Relation between sound transfer function from diffuse sound field to the eardrum and temporary threshold shift

Twelve volunteers with normal hearing (9 males and 3 females) participated in this work The sound transfer functions (STFS) from diffuse sound field to the subject's eardrums were measured and correlated to the temporary threshold shift (TTS) due to fiffuse-exposure.A probe tube with a miniature microphone was used for STF measurements in which successive 1/3 oct bandwidth random noise with central frequency from 0.25 kKz to 8 kHz were used. The subjects were divided into two groups, with the STF maxima at 2 kHz and 4 kHz respectively Pre- and post- exposure sweep Bekesy audiograms were recorded and the temporary thresh old shift calctilated as the difference between the two. Frequency of the maximum TTS was correlated to that of the maximum STF. The average TTS was very small or zero at frequen cies below the band noise exposure , but was noticeable even at the highest measured frequency (8 kHz) for beyond the noise band. Also individual differences in STF were found at frequencies between 2 kHz and 4 kHz

Sound Source Localisation for a High-Speed Train and Its Transfer Path to Interior Noise

Noise is one of the key issues in the operation of high-speed railways, with sound source localisation and its transfer path as the two major aspects. This study investigates both the exterior and interior sound source distribution of a high-speed train and presents a method for performing the contribution analysis of airborne sound with regard to the interior noise. First, both exterior and interior sound source locations of the high-speed train are identified through in-situ measurements. Second, the sound source contribution for di erent regions of the train and the relationships between the exterior and interior noises are analysed. Third, a method for conducting the contribution analysis of airborne sound with regard to the interior noise of the high-speed train is described. Lastly, a case study on the sidewall area is carried out, and the contribution of airborne sound to the interior noise of this area is obtained. The results show that, when the high-speed train runs at 310 km/h, dominant exterior sound sources are located in the bogie and pantograph regions, while main interior sound sources are located at the sidewall and roof. The interior noise, the bogie area noise and the sound source at the middle of the coach exhibit very similar rates of increase with increasing train speed. For the selected sidewall area, structure-borne sound dominates in most of the 1/3 octave bands.

Negative Transfer of Guanzhong Plain's Dialect on the Acquisition of English Sound

Pronunciation learning is the key factor in second language acquisition,which is also the soul of the language.Thereforeit is very vital for beginners to learn the right sounds.However,In the second language acquisition,the sounds of learners’first lan-guage unavoidably have some positive and negative transfer on the target language acquisition.To the Chinese learners,as Chineselanguage belongs to Sino-Tibetan system while English belongs to Germanic language system,the negative transfer is much moreobvious.Guanzhong plain lies in the central of Shaanxi province of China.The dialect here belongs to one of the sub-branches ofNorthern Mandrarin Dialect.Which shares little similarities with English in phonetics.The paper bases on the research of 25 stu-dents whose first language are Guanzhong Plain’s dialect to compare the phonemes of two languages in general and to further ana-lyze the negative transfer of Guanzhong Plain’s dialect to English Phonetic and give the related solutions.

基于卷积自编码器的座椅电机故障诊断

故障数据的缺失一直是制约设备故障诊断发展的重要因素,现有研究通过刻意损坏设备的方法来采集故障数据。为实现座椅电机的无损故障诊断,文章对座椅电机的故障机理进行分析,确定可能发生的故障类型,通过在座椅电机表面粘贴微型喇叭并播放故障声音,来模拟故障的发生。在自编码器系统的基础上,引入卷积操作,使用卷积层代替全连接层,通过输入数据维度、卷积核的尺寸和数量以及池化、正则化等操作对模型结构进行调整。采用IDMT Isa Electric Engine数据集作为源域数据,对模型进行预训练。使用迁移学习方法将源域中已经学习到的数据分布迁移到座椅电机故障诊断任务中,并与各类模型检测结果进行对比。结果显示,文中方法在召回率保持1.00的情况下,曲线下面积达到0.86,检测结果可靠,具有实际应用价值。

