基于二指向性接收阵元强度差的定向方法

水声领域中常用的高频定向算法通常基于时延或相位,这些方法受半波长布阵的限制,当信号频率超过一定限度时会产生角度模糊,从而影响方位估计效果。本文提出利用声轴方向有一定开角的有指向性水听器来引入不同阵元接收信号的强度差,利用强度差来估计目标的方位。这种方法由于不涉及相位或时延信息,一定条件下解决了高频声源定向过程中的角度模糊问题,并通过仿真和试验数据对算法性能进行了验证。     

强干扰下空间抗混叠宽带波达方位估计

提出了基于改进频率差分(FD)技术的空间抗混叠波达方位(DOA)估计方法,实现了阵元稀疏排布,即在阵元间距远大于入射信号波长时,存在栅瓣模糊情况下多水下声学目标的方位估计。首先,确定目标方位角度搜索范围,建立阵列信号处理模型,对宽带信号不同频率成分之间进行频率差分处理,从而降低信号频率以满足阵元稀疏排布阵列的空间奈奎斯特采样要求。然后,基于投影子空间正交性检验(TOPS)算法构建一个对角变换矩阵,利用对角酉变换矩阵正交性直接对阵列流形进行频率差分处理,使其频率差分处理输出的信号个数与输入信号个数相等。最后,进一步推导频率差分域等效目标方位与真实入射信号角度等价的条件,并基于该等价条件进行频率筛选,最终获得无模糊的空间方位谱结果。经仿真实验验证,所提算法在信噪比为-10～20 dB范围内,估计结果均方根误差低于0.1°,有效抑制了栅瓣且受干扰强度影响较小。经海试数据验证,所提算法可以有效估计出目标方位,并避免空间混叠项干扰。所提空间抗混叠波达方位估计方法能够有效抑制栅瓣模糊,提高目标方位估计精度,且在强干扰条件下仍具有较好的角度估计性能。     

室内两步法监督式学习双耳声源距离估计

提出一种室内环境下两步法监督式学习双耳声源距离估计算法,该算法通过预先估计声源方位角信息以克服声源方位角的变化对声源距离估计性能的不利影响.该算法第1步利用深度神经网络模型估计声源的方位角,并将不同方位角的双耳信号分类;第2步中对每个方位角的双耳信号采用独立的深度神经网络模型进行声源距离估计,其中距离特征选用双耳信号的一些双耳特征和统计特性。在仿真和实际环境下,本文提出的两步法声源距离估计算法的距离估计准确率比现有算法提高了3%~5%左右,并且在各种不匹配环境下的距离估计准确率比现有算法高出5%~10%左右。实验结果表明利用声源方位角信息可以有效提高双耳声源距离估计算法的性能。      

某型振动轮噪声数值模拟及优化分析

空中声源的辐射噪声谱包括宽带连续谱和窄带线谱,线谱能量高于连续谱。与水下声源相比,空中声源的运动速度普遍较高,线谱多普勒频移明显,可用于进行水下对空中声源的运动参数估计。首先通过时频分析提取接收信号的瞬时频率,而后利用非线性最小二乘法将瞬时频率提取值与预测值相拟合,进而估计声源的运动参数(声源的运动速度、静止频率、与接收器最小水平距离及经过最近点时刻)。仿真与实验均能较为准确地估计出声源运动参数,同时在实验中实现了水下对空中运动声源的测距和定位,测距误差小于15.8%。在满足一定信噪比和保证足够多普勒信息的情况下,该参数估计方法具有很好的适用性。     

声学滑翔机联合的深海水下声源定位

为了验证多台滑翔机用于声源位置估计的可行性,提出了一种基于声学滑翔机的联合水下声源定位方法。首先利用水下滑翔机在东印度洋北部海域获取的声传播数据,分析了宽带脉冲信号的多途传播特性,然后提出了利用单水听器基于脉冲波形结构匹配的声源距离估计方法,在此基础上通过两台水下声学滑翔机联合定位的方式,实现了水下声源距离和方位的同步估计。结果表明:在印度洋深海非完全声道条件下,在100 km范围内,使用单台滑翔机估计的声源距离整体较为准确,但仍有估计误差较大点;联合两台滑翔机进行水下声源定位可进一步提高精度,对于200 m深度的声源,距离估计均方根误差为2.5 km,相对误差小于4%,方位估计均方根误差为2.4°。     

