矢量水听器自动校准系统的研究及实现

研制的矢量水听器自动校准系统在水声计量领域具有重要的应用价值,能够实现低频范围内矢量水听器的自动校准。利用动态信号采集卡采集被测信号和标准水听器的输出信号,对驻波管内的声场分布进行了测量分析,对系统的测量不确定度进行了分析评定,对声压灵敏度进行了比对测试。该系统校准矢量水听器的扩展不确定度为1.6dB。     

矢量水听器的低频相位校准方法

描述了一种在平面驻波声场中,对矢量水听器进行相位校准的方法,该方法可以在20Hz～2kHz频率范围内,对矢量水听器的矢量通道和声压通道之间的相位差进行校准.     

变温变压环境中大面积水听器灵敏度低频校准方法

针对在变温变压环境中缺少低频大面积水听器灵敏度校准手段的问题,提出了在行波管中校准水听器的半行波管法:将待校准水听器放置于行波管中,通过控制行波管两边的有源终端,在待校准水听器与辅助换能器之间形成行波场,与主发射换能器之间形成驻波场。推导了水听器灵敏度的校准公式。在常温常压环境下,通过与传统低频校准方法的比对,校准结果具有良好的一致性,证明该方法可以有效校准大面积水听器的灵敏度;在不同温度与压力环境下对水听器灵敏度的校准结果,说明了该方法在变温变压条件下校准水听器的可行性,为大面积水听器灵敏度的校准提供了一种方法;对该方法进行了测量不确定度评定,其扩展测量不确定度为3dB。     

5Hz~10kHz频率范围矢量水听器国际主导比对

利用VHS56、VHS90和KPG-10作为比对传递用矢量水听器,中国杭州应用声学研究所与俄罗斯VNIIFTRI开展了 5Hz～10kHz 频率范围矢量水听器校准国际比对。利用各自的自由场互易法和垂直驻波管比较法校准装置,校准了3只矢量水听器X、Y、Z通道的灵敏度。从校准结果看,一致性较好,174个频率点中,仅有一个频点的校准值与参考值的偏差略微超过参考扩展不确定度,绝大部分频率点的测量偏差都小于±0.5dB,检验和验证了中俄双方矢量水听器校准装置的准确性和可靠性。     

行波管校准技术

本文介绍静水压在0.1～10MPa,频率在20～4000Hz,温度在4℃～40℃范围内连续可变的水声换能器校准设备——行波管校准装置.校准装置利用有源消声原理在声波导管中产生平面行波.在500～2000Hz范围内可对标准水听器进行互易校准.校准精度优于±0.5dB;在整个频率范围内可对声呐换能器或测量水听器作比较校准,精度优于±0.7dB.     

数学摆台法的超低频加速度校准

建立了基于数学摆台法的超低频加速度校准装置,解决了线振动台超低频加速度信噪比低的问题,对相关校准具有参考价值和借鉴作用。根据低频噪声理论,在建立激光测振仪的功率谱密度模型基础上,提出了位移噪声的定量评价方法,通过实验验证了所提方法的正确性。对数学摆台的虚拟摆臂、激励传递系数进行了实验测量,对校准装置的测量不确定度进行了评定。该装置实现了加速度计在频率范围0.001～0.1Hz、加速度范围5×10^-7 ～1×10^-2m/s² 的绝对法校准。     

矢量水听器校准装置的不确定度评定

本文介绍了矢量水听器校准装置的工作原理,系统组成及校准矢量水听器灵敏度和指向性的工作流程,并对该装置的不确定度进行分析评定。     

水听器复数灵敏度的激光法校准

利用激光测振技术直接检测声场作用下的水介质质点振速,通过推算得到声场中该点声压的幅值和相位,从而可精确校准水听器的复数灵敏度.利用该技术,我们在10～100 kHz频段建立了一套水听器复数灵敏度的校准装置.本文简要介绍了装置的校准原理、方法以及各组成部分,并对Φ20球形水听器进行实验测试.结果表明,激光测振技术是一种有效的校准水听器复数灵敏度的方法,校准结果具有很高的精度.     

