RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.

Leak Detection of Gas Pipelines Based on Characteristics of Acoustic Leakage and Interfering Signals

When acoustic method is used in leak detection for natural gas pipelines,the external interferences including operation of compressor and valve,pipeline knocking,etc.,should be distinguished with acoustic leakage signals to improve the accuracy and reduce false alarms.In this paper,the technologies of extracting characteristics of acoustic signals were summarized.The acoustic leakage signals and interfering signals were measured by experiments and the characteristics of time-domain,frequency-domain and time-frequency domain were extracted.The main characteristics of time-domain are mean value,root mean square value,kurtosis,skewness and correlation function,etc.The features in frequency domain were obtained by frequency spectrum analysis and power spectrum density,while time-frequency analysis was accomplished by short time Fourier transform.The results show that the external interferences can be removed effectively by the characteristics of time domain,frequency domain and time-frequency domain.It can be drawn that the acoustic leak detection method can be applied to natural gas pipelines and the characteristics can help reduce false alarms and missing alarms.

Acoustic field simulations of logging while drilling by cylindrical finite difference with variable grids

This study proposes an elastic finite difference(FD)time domain method with variable grids in three-dimensional cylindrical coordinates.The calculations will diverge and become less accurate by conventional cylindrical FD as the grid size gradually becomes more extensive with the increasing radius.To prevent grids from being too coarse in far fields,we compensate for the grid cell infl ation by refi ning the grid step in the azimuthal direction.The variable grid FD in the cylindrical coordinate systems has a higher effi ciency in solving acoustic logging while drilling(LWD)problems because the grid boundaries are consistent with those of the drill collar and the borehole.The proposed algorithm saves approximately 94%of the FD grids,80%of the computation time,and memory with a higher calculation accuracy than the FD on rectangular grids for the same models.We also calculate the acoustic LWD responses of the fl uid-fi lled borehole intersecting with fractures.Refl ections are generated at the fractures,which can be equivalent to an additional scattering source.The mode conversions between the collar and the Stoneley waves are revealed.The Stoneley spectra are more sensitive to the fracture.Finally,the logs in a heterogeneous formation with two refl ectors far from the borehole are modeled,and a means of estimating the azimuth of geological interfaces from refl ections is proposed.

A feedback control method for phase signal demodulation in fber-optic hydrophones

In the realm of acoustic signal detection,the identification of weak signals,particularly in the presence of negative signal-to-noise ratios,poses a significant challenge.This challenge is further heightened when signals are acquired through fiber-optic hydrophones,as these signals often lack physical significance and resist clear systematic modeling.Conventional processing methods,e.g.,low-pass filter(LPF),require a thorough understanding of the effective signal bandwidth for noise reduction,and may introduce undesirable time lags.This paper introduces an innovative feedback control method with dual Kalman filters for the demodulation of phase signals with noises in fiber-optic hydrophones.A mathematical model of the closed-loop system is established to guide the design of the feedback control,aiming to achieve a balance with the input phase signal.The dual Kalman filters are instrumental in mitigating the effects of signal noise,observation noise,and control execution noise,thereby enabling precise estimation for the input phase signals.The effectiveness of this feedback control method is demonstrated through examples,showcasing the restoration of low-noise signals,negative signal-to-noise ratio signals,and multi-frequency signals.This research contributes to the technical advancement of high-performance devices,including fiber-optic hydrophones and phase-locked amplifiers.

Feature analysis of acoustic emission sources for rail crack detection by the finite element method

The safety of rail is very important for the development of high speed railway, and it is necessary to investigate the features of inner cracks in rail. In order to obtain the features of Acoustic Emission （AE） sources of inner cracks in rail, AE sources with different types, depths and propagation distances are examined for crack in rail. The finite element method is utilized to model the rail with cracks and the results of experiment demonstrate the effectiveness of this model. Wavelet transform and Rayleigh-Lamb equations are utilized to extract the features of crack AE sources. The results illustrate that the intensity ratio among AE modes can identify the AE source types and the AE sources with different frequencies in rail. There are uniform AE mode features existing in the AE signals from AE sources in rail web, however AE signals from AE sources in rail head and rail base have the complex and unstable AE modes. Different AE source types have the different propagation features in rail. It is helpful to understand the rail cracks and detect the rail cracks based on the AE technique.

