声强测量技术在水下结构辐射噪声近场测量中的应用

本文介绍了强测量技术在水下结构辐射近场测量中的实际测量系统，特别是水下声系统的扫描平面的实现方法及定位误差控制方法，最后讨论和分析了实际测量结果，从而说明该系统用水下声强测量是可行的。     

水下噪声目标被动测距技术研究

运用被动测距声纳中的三元测距技术，通过直接测1、3阵元的时延差来实现时延估计。仿真结果表明，改进的时延估计方法可提高时延估计精度，从而改善测距精度。此外，定义临界距离，并以此为分界点，分别采用K系数分配法和直接测量法对中远程和近程目标进行测距，解决了被动声纳的近程测距模糊问题。将其应用于声纳系统中，可显著提高声纳的被动测距能力，使被动测距声纳可全程测距。     

水下运动目标激光扫描测距方法研究

相对于传统水下光电成像,水下激光扫描成像系统可以获得更远的作用距离和更好的图像质量.基于激光同步扫描技术,提出了水下运动目标的测距方法,并对测距误差进行了定量分析,为水下目标测距提供了一个新的途径.其中单探测头水下激光扫描测距方法能对合作目标进行测距,在近距离时具有较高的测距精度,双探测头水下激光扫描测距方法能对非合作...     

基于水下滑翔机的海洋环境噪声测量系统*

水下滑翔机是一种新型的水下潜器,将其用于海洋环境噪声测量具有很大的应用潜力。选择的平台是“Petrel II”滑翔机,为其设计和实现了深水水听器和数据采集系统。深水水听器具有耐高静水压和高灵敏度的特点,并通过了60MPa的高静水压力试验;数据采集系统具有体积小、功耗低、控制灵活和易于扩展的特点。搭载声学测量系统的滑翔机顺利通过水池测试和海上试验,测试结果验证了技术方案的可行性和系统工作的稳定性,可为深入进行海洋环境噪声时空特性实验研究提供技术支持。     

氢钟测量死时间导致的光频测量统计不确定度分析

利用87Sr光晶格钟与氢钟的频率比对测量了氢钟的频率稳定度。在89%的光晶格钟有效运行率下,经过约10 d的测量得出氢钟的频率稳定度,并由此推导出氢钟噪声模型的相关参数。根据氢钟噪声模型生成的随机噪声序列,对由测量死时间导致的频差进行了100次模拟,并以模拟结果的1倍标准差为测量不确定度。不同有效运行率下,氢钟测量不确定度的计算结果表明,由氢钟测量死时间导致的不确定度随有效运行率的增加而减小,且在有效运行率小于10%时,增加总的测量时间可以显著减小测量不确定。     

半混响环境中水下结构辐射声功率测量

本文参照空气声学的方法,在水池的半混响环境中,测量了两个相似加肋圆柱壳模型的水下辐射声功率,并利用声辐射的理论相似关系进行校验,在高频段测量偏差为1-2dB。     

水下低噪声目标辐射噪声垂直嵌套阵测量方法

研究了一种水下低噪声目标辐射噪声垂直嵌套阵测量方法。首先通过分析试验水域背景噪声和被测目标辐射噪声特性,掌握不同测量频段的增益需求;然后采用凸优化方法,建立波导环境中超宽带、高稳健恒定束宽波束形成技术,推导水下目标辐射噪声垂直嵌套阵测量及空间阵列信息处理方法;最后研制垂直嵌套阵测量系统,并开展湖上试验验证。研究结果表明该测量方法具有测量带宽大、稳健性高、测量不确定度低等优点,辐射噪声测量不确定度约2 dB。     

水下噪声及其控制技术进展和展望

本文主要介绍近年来船舶行业水下噪声研究进展情况，包括水下噪声形成机理和预报；水下噪声控制技术；水下噪声近代测量分析技术，并提出对水下噪声研究工作的展望。     

广义对角切片谱及用于水下目标特征提取的性能分析

人眼分类双谱图时具有沿副对角线方向进行观察的特点,为了分类不同的水下目标辐射噪声以实现目标识别,在已有对角切片的基础上提出广义对角切片及其谱定义,并通过对各切片幅值进行简单求和或取最大值得到两种特征向量,引入Fisher可分性测度对特征向量进行降维处理,利用支持向量机的一对一方法对实测水下目标辐射噪声进行分类实验。实验结果表明:对广义对角切片谱各切片幅值进行求和得到的特征向量具有极高的分类正确率,且分类稳定性优良。     

多路噪声测量系统的研制

本描述了多路噪声测量系统的建立,该系统是一以微机为中心的数字化系统,可实现对４路稳态宽带噪声的测量,测量参数是线性声压级和倍频带声压级。系统由微机、ＴＭＳ３２０Ｃ３０板、多路ＡＤ板、传感器、放大器等设备构成硬件系统,并通过编制Ｃ３０板嵌入式软件和微机主控程序实现系统功能。在软件编制中结合数字信号处理技术,并结合硬件特性优化程序设计,本系统测量方法简易,快捷和精度高,在噪声测量领域具有较高实用价值     