基于激光绝对法冲击校准技术的动态力测量方法的研究

本文讨论测量原理相似的落锤式动态力标准装置和冲击力法的冲击加速度校准装置的工作原理、力值复现方法 ;分析落锤式动态力标准装置校准方法的缺陷 ;重点介绍瞬态冲击力绝对法校准系统中采用的质量块碰撞式力源、外差式激光干涉绝对法冲击加速度测量技术、有限元法的加速度修正等内容 ;并就我国冲击力标准装置的发展提出建议和设想     

矢量水听器测试方法研究与应用

声呐作为水下探测、通信的重要设备,无论在民用探鱼或军事探测水下目标上都有着不可或缺的重要作用。随着传感器技术以及信号处理技术的迅猛发展,更尖锐地指向性成为了水听器发展的主要方向,矢量水听器可以同时获得声压信号和质点振速信号,在各种水下测量设备中都有着重要的应用。因此,矢量水听器的校准就显得尤为重要,其x正轴方向的确定、灵敏度及指向性都会直接影响实际应用。本文依据水听器校准规范的要求,结合水听器使用的实际情况,对一种胶囊形三维矢量水听器的性能做了测试,给出了不同频率下的指向性图,并对今后的水听器的发展及信号处理方法做了展望。     

Calibration of a focusing transducer and miniature hydrophone as well as acoustic power measurement based on free-field reciprocity in a spherically focused wave field

The free-field transmitting voltage response at the pressure focus of a spherically focusing transducer was defined and calibrated based on the reciprocity theorem of a free-field spherically focused acoustic wave. The acoustic power, the radiation conductance, and the pressure at the pressure focus were derived and measured accordingly from the transmitting current response on the imaginary mirror symmetric spherical surface of the radiating surface. A miniature hydrophone was calibrated by the self-reciprocity of the spherically focusing source. Comparison results show that the measured acoustic power deviation between the reciprocity method and the radiation force balance method are within +/- 5% for two air-backed focusing transducers at 1.53 MHz and 5.27 MHz, respectively, and the maximum deviation of a hydrophone calibration between the new method and the free-field plane wave reciprocity method is within 1.4 dB in the frequency range from 1 MHz to 2 MHz in experiments.     

中频同振柱型矢量水听器及其支撑结构设计

针对同振型矢量水听器后期悬挂金属弹簧或橡胶绳给使用者带来不便的问题,提出一种中频同振柱型矢量水听器及其支撑结构的设计方案。通过矢量水听器振动系统对其声学特性进行分析,通过ANSYS有限元软件,利用Mooney-Rivlin理论对圆环形橡胶弹簧在压缩情况下的水平剪切刚度进行仿真计算,分析了Rivlin参数对橡胶弹簧剪切刚度的影响,并研制出矢量水听器样机。在1000~4000 Hz频率范围内,对矢量水听器进行了测试,并给出了测试结果。在1 k Hz时,声压灵敏度为-195 d B,指向性凹点深度大于20 d B。测试结果表明,此种设计免除了反复悬挂金属弹簧或橡胶绳带来的负面效应。     

Primary calibration of hydrophones with extended frequency range 1 to 70 MHz using optical interferometry

A technique for the primary calibration of hydrophones based on an optical principle is presented. An interferometer determines the displacement of a pellicle mounted on the surface of the tank fluid perpendicular to the sound propagation axis; the known acoustic field is then measured using the hydrophone. The application range extends from 1 to 50 MHz and, with a lesser accuracy, to 70 MHz. The loaded and the open-circuit sensitivity are obtained pointwise, and the frequency and the number of the measurement points can be arbitrarily chosen. As an example, two membrane hydrophones with a spot diameter of 0.5 mm are calibrated, and the comparison with a theoretical model describing the acoustic and electrical properties of the hydrophone shows good agreement.     

250Hz～8kHz频率范围水听器自由场校准补充比对

介绍了以杭州应用声学研究所作为主导实验室与俄罗斯国立物理技术和无线电工程测量研究院开展COOMET.AUV.W-S1:250 Hz~8 kHz频率范围水听器自由场校准国际补充比对的结果。比对校准了两只标准水听器TC 4033和GI 55。互易法和比较法及其校准装置被用于评估中俄两国在水听器自由场低频校准方面的当前水平。结果显示,中俄两国得到的两只标准水听器的自由场灵敏度校准结果具有很好的一致性,绝大多数频率点的校准结果与参考值的差值小于0.40 dB,最大偏差为0.59 dB。结果证明,中俄两国的自由场水听器校准低限可扩展至250 Hz。     

Wide-band piezoelectric polymer acoustic sources

The design of a wideband acoustic source made of the piezoelectric polymer polyvinylidine fluoride (PVDF) is described. The source was developed for the characterization and absolute calibration of ultrasonic hydrophone probes. Construction details are described and performance characteristics of the wideband PVDF transmitter, including its transmitting voltage response and directivity patterns, are compared with theoretical predictions in the frequency range up to 40 MHz. The Krimholtz-Leedom-Mattaei (KLM) model was used to examine the influence of the PVDF polymer film thickness, the backing acoustic impedance, the cable length, and the electrical source resistance on overall transmit transfer characteristics. A comparison is made with traditional piezoelectric ceramic acoustic sources, and it is shown that piezopolymer transmitters exhibit some improved properties and are well suited for certain ultrasound dosimetry applications. In particular, the polymer sources have been found useful in measurements based on swept-frequency excitation. Those measurements allow characterization of transmitters and receivers to be performed as a virtually continuous function of frequency.     

