电力变压器绕组振动声纹特性分析*

为更加准确分析变压器绕组的状态特征,本文提出一种基于多物理场耦合仿真的变压器绕组振动声纹特性分析方法。根据实验条件,建立变压器绕组振动噪声模型,考虑变压器绝缘油在噪声传播过程中的作用,对S13-M-200/10型号的油浸式变压器进行短路实验,测量油箱表面的振动加速度以及周围空间的声音信号。仿真结果与实测数据对比分析,油箱表面的振动加速度集中频率为100Hz,空间声音信号集中频率为100Hz和200Hz,验证仿真模型的有效性。最后,建立变压器机械故障的仿真模型,分析得到变压器发生机械故障时,声音信号中100Hz频率分量减少,200Hz频率分量增加,为变压器绕组故障诊断提供依据。     

求解随机振动结构声辐射的统计边界元方法

机器的机械振动在音频范围内大多是具有明显随机性的随机过程,普通边界元方法不能计算这类具有随机边界条件的结构声辐射问题。本文提出将边界元方法和统计方法相结合的统计边界元方法,导出了求解随机振动物体所辐射噪声声场的计算公式。通过求解随机声场算例的计算,表明本文所提出的方法是正确的。     

水下弹性球壳被激振动和辐射声的时域特性研究

本文在时域上对水下球壳在球冠形均匀单频填充脉冲力源作用下的振动和辐射声问题进行分析和计算。结果表明:在长脉冲力作用下,根据填充频率不同,会激起不同模态振动和产生长的共振辐射声或拍频辐射声,但有一部分模态对远场声辐射的贡献甚微;在短脉冲力作用下,脉冲波在球壳上传播一般会发生展宽和变形。文中还应用DAA2方法简化水——壳体耦合关系和边界元方法计算辐射声场。与精确解比较可知,DAA2方法的结果是令人满意的。     

阻尼贴片式高速列车车轮振动声辐射试验分析

为了研究辐板不同阻尼贴片装置对高速列车车轮的减振降噪效果,在半消声室内进行标准车轮与阻尼贴片式车轮自由状态下的振动声辐射试验研究,并基于有限元法对车轮模态进行了仿真计算。研究结果表明：施加辐板阻尼贴片后,两种阻尼贴片车轮的固有频率与标准车轮相比变化不大,但对于频率在1600Hz以上各阶模态阻尼比显著增加。径向与轴向激励下的降噪效果均达到10dB(A)以上,可见两种阻尼贴片装置均具有良好的降噪效果。其中在多了0.3mm铝合金薄板的情况下,W2车轮的降噪效果要略优于W1车轮,轴向激励下更加明显。     

加肋双层圆柱壳振动声辐射数值计算分析

利用有限元软件ANSYS和边界元软件SYSNOISE对一双层加肋圆柱壳的水下受激振动与声辐射作了数值计算分析研究.该双层柱壳为环向加肋,并且两端带有半球帽.利用ANSYS软件数值计算了双壳的轴对称模态,及当双壳在水下受点力激励时外表面的法向位移、法向质点振速及表面声压和法向声强的频率响应。然后,将法向位移数据传递给SYSNOISE软件,利用边界元技术计算了双壳的辐射声功率及辐射效率的频率响应,及其近场的声压和声能流分布和远场指向性。     

The effects of sound level and vibration magnitude on the relative discomfort of noise and vibration

The relative discomfort caused by noise and vibration, how this depends on the level of noise and the magnitude of vibration, and whether the noise and vibration are presented simultaneously or sequentially has been investigated in a laboratory study with 20 subjects. Noise and vertical vibration were reproduced with all 49 combinations of 7 levels of noise and 7 magnitudes of vibration to allow the discomfort caused by one of the stimuli to be judged relative to the other stimulus using magnitude estimation. In four sessions, subjects judged noise relative to vibration and vibration relative to noise, with both simultaneous and sequential presentations of the stimuli. The equivalence of noise and vibration was not greatly dependent on whether the stimuli were simultaneous or sequential, but highly dependent on whether noise was judged relative to vibration or vibration was judged relative to noise. When judging noise, higher magnitude vibrations appeared to mask the discomfort caused by low levels of noise. When judging vibration, higher level noises appeared to mask the discomfort caused by low magnitudes of vibration. The judgment of vibration discomfort was more influenced by noise than the judgment of noise discomfort was influenced by vibration.     

