孔板隔声罩优化设计

以某型柴油机的油底壳作为研究对象,对其声振特性进行识别与分析,确定设计穿孔板隔声罩的共振频带范围。使用粒子群算法针对共振频率进行穿孔板参数的优化设计,再通过阻抗管试验确定小孔分布对吸声性能的影响,并对穿孔板隔声罩进行多目标形貌优化设计以避开共振及激励频率。目标柴油机上加装优化的油底壳穿孔板隔声罩后,整机总声压级降低0.5 d B,降噪效果较好。

基于CFD仿真的炮口制退器性能影响因素研究

目的 在降低火炮后坐力的同时,保证炮手区域超压和温度符合要求。方法 利用流体仿真软件进行炮口流场的数值模拟,对制退器性能影响因素进行仿真分析。根据分析结果,得到改进后的制退器模型,并进行仿真和试验对比。结果 加装侧孔外反射挡板和侧孔倾斜对制退器性能的影响较大,并随角度的变化而变化,加装吹孔能有效降低炮后超压和温度。改进后,制退器的效率提升8.33%,炮后超压值平均降低44.10 kPa,炮后温度值平均降低358.28 K。结论 改进后的制退器具有更高的制退效率以及较低的炮后超压值和温度值。

超声波无线电能传输的声电通道设计

为了解决磁耦合方式无线电能传输技术在金属障碍环境下因涡流效应而效率低下问题,该文开展了金属障碍环境下超声无线电能传输技术研究。首先从声学的角度分析能量传输通道参数对声波透射系数的影响规律,并指导完成通道参数的配置。然后,采用同时共轭阻抗匹配技术完成通道输入端口与输出端口的阻抗匹配网络设计,并通过实验验证阻抗匹配网络的有效性。测试结果表明,该文所设计的超声波无线电能传输系统透11 mm厚304不锈钢障碍的理论最佳传输效率为68%,进行同时共轭阻抗匹配后通道的实际能量传输效率为56.25%,传输功率达51.53 W。该研究所达到的能量传输效率和传输功率均能满足绝大部分使用需求。该技术在军事、航天等领域具有较好的应用前景。

动车组头车声固耦合模态分析及多目标优化

目前针对高速列车领域声固耦合共振现象的产生机理和影响因素尚缺乏深入探讨,并且基于声固耦合共振理论的车体优化设计也需进一步开展。该研究基于模态等效和质量等效原则建立动车组头车有限元模型,分别进行结构模态、声场模态和考虑内外声场影响的声固耦合模态分析。分析结果表明:结构模态频率符合头车设计规范;声场模态存在与结构模态相近的特征频率,为后续耦合共振优化提供依据;内外声场的耦合作用导致结构和声场系统的模态参数变化,论证了模态分析中考虑声固耦合因素的必要性。基于模态分析结果,对动车组头车结构进行了两项优化设计:以车体质量最小化为目标,车身厚度为设计变量,在满足一阶垂弯模态频率约束条件下进行车体减重设计;为避免耦合共振影响,提取结构和声场固有频率值接近的模态阶次,将二者的频率差最大化作为优化目标,引入车体减重设计模型,形成头车轻量化与舒适性指标同步提升的多目标优化体系。

Influence of Surrounding Structures upon the Aerodynamic and Acoustic Performance of the Outdoor Unit of a Split Air-Conditioner

DC-inverter split air-conditioner is widely used in Chinese homes as a result of its high-efficiency and energy-saving. Recently, the researches on its outdoor unit have focused on the influence of surrounding structures upon the aerodynamic and acoustic performance, however they are only limited to the influence of a few parameters on the performance, and practical design of the unit requires more detailed parametric analysis. Three-dimensional computational fluid dynamics（CFD） and computational aerodynamic acoustics（CAA） simulation based on FLUENT solver is used to study the influence of surrounding structures upon the aforementioned properties of the unit. The flow rate and sound pressure level are predicted for different rotating speed, and agree well with the experimental results. The parametric influence of three main surrounding structures（i.e. the heat sink, the bell-mouth type shroud and the outlet grille） upon the aerodynamic performance of the unit is analyzed thoroughly. The results demonstrate that the tip vortex plays a major role in the flow fields near the blade tip and has a great effect on the flow field of the unit. The inlet ring＇s size and throat＇s depth of the bell-mouth type shroud, and the through-flow area and configuration of upwind and downwind sections of the outlet grille are the most important factors that affect the aerodynamic performance of the unit. Furthermore, two improved schemes against the existing prototype of the unit are developed, which both can significantly increase the flow rate more than 6 %（i.e. 100 m3·h～（-1）） at given rotating speeds. The inevitable increase of flow noise level when flow rate is increased and the advantage of keeping a lower rotating speed are also discussed. The presented work could be a useful guideline in designing the aerodynamic and acoustic performance of the split air-conditioner in engineering practice.