A rapid audio event detection method by adopting 2D-Haar acoustic super feature vector

For accuracy and rapidity of audio event detection in the mass-data audio pro- cessing tasks, a generic method of rapidly recognizing audio event based on 2D-Haar acoustic super feature vector and AdaBoost is proposed. Firstly, it combines certain number of con- tinuous audio frames to be an ＂acoustic feature image＂, secondly, uses AdaBoost.MH or fast Random AdaBoost feature selection algorithm to select high representative 2D-Haar pattern combinations to construct super feature vectors; thirdly, analyzes the commonality and differ- ences between subcategories, then extracts common features and reduces different features to obtain a generic audio event template, which can support the accurate identification of multi- ple sub-classes and detect and locate the specific audio event from the audio stream accurately. Experimental results show that the use of 2D-Haar acoustic feature super vector can make recog- nition accuracy 5% higher than ones that MFCC, PLP, LPCC and other traditional acoustic features yielded, and can make tile training processing 7 20 times faster and the recognition processing 5-10 times faster, it can even achieve an average precision of 93.38%, an average recall of 95.03% under the optimal parameter configuration found by grid method. Above all, it can provide an accurate and fast mass-data processing method for audio event detection.

A rigorous real-time acoustic positioning method for ocean bottom seismic exploration

The conventional technique for positioning seafloor geophones in ocean bottom seismic exploration encounters several challenges,including the significant impact of outliers on positioning results,underutilization of high-precision observations,and low efficiency in real-time data processing.These issues inevitably affect the quality of seismic exploration outcomes.To address these challenges and enhance the accuracy of geophone positioning,this paper proposes a rigorous real-time acoustic positioning method for geophones based on sequential adjustment and Baarda's outlier detection approach.The proposed method comprises three key steps:grouping the original acoustic observations,constructing the intra-group acoustic positioning model,and synthesizing the positioning results across the different groups.The validity and practicality of this approach are confirmed through a simulation experiment as well as the field experiment conducted in the Bohai Sea,China.The results demonstrate that the proposed method effectively eliminates outliers in the original observations and maximizes the utilization of high-quality observations.Compared to traditional acoustic positioning methods,it significantly reduces positioning errors from meters to decimeters,and in some cases can achieve centimeter-level precision.When the sound velocity profile in the operating sea area is measured,the method can attain the posterior standard deviation at the millimeter level and positioning errors within 10 cm.When the sound velocity profile is unknown,the method can achieve the posterior standard deviation at centimeter-level and positioning errors of approximately 20 cm.

声波透射法检测技术在桩基检测中的应用

随着我国城市化进程加快,基础设施建设需求不断增长。桩基是工程项目建设的重要基础,桩基工程具有明显的特殊性和复杂性,其施工质量和桩体状态检测是保障工程质量和安全的关键。声波透射法作为一种先进的非破坏检测技术,能够准确、快速地检测桩体的内部结构和缺陷。阐述了声波透射法检测技术的原理,并结合具体项目,分析了声波透射法检测技术在桩基检测中应用的实例,旨在充分发挥声波透射法检测技术优势,提高桩基检测质量。

声波法在输油管道上的可检测泄漏率分析

为了确保输油管道出现泄漏时能够及时检测到泄漏,对声波法在输油管道上的可检测泄漏率进行了分析。首先,建立了声波产生和传播衰减模型,根据模型分析了声波在管道内的衰减性,得到管道两端声波衰减幅值的计算方法;其次,采用基于互信息优化的自适应噪声完备集合经验模态分解(complete ensemble empirical mode decomposition with adaptive noise,简称CEEMDAN)和互谱分析相结合的去噪算法对采集的信号进行去噪,并实验验证了衰减模型可准确估计声波的衰减幅值,去噪算法可以有效消除信号中的噪声;最后,分析了管道特性与声波法在输油管道上的可检测泄漏率之间的关系。研究表明,管道特性在一定程度上决定了声波法的可检测泄漏率,声波法在输油管道上的最小可检测泄漏率可达0.45%。