Development of vibration signature analysis using multiwavelet systems

In this paper the vibration analysis for local faults and transient phenomena detection, using multiwavelet systems, is developed. Unlike the scalar wavelet systems, in which their coefficients are scalar parameters, the transformation coefficients of multiwavelet systems are vector valued, and their calculation requires specialized techniques. In this investigation, having considered the technique used to obtain the scalar wavelet system coefficients, the transformation coefficients of the multiwavelet system are calculated, and by applying the method to artificial vibration signals, decomposition of the signal into different multiscale and multiwavelet functions (as introduced by Donovan, Geronimo, Hardin and Massopust) is examined, as well as the capability of this multiwavelet system for transient phenomena detection. By analyzing the vibration signal of a faulty gearing system the applicability of Donovan, Geronimo, Hardin and Massopust multiwavelet system for local fault detection of the mechanical systems is shown. The results confirm that using the multiwavelet system, not only can the fault in the gearing system be diagnosed, but also its location can be determined precisely.     

Multi-purpose explosion chamber with sound muffling and vibration cutting means

Abstract

An explosion chamber is operating for more than 13 years successfully. The chamber is used for procucing wBN powder and various dynamic high pressure experiments. The capacity of the chamber is 200 cubic meter by volume and 10 kg by the quantity of the explosives to be exploded. Safety means are equipped sequentially, transmitted sound level is less than 65 db at 60 m point from the chamber and earth vibrations cannot be detected at its periphery. The strength of the chamber was designed by simple static gas pressure model.     

某汽车传动系扭振测试、诊断与数据处理分析

本文针对某轻型卡车由于传动系扭振导致加速过程中驾驶室内出现异常振动与轰鸣噪声现象进行研究。首先,为弄清车内振动噪声产生机理,对整车的扭振和车内振动噪声进行了实车道路试验;其次,对整车试验异常数据进行后处理,通过低通滤波和设置电压波动缓冲区的方法对其进行去噪和再生成,消除了加速工况下转速曲线失速和异常峰值的现象;最后,通过分析转速、振动和噪声数据得出：样车加速过程中发动机2阶激励频率达到整车传动系的固有频率时,引起了传动系扭转共振,连同传动轴的不平衡转动自振,通过悬置、中间支撑和后桥板簧传入到车内,引起驾驶室异常振动和轰鸣噪声。     

Active control of sound radiated by a submarine in bending vibration

This paper theoretically investigates the use of inertial actuators to reduce the sound radiated by a submarine hull in bending vibration under harmonic excitation from the propeller. The radial forces from the propeller are tonal at the blade passing frequency and are transmitted to the hull through the stern end cone. The hull is modelled as a fluid loaded cylindrical shell with ring stiffeners and two equally spaced bulkheads. The cylinder is closed by end-plates and conical end caps. The actuators are arranged in circumferential arrays and attached to the prow end cone. Both Active Vibration Control and Active Structural Acoustic Control are analysed. The inertial actuators can provide control forces with a magnitude large enough to reduce the sound radiated by the vibrations of the hull in some frequency ranges.     

Responses of pigeon vestibular nerve fibers to sound and vibration with audiofrequencies

Single unit recordings were made from the nerve branch innervating the crista in the horizontal semicircular canal of a pigeon. The vestibular organ was either stimulated with sound through the ear canal or with a vibrator in contact with the membraneous ampulla roof. Units responding to sound or vibration showed tuning with a best frequency of approximately 0.7 kHz. The average low-frequency slope of the tuning curves is--16 dB/oct; the average high-frequency slope 20 dB/oct. The threshold amplitude for vibrator stimulation is 30 nm. This value comes close to the calculated threshold value for cupula deflection in the human semicircular canal.     

