Reduction of the error of hydrophone calibration with respect to the field in a hydroacoustic tank by the reciprocity method

A hydrophone calibration procedure that considerably reduces the error caused by the acoustic field distortions in a hydroacoustic tank is proposed. The procedure is based on the definition of the reduced electric transfer impedances of transducers (i.e., the electric transfer impedances reduced to the spherical wave propagation law) and consists in measuring the electric transfer impedances for different distances between hydroacoustic transducers. The sensitivity of the hydrophone under calibration is calculated from the far-field values of the reduced electric transfer impedances. The latter are determined using a mathematical model of the hydrophone in the form of a system that contains a point sensing element and a finite number of point sources of acoustic signals (point reflectors). A method of determining the number and coordinates of the point reflectors from the analysis of the acoustic “images” of the hydrophone’s reflecting surface is proposed. The measuring technique, the algorithms of mathematical processing, and the results of experimental studies are considered. A comparative analysis of the results of the hydrophone calibration with respect to the field by the reciprocity method is performed for the cases of using the conventional technique and the proposed method.     

充水阻抗管中测量材料声学性能的校准方法研究

提出了一种在充水阻抗管中,应用传递函数测量材料声学性能的三参数校准方法。在双传感器传递函数法的基础上,考虑充水阻抗管中水听器间不一致性和管内结构对声场局部扰动等因素的校准,导出了三个综合的无量纲校准参数。通过改变充水阻抗管中测量面的三个已知反射系数,测量出对应的三个传递函数,可以求出这三个校准参数。在充水阻抗管中分别对水/空气界面和一种水声材料进行了测量试验,应用该方法对测量结果的进行了校准,并对校准前后的结果进行了分析比较。      

深海中利用单水听器的影区声源无源测距测深方法

在典型深海情况下当声源与接收水听器位于海水表层时,在影区内由声源海底接收器、声源海面海底接收器、声源海底海面接收器和声源海面海底海面接收器4条声线形成声场干涉结构,声强随着频率具有两种干涉周期,随着收发距离的增加而增大,分别随着声源深度、接收水听器深度的增加而减小。因此由单水听器记录的声场干涉结构即可实现宽带声源目标的无源测距测深,仿真分析验证了其有效性。在南海深海声学实验中观测到海面宽带噪声源在声场影区所形成的声场干涉结构,数据分析结果验证了深海声场干涉结构用于声源无源定位的有效性。与传统无源定位方法相比,该方法不需要宽带引导声源、精确的海底声学参数和大规模的拷贝场计算。      

联合特征子空间分布对齐的标定迁移方法

近红外光谱分析技术近年来在各种领域的定性、定量分析等方面得到广泛的应用。多元标定技术则是光谱分析领域中最先进的技术,而环境条件、测量仪器或测量物质自身的变化,都可能导致多元标定模型不再适用于新样本的预测。重新标定和重新建模必然会浪费大量时间和资源。一种解决方案是标定迁移,将源域已有的标定模型扩展到目标域中,避免重复建模的代价。在化学计量学的相关文献中,绝大多数迁移方法都需要在两台仪器相同条件下都测量一组迁移标准样品,但在近红外光谱测量技术中,由于标准样品具有挥发等特性,使得构建仪器标定迁移方法的标准样品难以获得和保存。针对这些问题,提出了一种联合特征子空间分布对齐（JSDA）的标定迁移方法,此方法可以在从仪器没有标准样本的情况下建立标定迁移模型。JSDA首先建立源域和目标域数据特征的联合主成分分析（PCA）子空间;然后通过对齐映射在联合特征子空间中的源域特征分布和目标域特征分布来校正标定模型;最后,应用最小二乘模型构建校正后源域上的标定模型,该模型可直接用于目标域的标定。实验结果表明与已有成熟的标定迁移方法相比,JSDA在公开的真实数据集上的预测性能比较有优势,验证了该模型在实际应用中的有效性和优越性。     

Experimental measurement of the nonlinearities of electrodynamic microphones

This paper presents an experimental way of characterizing the nonlinearities of electrodynamic microphones used as acoustical sources. This functioning occurs for reciprocal calibration techniques. For this purpose, its electrical impedance is measured with a Wayne Kerr wedge which has an excellent precision. Moreover, it can be noted that the Thiele and Small model is used to characterize its electrical impedance. Furthermore, an experimental method based on Simplex algorithm allows us to construct polynomial laws which describe the dependence of the Thiele and Small parameters with the input voltage. The nonlinear variations obtained allow us to determine the nonlinear differential equation of the electrodynamic microphone. Then, this equation is solved numerically in order to confirm the accuracy of the polynomial laws obtained by the Simplex algorithm. The distortions are measured with a laser Doppler velocimeter and compared with the ones obtained by the numerical solving of the nonlinear differential equation. The experimental displacement spectrum is consistent with the theoretical one.     

