灯芯绒吸声特性的实验研究

灯芯绒是一种常用的服装布料,又是建筑室内装饰常用的帘幕材料。主要考量用于帘幕时的吸声性能。选择两种绒面的灯芯绒试件,通过测量混响室吸声系数,采用平均吸声系数与降噪系数NRC的评价方法进行分析,探讨在实际使用时影响吸声性能的因素及工程应用。     

材料吸声性能的单值评价及产品分级方法

建筑物内表面及其装饰材料的吸声性能,对室内声环境有着十分重要的影响.介绍了国家和国际标准对材料吸声性能采用的单值评价和产品吸声性能的分级方法.     

吸声泡沫玻璃的材料特性及其吸声性能的提高

吸声泡沫玻璃是一种无机多孔材料,它具有良好的防火和耐水性能。介绍了它的材料特性,根据测量的吸声系数分析了密度、板厚、空腔和吸湿对吸声的影响,并且采用板面钻孔和边缘留缝的方法提高其吸声性能。     

玻纤装饰板的吸声特性

玻纤装饰板是玻璃纤维材料的一种新型吸声制品。介绍了玻纤吸声产品的进展、装饰吸声板的构造以及材料的特点,根据实验数据分析了板厚、饰面和空腔深度对吸声的影响及其应用。     

铝蜂窝穿孔板的吸声特性

铝蜂窝穿孔吸声装饰板是一种刚度大、强度高的金属高效吸声制品,具有良好的物理力学和耐候性能,介绍了板材构造和特点.通过实验探讨板材后背空腔和放置方式对吸声性能的影响.     

扩散吸声体的最新研究进展

近年来,扩散吸声体（Diffsorber）得到广泛应用和认同。对于如何设计和应用扩散吸声体,理论上的工作以及实验测量技术远远没有跟上实践发展的需要。从其应用背景的研究、设计方法的更新,及实验技术的发展三方面进行阐述,对扩散吸声体的相关研究进行合理总结,并指出目前该声学结构发展需要解决的若干问题。     

声场计算机模拟中吸声系数的修正

计算机声场模拟中,房间表面的吸声性能通常采用混响室法吸声系数来表示.该吸声系数的测量方法是建立在扩散声场基础上得到的,而实际混响室中放置吸声材料后声场并非为扩散场,由此将导致吸声系数的测量误差,影响声场计算机模拟的准确性.通过对混响室声场的模拟计算,建立材料吸声系数与混响时问的关系,并对实测的吸声系数进行修正可提高声场计算机模拟的精度.     

现场测量吸声系数方法概述

吸声系数测量是声学测量中一个重要方面.在实际应用中,主要采用驻波管和混响房问测量2种方法.这2种方法都需要专用的设备和实验环境、专业的测试人员在实验室中才能完成,步骤较为复杂.介绍了能够在现场测量吸声系数的3种方法,概括总结了各种方法的优缺点,为在声学材料和建筑声学领域的应用提供了指导.     

消声室用吸声结构

根据消声室的使用目的,确定消声室内符合容许偏差的模拟自由声场的大小,从而设计消声室的大小和吸声结构的吸声频率特性,吸声结构的设计是消声室设计中的关键步骤。     

半被动多层压电吸声技术及其电路模型

提出了一种吸声新技术--半被动压电吸声技术,并对其进行了等效电路模型分析.该吸声结构采用在压电片电极两端串联负电容、电感和电阻分支电路,利用这种半被动结构中低频能量损耗因子较高及带宽较大的优良性能,构成新的压电吸声结构,建立了多层吸声结构的梅森等效电路模型,对其吸声系数等进行了数值模拟,表明其具有优良的宽带中低频吸声性能.     

柱面声透镜声场分析

从惠更斯原理出发,采用点声源合成法对柱面型声透镜声场的分布及声场分布与透镜几何参数间的关系等作了分析.分析表明,如果对声透镜表面的划分足够小,则点声源合成法在一定程度上可用来对声透镜的声场作近似分析,同时发现柱面聚焦声透镜形成的线聚焦声场的分布和焦域声压幅值与声源频率、透镜长度、宽度及其几何半径均有复杂关系.     

