共查询到19条相似文献,搜索用时 93 毫秒
1.
2.
针对北极冰层冰水界面具有小尺度粗糙界面的情况,给出由冰层造成的混响平均强度的理论预报公式。首先将北极冰层等效为具有粗糙界面的弹性介质,并且采用小粗糙度微扰理论在精细拟合粗糙度谱的基础上,建立粗糙冰层的三维散射强度模型,然后建立三维双基地声呐几何模型确定有效散射区域,最后给出双基地冰下混响平均强度的估算公式,并在所拟合的粗糙度谱的情况下,利用该预报公式计算双基地声呐配置参数和海冰物理及声学特性对冰下混响强度的影响算例。数值仿真表明该公式能够估算出北极冰下双基地声呐产生的混响平均强度,并且分析出了时延、基线长度等声呐配置参数和冰层声速比、密度比等海冰物理参数会对混响强度造成的影响。声呐的配置参数主要影响散射的有效面积,海冰的物理参数则影响着冰层的散射强度。其中,冰层声速比不仅影响混响强度的大小,还会影响混响强度随时间的衰减速度。 相似文献
3.
4.
为揭示深海多途传播效应及界面参数对本地界面混响强度的影响规律,将界面混响表述为不同多途混响衰落过程的非相干叠加结果,并结合界面散射的若干物理机制,建立了以海面海底物理参数为变量的混响强度模型.通过数值仿真和理论分析研究了不同多途混响强度的衰落特性、到达角的空间分布及部分物理参数对混响强度的影响,并利用南海海盆(典型泥质海底)实验数据对模型有效性进行验证.仿真结果表明,界面混响强度随时间变化呈现多峰结构,峰值时间与多途混响的到达时间分布一致。声源与接收器均位于近海面处时,首峰的峰值强度及其衰落过程由海面风速决定,其它峰的峰值强度由海面海底参数共同决定,但其衰落过程主要受到底质参数的影响. 相似文献
5.
6.
研究了浅海非线性内波对远程混响场的影响。通过分析非线性内波活动引起声源到海底散射元以及散射元到接收点之间的声传播变化,给出了非线性内波引起远程混响强度变化的表示,建立了非线性内波存在下的浅海远程混响模型,数值计算了非线性内波运动引起远程混响强度的变化。理论和数值计算表明,非线性内波的活动能够引起远程混响强度的变化,在某些情况下会导致远程混响强度增强。通过讨论非线性内波引声简正波的耦合效应,给出了其引起远程混响强度增强的原因。 相似文献
7.
针对傅氏空时二维谱估计分辨率低以及声呐空时采样数据样本数不足给角度-多普勒成像带来困难的问题,提出一种水声信号稀疏重构的高分辨角度-多普勒成像方法和抗混响空时滤波器的稀疏重构方法。该方法在声呐阵列单测量向量的极少观测样本条件下,建立阵列信号的空时稀疏表示模型,应用稀疏表示的匹配追踪算法和基追踪算法重构回波与混响的高分辨角度-多普勒像。并根据运动声呐回波与混响的空时分布规律及声呐待检测距离单元位置的先验信息,沿着混响空时分布脊线设计混响稀疏表示的专用空时导向向量字典,通过重构抗混响空时滤波器来抑制角度-多普勒平面的混响干扰。对运动声呐前视和侧视阵列的计算机仿真结果表明,在混响背景中,该方法采用声呐阵列单测量向量重构了低速运动目标多亮点回波的高分辨角度-多普勒像,频率分辨率突破傅里叶分辨率,角度分辨率突破阵列瑞利限,分辨率明显优于傅氏空时谱估计。 相似文献
8.
9.
《物理学报》2021,(17)
收发设备在海面附近的深海混响实验中,多途时延使得最先到达水听器的为海面混响信号,且不受海底散射声场的干扰.本文利用射线理论描述深海声传播的格林函数,采用粗糙界面一阶小斜率近似方法描述全角度海面散射,给出海面混响声场的表达式.同时考虑了海面表层气泡散射的贡献,获得了海面混响理论.通过数值仿真数据和深海实验数据的比较对海面混响模型进行验证,分析了不同接收深度、频率下的海面混响强度衰减趋势.结果表明:低海况条件下,低频海面混响由粗糙界面散射主导,气泡散射可以忽略,随频率升高,气泡散射对海面混响的贡献逐渐增大,海面附近收发深度的小幅变化对混响衰减曲线的影响不明显.基于该模型提出一种反演海面粗糙界面谱参数的方法,数值计算结果验证了该模型能够在风速已知的前提下,通过海面混响数据提取海面粗糙界面谱参数. 相似文献
10.
本文讨论了有源声呐设计中的三大要素(声呐波形、声呐信道和接收机)之间的相互关系,着重讨论有源声呐信道(包括混响、传播和目标散射过程的信息模型),提出用统一的推广散射函数和相干函数来描述,并通过对信道输出相关函数以及匹配滤波输出的分析指出这两个函数的物理意义和测量方法,最后还讨论声呐最佳波形和最佳接收机设计的基本原则。 相似文献
11.
The problem of estimating the parameters of a reverberation signal generated due to scattering of acoustic waves on a rough
surface is considered for a bistatic localization scheme using the example of tone and tone-pulse signals. Relatively simple
calculation schemes that make it possible to recalculate three-dimensional space-time roughness spectra into angular-frequency
reverberation characteristics and determine the positions of the surface regions that mainly contribute to the integral reverberation
level are found. A reverberation spectrum is calculated for the wind waves typical for shallow-water closed basins, and the
positions of the scattering regions forming the components of this spectrum are determined. 相似文献
12.
13.