Determination of the parameters of a linear-viscoelastic thin layer using the normally-incident ultrasonic waves

This paper proposes a method of simultaneous determination of the four layer parameters (mass density,longitudinal velocity,the thickness and attenuation) of an immersed linear-viscoelastic thin layer by using the normally-incident reflected and transmitted ultrasonic waves.The analytical formula of the layer thickness related to the measured transmitted transfer functions is derived.The two determination steps of the four layer parameters are developed,in which acoustic impedance,time-of-flight and attenuation are first determined by the reflected transfer functions.Using the derived formula,it successively calculates and determines the layer thickness,longitudinal velocity and mass density by the measured transmitted transfer functions.According to the two determination steps,a more feasible and simplified measurement setups is described.It is found that only three signals (the reference waves,the reflected and transmitted waves) need to be recorded in the whole measurement for the determination of the four layer parameters.A study of the stability of the determination method against the experimental noises and the error analysis of the four layer parameters are made.This study lays the theoretical foundation of the practical measurement of a linear-viscoelastic thin layer.     

一种基于简正波模态消频散变换的声源距离深度估计方法

针对浅海环境中传播的低频宽带水声脉冲信号,基于简正波水平波数差和波导不变量之间的关系,本文提出了一种利用距离-频散参数二维平面聚焦测距与匹配模态能量定深的目标声源定位方法.首先,通过将由频散参数和波导不变量表示的前几阶模态相速度与由环境模型计算的相速度进行对比分析,从而估计出前几阶模态的频散参数和环境的波导不变量.其次,利用估计出的频散参数值和波导不变量对接收信号进行消频散变换处理,只有当接收信号的距离参数等于目标声源距离时,各号简正波的幅度均达到最大值,在距离-频散参数二维平面上,出现声压聚焦的现象,利用此现象可以估计目标声源的距离.不仅如此,消频散变换后的接收信号,前几阶模态在时域上明显地分离开来,可以准确地估计出前几阶模态的能量,采用多模态能量匹配的方式,可以估计出目标声源的深度.最后,通过对仿真和冬季获得的气枪信号数据处理结果验证了本文方法的有效性.     

Features of the dynamics of postdetonation waves

We present the results of numerical investigations of the parameters of postdetonation waves forming at a passage from the zone occupied with a bubbly liquid formed by the detonation wave to a zone filled with a liquid without bubbles. The dependence of the pressure amplitude of detonation waves and postdetonation waves on the gas volumetric content of bubbles has been studied. A possibility of the detonation transfer through the layer of a bubble-free liquid separating the regions of the bubbly liquid has been shown, the map of possible situations at the detonation transfer through the layer of this liquid has been presented.     

Medium characterization from interface-wave impedance and ellipticity using simultaneous displacement and pressure measurements

The interface-wave impedance and ellipticity are wave attributes that interrelate the full waveforms as observed in different components. For each of the fluid/elastic-solid interface waves, i.e., the pseudo-Rayleigh (pR) and Stoneley (St) waves, the impedance and ellipticity are found to have different functional dependencies on Young's modulus and Poisson's ratio. By combining the attributes in a cost function, unique and stable estimates of these parameters can be obtained, particularly when using the St wave. In a validation experiment, the impedance of the laser-excited pR wave is successfully extracted from simultaneous measurements of the normal particle displacement and the fluid pressure at a water/aluminum interface. The displacement is measured using a laser Doppler vibrometer (LDV) and the pressure with a needle hydrophone. Any LDV measurement is perturbed by refractive-index changes along the LDV beam once acoustic waves interfere with the beam. Using a model that accounts for these perturbations, an impedance decrease of 28% with respect to the plane wave impedance of the pR wave is predicted for the water/aluminum configuration. Although this deviation is different for the experimentally extracted impedance, there is excellent agreement between the observed and predicted pR waveforms in both the particle displacement and fluid pressure.     

热声系统中回热器特征阻抗与传播常数的研究

针对本实验室一台声驱动热声系统,采用传递函数法研究声驱动系统中回热器的特征阻抗和传播常数.通过调节谐振管长度,改变回热器表面的阻抗,从理论上分析了回热器网络传输方程中的声传播常数、特征阻抗与系统网络元件中的阻抗、导纳和流的关系.并且进一步讨论有无换热器以及不同的加热功率对回热器网络参数的影响.结论有利于进一步量化回热器的网络参数.     