噪声对超导量子比特测量系统的影响

详细介绍了噪声对超导量子比特测量系统的影响。测量系统通过对时间的测量来获得单个约瑟夫森结跳变电流统计分布P(I)。在测量电路中采取了一系列的降噪措施,使得实验所能测到的约瑟夫森结的最低等效温度进一步的降低。     

机动目标的噪声识别和定位系统的研究

本文介绍了一种机动目标噪声识别和定位系统硬件组成，工作原理及系统的软件设计方法，对于在系统中解决的几个主要技术问题进行了论述。     

轻轨桥架声屏障降噪效果的测量与分析

在轻轨桥架两侧设置声屏障是控制轨道交通噪声的主要措施之一，对上海轻轨明珠线桥架两侧设置不同高度声屏障实际降噪效果的测量与分析，对声屏障的实用设计有重要的参考价值。     

圆锯机空气动力噪声

本文通过对圆锯空载时空气动力噪声的发声机理研究，探讨这类噪声（气动噪声）的主源及其辐射特征，最后提出低噪据片的改进型结构。     

Self-mixing instrument for simultaneous distance and speed measurement

A novel instrument based on Self-mixing interferometry is proposed to simultaneously measure absolute distance and velocity. The measurement method is designed for working directly on each kind of surface, in industrial environment, overcoming also problems due to speckle pattern effect. The laser pump current is modulated at quite high frequency (40 kHz) and the estimation of the induced fringes frequency allows an almost instantaneous measurement (measurement time equal to 25 µs). A real time digital elaboration processes the measurement data and discards unreliable measurements. The simultaneous measurement reaches a relative standard deviation of about 4·10⁻⁴ in absolute distance, and 5·10⁻³ in velocity measurement. Three different laser sources are tested and compared. The instrument shows good performances also in harsh environment, for example measuring the movement of an opaque iron tube rotating under a running water flow.     

Measurement network for urban noise assessment: Comparison of mobile measurements and spatial interpolation approaches

This paper investigates the relevance of different interpolation techniques to improve the spatial resolution of urban noise maps, in complement to measurements achieved at fixed stations. Interpolation techniques based on mobile measurements are compared to usual spatial interpolations techniques, namely Inverse Distance Weighting and Kriging. The analyses rely on a measurement campaign, which consisted of nearly 8 h of geo-referenced mobile noise measurements performed at random moments of the day, conducted simultaneously with continuous measurements collected at five fixed stations located on the inner city of Gent, Belgium.Firstly, a procedure is proposed to build a noise map with a high spatial resolution (one point every 5 m). The procedure relies on both mobile and fixed measurements: the mobile measurements are used to capture spatial variations on the network, and the measurements at fixed stations are used to capture the temporal variations. The map produced is then used as reference to compare the interpolation techniques based on a significantly more sparse measurement set.The spatial interpolation techniques tested fail in predicting accurately the noise level variations within streets. The explanation given is that they do not offer a sufficient covering of the network, and assume spatial variations which are not coherent with traffic dynamics or street configurations. Inversely, mobile measurements cover the entire network. As a result, they allow a more accurate prediction of noise levels even if very short samples are used, provided that the procedure used to estimate noise levels includes a spatial aggregation, which aims at smoothing the high spatial variations inevitable with short samples. Moreover, mobile measurements can advantageously be used to optimize, through a Genetic Algorithm, the locations where to install fixed stations, promising an efficient noise monitoring at reduced operational costs.     

红外光电立靶测试系统软件设计

介绍了红外光电立靶射击密集度的计算方法,设计了一种高效率的靶场测试软件。应用结果表明,该软件能够实时精确测量弹丸射击密集度,可提供多种射击密集度的数据。     

Decoherence–fluctuation relation and measurement noise

We discuss fluctuations in the measurement process and how these fluctuations are related to the dissipational parameter characterizing quantum damping or decoherence. On the example of the measuring current of the variable-barrier or QPC problem we discuss the extra noise or fluctuation connected with the different possible outcomes of a measurement. This noise has an enhanced short time component which could be interpreted as due to “telegraph noise” or “wavefunction collapses”. Furthermore, the parameter giving the strength of this component is related to the parameter giving the rate of damping or decoherence.     

Assessment criterion for indoor noise disturbance in the presence of low frequency sources

Several studies have presented the effects of environmental noise in and around buildings and communities in which people live and work. In particular, the noise introduced into a building is mostly evaluated using the A weighted sound pressure level (L_Aeq) as the only parameter to determine the perceived disturbance. Nevertheless, if noise is produced by activities or sources characterised by a low frequency contribution, the measurement of L_Aeq underestimates the real disturbance, in particular during sleeping time.