脉冲法测半透声障板的插入损失

本文介绍一种用脉冲响应技术测量条形隔声障板插入损失的方法,其中包括基于惠更斯原理和基尔霍夫公式的理论计算以及同该脉冲法所进行的实际测量结果的比较.预测值和实测值有着较好的吻合.该测量方法的最大优点是不需要特殊的声学设施,并且整个系统可满足便携要求.同时本文还给出了标准ISO140^[1]测量得到的结果.     

水声无源材料插入损失虚拟聚焦测量方法

提出了一种适合在有限尺寸水池中测量水声材料插入损失的方法,称为\     

The insertion loss of perforated porous plates in a duct without and with mean air flow

Measurements of the acoustic insertion loss of poroelastic plates with different perforation ratios, mounted transversely across a flow duct, without and with flow have been made at various locations in the duct. For the lower perforation ratio the insertion loss is found to be approximately 3 dB higher with air flow than without over the frequency range of the measurements. A parallel impedance model has been formulated to predict the effects of perforation on the insertion loss without flow. Measurements and predictions without flow have been found to be in reasonable agreement.     

水声材料透声性能测量技术的改进

本文对传统的水声无源材料透声性能测量技术提出了几点改进,以便在小型消声水池中测量有限尺寸的大面积材料的插入损失（透射系数）随频率的变化规律。材料样品的典型尺寸为 １×１ｍ２左右,测量频率范围为 ２－２０ ｋＨｚ．文中对标准样品进行了声学性能测量,测量结果和平面波理论模型计算值有较好的吻合。     

具有单相单向换能器的水平剪切声表面波压力传感器插入损耗特性

为实现水平剪切声表面波压力传感器低损耗设计,系统研究了均匀叉指换能器(IDT)和单相单向换能器(SPUDT)器件的声波能量损耗性能。在确定最优反射系数的SPUDT结构的基础上,建立3D周期性有限元仿真模型,计算器件表面振动位移和双向输出电压瞬态响应。通过对电压信号进行傅里叶变换获得器件模型的插入损耗,并制备两种不同换能器的声学传感器,测试其频率特性和灵敏度。与均匀IDT相比,基于SPUDT器件插入损耗的仿真和实验结果分别降低了5.2 dB和5.6 dB,SPUDT器件灵敏度约为均匀IDT器件的两倍。结果表明,SPUDT能有效降低SH-SAW压力传感器声波能量的单向损耗,提高检测灵敏度,且构建的3D周期性有限元仿真模型有助于声学传感器的声波损耗分析,实现高精度和小型化的声学测量系统。     

A concise design of 16 × 16 polymer AWG with low insertion loss and crosstalk

In this paper, a 16-channel arrayed waveguide grating multiplexer (AWG) has been designed using polymer materials with 1.5% refractive index difference. Certain important parameters are optimized using the coupling mode theory and Beam Propagation Method. The factors that affect the insertion loss and the crosstalk are analyzed in this paper. In our design we introduced the parabolic taper structure and evaluated the suitable number of the arrayed waveguide, obtaining a total insertion loss of 2.19 dB. For obtaining a low crosstalk we evaluate the pitches of adjacent input/output waveguides ΔX and arrayed waveguides d as different values. We chose the value of ΔX about 2.5 times of d by enlarging the pitches of adjacent input/output waveguides. The crosstalk of the designed AWG is lower than −40 dB.     

脉冲响应法测量混响时间技术的研究

本文介绍了一种根据厅堂脉冲响应特性,利用计算机数字信号处理技术,迅速,准确地测量混响时间的实现方法。     

1.3μm光学环行器正向损耗及反向隔离比的理论及实验研究

在理论及实验上分析了影响光环行器插入损耗及反向隔离比的因素,讨论了环行器中起、检偏镜参数对其性能的影响.结果表明,起、检偏镜的各组参数存在最佳选择,以保证环行器具有低插损、高隔离比及与偏振无关的特性.作者研制的环行器正向损耗小于1dB,反向隔离比在25.5dB与28dB之间.     