基于纠缠光子方法测量光电探测器量子效率的研究

光辐射传感器的定标是保证遥感数据精度及可利用价值的基础支撑技术。现行辐射定标方法都需要建立高精度初级标准及标准传递链，传递环节是误差的主要来源。纠缠光子理论为实现“无标准传递”的辐射定标开辟了崭新的技术途径。报道了在光子计数模式下利用非线性光学的非经典效应绝对定标光电探测器的新方法，测量是通过BBO非线性晶体的参量下转换形成的702nm简并的纠缠光子方法来实现的。实验测得光电倍增管在该波长处的量子效率，结果显示有0.1%的偏差。该方法本身具有绝对性，不依赖于任何外部定标的辐射标准。     

光纤水听器灵敏度测试研究

研制了一套简单可行的光纤水听器灵敏度校准装置,提出了一种简便的测量方法——比对法:将标准压电水听器探头和光纤水听器探头置于同一声场中，并将两探头的输出同时接到数字示波器上进行比对测量.研究表明,振动系统中的盛水容器具有一定的壁厚（>10 mm或1/10桶的外径）时，可将振动系统的谐振峰移出工作频段范围（3~1000 Hz）外.利用此装置结合比对法,校准系统简单，校准速度快,实验的误差小于0.5 dB,能满足一般光纤水听器灵敏度的校准需求.     

Evidence of Doppler-shifted Bragg scattering in the vertical plane by ocean surface waves

A set of narrowband tones (280, 370, 535, and 695 Hz) were transmitted by an acoustic source mounted on the ocean floor in 10 m deep water and received by a 64-element hydrophone line array lying on the ocean bottom 1.25 km away. Beamformer output in the vertical plane for the received acoustic tones shows evidence of Doppler-shifted Bragg scattering of the transmitted acoustic signals by the ocean surface waves. The received, scattered signals show dependence on the ocean surface wave frequencies and wavenumber vectors, as well as on acoustic frequencies and acoustic mode wavenumbers. Sidebands in the beamformer output are offset in frequency by amounts corresponding to ocean surface wave frequencies. Deviations in vertical arrival angle from specular reflection agree with those predicted by the Bragg condition through first-order perturbation theory using measured directional surface wave spectra and acoustic modes measured by the horizontal hydrophone array.     

Interlaboratory evaluation of hydrophone sensitivity calibration from 0.1 to 2 MHz via time delay spectrometry

Knowing the low-frequency response of hydrophones, down to 100 kHz at least, is important for accurate biomedical ultrasound measurements. However, current international standards do not extend below 500 kHz. Furthermore, commercial hydrophone sources typically do not supply sensitivity data below 1-2 MHz. Therefore, to help identify and validate practical calibration methods below 2 MHz, the authors have extended their previous individual efforts in an interlaboratory evaluation of sensitivity calibration using the swept-frequency technique, time delay spectrometry (TDS). Calibrations were performed for needle and membrane PVDF hydrophones using each laboratory's TDS system. Each site employed the same purpose-built broadband source transducers, comprising both plano-concave and biconcave 1-3 piezocomposite elements 4 cm in diameter, with maximum and minimum thicknesses of approximately 1.5 and 0.1 cm. Agreement between laboratories was within the estimated measurement precision of +/-0.6 dB. The results demonstrated that a TDS system employing such transducers constitutes a viable method for hydrophone calibrations in this frequency range.     

Characterization of an optical multilayer hydrophone with constant frequency response in the range from 1 to 75 MHz

The performance of an optical multilayer hydrophone for ultrasound measurements is investigated both in theoretical terms and experimentally. The optical measurement system comprises a thin high-finesse dielectric interference filter structure that is deposited onto a plane glass plate. An incident acoustic pressure wave deforms the layer system, and the induced variation of the optical reflectance is determined. Applying the concept of an optical off-axis detection scheme offers good sensitivity and a simple and low-cost setup. A primary interferometric calibration technique is applied to experimentally determine the pressure-voltage transfer function in the range from 1 to 75 MHz. Within the measurement uncertainty a constant transfer factor is obtained for the whole frequency range. Measurements of broadband ultrasound pulses are influenced neither by acoustic resonances of the very thin sensing element nor by diffraction phenomena that are known to cause waveform distortions in small probe hydrophone measurements. High temporal and spatial resolution is combined with high durability of the probe, which is why the optical multilayer hydrophone is well suited for use as a reference for secondary hydrophone calibration.     