基于优化变分模态分解的混凝土浅层空洞病害识别

针对开放环境下混凝土空洞病害检测的病害特征识别中噪声干扰、成分识别问题进行了研究,提出了基于优化变分模态分解(improved variational mode decomposition,IVMD)与自由振动衰减速度的混凝土浅层病害声振信号识别方法。该研究建立了混凝土浅层空洞病害的理论模型,仿真了不同工况下的病害特征频率及其变化规律;提出了基于IVMD的信号分解方法,设计了基于Tent混沌与柯西变异优化的麻雀搜索算法联合搜索变分模态分解的关键参数k和α,在最佳分解的基础上提出了基于自相关函数图形、相关系数、衰减系数与频域分布情况的浅层空洞病害本征模态函数(intrinsic mode function,IMF)识别方法;选取幅值衰减评估了特征IMF的衰减速度,得出了基于振动衰减特征的空洞病害识别方法;通过预埋病害模型试验对比分析,验证了所提方法的有效性。研究结果表明,基于IVMD的分解方法能够有效降低噪声及其他成分的干扰,提高空洞病害识别精度和准确度。

声波法在直埋供热管道泄漏检测中的工程应用

利用声波法对城市内2段直埋供热管道的泄漏情况进行非开挖式工程实测,分析了不同工程条件下的泄漏声波信号特征,并采用傅里叶滤波进行声波振动信号的降噪处理。研究表明,傅里叶滤波可有效提升泄漏定位精度,实测漏点定位误差小于2%,基于傅里叶滤波降噪的声波法直埋供热管道泄漏检测技术具有较好的工程应用价值。

多层复合材料黏接缺陷的声阻法检测

用于直升机桨叶的新型多层复合材料以不锈钢、橡胶、加热组件和玻纤黏接而成,因其结构复杂且工作环境恶劣,亟需进行严格的质量控制。常规超声检测信号混叠现象严重,无法检出橡胶与玻纤黏接层缺陷。在分析复合材料机械阻抗的基础上,搭建了基于声阻法检测该复合材料的模型,并推导出两个用以表征黏接缺陷信息的参量。试验结果表明,使用机械阻抗的相位与幅值能较好地表征材料缺陷的深度与大小信息,声阻法检测复材黏接缺陷具有较高的可靠性和缺陷检出率。

嗓音声学检查的研究分析

语言交流在人际交往中扮演着举足轻重的角色,随着时代的发展和部分工作的需要,越来越多的人出现了过度用嗓情况,嗓音疾病的患病率也在逐年增加。嗓音声学正是针对该问题衍生出来的新兴学科,其作为一个重要的医学领域,同时也是耳鼻咽喉科的一个重要分支,近年来受到了人们广泛关注。随着人们对生活质量要求的不断提高,罹患嗓音相关疾病的患者和从事嗓音相关职业的人群对嗓音质量评估的关注度也越来越高。因此,通过医学手段来评估嗓音质量的方法也越来越多。如何准确、客观地评估被检测者的嗓音质量和恢复情况,对嗓音声学的研究具有重要意义。该文就嗓音声学检查的研究进展进行综述,探讨国内外在这一领域的研究现状、存在的问题及未来发展方向。

钢管和PE管两种燃气管道的泄漏声源特性分析

【目的】分析钢管和PE管这两种燃气管道的泄漏声源特性。【方法】通过燃气管道泄漏检测实验平台,采用声波法分别对PE管和钢管进行声源泄漏实验。【结果】结果表明:在中、低压条件下钢管和PE管泄漏点处参数特征随着管道压力的增大而增大;当压力和孔径一定时,钢管泄漏的时域幅值比PE管泄漏时大;当压力和孔径一定时;钢管的ASL、RMS值均大于PE管。【结论】实验结果有助于预防管道泄漏,可为城镇燃气管道泄漏检测提供理论支持。