压电复合材料梯度分布声学特性研究

目前,压电复合材料在吸声降噪领域应用广泛,但其低频吸声性能并不理想。为解决此问题,以0-3型压电复合材料为研究对象,提出使压电陶瓷体积含量呈梯度分布以提高其低频吸声系数的方法。首先,基于声电类比法和传递矩阵法,推导多梯度分布的理论公式,并通过文献构型对其进行验证;其次,将均匀分布与梯度分布的吸声系数进行比较,发现梯度分布会改变材料的声阻抗,从而改变吸声系数。最后,进行梯度分布压电复合材料数值分析,结果表明,同等条件下,当压电陶瓷体积含量呈梯度递减,且梯度差和第一梯度的厚度增加时,可明显提高低频吸声系数。

管内点声源声学特征对气固换热特性的影响

针对实际工程问题,采用点声源模型,使用Fluent软件对点声源强化传热性能进行仿真模拟研究,通过udf程序精确控制点声源的位置、振幅和频率,模拟实际工程问题中气体流动受到声波作用对换热性能的影响。结果表明,在前后管径发生突变的流道中,声源位置在管正中间时,传热系数相较无声波时提高477.3%。同时,强化换热效果随声波频率的增加先增加后减小,随振幅的增加而增加。

北京艺术中心开放式吊顶的吸声措施与施工技术

为满足北京艺术中心公共空间的严格声学标准,特别选择了玻璃丝棉作为开放式吊顶区域的吸音体材料。通过采用离心玻璃棉外包玻璃丝布的结构形式,确保了吸音效果的持久稳定性。在施工过程中,我们从材料的选择到每一个施工步骤都实施了严格的控制,以保障吸音体结构的卓越质量。最后,通过传递函数法的声学测量,验证了吸音体在中高频段表现出色,但同时也意识到在低频段仍有提升的空间。通过深入的施工设计和严格的质量控制,北京艺术中心的玻璃丝棉吸音体成功取得了显著的吸声效果,为公共空间提供了一流的声学解决方案。

多胞复合型声学结构吸声性能研究

针对一种多胞复合型吸声结构进行声学性能研究,其具有吸声频带宽、声学性能突出、设计自由度高的特点。利用马氏理论和Delany-Bazley模型分别构建微穿孔板和多孔性吸声材料层,通过传递矩阵法和声电类比等效电路法建立平行排列的多胞复合型声学结构理论模型,利用有限元法构建阻抗管仿真模型并对多胞复合型声学结构进行声学分析。对比理论计算结果和仿真试验数据,发现两者具有较好的拟合度。研究表明:多胞复合型吸声结构在全频率段内具有较好的吸声性能,通过调整各吸声单元的设计参数和变量,例如排列组合方式、微穿孔板的穿孔率以及微穿孔板后空气层厚度等,可以对不同频率段内的噪声进行有效吸收。

某纯电SUV车型低频路噪问题分析及优化

为优化某纯电运动型多用途汽车(SUV)的若干低频路噪问题,文章依据路噪产生的机理,通过路噪传递路径分析,并结合整车模态分布,对该车型激励源、传递路径和响应进行了详细排查分析优化,并有效抑制了整车低频路噪。文章对整车前后排的不同频率噪声进行识别,分别为前排30 Hz附近耳压感、前排200 Hz附近空腔声和后排75 Hz附近敲鼓声,通过路噪源头控制、路径隔振提升及响应优化将整车低频路噪控制到较好水平,主观评价良好。文章所识别的低频路噪问题是整车路噪开发过程中较典型的问题点,分析优化思路对整车路噪问题分析排查及试验方法有一定的指导意义。

基于迁移学习的心音心脏疾病检测算法

心脏疾病一直是全球范围内重要的健康挑战,早期的诊断和检测至关重要。研究旨在开发一种基于迁移学习的心音心脏疾病检测算法,以提高心脏疾病的早期诊断准确性。训练时使用迁移学习增强了模型的稳定性和泛化能力。另外,提出一种基于HTS-AT模型的改进的心音识别模型HTS-AT V2,对心音信号进行特征提取和分类。结果表明,改进的算法在心音检测方面取得了显著成功,在检测效果有提升的同时,加快了推理速度、减少了模型大小。

