共查询到20条相似文献,搜索用时 203 毫秒
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根据被动声纳工作原理,构建被动声纳探测水下目标物概率数学模型。利用声学调查实测数据,综合考虑传播损失、环境噪声、和水文环境分布及季节变化,研究温跃层垂直分布及季节变化对声纳检测概率的影响。结果表明:温跃层对被动声纳影响巨大,逆温跃层环境中,声纳检测概率从海表向下逐渐减小;正温跃层对声纳总的影响与逆温跃层相反,在正温跃层上界,检测概率从表层向下先减小后增大;逆温跃层对被动声纳检测概率的影响随目标物与声纳距离的增大而增大,正温跃层影响相反。 相似文献
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由于自主小平台声纳孔径有限,对声纳探测的分辨率的提高有所限制。小平台的机动可以有效的与声纳探测方法相结合来提高声纳探测性能。针对这一特点,提出一种基于多普勒频移技术的被动合成孔径声纳探测方法。该方法根据自主小平台的机动所引起声纳的接收信号多普勒频移的变化,进行目标的频率与方位联合估计。本文将自主小平台的机动引入到波束形成技术当中形成一种新的被动合成孔径技术。数值仿真表明,该方法可以有效的进行目标方位估计,并且获得较高的方位分辨率,改善了自主小平台的探测性能。 相似文献
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礁石和海洋动物引起的混响是主动声纳最严重的干扰, 如何区分礁石、鱼群和水中目标一直是制约主动声纳识别技术的难点问题. 针对礁石与目标回波难以区分的问题, 从特征识别的应用角度, 研究水中复杂目标全方位回波亮点特征的有效表征和应用方式, 基于目标回波亮点模型, 提出拷贝相关器输出的目标散射函数估计方法, 给出对目标回波亮点相对关系进行定量分析的目标回波特征统计表征方式, 并基于湖上实验提取了物理机理明确的目标回波亮点统计特征, 使得目标时间-角度谱中所蕴含的目标特征信息能够很直接地转化为主动声纳易于应用的目标特征.
关键词:
水中目标
回波亮点
统计特征 相似文献
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介绍了中国古乐律,半根据中国古乐律制作了相应的发声体,从实验上再现中国古乐律的制定原则,测定了发声体的频率,并将其和理论值进行了比较。 相似文献
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随着降噪消声技术的发展,如何有效被动检测低噪声目标,成为声纳研发者面临的主要问题之一。本文基于频谱感知、多频带联合检测及信息融合技术,提出了具有环境噪声利用和背景噪声抑制功能的多频带联合包络调制谱检测技术。此技术侧重基频调制谱检测,将可用带宽分为多个子频带,动态感知子频带内强频谱区域,将其峰值频率作为解调载波频率。并通过降采样和时间积累,提高调制谱频率分辨率和信噪比,通过联合检测和信息融合,提高调制谱检测率。仿真和海试数据分析验证了方法的有效性。此方法具有一定的应用价值和实际意义,将来还需要对方法理论和机理进行深入研究。 相似文献
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特征提取是水下无源声呐目标分类识别的关键步骤,提出了一种基于听觉Patterson-Holdsworth耳蜗模型的听觉域张量特征提取方法。将耳蜗模型的滤波器冲激响应视为信号分解的基函数,根据听觉模型非线性尺度或常规线性尺度确定不同通道的中心频率,然后计算出相应通道的增益和带宽,并量化冲激响应的阶数和相位参数,得到信号分解基,再根据信号分解原理得到通道数×阶数×相位数的三阶张量特征,并通过计算测试样本张量特征与训练样本张量特征间的相似性实现了水下无源声呐目标的分类识别。海上实录无源声呐目标的分类识别实验表明,提取的张量特征具有比较好的分类识别性能,听觉模型等效矩形带宽尺度优于线性尺度划分中心频率,能够提高无源声呐的目标指示能力。 相似文献
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《声学学报:英文版》2020,(3)
Feature extraction is a key step for underwater passive sonar target classification and recognition.A kind of tensor feature extraction method based on auditory PattersonHoldsworth cochlear model is proposed.First,the filter impulse response of the cochlear model is regarded as the basis function of signal decomposition,and the center frequency of different channels is determined according to the nonlinear scale or conventional linear scale of the auditory model.Then,the gain and bandwidth of the corresponding channel are calculated,and the order and phase parameters of the impulse response are quantified to obtain a relatively complete signal decomposition basis.And according to the principle of signal decomposition,the third-order tensor features of channel number-order number-phase number are obtained.Finally,the classification and recognition of the underwater passive sonar target is realized by calculating the similarity between the testing sample tensor feature and training sample tensor feature.The experiment on passive sonar target classification and recognition shows that the extracted tensor features have better classification and recognition performance,and the equivalent rectangular bandwidth scale of the auditory model is better than the linear scale to divide the center frequency,which can improve the target indication ability of passive sonar. 相似文献
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Cepstral processing techniques in principle allow the separation of superposed pulses, such as those which occur in acoustic reflection, where a reflected pulse is a delayed and distorted version of the incident pulse. Additionally, the impulse response of the reflecting system, or equivalently its reflection coefficient, can also be determined. In practice, the accurate extraction of the impulse response is rendered difficult by the mathematical and computational properties of the power cepstrum procedure. In particular, spectral irregularity of the incident pulse, experimental noise and cepstral aliasing can cause the impulse response in the cepstrum to be masked. However, by careful selection of the incident signal, anti-aliasing filter, sampling frequency and echo delay in relation to the total sampling time, and the use of signal processing techniques such as time domain averaging, recursive filtering in the cepstral domain and zero padding, it is possible to produce good quality cepstra in which the reflector impulse response appears as an isolated feature. Experiments conducted on an electrical analogue of the acoustical reflection process have allowed the cepstral technique to be developed and evaluated. The acoustical reflector is simulated by a passive electrical filter network; the objective of the measurement and subsequent processing is the determination of the transfer function of this network. Good agreement is obtained between theoritical and measured transfer functions for a variety of filter networks indicating that cepstral techniques may be useful for acoustical reflection measurements given adequate transducer properties and environmental conditions. 相似文献