高速公路旁校园建筑立面声屏障设计

传统声屏障外观在降噪改造中往往显得突兀而单调,难以融入周边环境,有必要将建筑形式和景观需求相结合对声屏障形式进行一定设计。以广州市一高速公路旁某中小学为例,对校园室内外声环境现状进行实测分析,运用SoundPLAN软件对校园声环境现状进行模拟。在满足降噪效果的基础上,结合建筑立面形式和景观要求设计了3种立面声屏障,并利用Odeon Combined软件对不同设计形式的屏障进行模拟,探究其对教室内声环境的改善效果。研究表明,在门窗全开的情况下,不同形式的屏障降噪效果在5~9 dB(A)之间,对教室内语言传输指数(Speech Transmission Index,STI)的提升效果在0.09~0.15之间,能较好地缓解教室内声环境现状。

电动隐藏式外门把手噪声分析和优化设计

随着新能源汽车的发展,越来越注重车辆智能化和电动化,电动隐藏式外门把手被越来越多地应用在新能源汽车上。电动隐藏式外门把手在开启与关闭时,执行器产生工作噪声,噪声过大或声品质不好会引起用户抱怨。分析电动隐藏式外门把手工作噪声产生的原因,从外门把手本体结构、结构传递路径、空气传递路径和工作控制策略等4个方面进行分析和优化设计,有效降低电动隐藏式外门把手的本体噪声及乘客舱内的辐射噪声,对汽车电动隐藏式外门把手噪声的优化设计具有一定参考价值和指导意义。

航空发动机风扇机匣声衬与进气道声衬联合设计方法

对于现代的大涵道比涡扇发动机,风扇噪声是主要的噪声源。风扇机匣声衬(风扇前)与进气道声衬能显著降低风扇前传噪声。该两段声衬距离接近,所处的声场互相影响,有必要研究风扇机匣声衬(风扇前)与进气道声衬的联合设计方法。首先结合国内外进展,对声衬优化设计方法、声传播计算模型、声源模型、声阻抗模型、代价函数等声衬设计的关键环节进行讨论,并选择合适的方法形成一套完备的声衬设计体系与设计工具。同时,对航空发动机风扇机匣声衬(风扇前)与进气道声衬进行联合设计,得到单自由度与双自由度声衬两套方案,证明该工具的工程可行性与有效性。最后,对两种声衬方案进行了不同方面的评估,包括叶片通过频率(blade passing frequency,BPF)噪声降噪效果、宽频降噪效果等。评估表明,在该设计思路下,两方案在飞越、边线、进场前两阶BPF噪声都能得到很好的降噪效果,并且双自由度声衬能够在更宽的频率范围内显示出降噪优势。但是,如果代价函数能够进一步囊括声衬的宽频吸声效果,双自由度声衬能够具有更优的宽频降噪效果。

飞行器舱室内壁蛛网仿生薄膜声学超材料设计

飞行器舱室内部噪声对乘员及飞行操控和通信构成了显著威胁,薄膜声学超材料(MAM)在满足轻量化要求的同时具有出色的降噪性能,能够满足航空工业领域对降噪和飞行器重量的双重要求。受蛛网启发,本文通过结合膜、框和一组振子设计了一种仿生薄膜声学超材料。计算和试验结果表明,仿生模型的振子质量减少了19%,降噪带宽扩展了61%。此外,本文研究了三种设计参数(薄膜形状、振子位置和模型大小)对结构降噪性能的影响规律,并分析了其多级反共振模态。结果表明,圆形模型在降噪性能上优于两个方形模型。当振子位置在半径比为0.54时,可获得最佳的降噪性能。模型在尺寸减小时仍有较大的降噪效果,但当尺寸增大时有失效的可能。非固定框在2×2阵列模型中有助于形成反共振模态,而在3×3阵列模型中作用则相反。根据不同的频率需求调节设计参数,能够适配于飞行器内部复杂、多变的噪声环境。

基于神经网络的声学参数预测方法研究

为更加准确高效地预测建筑声学客观音质参数,该文基于机器学习的室内中频混响时间和语言传输指数的神经网络预测方法。将基于机器学习的神经网络技术与计算机声学模拟仿真技术相结合,提取800个厅堂建筑的10个典型特征参数和3个目标参数,利用Odeon声学仿真平台,针对不同音质参数指标建立多个数值矩阵训练样本数据库,采用机器学习理论对混响时间、语言传输指数等指标进行BP神经网络数据拟合训练。对训练结果的均方误差、误差分布及回归系数进行评估,结果显示混响时间参数的训练均方误差小于0.05 s,语言传输指数参数的训练均方误差小于1.5×10^(-4),所有目标参数的回归系数R值均优于0.95。评估结果表明,该神经网络具备良好的预测准确性、数据泛化性和应用适用性。经实例验证,依托该神经网络编译和封装的应用程序可以实现对目标参数的快速评价,减少人力物力,提高工作效率。