A further study of a mathematical model for a screen in open-plan offices

In order to obtain a good acoustical environment in open-plan offices, the acoustic performance of a single screen needs to be well estimated. Based on the sound pressure or the sound energy summation, the models proposed by previous investigators provided the predictions of the speech intelligibility index (SII) at the receivers behind a single screen in the open-plan offices. In the development of these models, the expression describing the diffracted field of a screen was an empirical formula and the sound diffraction is assumed to be appeared in the shadow region of the screen. In the present study, the MacDonald analytical formula is applied to describe the diffracted field of a screen, and both the diffractions in the visible region and in the shadow region are considered in the proposed model though it seems that the diffraction in the visible region is small compared with that in the shadow region. The comparison of the predicted and experimental results of the Wang and Bradley and the predicted results of the improved model shows that the improved model can provide a more accurate prediction, and further calculations indicate that the improvement is mostly due to the application of the MacDonald analytical diffraction formula.     

新型高性能光控高温超导微波可变衰减器研制

 提出了一种用于高温超导系统的新型星载光控高温超导微波可变衰减器，详细介绍了设计过程，并针对测试结果进行了分析。该衰减器的实质是利用液氮温区高温超导薄膜极低的微波表面电阻和卓越的激光响应特性，实现优良的衰减功能。在器件结构的设计上引入过渡材料和透明有机材料以保证器件良好的接地性能以及激光光束的对准。主要结论如下：光控高温超导微波可变衰减器在液氮温区工作，电路尺寸为12 mm×8 mm×0.5 mm，可单独使用也可集成于高温超导系统中，可大幅减小系统的体积与质量；高温超导衰减器的插损小于0.2 dB，比常规衰减器低1个量级；高温超导衰减器的可变衰减步进值小于0.01 dB，比常规衰减器低1～2个量级。根据激光功率大小对衰减器插损变化特性的影响，该衰减器也可以实现步进式调谐。     

Insertion loss prediction of floating floors used in ship cabins

In this paper, vibration reduction in ship cabins by using floating floor is studied. Two theoretical models are developed and predicted insertion losses of floating floors are compared to experimental results, where measurements are done in the mock-up built for simulating typical ship cabins. The floating floor consists of upper board and mineral wool, which is in turn laid on the deck plate. The first model (M-S-Plate Model) is that upper plate and mineral wool are assumed as a one-dimensional mass-spring system lying on the simply supported elastic floor. The second model (Wave Model) is that mineral wool is assumed as elastic medium, in which longitudinal wave propagates. The comparisons show that M-S-Plate model is in good agreement with experimental results, while mass-spring model on the rigid floor behaves very poorly in the low frequency ranges, particularly near the natural frequency associated with mass-spring system. On the other hand, the wave model significantly underestimates the insertion loss. It is found that including elastic behavior of the deck plate is essential in improving accuracy of the insertion loss prediction for low frequency range below 100-200 Hz.     

Y型光波导分束比和插入损耗测量技术研究

Y波导在集成光学系统中得到了广泛的应用,并拥有很大的潜力,近年来备受关注。因此了解它的各项指标至关重要。在Y波导的诸多指标中,分束比和插入损耗是2个重要指标。着重介绍了2个指标的测量装置及测量方法。对于分束比,分别采用波长为1300nm和1550nm的激光光源测量Y波导两尾纤的输出光功率。根据公式计算出分束比后,分析影响测量结果的主要因素,进行测量不确定度评定。对于插入损耗,主要是按照测量原理搭建测量装置,从理论上分析影响插入损耗测量的因素。通过对Y波导2个指标的测量,有助于更好地了解Y波导的性能。     

Scale model study of balcony insertion losses on a building façade with non-parallel line sources

The screening effect of balconies on a building façade in the case where the noise source is not parallel to the façade is studied using scale model experiment in the present study. Results show that the angle of source inclination to the façade has substantial effects on the balcony insertion loss in the presence of a traffic noise spectrum. Less amount of noise amplification is observed when the source is inclined compared to the case of parallel source in the presence of balcony ceiling reflections. Regression formulae in terms of three independent angles which determine the positions of the balcony and its ceiling relative to the noise source are developed for the prediction of balcony insertion loss. The discrepancy between measurements and predictions is within engineering tolerance.     