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C W Thorpe R H Bates S M Dawson 《The Journal of the Acoustical Society of America》1991,90(6):2931-2934
A sonar system's echolocation capabilities can be inferred from the ambiguity distribution (defined here in terms of the conventional signal response function) of each of its transmitted signals. Several records of sounds emitted by Hector's dolphin are analyzed. The computed ambiguity distributions indicate that the sonar clicks of Hector's dolphins should be capable of resolving the ranges of targets as close together as 2 cm apart, but that target velocities cannot be resolved to any useful degree from a single echo. 相似文献
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Feuillade C Meredith RW Chotiros NP Clay CS 《The Journal of the Acoustical Society of America》2002,112(6):2702-2712
During August 1998, a bottom scattering tank experiment was performed at the Applied Research Laboratory, University of Texas to measure wideband acoustic reverberation from multiple objects (e.g., cobbles and pebbles) placed on a sediment simulation of the sea floor. In preparation for processing and analyzing the experimental data, time domain scattering measurements made with stainless steel and glass balls suspended in the water column were used to calibrate the sonar transceiver system by deconvolving the theoretical impulse response for steel and glass spheres, obtained via the Faran elastic sphere scattering model, from the scattered time signals. It is the analysis of these calibration measurements which forms the subject of this paper. Results show the critical importance of accurate input-output system calibrations for time domain sound scattering research, and successfully demonstrate a time domain method for accurately calibrating the complete sonar transceiver function, i.e., both the amplitude and time dependence, using a known reference target. The work has implications for boundary and volume scattering applications. 相似文献
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This paper investigates the applicability to sperm whales of the theory of sound radiating from a piston. The theory is applied to a physical model and to a series of sperm whale clicks. Results show that wave forms of off-axis signals can be reproduced by convolving an on-axis signal with the spatial impulse response of a piston. The angle of a recorded click can be estimated as the angle producing the spatial impulse response that gives the best match with the observation when convolved with the on-axis wave form. It is concluded that piston theory applies to sperm whale sonar click emission. 相似文献
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三维成像声呐的成像结果是三维点云,基于点云的三维成像声呐目标分类方法具有网络结构复杂,计算量大的特点,针对这一问题本文提出了一种将三维成像声呐成像结果从三维点云投影至二维图像的方法,并且使用轻量化卷积神经网络实现了三维成像声呐快速目标分类。该方法首先对三维成像声呐波束形成后的波束域数据进行最大值滤波和阈值滤波,降低点云数据维度;接着,依据三维成像声呐的波束方向,将点云投影为深度图和强度图,分别保存点云的位置信息和强度信息;然后,利用深度图和强度图分别作为第一个通道和第二个通道构建混合通道图,将混合通道图作为目标分类网络的输入,从而将三维点云的目标分类问题转换为二维图像的目标分类问题;最后使用MobileNetV2网络实现了三维成像声呐快速目标分类。实验结果表明,通过本文提出的投影方法可以用二维图像分类网络完成三维成像声呐点云的目标分类任务;而且混合通道图比单独的强度图和深度图收敛速度更快,结合目标识别网络可以25fps实时的进行目标分类,在真实数据集上分类精度达到了91.13%。 相似文献
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Islas-Cital A Atkins PR Foo KY Picó R 《The Journal of the Acoustical Society of America》2011,130(4):1880-1887
The phase angle component of the complex frequency response of a sonar system operating near transducer resonance is usually distorted. Interpretation and classification of the received sonar signal benefits from the preservation of waveform fidelity over the full bandwidth. A calibration process that measures the phase response in addition to the amplitude response is thus required. This paper describes an extension to the standard-target calibration method to include phase angle, without affecting the experimental apparatus, by using dual-frequency transmission pulses and frequency-domain data processing. This approach reduces the impact of unknown range and sound speed parameters upon phase calibration accuracy, as target phase is determined from the relationship of the two frequency components instead of relying on a local phase reference. Tungsten carbide spheres of various sizes were used to simultaneously calibrate the amplitude and phase response of an active sonar system in a laboratory tank. Experimental measurements of target phase spectra are in good agreement with values predicted from a theoretical model based upon full-wave analysis, over an operating frequency of 50-125 kHz. 相似文献