强度解调的F-P干涉型光纤传声器

F-P干涉型光纤传声器具有灵敏度高、结构简单、抗电磁干扰等优势,论文针对基于强度解调的F-P干涉型光纤传声器展开研究。采用多光束干涉理论建立了系统光学模型,采用薄板小挠度弯曲理论建立了传声器振膜的声学模型,在此基础上得到传声器灵敏度的表达式。通过理论分析和仿真,得到了敏感单元结构参数对传声器灵敏度和响应频率的影响关系,并对F-P敏感结构的腔长和端面反射率进行了优化设计。应用厚度为3μm的镍膜,研制出光纤传声器样机,测得其灵敏度为268 mV/Pa、频响特性为±3 dB@50 Hz~4 kHz,可应用于恶劣环境下的声音传感。     

硅微ZnO压电薄膜传声器的研制

本文介绍了一种利用ZnO压电薄膜为换能器的硅微压电薄膜传声器的制备,并且对微机械加工工艺过程进行了较为详细的描述。本文对传声器的部分结构进行改进,与通常设计相比较大幅提高了传声器的性能,1000Hz基准频率的灵敏度达到-85dB(相对于1V/Pa),500Hz到10000Hz的频率响应的平坦度在±3dB范围内。     

基于微电子机械系统技术的高灵敏度电容式微传声器的研制

基于微电子机械系统（ＭＥＭＳ）技术的微传声器是当前国际上研究的热点。使用 ＭＥＭＳＩ艺制备的薄膜一般有着不可忽视的残余应力,极大的降低了膜的机械灵敏度。理论分析和数值模拟表明,纹膜结构可在不改变工艺条件的前提下,显著的降低残余应力的不良影响,大幅度增加膜的灵敏度。本文提出了一种使用ＭＥＭＳ技术制作的纹膜结构电容式微传声器,其制作工艺简单、重复性好,所用材料也能与 ＩＣＩ艺很好的兼容。圆片级测试的结果表明,在 １０ Ｖ的偏置电压下,这种微传声器在 ７ ｋＨｚ以下具有平直的频响,开路灵敏度可达 ４０ ｍv／Ｐａ,而其占用的芯片面积仅为 １．５ ×ｌ．５ ｍｍ２。进一步的研究可望将信号处理电路集成于片内,形成完整的微声学系统。     

高声强下传声器灵敏度校准

本文对CH16和BK4136等型号的电容传声器在高声强声波作用下,其灵敏度变化作了估算和校准。用BK4221型高声压传声器校准器对上述型号的传声器作灵敏度校准,声压级从140dB至161.6dB,这些传声器之灵敏度变化一般不超过0.3dB。与活塞发生器校准结果比较,两者最大差值一般在0.4dB之内。另外,在168dB至173dB的高声强环境中做了类似实验,结果一致。实验结果和理论分析相符,证实了用活塞发生器校准得到的传声器灵敏度值,来校准高声强(声压级在170dB以下)是可行的,这对高声强测试工作提供了方便。     

光学薄膜鲁棒设计中膜系误差灵敏度控制

提出了一种基于膜系误差灵敏度控制的鲁棒膜系设计方法,建立了鲁棒膜系设计评价函数在膜层参数误差统计分布下的解析表达式,避免统计样本数目有限性造成的样本均值与总体期望的误差,以及过大数目样本造成的长的计算时间消耗,并通过宽带增透膜、中性分光膜和线性透射率滤光片等多种薄膜的鲁棒设计实验证实了其在膜层参数误差控制上的效果。结果表明:该新型鲁棒膜系设计方法具有内在的快速算法特性,其设计膜系对镀膜中的膜厚监控误差不敏感,对于高质量薄膜的重复制备和批量成品率的提高具有实用价值。     

基于柔性铰链的光纤光栅二维加速度 传感器的优化设计

为实现对待测表面两个方向的振动监测,基于圆形柔性铰链设计了一种布拉格光栅双向加速度传感器.首先,推导出该传感器的谐振频率及灵敏度的理论公式,然后基于圆形铰链刚度的理论公式,推导并验证了铰链的刚度经验公式.通过MATLAB对传感器的数学模型进行优化设计,得到在满足工作要求时,传感器灵敏度达到最大时的尺寸参数.激振实验结果表明,该传感器的谐振频率约为368Hz,灵敏度约为107.3pm/g,横向抗干扰度为4.8%,谐振频率和灵敏度理论值与实际值的误差分别为-4.2%和7.0%.     