Method of array shape calibration based on time delay estimation using two auxiliary sources

As for a flexible horizontal array deployed in the sea, it is difficult to obtain each sensor's precise relative position. Therefore a method of array shape calibration is proposed. The method is described as follows. Firstly two separate auxiliary sources are deployed. Secondly tune delay of each sensor's received signal is estimated. Finally, with the aid of GPS location of the sources and the horizontal array, relative sensor positions of the horizontal array can be determined. The estimation of relative sensor positions is unbiased. Simultaneously, simulation analysis has been done to estimate its standard variance, and the optimal flare angle of the two sources has been derived. Data of 2001 Asian Sea International Experiment have been used to validate the method. After array calibration, measured source azimuth angle agrees with the real one, and measured array gain agrees with the theoretical gain. In conclusion, the theoretical and experimental results both show that the method can determine each sensor's relative position precisely.     

On the selection of loads in the multiload method for measuring the acoustic source parameters of duct systems

The in-duct source can be characterized by two acoustical parameters such as the source strength and the source impedance, which permit the prediction of radiated sound pressure or insertion loss of the whole duct system. One-port acoustic characteristics of an in-duct source can be measured by the multiload method using an overdetermined set of open pipes or side-branch pipes with different lengths as applied loads. The input data, viz. load pressure and load impedance, are usually contaminated by measurement error in the actual measurements, which result in errors in the calculated source parameters. In this paper, the effects of the errors in the input data on the results have been studied numerically, varying the number of loads and their impedances in order to determine what combination of the loads will yield the best result. It is noted that, frequently, only a set of open pipes is used when applying the multiload method to the internal combustion engine sources. A set of pipe lengths, which cause the calculated results to be least sensitive to the input data error, can be found when using open pipe loads. The present work is intended to produce guidelines for preparing an appropriate load set in order to obtain accurate source properties of fluid machines.     

20 Hz~10 kHz光纤水听器相移灵敏度校准

利用相位生成载波解调技术精确测量光纤水听器的光相移量,在20 Hz~10 kHz频率范围实现了光纤水听器探头相移灵敏度的校准.20 Hz~1.25 kHz频段采用驻波管比较法进行校准,1.25 kHz~10 kHz频段采用自由场脉冲比较法进行校准.利用本文建立的校准系统,对TMD 35#光纤水听器的相移灵敏度进行校准,校准结果表明,两种方法测得的相移灵敏度具有很好的一致性,在1.25 kHz频率点的相移灵敏度值偏差为0.8 dB.不确定度分析表明,该校准系统的扩展不确定度(k=2)为0.9 dB.     

用于光谱基准定标传递技术的传递辐射计研究综述

传递辐射计是实现卫星遥感仪器在轨光谱辐射定标传递的核心设备,也是地面实验室高精度光谱定标系统的关键。介绍了不同机构研制的覆盖350～700, 700～2 500 nm谱段的多个传递辐射计的结构组成、工作原理及辐射定标基准传递方式,及其异同点的比对,再通过它们在不同谱段的定标过程中所应用的关键技术的分析,说明每种技术的优缺点和所能达到的精度,及其应用条件。文中通过对国际上标准计量机构采用的光谱辐亮度基准定标传递过程的介绍,突出了传递辐射计系统的重要作用,再结合其对光谱仪等遥感器定标光源的定标监测应用,说明了传递辐射计在航天辐射定标领域的不可或缺性。最后,通过国内设计的新型传递辐射计的介绍,对传递辐射计未来研究的发展方向和关键问题进行了展望,并对传递辐射计搭配低温辐射计组成的未来实现可溯源国际单位制在轨基准定标传递系统所存在的研究难点予以预测分析。     

Calibration chain design based on integrating sphere transfer radiometer for SI-traceable on-orbit spectral radiometric calibration and its uncertainty analysis

In order to satisfy the requirement of SI-traceable on-orbit absolute radiation calibration transfer with high accuracy for satellite remote sensors,a transfer chain consisting of a fiber coupling monochromator(FBM) and an integrating sphere transfer radiometer(ISTR) was designed in this paper.Depending on the Sun,this chain based on detectors provides precise spectral radiometric calibration and measurement to spectrometers in the reflective solar band(RSB) covering 300–2500 nm with a spectral bandwidth of 0.5–6 nm.It shortens the traditional chain based on lamp source and reduces the calibration uncertainty from 5% to 0.5% by using the cryogenic radiometer in space as a radiometric benchmark and trap detectors as secondary standard.This paper also gives a detailed uncertainty budget with reasonable distribution of each impact factor,including the weak spectral signal measurement with uncertainty of 0.28%.According to the peculiar design and comprehensive uncertainty analysis,it illustrates that the spectral radiance measurement uncertainty of the ISTR system can reach to 0.48%.The result satisfies the requirements of SI-traceable on-orbit calibration and has wider significance for expanding the application of the remote sensing data with high-quality.