用激光自混合干涉测量扬声器的Q值

用激光自混合干涉方法测量扬声器振动,从扬声器振动引起的自混合干涉信号测量扬声器振动速率.由正弦波激振扬声器测量振速的幅频特性曲线,谐波中包含扬声器谐振频率的方波激振扬声器测量振速衰减曲线,分别按谐振法和衰减法测量得到扬声器的品质因数约13.3和10.2.由于方波激励时扬声器有谐波振动成分,由方波激励获得的衰减曲线测量得...     

激光二极管自混合干涉实验仪和微振动研究

用振动激励信号做频率电压变换的倒相触发信号,可以从激光二极管自混合干涉信号还原扬声器谐振时的振动波形,输出信号的振幅与扬声器的振幅成正比. 用正弦波、方波和三角波信号分别激励扬声器,利用自制的激光二极管自混合干涉实验仪观测了的扬声器振动特性,测量了扬声器的谐振曲线.     

对力学非线性和磁场非线性综合作用下扬声器低频跳变的探讨

力学非线性和磁场非线性是扬声器非线性现象的两个因素。本文分析了仅力学非线性的扬声器低频振动方程的临界跳变条件，采用等效线性化法讨论了磁场非线性对扬声器跳变的影响。证实了抑制扬声器跳变的有效途径是增大电磁耦合因子B1。     

利用自混合干涉效应的条纹计数法对扬声器振动特性的实验研究(英文)

基于半导体激光器的自混合干涉效应，通过实验研究了扬声器的振动特性。实验中，用粘在扬声器振膜上的反射镜作为目标物体（该反射镜的反射率为95％，扬声器用50Hz的正弦波驱动）,然后通过条纹计数法获得扬声器的振幅。实验结果表明，在一定范围内，扬声器的振幅与驱动电压呈线性关系。该实验装置极其简单紧凑，自混合干涉信号也十分清晰，实验方法迅速，价格低廉，易实现，而且不需要专用电源，也不需要其他的光学仪器，这一系列优点充分表明自混合干涉技术在振动测量领域具有广阔的发展前景。     

基于条纹投影的振动扬声器形变测量

动态傅里叶变换轮廓术是将结构光投影和傅里叶变换理论相结合的三维面形测量技术,它只需一帧变形条纹就可以恢复物体的三维面形,且速度快、精度高、易于实现,被广泛应用于各领域的动态三维测量。利用动态傅里叶变换轮廓术对扬声器在给定激励源频率下的振动过程进行动态测量,得到扬声器纸盆不同频率振动的三维面形数据。结合扬声器发声的机理,通过对振动扬声器三维面形数据的处理和分析,得到扬声器纸盆局部任意时刻的形变量,分析了产生纸盆自身形变量可能的原因,探究了纸盆振动对扬声器性能的影响,为扬声器的设计和改进提供依据。     

振动体及其辐射场的近场声全息实验研究

本文介绍我们自行研制的空气中近场声全息成像实验系统。用这一系统对单个扬声器，双扬声器及振动圆板等声源及其辐射场进行了测量，获得一些有意义的结果．这些结果与理论分析和计算机模拟良好地符合，表明近场声全息可以作为研究振动及其辐射场关系的有效手段．     

无内共振时的扬声器分谐波

研究了驱动频率低于扬声器辐射体薄壳轴对称模态最低固有频率的扬声器1/2分谐波失真。采用以位敏探测器作为光电传感器的激光三角法实验观测扬声器振膜的振动位移和模态,确定了参与的非轴对称模态的周向波数。采用多尺度法求解了扬声器的非线性模态方程。给出了扬声器分谐波的阈值电压公式。结果表明扬声器辐射体薄壳的分谐波失真源于直接激励的轴对称模态耦合激发了非轴对称模态的振动,这种耦合激励表现为参数激励。增大扬声器振膜材料的损耗因子、杨氏模量和厚度可提高产生分谐波的阈值电压。      

微型扬声器振动系统阻尼频率特性研究

受材料黏弹性的影响,微型扬声器振动系统的力阻与频率有关。通过理论推导建立了力阻与频率之间的模型,得到了微型扬声器振动系统力阻的计算公式,利用激光测振法测量得到的微型扬声器阻抗曲线和位移曲线可以方便地得到微型扬声器振动系统力阻频率响应,表明了其随频率增加而减小的频率特性。实验表明,采用该频率相关力阻模型计算阻抗曲线、位移曲线和频率响应曲线,与测量值吻合很好,明显好于传统频率非相关力阻模型所得曲线。     

磁流体扬声器特性的分析

本文分析了磁流体扬声器的特性并给出一些实验结果.磁流体可以提高扬声器的功率容量,防止音圈过热损坏.磁流体扬声器的输入电功率在音圈温度相同的条件下,比同类普通扬声器可以提高2倍多,从而增加了扬声器的声压灵敏度.磁流体的粘滞性具有阻尼音圈振动的作用,它改善了扬声器的频响,降低瞬态畸变.文中还讨论了磁流体扬声器设计中应注意的问题.     