空气中快速运动声源水下声场的波数积分模型

本文采用二维波数积分，对空气中高速运动声源激发的水下声场进行建模。针对二维波数积分计算声场时域解计算量大的问题，提出一种快速计算方法。用本文提出的方法，对深海和浅海情况下，空气中高速运动单频点声源激发的水下声场进行了计算和仿真。计算结果表明：在深海，水下接收信号的幅度和瞬时频率随时间发生变化；接收器深度、接收器与声源运动轨迹的最小距离对接收信号的变化快慢有较大影响，而声源高度的影响较小；在浅海中，接收信号呈现快速的幅度起伏，明显的多普勒频移和大的频率展宽效应。与简正波方法相比，本文方法主要适用于近场计算，而简正波方法适用于远场。另外，当声源频率较高时，二维波数积分方法的计算量将迅速增大。     

磁光调制方位传递系统中螺线管近轴区磁场影响分析

磁光调制方位传递系统中,交变电流驱动内置磁光材料的螺线管磁场至关重要,直接关系到方位信息的传递精度。研究了交变电流驱动的螺线管内磁场对方位信息传递精度的影响。首先,利用麦克斯韦方程构建空心螺线管电磁场模型,分析驱动信号频率对磁场的影响;然后结合安培环路定律建立内置磁光材料的螺线管内部磁场模型;最后分析无松弛极化介质、松弛极化介质、驱动信号频率等对系统方位传递精度的影响。结果表明:驱动信号频率是影响系统方位传递精度的重要因素,且方位传递误差存在规律性;无松弛极化介质与松弛极化介质对系统方位传递精度的影响程度相当。该结果为研究磁光调制方位传递系统的方位传递精度与系统优化设计提供了参考。     

北极跨冰层水中声源方位估计实验与分析

为了获取北极冰下声源方位信息,在北极冰层上方布放检波器和冰下投放声弹声源开展了冰下声源的分频段方位估计实验.研究结果表明,冰下声源方位估计的误差、准确率与检波器接收信号频段(或冰下声源信号频段)有关.采用低频段的接收信号进行方位估计时准确率较高,误差均值较小,所用接收信号频段≤250 Hz时,方位估计准确率可达72.9...     

基于频谱特征提取的轨道移频信号检测的兼容性设计与实现

提出了一种基于频谱特征提取的轨道移频信号检测的兼容性算法,并在单芯片的微控制器STM32F405RGT6上利用该算法实现了对国产18信息移频信号和ZPW-2000移频信号的兼容性检测。通过综合分析两类移频信号的时频域特征,将过采样、ZFFT频谱细化、频率校正及频谱特征提取结合起来,通过两类不同的数字滤波器适应不同的算法设计需要,通过频谱特征提取实现不同频谱状态下的频率计算方式,有效地提高了频率的检测精度,拓展了调制频率的测量范围。实验结果证明,对国产18信息移频信号和ZPW-2000移频信号的中心频率、上下边频的检测误差不超过±0.1Hz,调制频率的检测误差小于±0.01Hz,在采样数据小于1S情况下,调制频率的测量范围可达到6~30Hz。     

平面阵的方位估计算法及其误差分析

提出了一种基于信号相位匹配原理的平面阵方位估计的奇异值分解(SVDSPM)算法.推导了方位搜索需要的时延计算的一般公式,仿真分析了几种典型平面阵的方位估计性能,仿真结果表明: SVDSPM方位估计算法的性能优于MUSIC算法;理论分析了目标距离、传声器位置误差和接收通道幅度和相位不一致性等对定向性能的影响;以十字平面阵为例,仿真分析了上述几种因素对方位估计精度的影响,仿真结果表明:当传感器安装误差小于10 mm,接收通道幅度不一致性小于1.5 dB,接收通道相位不一致性小于10°和目标初始俯仰角大于45°时,方位估计的标准差小于0.5°.     

The impact of early reflections on binaural cues

Animals live in cluttered auditory environments, where sounds arrive at the two ears through several paths. Reflections make sound localization difficult, and it is thought that the auditory system deals with this issue by isolating the first wavefront and suppressing later signals. However, in many situations, reflections arrive too early to be suppressed, for example, reflections from the ground in small animals. This paper examines the implications of these early reflections on binaural cues to sound localization, using realistic models of reflecting surfaces and a spherical model of diffraction by the head. The fusion of direct and reflected signals at each ear results in interference patterns in binaural cues as a function of frequency. These cues are maximally modified at frequencies related to the delay between direct and reflected signals, and therefore to the spatial location of the sound source. Thus, natural binaural cues differ from anechoic cues. In particular, the range of interaural time differences is substantially larger than in anechoic environments. Reflections may potentially contribute binaural cues to distance and polar angle when the properties of the reflecting surface are known and stable, for example, for reflections on the ground.     