Insertion loss of sound waves through composite acoustic window materials

This study evaluated the insertion loss of sound waves through composite acoustic window materials for sonar dome applications, and examined the influence of dome shape on the sonar performance. The insertion loss of sound waves through acoustic window materials was experimentally measured as a function of frequency at normal incidence. The insertion loss was also theoretically estimated with three- and four-medium layer models. The theoretical estimation of insertion loss showed good agreement with the experimental measurements. The insertion loss was also measured as a function of angle of incidence. The characteristics of longitudinal and converted shear waves were observed at various angles of incidence. This study will be useful to select acoustic window materials with the appropriate acoustic characteristics for practical sonar dome applications.     

Reduction of insertion loss after annealing of silicon oxynitride optical waveguides

The insertion losses of silicon oxynitride (SiON) waveguides have been measured in the 1550 nm wavelength region. The waveguide structure consisted of a 2.0μm SiON waveguide core with a refractive index of 1.50, a 0.5μm SiO₂ upper cladding and a 5.0μm SiO₂ lower cladding with a refractive index of 1.45. It was found that the wavelength-dependent insertion losses of the waveguide were greatly reduced by annealing, and the loss was decreased more than 5.7 dB/cm at 1550 nm after annealing at optimum conditions. The former was attributed to the reduction of the absorption caused by N-H and Si-H vibration modes, and the latter was due to the improvement of the interface roughness and homogeneity in the waveguides after annealing.     

Multiple-scale analysis of open quantum systems

In this work, we present a multiple-scale perturbation technique suitable for the study of open quantum systems, which is easy to implement and in few iterative steps allows us to find excellent approximate solutions. For any time-local quantum master equation, whether markovian or non-markovian, in Lindblad form or not, we give a general procedure to construct analytical approximations to the corresponding dynamical map and, consequently, to the temporal evolution of the density matrix. As a simple illustrative example of the implementation of the method, we study an atom-cavity system described by a dissipative Jaynes-Cummings model. Performing a multiple-scale analysis we obtain approximate analytical expressions for the strong and weak coupling regimes that allow us to identify characteristic time scales in the state of the physical system.     

测量白油中声透射损失的教学实验装置

通过实验发展：在测量范围内，声透射损失随含气量线性增大。在气泡大小、分布一定的情况下，可以由声透射损失来测量油中的含气量。     

MIRE-IL methodology applied to measuring the noise attenuation of earmuff hearing protectors

This article describes an objective methodology for measuring the noise attenuation of earmuff hearing protectors using as a reference the method known as microphone-in-real-ear (MIRE). The methodology implements the insertion loss (IL) paradigm, in which IL is measured using miniature microphones, specially designed to comply with ANSI and ISO standards for the MIRE technique. The results for four different hearing protectors are compared with the subjective method known as real-ear-attenuation-at-threshold (REAT). Correction factors are included in the methodology to account for external effects such as physiological noise and bone conduction. The objective method predicted well the real protection of the earmuffs and the proposed methodology showed lower standard deviation values than the REAT method.     

An investigation on the acoustic characteristics of microperforated muffler

I.lntroductionTheac0usticperformanccofmicropcrforatedmumerhasbeengreatlynoticedinre-ccntyears.Especially,itshighsi1encingva1ueandbroadsi1encingfrequencyrangeenableittobeusedwidelyinmanyyiclds,suchasvehicleexhaustsystem,ventilator.Butitisdifficulttodesignagoodsilcnccrbecauseoritscomp1exacousticperformanccwithinPerforatedtubes.Thegoverningwaveequationofmicroperforatedmufflerisnotlinearduetothenonuniformmassflowofgasaswc11asthetcmpcraturegradientalongthePerforatedducts.Inordertoutilizethegoodsi…