声学

However, existing systems have disadvantages of bulkiness, perplexing operation, limited position range and low precision, resulting in their incompetence of satisfying many application needs.

声学、信号处理理论逐步成熟；电子技术，如DSP、DGPS技术的发展，为我们提供了开发更先进的定位系统的可能。

St. Louis-based Solutia is touting the opportunity to use its polyvinyl butyral film inner layer with enhanced acoustic performance to shave a few millimeters of glass from windshields, which will cut about 5 pounds in weight off the average car, Leroux said.

总部位于圣路易斯的Solutia是招徕机会利用其聚乙烯醇缩丁醛薄膜内层增强声学性能的刮脸几毫米的玻璃从挡风玻璃，其中将裁员约5磅的体重从平均车，勒鲁说。

In this thesis, we consider the problem of acoustic echo cancelation for a time varying environment.

在本篇论文里，我们探讨在时变环境里声学回音消除的问题。

Then the boundary element integral equation of interior and exterior form is deduced in detail, also the form with corner coefficient. The significance for numerical calculation and principle of the singular integral is analyzed, and a non-isoparametric transformation method is presented to calculate weak singular integral and Cauchy integral, the method presented provides us a very simple way to computer the two kinds of singular integral of Helmholtz boundary integral equation, and it is easy to program in computer. After the difficulty of the calculation for multi-frequency of Helmholtz boundary element is explained, a method named SECHIEF (Series Expansion Combined Helmholtz Integral Equation Formulation), which is focused on the computational efficiency, is presented.

对结构声辐射的边界积分方程的内部形式与外部形式进行了详细的推导，给出了角点系数的计算方法与边界积分方程的形式，在此基础上，分析了奇异积分产生的原理及其对数值计算的重要性，提出了一种计算奇异积分的非等参(来源：Ae8a8BC论文网www.abclunwen.com)单元的变换方法，该方法给Helmholtz 声学边界积分方程中的弱奇异积分与Cauchy 奇异积分的计算以及编程提供了极大便利。

The relationship between the Q value of ultrasonic resonant cavity and attenuation coefficient is educed for the first time,which supplies theoretic support to get the coefficient accurately by interferometry,and a practical method is introduced.

通过测量介质的声学特征量得到介质的某些理化常数的技术称为声探测技术。如测量液体的密度、浓度、粘度、流量、液位以及固体的致密度、晶粒度或球化率、弹性、硬度、厚度

The influence on absorption coefficient brought from shape choice with cylindrical or cone-shaped cavity, square or hexagonal profile, from different closure as air or water, from different material properties and structure sizes, are analyzed based on the numerical calculations. Some general characteristics are summarized. It shows that lowest resonance frequency of sound absorbent coefficient is inversely proportional to volume of cavity and sound absorbent coefficient is proportional to perforated percentage.

2通过数值方法研究了吸声结构内腔为圆柱腔和圆锥腔、基材的剖面形状为正四边形和正六边形、不同背衬、基材材料特性、尺寸大小对整体吸声效果的影响，总结了这些情况下非旋转对称吸声结构的声学特性变化规律，得出腔体体积越大，吸声系数最低共振频率越低；穿孔率越大，吸声系数越大的结论。

Spectral element methods for partial differencial equation is introduced in this study from viewpoint of the collocation approximation of Chebyshev polynomial. Wave Equation and its space discretization are deduced. Two time integral methods, central difference method and implicit Newmark method, are introduced, and their stability and applicability are also discussed in some details. The significance of absorbing boundary conditions in spectral element methods for Aeroacoustics is explained, and Clayton-Engquist-Majda absorbing boundary conditions is emphasized and introduced, then the discrete scheme of this boundary conditions is deduced and applied to spectral element methods for wave equation.

本文从Chebyshev多项式逼近理论出发，详细介绍了谱元方法求解偏微分方程的过程；推导了流体中的声波动方程并在空间上对其进行了谱元离散；详细讨论了两种时间积分方法──中心差分法和Newmark方法，分析了它们的稳定性条件，并从理论上对比了两种方法的优缺点和适用范围；将吸收边界条件推广应用于谱元方法求解气动声学问题中，重点介绍了Clayton-Engquist-Majda吸收边界条件的原理和公式，推导了该吸收边界条件的变分形式，并将其引入波动方程的离散形式中。

Yingying chita tower, known as the world because it has a special acoustic effect -"wa ming ", such an effect in the local records were referred to as the "Voice of universalist toad", and was classified as "Yongji Hakkei" one.

莺莺塔被称为世界奇塔，是因为它具有特殊的声学效应——"蛙鸣"，这种效应在方志中被称为"普救蟾声"，并被列为"永济八景"之一。

The relationship between in situ target strength and depth of chub mackerel was established by selecting the length composition of mackerel was larger than 90%. Results showed that the in situ target strength of chub mackerel was changed significantly depend on depth up to 8.7 dB. And it indicated that the measurement of in situ target strength of fish with swim bladder should be modified by the relationship of target strength and depth, especially in chub mackerel, it may be led to overestimate the standing crop to 7.4 times of the assessment.

将科学鱼探所收录到的白腹鲭声学资料使用线性回归来检定现场标物反射强度与样本所在水深关系，检定结果显示出白腹鲭在不同水深时所反射的现场标物反射强度均会随著深度改变，并且呈现负相关的显著水准(p.01)，现场标物反射强度变动有8.7dB差异量，对白腹鲭鱼群现存量会超估7.4倍的差异。

The paper introduces a kind of acoustics principle,and a new method which measuring resonance frequency of the circular saw blades by means of a sound level meter,inorder to provide the reference of testing resonance frequency parameter for all kinds of woodworking cutting tools.

介绍了一种利用声学原理，采用声级计为传感器的木工圆锯片固有频率测量的新方法，以期为各类木工刀具的固有频率参数测试提供借鉴。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。