传声器次声段灵敏度校准的误差机理研究*

次声波广泛存在于自然界与人类活动中,由于次声波具有穿透能力强、衰减小等特点,隔离和消除十分困难,对次声的监测防护与利用成为人们关注的焦点。次声波的定量研究依托传声器的测量实现,对传声器的灵敏度原级校准是保证测量精度的前提。该文基于活塞发生器校准原理下的压力泄漏与热传导耦合衰减模型,在COMSOL多物理场仿真软件中对校准腔和传声器后腔内的声场特征进行了数值仿真。创新性地提出了模型比较法,准确量化了次声段校准核心的泄漏、热传导独立与耦合修正量,验证并揭示了声压泄漏与热传导损失的幅值与相位变化机理。进一步地对传声器的次声段灵敏度校准过程进行了联合数值模拟,仿真结果表明,内外均压校准声场下传声器灵敏度的幅相频响应存在明显差异,但与校准腔内的泄漏与热传导效应无关。基于搭建的活塞发生器原级校准平台对传声器系统进行了原级校准,通过实验手段初步揭示了内外均压校准机制下传声器幅值灵敏度与相位灵敏度的显著差异。     

基于单极性驻极体薄膜的振动能俘获研究

利用电晕充电方法成功制备了单极性交联聚丙烯(IXPP)驻极体膜,并设计、制备了基于该驻极体膜的振动能量采集器.通过表面电位的测量,研究了IXPP驻极体膜的电荷储存稳定性;通过测量振动能量采集器样品的准静态和动态电荷灵敏度,考察了能量采集器的机电耦合性能,研究了能量采集器在{3-3}模式下对环境振动能的俘获.结果表明,用-13 kV的电晕电压与-2.0 kV的栅极电压给单面镀铝电极的IXPP样品充电,在实验室环境下放置15天后获得-680 V稳定的表面电位;利用准静态方法测量器件样品的电荷灵敏度,在1.3 kPa压强下,样品的准静态电荷灵敏度M高达1800 pC/N;对于有效面积为13 cm~2的能量采集器,当振子质量为42.2 g,在共振频率70 Hz处,样品在最佳负载电阻80 M?附近的输出功率为5μW.     

聚苯乙烯薄膜对自支撑锆薄膜的性能改善

 利用直流磁控溅射方法和提拉法制备了自支撑Zr/C₈H₈复合滤光膜和C₈H₈滤光膜。用同步辐射光源测量了滤光膜对软X射线的透射率，用俄歇电子能谱分析了膜中的元素含量。结果表明，虽然C8H8薄膜的加入在一定程度上降低了Zr滤光膜在软X射线波段的透射率，但较好地阻止了存储和使用过程中氧、氮等杂质对Zr金属膜的入侵，有效地改善了滤光膜的环境稳定性；同时很好地改善了Zr滤光膜的力学性能和表面面形，使制备的成品率提高了20%。     

用SiC薄膜作防氚渗透阻挡层的研究

采用分步偏压辅助射频溅射法在316L不锈钢表面制备SiC薄膜，作为聚变堆第一壁及包层结构材料的氚渗透阻挡层，扫描电镜观察表明，制备的膜致密，均匀，且与基体结合牢固。X射线衍射分析表明，膜具有（111）面择优取向的β-SiC微晶结构。傅里叶变换红外光谱分析发现，对应于β-SiC的Si-C键存在伸缩振动吸收峰，采用中间复合过渡层技术，可以提高SiC膜与不锈钢基体的结合强度。测量了500℃时带有SiC膜的316L不锈钢的氚渗透率，与表面镀钯膜的316L相比，氚渗透率减低因子（PRF）值达到10^4以上，溅射时衬底偏压和射频功率要影响膜的结构，从而影响PRF值，根据分析结果，从不同的膜制备工艺中初步筛选出了合适工艺。     

Wind noise at microphones within and across hearing aids at wind speeds below and above microphone saturation

The variation of wind noise at hearing-aid microphones with wind speed, wind azimuth, and hearing-aid style was investigated. Comparisons were made across behind-the-ear (BTE) and completely-in-canal (CIC) devices, and between microphones within BTE devices. One CIC device and two BTE devices were placed on a Knowles Electronics Manikin for Acoustic Research. The smaller BTE device had vented plastic windshields around its microphone ports while the larger BTE device had none. The microphone output signals were digitally recorded in wind generated at 0, 3, 6, and 12 m/s at 8 wind azimuths. The microphone output signals were saturated at 12 m/s with wind-noise levels of up to 116 dB SPL at the microphone output. Wind-noise levels differed by up to 12 dB between microphones within the same BTE device, and across BTE devices by up to 6 or 8 dB for front or rear microphones, respectively. On average, wind-noise levels were lowest with the CIC device and highest at the rear microphone of the smaller BTE device. Engineering and clinical implications are discussed.     

Dynamic stiffness of biological tissues in a model with assigned displacements at the surface of a half-space

The results of developing a model that describes the formation of the dynamic stiffness of biological tissues are presented for the case where the dynamic stiffness is measured by pressing a circular flat vibrating disk into the tissue normally to its surface while both the disk and the stationary frame of the measuring device are in contact with the tissue surface. Analytical expressions in quadrature form are derived for the dynamic stiffness of tissues by using the model of a half-space with preset displacements of its surface. Numerical calculations are performed, and the agreement with the experiments is demonstrated for the effects caused by the tight contact of the tissue surface with the stationary frame of the measuring device.     