基于DirectSound实现三维真实感声音生成

听觉通道是虚拟环境系统中最重要的接口之一,真实感声音模拟是构建高度真实感和沉浸感虚拟环境不可或缺的一部分。DirectSound对三维真实感声音模拟提供了很好的支持,是目前在真实感声音生成领域非常优秀的开发接口。该文简要介绍了真实感声音生成的相关理论,使用DirectSound模拟真实感声音涉及到的几个接口对象,详细论述了影响虚拟环境中三维声音听觉效果的因素,以及如何利用DirectSound程序开发接口实现这些因素对三维声音听觉效果的影响。最后给出了使用DirectSound生成三维真实感声音的具体步骤,并开发了一个简单的测试程序。

超声波声速测量及悬浮传送装置设计

阐述基于单片机和外围电路的超声波声速测量及悬浮传送装置设计,该装置可以实现测量声速、悬浮平面、无接触传送的功能。

基于HyperMesh的乘用车驾驶室NVH性能分析

为测定某乘用车驾驶室噪声、振动、声振粗糙度(noise vibration harshness,NVH)性能,采用有限元软件ANSA建立车辆内饰车身模型,HyperMesh建立驾驶室声腔模型,并采用HyperMesh将车身模型与声腔模型耦合连接,进行声腔模态分析和噪声传递函数分析。声腔模态分析结果表明:驾驶室声腔模型各阶次声压分布基本处于对称状态,符合车内声压分布规律,声腔模态结构合理。噪声传递函数分析结果表明:在不同方向、不同位置的激励作用下,驾驶员右耳处最大声压级为55.60 dB,未超出57 dB的限值规定;后排乘客右耳处最大声压级为56.25 dB,未超出58 dB的限值规定,车辆驾驶室满足NVH性能要求。

切向流作用下含机械阻抗的声衬建模及分析

为提高声衬低频吸声能力,在声衬中引入机械阻抗结构,建立系统声阻抗模型并开展分析。首先,基于声传播方程,结合传递矩阵法建立均匀管道声传播模型。通过引入穿孔板及机械阻抗声学协调条件,进一步得到切向流作用下含机械阻抗的声衬阻抗模型。通过与现有文献及有限元法进行对比来验证给出方法的可靠性。对含机械阻抗的双自由度声衬开展数值分析,其结果表明,引入机械阻抗能显著提升声衬的低频吸声性能,声衬整体吸声量随流动马赫数的增大而先增大后减小,且较小的机械阻抗质量能够获取更好的低频吸声效果,低频吸声峰值频率随机械阻抗固有频率的增大而增大,峰值高度随机械阻抗阻尼的增大而减小。

多层微穿孔板吸声特性研究

本文研究了在大背腔情况下多层微穿孔板结构的设计与吸声特性问题.在实际应用中,根据电-力-声类比法,微穿孔板吸声结构可以等效为电阻-电容串联的电路系统.但随着背部空腔深度的不断增加,传统的电-力-声类比法在分析多层微穿孔板结构吸声特性时变得十分复杂,且计算精度较低.鉴于此,本文提出了一种传递矩阵的计算方法,用于分析多层微穿孔板结构的吸声特性.并结合有限元仿真分析方法,通过数值算例验证了该方法的正确性与有效性.

多层微穿孔板吸声性能的理论分析与参数优化

论文基于微穿孔板理论对单层、双层、三层微穿孔板在声波频率为0~1500 Hz下的吸声性能进行分析,运用声电类比法和传递矩阵法分别计算双层微穿孔板、三层微穿孔板的吸声系数。首先使用控制单一变量法对影响微穿孔板吸声性能的各个参数做定性分析,确定各个参数与吸声性能是正相关还是负相关,其次使用有限元软件COMSOL Multiphysics对微穿孔板的吸声系数进行仿真计算,将有限元仿真的结果与数值仿真的结果进行对比,从而验证数值仿真的可靠性,再使用主成分分析法对微穿孔板的各个参数对吸声性能的影响进行定量分析,确定微穿孔板各个参数对第一吸声峰值对应频率的影响程度,给实际工艺中减小第一吸声峰值的频率提供理论的指导,最后通过改进遗传算法优化多层微穿孔板结构,给微穿孔板各个参数取一个合理的值使多层微穿孔板在0~1500 Hz下具有良好的吸声性能,优化后的结果表明随着微穿孔板层数的增加其对低频声波的吸收能力会有所增强。