Underwater reverberation environments that satisfy the conditions of uniformity and isotropy of the diffuse field can be used to measure the acoustic characteristics of underwater targets. This study combines two practical indicators — the standard deviation of the absolute sound pressure field (to indicate uniformity) and the analysis of the wavenumber spectrum in the spherical harmonics domain (to indicate isotropy) — for an accurate evaluation of the diffusion of the sound field in a reverberation tank. A method is proposed that can improve the narrow-band diffusion of the sound field by employing a randomly fluctuating surface. An acoustic experiment was performed in a reverberation water tank (1.2 m×1 m×0.8 m), where a randomly fluctuating surface was generated by making waves. The experimental results show that as the wave motion contributes effectively to the random reflection of sound rays in all directions, the uniformity and isotropy are improved significantly when the surface is fluctuating randomly. This work helps to ensure accurate measurements of the characteristics of underwater targets in reverberation tanks. 相似文献
14.
Metallic plates are used in recording studios to create artificial reverberation. In this paper, the flexural vibrations of such plates are analysed in order to better understand the influence of geometry and materials on the quality of plate reverberation. A comparison is made with acoustic reverberation, both in the time and frequency domain. This comparison is supported by objective criteria such as modal density and density of reflections. From a physical point of view, the internal and external damping mechanisms are examined in detail since they determine the frequency dependence of the reverberation time. Theoretical results are validated through comparison with experiments performed on an EMT140 reverberation plate. The underlying model is aimed at developing numerical simulations of plates (virtual reverberators) allowing a large variety of reverberations based on variations of geometry and materials as input parameters. 相似文献
15.
16.
在构建混响语声数据集时,由于缺乏真实长混响房间脉冲响应且模拟的房间脉冲响应与真实不符,因而导致数据驱动的混响时间盲估计模型性能下降。提出了一种基于条件生成对抗网络的房间脉冲响应模拟法,该方法利用真实的房间脉冲响应训练条件生成对抗网络,可以根据指定的混响时间模拟更加真实的房间脉冲响应。使用不同方法模拟的房间脉冲响应构建训练集用于训练盲估计模型,通过声学实验评估模型性能。实验结果表明,由该方法模拟的房间脉冲响应训练的估计模型在不同信噪比下均具有最小的均方根误差且在长混响情况下显著优于其他模型。 相似文献
17.
R. A. Vadov 《Acoustical Physics》2007,53(2):172-180
In experiments on the long-range propagation of explosion-generated signals, a noise background accompanying the classical signal quartets are repeatedly observed. The background smoothly increases before the arrival of the first signal of the quartet, then decreases, and completely vanishes after the arrival of the last signal of the same quartet. The data of an experiment performed in winter in a deep-water region of the northwestern Pacific are considered. These data are used to demonstrate the phenomenon at hand and to show that the noise background of the quartets is the manifestation of the bistatic reverberation caused by sound scattering by the rough ocean surface towards the receiver located a long distance from the source. An easy-to-use technique is proposed for calculating the time relations between the direct signal and the surface-reverberation one. Calculations are performed for the time structure of the bistatic surface reverberation to explain the observed features of the phenomenon. 相似文献
18.
The increasing presence of low frequency sources and the lack of acoustic standard measurement procedures make the extension of reverberation time measurements to frequencies below 100 Hz necessary. In typical ordinary rooms with volumes between 30 m3 and 200 m3 the sound field is non-diffuse at such low frequencies, entailing inhomogeneities in space and frequency domains. Presence of standing waves is also the main cause of bad quality of listening in terms of clarity and rumble effects. Since standard measurements according to ISO 3382 fail to achieve accurate and precise values in third octave bands due to non-linear decays caused by room modes, a new approach based on reverberation time measurements of single resonant frequencies (the modal reverberation time) has been introduced. From background theory, due to the intrinsic relation between modal decays and half bandwidth of resonant frequencies, two measurement methods have been proposed together with proper measurement procedures: a direct method based on interrupted source signal method, and an indirect method based on half bandwidth measurements. With microphones placed at corners of rectangular rooms in order to detect all modes and maximize SNRs, different source signals were tested. Anti-resonant sine waves and sweep signal turned out to be the most suitable for direct and indirect measurement methods respectively. From spatial measurements in an empty rectangular test room, comparison between direct and indirect methods showed good and significant agreements. This is the first experimental validation of the relation between resonant half bandwidth and modal reverberation time. Furthermore, comparisons between means and standard deviations of modal reverberation times and standard reverberation times in third octave bands confirm the inadequacy of standard procedure to get accurate and precise values at low frequencies with respect to the modal approach. Modal reverberation time measurements applied to furnished ordinary rooms confirm previous results in the limit of modal sound field: for highly damped modes due to furniture or acoustic treatment, the indirect method is not applicable due to strong suppression of modes and the consequent deviation of the acoustic field from a non-diffuse condition to a damped modal condition, while standard reverberation times align with direct method values. In the future, further investigations will be necessary in different rooms to improve uncertainty evaluation. 相似文献
19.
混响是室内声学中的重要现象,在室内设计与音频信号处理中都需要测量或估计混响时间。本文改进了一种基于最大似然估计的混响时间盲估计方法,即采用说话人在房间中自然说话时发出的混响语音信号来估计混响时间的方法。该方法首先确定语音衰减段的最优边界,其次计算该衰减段的两个额外参数,据此筛选出符合条件的语音段,最后将满足条件的语音段采用最大似然估计得到混响时间估计值。在五个不同混响时间条件下的仿真表明,与已有方法相比,改进方法估计的混响时间同真实混响时间的偏差更小,方差更低,估计准确性较高。 相似文献