Robust algorithm of direction of arrival estimation for coherent wideband sources in unknown correlated noise fields

A robust algorithm of direction of arrival (DOA) estimation for coherent wideband sources in unknown correlated noise fields was investigated. The noise is usually unknown and correlated among sensors in practical applications, especially for arrays with comparatively small apertures. The spatially correlated noise incurs an increase in focusing error and a severe degradation in the DOA estimation, and therefore a method of focusing transformation based on differentiating covariance matrix was proposed to eliminate noise, hence reduce the focusing error. The simulation and experimental results demonstrate the effectiveness of the proposed method.     

Acoustic Calculation for Supersonic Turbulent Boundary Layer Flow

An approach which combines direct numerical simulation （DNS） with the Lighthill acoustic analogy theory is used to study the potential noise sources during the transition process of a Mach 2.25 flat plate boundary layer. The quadrupole sound sources due to the flow fluctuations and the dipole sound sources due to the fluctuating surface stress are obtained. Numerical results suggest that formation of the high shear layers leads to a dramatic amplification of amplitude of the fluctuating quadrupole sound sources. Compared with the quadrupole sound source, the energy of dipole sound source is concentrated in the relatively low frequency range.     

Q值的影响因素分析及其参数化

针对高散射特性的二类水体中难以测量的双向性函数Q,利用HYDROLIGHT模拟观测角为太阳天底角下440 nm处的Q值,并分析环境及水体光学特性对Q值的影响.结果表明,在高散射特性的近岸水体或内陆湖泊水体中,由于散射次数的增加,使得风速、散射相函数等影响因素对Q值影响相对减小,单次散射反照率W.和太阳天顶角θ成为Q值的主要影响因素;随着深度的增加,双向性函数Q受边界条件和光线入射状况影响的程度逐渐减少,直至不受其影响,而成为只与固有光学量相关的内秉光学量;利用Q值的主要影响因素W<,0>、θ和上行辐亮度的漫衰减系数K<,L<,u>>分别对Q值进行参数化,得到Q值的2种参数表达式.     

《应用声学》征稿简则

《应用声学》是由中国科学院主管,中国科学院声学研究所主办,中国声学学会、《应用声学》编辑委员会编辑出版的学术刊物。1982年创刊,双月刊,国内外公开发行。办刊的宗旨是繁荣应用声学事业,促进新成果的开发与推广,加强科研、工程技术人员与生产实践者之间的相互了解和合作。《应用声学》多年来被国内重要检索系统收录。是中国科技核心期刊、中文核心期刊;是《中国科学引文数据库》、《中国科技论文统计源数据库》、《中国学术期刊综合评价     

Study on vibro-acoustical characteristics of damped composite boxlike shells in water

Based on the structural FEM and the acoustic BEM, a numerical model of coupled elastic layer and viscoelastic layer and outside sound field is established and the vibro-acoustical characteristics of damped composite boxlike shells are studied systematically. It can be concluded that the structural vibration responses and the sound radiation are reduced significantly due to the viscoelastic layer and its effects are dependent on the geometric, physical parameters of the layer and the excitation frequency. It is also shown that compared with the bare elastic shells, the influence of the fluid compressibility on the vibration responses of shells covered with a damping layer is not evident and the effects of the free surface and the rigid plane are weakened.     

“深海圆柱水声换能器”专题通过验收

由中国科学院声学研究所承担的国家863计划“深海圆柱水声换能器研制”专题于2006年3月8日顺利通过专家组验收，所研制的深海水声换能器达到、部分指标超过国外某些同类产品水平。该专题是面向国家863计划重大专项“7000m载人潜水器”的技术储备研究，主要是研发可用于7000m水下工作的深海水声换能器，掌握其相关设计技术和制造方法。     

利用脂肪酸组成对26种(株)海洋微藻聚类分析研究

在160μmol/(m2.s)光强、温度(20±1)℃下对26种(株)海洋微藻进行培养,在指数生长期进行离心收集,冷冻干燥后用Bligh-Dyer法提取总脂,皂化后进行脂肪酸的气相色谱-质谱定性定量分析,共鉴定出40种脂肪酸.以所测定的每种脂肪酸的相对含量为变量,欧几里德距离平方作为聚类统计量,应用统计分析软件(SPSS11.5)对微藻进行分层聚类分析.结果表明,此培养条件下的聚类分析结果与现行国际通用的海洋微藻的分类结果相吻合.因此,微藻脂肪酸的聚类分析结果可用来作为微藻分类的辅助技术手段。     

演艺建筑声学设计面临的机遇和挑战

在经济建设取得巨大成就的同时,随之兴起了演艺建筑和文体建筑的高潮,2008年奥运申办 成功,促进了发展的势头。为确保各类厅堂具有良好的音质,声学工程师肩负着设计的重任。本文简 述建筑声学面临的机遇和挑战。     

Two-dimensional wideband direction of arrival estimation with acoustic vector-sensor array

A closed-form algorithm for two-dimensional wideband Direction-of-Arrival (DOA) estimation with an acoustic vector-sensor array was presented. The proposed algorithm can deal with coherent sources without loss of array aperture, and does not require a search procedure for the DOA parameters. The estimated azimuth and elevation angles can be automatically paired. Simulation results are presented to demonstrate the effectiveness of the proposed method.     

温伯格致初涉科研学生的四点忠告

 当我拿到大学文凭时--那是在很久以前了,物理学著作对我而言如同一片尚未勘探的浩瀚海洋,在开始自己的任何研究之前,我不得不为其每一部分绘制航海图。不在详尽地了解前人工作的基础上,我怎能做任何研究呢?幸好在研究生院的第一年,我有幸碰到一群资深物理学家,他们不顾我忧心忡忡地反对,坚持认为我必须马上开始研究工作,并且随着工作的进展,用什么、学什么。如此一来,沉浮全看自己。出乎意料的是,我发现这种方式很有效。我努力提前拿到了博士学位--尽管那时我对物理几乎一无所知。但我确实学到了重要的一点:没有人无所不知,也没必要无所不知。另一点值得借鉴的经验可以延用我关于海洋的比方,如果你已经在游泳而不至于沉没,那么