气流扬声器振动系统的设计原理

本文用等效电路方法分析了电动气流扬声器振动系统的特性,求得了气流扬声器的输入阻抗和位移振幅的频率特性,并把结果用于典型扬声器,说明用等效电路分析指导气流扬声器设计的作用。气流扬声器振动系统所需的电功率与其机械共振频率的四次方成正比,其声辐射主要限于共振频率以下,因而高频特性较差。求得了在共振频率以下,频率响应平直的最佳条件,实验表明,在最佳条件下,气流扬声器的高频特性随着磁隙中的磁感应强度的增加仍稍有提高。实验结果符合理论分析,测得气流扬声器喇叭喉部的声压级在不同情况下达181分贝或184.8分贝(零分贝等于2×10^-5牛顿/米²)。     

平板扬声器用于结构声有源噪声控制实验研究

对NXT技术的分布式平板扬声器和集中参数扬声器的频响和指向性等进行了对比测量，通过对组合平板扬声器的声场研究及有源消声实验，证明了平板扬声器用于有源噪声控制的可行性。综合平板扬声器和集中参数扬声器的物理特点和声场特性，根据基于平面声源有源噪声控制的已有的理论研究结果和本文的实验结果，可以认为，NXT平板扬声器适合作有源噪声控制的次级源，有利于有源噪声控制的工程推广应用。     

应用变分模态分解及能量熵的扬声器异常声分类

为更准确地实现扬声器异常声分类以及促进其分类的自动化,提出一种基于变分模态分解(Variational Mode Decom-position,VMD)能量熵和遗传算法优化的支持向量机(Genetic Algorithm-Support Vector Machines,GA-SVM)的扬声器异常声分类方法.首先对测得的...     

Experimental research on vibrating objects and its radiation field by using nearfield acoustic holography

I.IntroductionThetheoreticalanalysisofthcimagingmethodandcharacteristicsoftheNcarfieldAcousticalHo1ography(NAH)wassystcmatica11yexpoundedinthepapersabroadandourownrescarchcs["21,fromwhichweknowthatNAHcanbcimplcmentcdinanyseparablecoordinatcSystem.HowevertheexpcrimentalrescarchinthispaperwillbcprimariIyrestrictedtoplanarholography.Forp1aneholography,becausctheho1ogramdataisrecordcdinthehologramplaneveryc1osetothetestedsourceorvibratingsurface(i.e.d<相似文献   

扬声器的特性不匹配对虚拟声像的影响

本文从理论和实验上探讨了扬声器的特性不匹配对重放虚拟声像的影响。结果表明,用两扬声器进行虚拟听觉重放时,在某些频率段和虚拟声像角度,两扬声器间很小的幅频特性差异或相频特性差异都足以对虚拟声像方向产生明显的影响。扬声器特性的差异对前方范围的声像影响较小,但对侧向范围的声像影响较大,因而两扬声器的特性不匹配也是导致虚拟听觉重放时侧向声像位置畸变的重要原因之一。而在实际应用中要特别注意两扬声器的特性匹配,或者要用信号处理的方法对两扬声器的特性进行校正。     

Theoretical and experimental analysis of the electromechanical behavior of a compact spherical loudspeaker array for directivity control

Sound directivity control is made possible by a compact array of independent loudspeakers operating at the same frequency range. The drivers are usually distributed over a sphere-like frame according to a Platonic solid geometry to obtain a highly symmetrical configuration. The radiation pattern of spherical loudspeaker arrays has been predicted from the surface velocity pattern by approximating the drivers membranes as rigid vibrating spherical caps, although a rigorous assessment of this model has not been provided so far. Many aspects concerning compact array electromechanics remain unclear, such as the effects on the acoustical performance of the drivers interaction inside the array cavity, or the fact that voltages rather than velocities are controlled in practice. This work presents a detailed investigation of the electromechanical behavior of spherical loudspeaker arrays. Simulation results are shown to agree with laser vibrometer measurements and experimental sound power data obtained for a 12-driver spherical array prototype at low frequencies, whereas the non-rigid body motion and the first cavity eigenfrequency yield a discrepancy between theoretical and experimental results at high frequencies. Finally, although the internal acoustic coupling affects the drivers vibration in the low-frequency range, it does not play an important role on the radiated sound power.     