A Comparison on the Localization Performance of Static and Dynamic Binaural Ambisonics Reproduction with Different Order

Ambisonics is a series of spatial sound reproduction system based on spatial harmonics decomposition and each order approximation of sound field. Ambisonics signals are originally intended for loudspeakers reproduction. By using head-related transfer functions (HRTFs) filters, binaural Ambisonics converts the Ambisonics signals for static or dynamic headphone reproduction. In present work, the performances of static and dynamic binaural Ambisonics reproduction are evaluated and compared. The mean binaural pressure errors across target source directions are first analyzed. Then a virtual source localization experiment is conducted, and the localization performances are evaluated by analyzing the percentages of front-back and up-down confusion, the mean angle error and discreteness in the localization results. The results indicate that binaural Ambsonics reproduction with insufficiently high order (for example, 5-10 order) is unable to recreate correct high-frequency magnitude spectra in binaural pressures, resulting in degradation in localization for static reproduction. Because dynamic localization cue is included, dynamic binaural Ambisoncis reproduction yields obviously better localization performance than static reproduction with the same order. Even a 3-order dynamic binaural Ambisoncis reproduction exhibits appropriate localizations performance.     

The bat head-related transfer function reveals binaural cues for sound localization in azimuth and elevation

Directional properties of the sound transformation at the ear of four intact echolocating bats, Eptesicus fuscus, were investigated via measurements of the head-related transfer function (HRTF). Contributions of external ear structures to directional features of the transfer functions were examined by remeasuring the HRTF in the absence of the pinna and tragus. The investigation mainly focused on the interactions between the spatial and the spectral features in the bat HRTF. The pinna provides gain and shapes these features over a large frequency band (20-90 kHz), and the tragus contributes gain and directionality at the high frequencies (60 to 90 kHz). Analysis of the spatial and spectral characteristics of the bat HRTF reveals that both interaural level differences (ILD) and monaural spectral features are subject to changes in sound source azimuth and elevation. Consequently, localization cues for horizontal and vertical components of the sound source location interact. Availability of multiple cues about sound source azimuth and elevation should enhance information to support reliable sound localization. These findings stress the importance of the acoustic information received at the two ears for sound localization of sonar target position in both azimuth and elevation.     

Modeling binaural loudness

A survey of data on the perception of binaurally presented sounds indicates that loudness summation across ears is less than perfect; a diotic sound is less than twice as loud as the same sound presented monaurally. The loudness model proposed by Moore et al. [J. Audio Eng. Soc. 45, 224-240 (1997)] determines the loudness of binaural stimuli by a simple summation of loudness across ears. It is described here how the model can be modified so as to give more accurate predictions of the loudness of binaurally presented sounds, including cases where the sounds at the two ears differ in level, frequency or both. The modification is based on the idea that there are inhibitory interactions between the internal representations of the signals at the two ears, such that a signal at the left ear inhibits (reduces) the loudness evoked by a signal at the right ear, and vice versa. The inhibition is assumed to spread across frequency channels. The modified model gives reasonably accurate predictions of a variety of data on the loudness of binaural stimuli, including data obtained using loudness scaling and loudness matching procedures.     

DISSIMILARITY JUDGMENTS IN RELATION TO TEMPORAL AND SPATIAL FACTORS FOR THE SOUND FIELD IN AN EXISTING HALL

In relation to the temporal and spatial factors of sound fields, dissimilarity judgments for different source locations on a stage were performed. This study is based on the model of the auditory-brain system, which consists of the autocorrelation and crosscorrelation mechanisms for sound signals arriving at two ears and the specialization of human cerebral hemispheres. There are three temporal factors (τ₁,φ₁ and τ_e) extracted from the autocorrelation function and four spatial factors (LL,IACC,τ_IACC and W_IACC) from the interaural crosscorrelation function of binaural signals. In addition to these temporal and spatial factors, the orthogonal factors of the subjective preference for sound field (Δt₁ and T_sub) were taken into account. The psychological distance between sound fields of different source locations on the stage were calculated by using these temporal, spatial and orthogonal factors of sound fields. Using these distances and their linear combination, dissimilarity can be calculated. Results of multivariable analysis show that the calculated scale values of dissimilarity agree well with the measured scale values.     

Experimental analysis of considering the sound pressure distribution pattern at the ear canal entrance as an unrevealed head-related localization clue

By analyzing the differences between binaural recording and real listening, it was deduced that there were some unrevealed auditory localization clues, and the sound pressure distribution pattern at the entrance of ear canal was probably a clue. It was proved through the listening test that the unrevealed auditory localization clues really exist with the reduction to absurdity. And the effective frequency bands of the unrevealed localization clues were induced and summed. The result of finite element based simulations showed that the pressure distribution at the entrance of ear canal was non-uniform, and the pattern was related to the direction of sound source. And it was proved that the sound pressure distribution pattern at the entrance of the ear canal carried the sound source direction information and could be used as an unrevealed localization clue. The frequency bands in which the sound pressure distribution patterns had significant differences between front and back sound source directions were roughly matched with the effective frequency bands of unrevealed localization clues obtained from the listening tests. To some extent, it supports the hypothesis that the sound pressure distribution pattern could be a kind of unrevealed auditory localization clues.     

