基于nCode DesignLife的车载扬声器盆架振动疲劳分析

针对某100 mm车载扬声器盆架结构的疲劳问题,采用基于功率谱密度(Power Spectrum Density,PSD)的频域分析法对其进行疲劳可靠性分析.应用ANSYS Workbench,先对扬声器单元进行有限元模态分析获得其固有频率和振型,再基于模态分析进行谐响应分析获得其频率响应函数(Frequency Response Function,FRF).将有限元分析结果导入到n Code Design Life,施加加速度PSD载荷进行振动疲劳分析,获得盆架在x,y和z方向上各自8 h的振动疲劳损伤,从而对盆架的疲劳可靠性进行评估.对照实物扬声器样品的疲劳耐久试验结果,为扬声器盆架结构设计提出一些建议.     

Giant Magnetostrictive Material Loudspeaker System Acoustic Radiation Simulation

An infinite panel model of giant magnetostrictive material loudspeaker system(GMMLS)is proposed by making use of finite element method(FEM).Bending wave eigenfunction is introduced to describe the acoustic radiation condition of the panel.Far-field response in different conditions is calculated by changing the mass surface density.Conclusion is obtained by analyzing the curves simulated,that panel which has larger mass surface density can hardly generate far-field acoustic radiation for lower frequency,while the panel has smaller mass surface density generates far-field acoustic radiation for lower frequency evenly and stronger.     

Giant Magnetostrictive Material Exciter for Panel Loudspeaker

The exciter component in a panel loudspeaker has a profound effect on the overall performance of the system. The equivalent circuit analysis of the combination of giant magnetostrictive material exciter and distributed mode panel is introduced and how exciter parameters influence panel lo＇udspeaker＇ s performance is discussed. Numerical predictions are given in order to show how these influences are manifested.     

基于声场重建的三维音频技术

近年来,随着人们对视听体验的要求不断提高,三维（空间）音频技术被广泛应用于娱乐影音等各领域,并取得显著进展。如何便捷地创造一个具有沉浸式空间听觉体验的环境是一直以来的研究热点。因此综述了主流三维声场重建的相关技术,并分析了其优缺点,主要讨论了三维声场的表达与维度、不同扬声器下的三维声场重建以及相应的混响均衡技术。最后,归纳了三维声场重建技术目前存在的问题,并展望未来发展的新方向。     

基于LabVIEW的摩擦噪声测试系统

虚拟仪器(VirtualInstrument,简称VI)是现代计算机软件技术、通信技术和测量技术相结合的产物。LabVIEW语言是美国NI公司推出的一款功能强大的虚拟仪器开发平台。小波变换的主要特点是通过变换能够充分突出某些方面的特征,它是研究信号时-频分析的重要方法。设计和实现了基于LabVIEW、利用小波变换的噪声测试系统;通过该测试系统可以对摩擦噪声进行测量和分析,有利于深入了解摩擦机理,改善摩擦条件,促进环保事业。     

二维小波变换及其在机械碰摩故障诊断中的应用

以机械碰摩信号为例，采用具有“时频局部化”性能和“方向极化”性能的二维小波变换，成功地分辨出故障信号与正常信号，避免了由于多信号转化成单信号带来的信息冗余以及能量的转化，同时能方便地分辨出故障信号的相位角，为解决机械故障诊断领域多信号、多特征的分析问题提出新的思路。     

碰摩转子系统振动响应的频率特征研究

以刚度为分段线性的 Jeffcott转子为转子与静子碰摩的简化模型 ,建立了系统的运动微分方程 ,在碰摩作用的时间间隔相同 ,且每次转子与静子接触时间极短的情况下 ,推导出了系统运动方程解的形式和系统振动响应的频率特征 ,证明了在这种假设下 ,系统呈周期或拟周期运动 ,数值计算也验证了这一结论     

Filtered gradient active fuzzy neural network noise control in an enclosure backed by a clamped plate

The performance of conventional linear algorithms in active noise control applications deteriorates facing nonlinearities in the system mainly because of loudspeakers. On the other hand, fuzzy logic and neural networks are good candidates to overcome this drawback. In this paper, the acoustic attenuation of noise in a rectangular enclosure with a flexible panel and five rigid walls is presented both theoretically and experimentally using filtered gradient fuzzy neural network (FGFNN) error back propagation algorithm in which the secondary path effect is implemented in derivation of updating rules. Considering this effect in updating rules leads to faster convergence and stability of the active noise control system. On the other hand, the primary path in the investigated system comprises an identified nonlinear model of loudspeaker inside the aforementioned box, parameters of which vary with the input current. The loudspeaker is identified using series‐parallel neural network model identification method. As a comparison, the performance of filtered‐x least mean squares and FGFNN algorithms are compared. It is observed that FGFNN controller exhibits far better results in the presence of loudspeakers with nonlinear behavior in primary path.Copyright © 2012 John Wiley & Sons, Ltd.     

Speech intelligibility and speech quality of modified loudspeaker announcements examined in a simulated aircraft cabin

Acoustic modifications of loudspeaker announcements were investigated in a simulated aircraft cabin to improve passengers’ speech intelligibility and quality of communication in this specific setting. Four experiments with 278 participants in total were conducted in an acoustic laboratory using a standardised speech test and subjective rating scales. In experiments 1 and 2 the sound pressure level (SPL) of the announcements was varied (ranging from 70 to 85 dB(A)). Experiments 3 and 4 focused on frequency modification (octave bands) of the announcements. All studies used a background noise with the same SPL (74 dB(A)), but recorded at different seat positions in the aircraft cabin (front, rear). The results quantify speech intelligibility improvements with increasing signal-to-noise ratio and amplification of particular octave bands, especially the 2 kHz and the 4 kHz band. Thus, loudspeaker power in an aircraft cabin can be reduced by using appropriate filter settings in the loudspeaker system.     

基于短时傅里叶变换的扬声器共振频率求解

通过分析在单一频率正弦信号和连续对数扫频信号下扬声器响应信号频谱的特点,提出在短时傅里叶变换的基础上,对扬声器共振频率进行求解。对扬声器扫频范围内的响应信号进行采集和短时傅里叶变换,并分析各个窗对应谐波分量的大小,进而得出共振频率。该方法能够快速获取扬声器的共振频率,测量结果准确,为扬声器在共振频率附近区域的检测提供保证。