Mechanical impedance of biological tissues in a model with preset displacements on the surface of a half-space

A model is developed to describe the formation of the mechanical impedance of biological tissues for the case where the impedance is measured by pressing a circular flat vibrating disk into the tissue normally to its surface while both the disk and the stationary frame of the measuring device are in contact with the tissue surface. Analytical expressions in quadrature form are derived for the mechanical impedance of tissues by using the model of a half-space with preset displacements of its surface. Numerical calculations are performed, and the agreement with the experiments is demonstrated for the effects caused by the tight contact of the tissue surface with the stationary frame of the measuring device.     

An active noise reduction earplug using a piezoelectric laterally radiating loudspeaker

This paper describes the electroacoustic behaviour of a new piezoelectric Active Noise Reduction (ANR) earplug device. The sensor is a microphone having suitable characteristics chosen from among commercially available electret microphones. The actuator is a cylindrical piezoelectric ceramic loaded with a thin fluid film. An analytic model of laterally radiating loudspeaker, based on fundamental equations of acoustics, which takes into account the effect of viscosity and heat conduction is adapted to describe the acoustic radiation of the actuator. Theoretical and experimental frequency responses in a small cavity and an example of the ANR that can be obtained with the earplug are presented.     

Comparison of the measured and theoretical performance of a broadband circular microphone array

The design and construction of a circular microphone array (CMA) that has a wide frequency range suitable for human hearing is presented. The design of the CMA was achieved using a technique based on simulated directivity index (DI) curves. The simulated DI curves encapsulate the critical microphone array performance limitations: spatial aliasing, measurement noise, and microphone placement errors. This paper demonstrates how the non-regularized DI curves for a given beamforming order clearly define the bandwidth of operation, in other words, the frequency band for which the beamformer has relatively constant and maximum directivity. Detailed and comprehensive experimental data that characterizes the CMA beamformer are also presented.     

Acoustic imaging device with one transducer

This paper presents a low profile imaging device using only one piezoelectric transducer and a microphone. The transducer is glued to an aluminum plate of non-regular geometry that acts as an acoustic cavity. Beam steering is achieved, and the acoustic waves should be focused anywhere in front of the plate. Finally, using a single microphone receiver working in echographic mode, our imaging device is able to locate any object placed in front of it.     

A computational study of the effect of windscreen shape and flow resistivity on turbulent wind noise reduction

In this paper, numerical simulations are used to study the turbulent wind noise reduction effect of microphone windscreens with varying shapes and flow resistivities. Typical windscreen shapes consisting of circular, elliptical, and rectangular cylinders are investigated. A turbulent environment is generated by placing a solid circular cylinder upstream of the microphone. An immersed-boundary method with a fifth-order weighted essentially non-oscillatory scheme is implemented to enhance the simulation accuracy for high-Reynolds number flow around the solid cylinder as well as at the interface between the open air and the porous material comprising the windscreen. The Navier-Stokes equations for incompressible flow are solved in the open air. For the flow inside the porous material, a modified form of the Zwikker-Kosten equation is solved. The results show that, on average, the circular and horizontal ellipse windscreens have similar overall wind noise reduction performance, while the horizontal ellipse windscreen with medium flow resistivity provides the most effective wind noise reduction among all the considered cases. The vertical ellipse windscreen with high flow resistivity, in particular, increases the wind noise because of increased self-generation of turbulence.     

光纤麦克风传感探头设计的理论分析

鉴于光纤传感器具有体积小、结构简单、灵敏度高、抗电磁干扰且光纤本身的低损耗、耐腐蚀和安全可靠等优良特性,将光纤传感器应用到麦克风中可使麦克风的体积显著降低而灵敏度和抗电磁干扰性显著提高。提出一种新型反射式光纤麦克风的设计方法,采用Y形单根多模反射式光纤传感探头结构形式,给出了光纤麦克风的系统框图。由光纤出射光场分布理论出发,给出弹性膜片在声场作用下,中心形变大小h与出射光光强调制函数I(Z″)的关系。根据实际应用中有关参数的取值,用Matlab软件模拟出膜片形变后变形量h与光强调制函数I(Z″)的关系曲线。     

传声器失配误差对差分传声器圆阵主瓣指向的影响特性

从理论上导出了传声器失配误差对适用于任意阵元数的一阶和二阶差分传声器圆阵的主瓣指向影响规律。揭示了传声器相位误差可造成一阶差分传声器圆阵主瓣指向产生反转现象,是影响其主瓣指向的主要因素。而对于二阶差分传声器圆阵,传声器相位误差和增益误差均可导致其主瓣指向产生反转现象和严重指向误差,进而造成阵列指向性因子严重下降,尤其在低频处失配误差的影响更为显著。然后给出了确保差分传声器圆阵主瓣指向正确时阵列设计参数所需满足的条件,并在此基础上进行了传声器失配误差的容差分析。分析结果表明,随着阵元数增多,失配误差的容差范围增大,差分传声器圆阵对传声器失配误差的敏感性相应降低。