耳道入口处声压分布模态作为听觉方向感知隐性线索的实验分析

通过分析双耳录音与真实听音之间的差别,推断存在影响听觉方向感知的隐性线索,而由头部及外耳结构引起的耳道入口处截面声压分布模态可能是其中一种。首先,通过听音实验利用反证法证明听觉方向感知隐性线索确实存在,并归纳总结出隐性线索的有效作用频段;然后,利用有限元仿真方法计算耳道入口处的声压分布,仿真结果表明耳道入口处声压分布是不均匀的,且分布模态与声源方向有关,从数值仿真的角度验证了耳道入口处截面的声压分布模态携带了声源方向信息,可以作为一种隐性定位线索;仿真计算所得前、后声源方向耳道入口处声压分布模态差异显著的频段与听音实验所得的隐性线索有效频段基本相符,在一定程度上支持耳道入口处声压分布模态是一种方向感知隐性线索的推测。      

Octave illusion elicited by overlapping narrowband noises

The octave or Deutsch illusion occurs when two tones, separated by about one octave, are presented simultaneously but alternating between ears, such that when the low tone is presented to the left ear the high tone is presented to the right ear and vice versa. Most subjects hear a single tone that alternates both between ears and in pitch; i.e., they hear a low pitched tone in one ear alternating with a high pitched tone in the other ear. The present study examined whether the illusion can be elicited by aperiodic signals consisting of low-frequency band-pass filtered noises with overlapping spectra. The amount of spectral overlap was held constant, but the high- and low-frequency content of the signals was systematically varied. The majority of subjects perceived an auditory illusion in terms of a dominant ear for pitch and lateralization by frequency, as proposed by Deutsch [(1975a) Sci. Am. 233, 92-104]. Furthermore, the salience of the illusion increased as the high frequency of the content in the signal increased. Since no harmonics were present in the stimuli, it is highly unlikely that this illusion is perceived on the basis of binaural diplacusis or harmonic binaural fusion.     

重放自由场虚拟源距离信息的动态双耳Ambisonics方法

双耳重放的目标之一是在耳机重放中产生不同方向和距离的虚拟源感知。本文研究了动态双耳Ambisonics重放自由场虚拟源方向和距离信息的简化信号处理方法。该信号处理方法包括两步:第1步是基于目标声场的球谐函数分解,合成采用扬声器的近场Ambisonics重放中逐级重构目标声场的信号;第2步是采用虚拟扬声器重放的方法,用动态头相关函数滤波处理将Ambisonics的扬声器重放信号转换为双耳重放信号并用耳机重放。进一步研究了动态双耳Ambisonics的阶数对定位效果的影响,为简化信号处理提供依据。对重放产生的双耳声压分析表明,5阶动态双耳Ambisonics重放足以提供听觉方向定位和距离感知的重要信息。同时心理声学的实验结果表明,结合声源距离相关的响度因素,5阶动态双耳Ambisonics重放可产生不同方向和1.0 m以下不同近场距离的自由场虚拟源的听觉感知。本文的方法仅需要固定距离的48个均匀空间方向的远场非个性化HRTF处理,实现了信号处理的简化。      

Ambisonics声捡拾与重放音色的双耳听觉模型分析与实验

提出用双耳听觉模型对空间声音色进行分析的普遍方法,并以Ambisonics为例进行了分析。Ambisonics是基于物理声场重构的空间声系统,其最终重构声场误差以及音色改变是由传声器捡拾和重放空间混叠误差共同引起的。采用修正的Moore双耳响度模型计算了Ambisonics重构声场的双耳响度级谱并和目标声场的情况比较,从而定量评价重构声场的音色改变。结果表明,在理想捡拾信号的情况下,无音色改变重放的上限频率和区域大小随Ambisonics的阶数而增加。而对于传声器阵列捡拾的情况,只要阵列的上限频率大于Ambisonics重放的上限频率,在重放的上限频率以下,传声器阵列空间混叠误差对最终重构声场及其感知音色的影响就可以忽略。在此基础上,提出了一种综合考虑捡拾与重放性能的Ambisonics系统优化设计方法。心理声学实验得到了和双耳听觉模型一致的结果,从而也验证了模型分析的有效性。