Study of vertical sound image control with parametric loudspeakers

A parametric loudspeaker utilizes nonlinearity of a medium and is known as a super-directive loudspeaker. In this paper, the sound localization in the vertical direction using the upper and lower parametric loudspeakers is confirmed by listening tests and physical measurements. The differences in levels between the upper and lower parametric loudspeakers are varied as a parameter. The direction of sound localization in the vertical plane can be controlled not only when the acoustical axis is set to the right ear but also when it is set to at 5 deg to the right of the right ear. The effect of the level difference between the upper and lower loudspeakers is weaker than the differences observed when using ordinary loudspeakers. We obtained interesting characteristics of the left-right sound localization in the horizontal plane with the upper and lower parametric loudspeakers in the vertical plane. It is found that by setting the parametric loudspeaker at the right ear (that is, the horizontal angle of a listener to it is only 3 deg to the right), the direction of sound localization in the horizontal plane moved approximately 10 deg to the right. Moreover, by setting the parametric loudspeaker 5 deg to the right, the direction of sound localization moves approximately 20 deg to the right. The ILD (Interaural Level Difference) using a dummy head is calculated from the measured left and right sound signals. It is determined that ILDs of the parametric loudspeaker are larger than those of the ordinary loudspeaker. A simple geometrical acoustic model is introduced and analyzed. The analysis helps to explain the measured characteristics.     

扬声器锥壳的全频段振动通解

为更好地理解扬声器数值计算结果,解析研究了扬声器锥壳轴对称振动在整个工作频段一致有效的通解,这些解以特殊函数的形式给出。在典型低频段,弯曲解仅表现为边界层效应;在典型转点频段,弯曲解存在于转点的外侧域;在典型高频段,弯曲解覆盖了整个扬声器锥壳。无矩解和弯曲解在转点频段是耦合的,该耦合特性表明在此频段不可能消除分割振动。      

Model and estimation method for predicting the sound radiated by a horn loudspeaker - With application to a car horn

This paper deals with a new car horn device made of a sound synthesizer and an electrodynamic horn loudspeaker. It presents an one-dimensional model allowing to predict the loudspeaker efficiency and a specific method to estimate experimentally the model parameters. First, this model aims at reducing the time spent in the design process. Second it aims at correcting the sound emitted by the sound synthesizer in order that the listener hears the sound designed for creating the warning message. The study gives a survey of the vast loudspeaker literature. It is based on the conventional electroacoustic approach used for electrodynamic loudspeakers and on wave propagation models used for characterizing acoustic horns. The estimation of the model parameter values is performed using measurements of the electrical impedance of the loudspeaker and of the acoustic impedance of the horn. The model is assessed by comparing the calculated and measured electrical impedances and horn efficiencies. Results show that the model predicts well the horn efficiency up to 2500 Hz, the limitation being due to the horn radiation impedance modelization.     

两扬声器虚拟声重放的双耳声压控制与定位性能

在两扬声器虚拟声重放中,通过精确重构双耳声压而产生不同的空间听觉感知。其重放的定位性能应该是由双耳声压控制的代价和稳定性所共同决定的。过去研究主要对双耳声压控制的稳定性进行分析,并以此作为扬声器布置和信号处理的依据。该文研究表明仅对双耳声压的稳定性分析是不足以完全衡量扬声器虚拟声重放的定位性能的。进一步采用虚拟声信号处理滤波器响应平均功率对双耳声压控制的代价进行分析。结果表明,缩窄左右对称扬声器布置的张角或采用非对称扬声器布置会明显增加产生侧向目标虚拟源时的双耳声压控制代价。虚拟源(虚拟声像)定位实验表明,双耳声压控制代价增加会引起虚拟源定位缺陷。实际应用中,为了有效产生侧向虚拟源,应避免采用过窄张角(如立体声偶极)和非对称的扬声器布置。     

基于 L-曲线参数优化的均匀声场重建算法

为了得到最小二乘法声场重建问题的稳定解,通常需要引入Tikhonov正则化方法。然而正则化程度取决于正则化参数的选择。针对这一问题,提出了一种基于L-曲线法参数选择的均匀声场重建算法。该算法根据重建误差与扬声器功率计算得到L-曲线,该曲线上曲率最大的点所对应的参数值作为Tikhonov正则化参数的选值。确定正则化参数后可进一步得到扬声器权系数以及重建均匀声场。针对不同正则化参数取值方法,对控制区域进行均匀声场重建以及重建性能仿真。仿真结果及实验表明,L-曲线法实现了重建误差与扬声器驱动信号功率之间的平衡。