A novel method for determining calibration and behavior of PVDF ultrasonic hydrophone probes in the frequency range up to 100 MHz

A new calibration technique for PVDF ultrasonic hydrophone probes is described. Current implementation of the technique allows determination of hydrophone frequency response between 2 and 100 MHz and is based on the comparison of theoretically predicted and experimentally determined pressure-time waveforms produced by a focused, circular source. The simulation model was derived from the time domain algorithm that solves the non linear KZK (Khokhlov-Zabolotskaya-Kuznetsov) equation describing acoustic wave propagation. The calibration technique data were experimentally verified using independent calibration procedures in the frequency range from 2 to 40 MHz using a combined time delay spectrometry and reciprocity approach or calibration data provided by the National Physical Laboratory (NPL), UK. The results of verification indicated good agreement between the results obtained using KZK and the above-mentioned independent calibration techniques from 2 to 40 MHz, with the maximum discrepancy of 18% at 30 MHz. The frequency responses obtained using different hydrophone designs, including several membrane and needle probes, are presented, and it is shown that the technique developed provides a desirable tool for independent verification of primary calibration techniques such as those based on optical interferometry. Fundamental limitations of the presented calibration method are also examined.     

Lower frequency of free-field calibration of hydrophones in emission of tonal signals in a non-anechoic water tank

An approach to estimation of the lower free-field calibration frequency as well as the required magnitude of the water tank for calibration of hydrophones in a specified frequency range from the cepstrum of a segment of the amplitude response of the electroacoustic system, projector – hydrophone – non-anechoic water tank – measurement path of standard facility, is proposed. Estimates of the lower calibration frequency of hydrophones in a water tank with minimal dimension of 6 m in the case of radiation of quadrature-added harmonic signals are presented.     

Primary calibration of ultrasonic hydrophone using optical interferometry

A primary calibration method for ultrasonic hydrophones which uses a Michelson interferometer to determine the particle displacement in an ultrasonic field is discussed. The acoustic pressure is derived from this measurement and used to determine the free-field sensitivity of a hydrophone in the frequency range 0.5-15 MHz. The random uncertainty of the method is typically 1%, whereas the systematic uncertainty varies from 2.3 to 6.6% over the frequency range. To obtain this accuracy, the performance of the system has been carefully examined and appropriate correction factors derived. The greatest difficulty in the method lies in determining the frequency response of the optical detection system, and two different approaches have been used to measure this response. Several acoustical effects have also been studied and the calibration procedure modified to take account of them. The calibration results are in agreement with those of other methods and with the theoretically predicted frequency response of a hydrophone. The method has been used to determine the temporal stability of a hydrophone over a period of two years.     

矢量水听器在水声通信系统中的应用

将矢量水听器应用于水声通信系统,利用矢量水听器的指向性屏蔽强干扰。建立了基于矢量水听器的多载波正交频分复用(OFDM)系统模型,对各向同性噪声场中矢量水听器的增益进行了推导,为抑制相干干扰提供了新的解决方案,并进行了仿真验证。仿真研究表明,该方案能够有效地增强系统的抗各向同性干扰的能力,达到提高信噪比的目的,降低了误码率,增加了系统的稳健性。湖上试验验证了该方法的有效性,表明基于矢量水听器的水声通信系统可为实现高速水声通信提供一种有效的途径。     

声压基阵误差单辅助矢量水听器快速校准方法

针对方位依赖的声压基阵误差校正困难问题,提出了声压基阵误差单辅助矢量水听器快速校准方法。利用精确校正的单只矢量水听器,就可以对声源方位及方位依赖的声压基阵幅度相位误差,进行无模糊的联合估计。由于阵元位置误差、互耦及通道的幅度相位误差均可以等效为方位依赖的基阵幅度相位误差,所以可以对多种同时存在的基阵误差进行校正。该方法适用于任意的阵列结构,不存在参数联合估计的局部收敛问题,只需参数的一维搜索,运算量小可实时在线完成。通过计算机仿真实验验证了该方法的有效性。