Acoustic Cryptanalysis

Many computers emit a high-pitched noise during operation, due to vibration in some of their electronic components. These acoustic emanations are more than a nuisance: They can convey information about the software running on the computer and, in particular, leak sensitive information about security-related computations. In a preliminary presentation (Eurocrypt’04 rump session), we have shown that different RSA keys induce different sound patterns, but it was not clear how to extract individual key bits. The main problem was the very low bandwidth of the acoustic side channel (under 20  kHz using common microphones, and a few hundred kHz using ultrasound microphones), and several orders of magnitude below the GHz-scale clock rates of the attacked computers. In this paper, we describe a new acoustic cryptanalysis key extraction attack, applicable to GnuPG’s implementation of RSA. The attack can extract full 4096-bit RSA decryption keys from laptop computers (of various models), within an hour, using the sound generated by the computer during the decryption of some chosen ciphertexts. We experimentally demonstrate such attacks, using a plain mobile phone placed next to the computer, or a more sensitive microphone placed 10 meters away.     

Acoustic holograms

The letter describes a method of reconstructing a holographic image by electronic means, thus avoiding the multiple images produced owing to ambiguity of angle.     

Acoustic holography

In the middle and late 1960s, holography, applied to acoustics, generated a considerable upsurge of activity in the already mature acoustic imaging technology. It brought both coherent optics and digital data processing to bear upon the problems of acoustic imaging and introduced fresh approaches to the visualization of sound fields. These developments are reviewed and the wide range of potential applications for acoustic holography is discussed. In most cases, the status is that of proved feasibility awaiting broader application.     

Acoustic Tomography

High-resolution measurements of the density field in the ocean are prohibitively expensive if traditional ship-borne instruments are used. Tomography uses acoustic remote sensing to infer ocean structure, and avoids many of the limitations of direct measurements. Sound pulses follow distinct trajectories through the water from source to receiver, and the travel time for a given pulse is a known functional of the sound speed field. This functional can be inverted to recover an estimate of the sound speed field through which it passed. The inversion is accomplished with either detenninistic linear matrix inversion or stochastic optimal estimation, and the sound speed field estimate returned can be converted to an estimate of density. A numerical simulation of the pilot tomography experiment is presented to demonstrate that tomography can be effective in reproducing significant ocean features.     

塑胶封装器件的全自动声像(声学显微镜)检测

全自动声像系统被用于塑胶和多芯片器件的成像及分析。声像及数据可非破坏识性地识别如芯片表面及芯片银胶层的分层等内部缺陷。不符合标准的器件将从装配线上除去。     

一种电容式声压水听器的热粘性声学仿真研究

为了满足多领域中水下复杂环境声压检测的需要,提出了一种基于微机电系统(MEMS)的电容式声压水听器,开发出注油孔及注油沟道设计,将传感器封装于硅油中,通过平衡振动薄膜内外压强可以提高其耐受静水压能力。使用Comsol Multiphysics仿真软件对水听器建模,采取热粘性声-结构多物理场对传感器进行静态分析、模态分析及谐波声信号扰动下的灵敏度分析,在用有限元法分析模型时考虑了热效应与粘滞效应对小尺寸声学换能器的影响,使仿真结果更具说服力。得到了在幅值为10 Pa,频率在1 Hz～10 kHz的谐波声信号扰动下水听器的接收灵敏度为-147 dB。仿真结果表明,设计的电容式声压水听器据有高灵敏度和宽频带等特点,可以满足不同领域对水下低频声压信号的测量需求。     

基于无线声阵列的目标定位系统设计

提出建立超大孔径声阵列来提高声探测装备的探测性能.为了能够简化系统布设,提出采用无线连接的方式组成声阵列.采用MSP430单片机作为中心处理器设计了无线传声器,为了保证各无线传声器同步进行数据采集采用了BD2和GPS双模授时技术.最后分别采用无线声阵列和有线声阵列进行了试验,采用MUSIC(Multiple Signal Classification)算法进行定向,结果表明无线声阵列能实现定向功能但精度稍差,在下一步的工作中采用相位一致性好的传声器能进一步提高精度.     

Acoustic bulk-surface-wave transducer

Bulk and surface waves are strongly coupled at a corrugated surface. Experiments have demonstrated transduction losses of less than 1dB and bandwidths of 20%. Methods of implementation at high frequencies are discussed.