基于单元辐射叠加法的水下矩形板声场重建

为解决等效源法在水下结构声源声场重建中存在的虚拟等效源配置位置难以确定、求逆过程中传递矩阵病态性过大的问题,本文提出了基于单元辐射叠加法的水下结构声源声场重建方法。该方法利用结构声源边界元法建模思想与声场波叠加原理,建立了声源表面振动与辐射声场之间的振声传递关系,得到可快速计算的振声传递函数,并利用该函数作为传递算子进行声场重建。通过对矩形板的声场重建仿真,验证了本文方法相比等效点源近场声全息具有更高的重建精度,且具有更大的有效全息距离。通过在不同阵元数、信噪比情况下的仿真分析,进一步证明了本文方法能够改善水下结构声源的声场重建精度。

Heat Transfer and Acoustic Properties of Open Cell Aluminum Foams

The aluminum open cell foams have been prepared by the conventional precision casting method to investigate the thermal and acoustic properties.A water heating system and silencers were organized as a first step for its applications.The temperature increase between the top and bottom of the foam became larger as the cell size increased in the heat transfer measurement.Sound absorption ratio of the close cell foams was 60%-100%, whereas the open cell aluminum foam showed only 10%-20% of sound absorption at low frequency.When the prototype electric water heater manufactured by combining aluminum open cell foam with a heater was heated to 100-400℃,the highest temperature of water was in the range of 16-46~C.This suggests that there could be potential for this type of heater to be used as a commercial electric water heater.Sound silencer made with the aluminum open cell foam was applied to exit of exhaustion side at air pressure line.Sound silencing effect of open-celled aluminum foam showed that the noise level went down by introducing smaller cell size foam.

传递路径分析在车内声品质优化中的应用

针对某款车型在40km/h粗糙路面行驶时,车内主驾耳旁噪声声品质主观感受较差的问题。首先,采用传递路径分析(Transfer Path Analysis,TPA)方法得到每条路径对于车内驾驶员耳旁噪声的贡献量。其次,基于遗传算法(Genetic Algorithm,GA)优化BP神经网络的权值和阈值建立车内声品质预测模型,实现传递路径分析与声品质相结合,有效识别出48条结构路径中后副车架左后、右后和右前安装点Z向三条路径对车内噪声烦躁度贡献最大。最后,结合模态分析和频谱分析确定为后副车架模态问题。通过调整后副车架衬套刚度,车内主驾耳旁噪声声品质得到有效改善。

A SEMI-ANALYTICAL AND SEMI-NUMERICAL METHOD FOR SOLVING 2-D SOUND-STRUCTURE INTERACTION PROBLEMS

Based on the transfer matrix method and the virtual source simulation technique, this paper proposes a novel semi-analytical and semi-numerical method for solving 2-D sound- structure interaction problems under a harmonic excitation.Within any integration segment, as long as its length is small enough,along the circumferential curvilinear coordinate,the non- homogeneous matrix differential equation of an elastic ring of complex geometrical shape can be rewritten in terms of the homogeneous one by the method of extended homogeneous capacity proposed in this paper.For the exterior fluid domain,the multi-circular virtual source simulation technique is adopted.The source density distributed on each virtual circular curve may be ex- panded as the Fourier's series.Combining with the inverse fast Fourier transformation,a higher accuracy and efficiency method for solving 2-D exterior Helmholtz's problems is presented in this paper.In the aspect of solution to the coupling equations,the state vectors of elastic ring induced by the given harmonic excitation and generalized forces of coefficients of the Fourier series can be obtained respectively by using a high precision integration scheme combined with the method of extended homogeneous capacity put forward in this paper.According to the superposition princi- ple and compatibility conditions at the interface between the elastic ring and fluid,the algebraic equation of system can be directly constructed by using the least square approximation.Examples of acoustic radiation from two typical fluid-loaded elastic rings under a harmonic concentrated force are presented.Numerical results show that the method proposed is more efficient than the mixed FE-BE method in common use.