基于开槽法的超声应力换能器LCR波检测深度校准研究

基于开槽法开展了超声应力换能器LCR波检测深度校准研究。其原理是当开槽深度超过LCR波渗透深度时,波的传播会受开槽的影响。首先,采用弹性波时域显式物理场,建立了LCR波渗透深度的有限元研究模型,仿真了LCR波的产生及传播过程,并且分析了槽型对LCR波及检测深度的影响。通过声时差与幅值变化幅度2个特征参数,得出矩形槽比梯形槽更适合用于校准换能器的检测深度。在此基础上,开展不同频率换能器检测深度校准试验,制定不同深度的矩形槽试块,分别校准了2.5、5、7.5 MHz频率下的LCR波渗透深度,并对2.5 MHz的实验结果开展不确定度评定。结果表明:2.5 MHz换能器的LCR波检测深度10次测量的平均值为2.85 mm,与标称值的误差为0.15 mm,合成标准不确定度为0.29 mm。研究结果对于校准不同频率下换能器检测深度及提高应力测量空间分辨率具有意义,并且可为LCR波渗透深度的经验公式提供实验参考。

基于改进阈值函数的直埋供热管网检漏研究

为提高声波法直埋热水供热管网泄漏应用的定位精度,在分析各种小波法阈值函数适用性的基础上,提出了改进阈值函数降噪方法,该方法理论上能够克服软阈值函数的恒定偏差和硬阈值函数信号振荡的缺点,设置调节参数,提升降噪能力,保留小于阈值点区域信号,避免有效信号丢失。在大型直埋热水循环管网中进行泄漏测试实验,研究表明采用本方法进行声波法直埋供热管道泄漏检测,可实现泄漏定位误差在±1 m内,定位精度可达0.11%~3.49%,最后选择北京市供热系统中实际工程案例,采用本方法进行声波法泄漏检测,泄漏定位误差为0.37%~0.66%,定位精度提升。

直埋热水供热管道泄漏声波特性实验研究

城市直埋供热管网泄漏精准智能定位是城市供热基础设施安全与节能降碳及智能化运行的关键环节。为提高利用声波法进行直埋热水供热管网泄漏的定位精度,建立DN300管径的大型模化供热实验系统,研究了有无泄漏时,管壁上声波信号随传播距离、温度、压力和流量变化的特性,分析了管道上水泵振动声波的时频特点,然后利用小波阈值法进行信号降噪,得到了供热管道泄漏的特征频段。研究表明,温度对泄漏声波频段影响显著,温度越高声波特征频段分布越大,温度从31℃升高到86℃后,特征频段从200~800 Hz扩展至50~1500 Hz;传播距离、压力和流量主要影响泄漏信号幅值,对特征频段范围影响较小;水泵声波能量主要集中在3000~4000 Hz处于泄漏信号频段范围之外。利用小波阈值法进行信号降噪,提高定位精度可达0.11%,实现定位距离偏差在±1 m内。

低应变法与声波透射法在桩基检测中的应用分析

桩基础工程具有较强的隐蔽性,在各种因素影响下易产生质量问题,进而降低建筑的耐久性和稳定性,因此,需做好桩基的检测工作。文中以某高层建筑桩基工程为例,通过对比分析低应变检测法与声波透射检测法在桩基检测中的具体应用,及时发现内部缺陷,并采取相应措施,以减少安全风险和隐患。

声波透射法在机场改扩建工程中基桩检测的应用分析

针对传统基桩检测方法存在的缺陷定位不准、检测结果精度低、分级评价容易出现偏差等问题,以长沙机场改扩建工程为例,分析声波透射法在基桩检测中的应用。通过初步检测与跨孔声波透射法结合,精确探测基桩缺陷范围,利用声波传播特征和参数变化,获取缺陷详细信息。采用PSD斜率法量化异常数据,提高定位精度。结合声学参数分析,对基桩完整性进行分类评估,指导建造工作,提升工程质量。实验结果表明:声波透射法可以直观的判断基桩是否存在缺陷,并进行详细定位,检测结果直观、精确、高效,提升作业效率,对于基桩质量的分级评估完全符合工程规范要求,具有很高的参考价值。

高层建筑中的桩基检测技术

针对高层建筑中的桩基检测技术展开探讨,采用案例分析法,以实际工程项目为主要研究对象,简要介绍了高层建筑的实际情况,利用声波透射法对桩基质量展开检测分析,明确了声波与振动的关系、能量和传播特点,进一步分析了固体介质中声波的能量衰减情况,以及实际检测过程中的技术要点,最后运用声波透射法对本项目桩基完整性进行检测和判断,为工程质量的有效控制提供了极大便利。此次研究结果可为类似工程项目提供参考,也可充实相关理论技术研究内容。