Experimental studies on sound and vibration of a two-tone Chinese Peace Bell

In order to examine whether the characteristics of the bell are coincident with the design and make some constructive suggestions for the tuning of bell, the frequency characteristics of sound and the vibrational modes of a two-tone Chinese Peace Bell have been studied. With Welch's spectral estimate, the main partials of radiated sound of the bell have been found out. With time-frequency analysis, the changes of the spectrum with time have been shown. By conditional mean frequency (CMF) of the spectrogram of the sound, the change in the pitch of the bell has been discussed. With an accelerator, the vibration distributions on the different points of the bell have been measured. With short time spectrum analysis, the vibrational modes at different frequencies have been reconstructed.     

水中有限长加肋圆柱壳体振动和声辐射近似解析解

加肋圆柱壳体是水下航行器的主要结构形式。将肋骨对壳体的作用简化为只有法向力,本文导出了水中有限长加肋圆柱壳体的振动和声辐射的近似解析解。其中肋骨的作用表现为在无肋的耦合振动方程中增加附加阻抗,因此壳体的振动和声辐射由壳体的机械阻抗、流体的辐射声阻抗和肋骨的附加阻抗所决定。数值计算例子表明,在低频情况下,加肋对辐射声功率影响不大,但将降低表面平均振速,从而增加声辐射效率。     

Two-dimensional model of vocal fold vibration for sound synthesis of voice and soprano singing

Voiced sounds were simulated with a computer model of the vocal fold composed of a single mass vibrating both parallel and perpendicular to the airflow. Similarities with the two-mass model are found in the amplitudes of the glottal area and the glottal volume flow velocity, the variation in the volume flow waveform with the vocal tract shape, and the dependence of the oscillation amplitude upon the average opening area of the glottis, among other similar features. A few dissimilarities are also found in the more symmetric glottal and volume flow waveforms in the rising and falling phases. The major improvement of the present model over the two-mass model is that it yields a smooth transition between oscillations with an inductive load and a capacitive load of the vocal tract with no sudden jumps in the vibration frequency. Self-excitation is possible both below and above the first formant frequency of the vocal tract. By taking advantage of the wider continuous frequency range, the two-dimensional model can successfully be applied to the sound synthesis of a high-pitched soprano singing, where the fundamental frequency sometimes exceeds the first formant frequency.     

Infrasonic sound pressure in dwellings at the Helmholtz resonance actuated by environmental noise and vibration

The Helmholtz resonator effect of a room with an open window or ventilation duct has been studied theoretically and experimentally. The effect results in a sound pressure buildup at infrasonic frequencies. For comparison, the frequencies of the standing-wave room resonances are above the infrasonic range for residential dwellings. The relations between the sound pressure inside a room and outside (environmental) sound pressure or vibration acceleration have been calculated for the third-octave frequency band incorporating the Helmholtz resonance frequency. The experiment on a small-scale model illustrated the Helmholtz resonator effect caused by environmental vibration.     

水下任意形旋转薄壳振动和辐射声的时域研究

本文通过采用DAA2方法,有限元模态展开和直接积分混合方法以及Kirchhoff推迟势的边界元解法在时域上对水下任意形旋转薄壳振动和辐射声进行研究。以水下椭球壳的端部轴对称激励问题为例,对力源的时间函数分别为单频填充脉冲和δ脉冲两种情况给出了一些典型的数值计算结果和实验结果,并进行了讨论。     

Acoustically induced vibration of,and sound radiation from,beams inside an enclosure

The velocity response of a single cylindrical beam to pure tone sound in a rectangular reverberation chamber is analysed. The variation of the response with position within the chamber and the effect of proximity of other similar, parallel beams is considered. A reciprocity relation is established between the response of a beam to sound in the chamber and the sound radiation by such motion when otherwise generated; this relation is found to be valid even for non-diffuse fields, below the Schroeder “large room” frequency (i.e., above this frequency, the average frequency spacing between modes is less than one-third of the bandwidth of a typical mode [1]). The mean square velocity response, averaged over all possible beam positions within the chamber, is found to be directly proportional to the radiation loss factor of that vibrational mode, and inversely proportional to (frequency)³. The maximum normalized response occurs when the beam is excited in its fundamental vibrational mode. One application is to the estimation of fatigue life of heat exchanger tubes in gas-cooled nuclear reactors; the large number of tubes necessitates an estimate of the variation of the tube response with position within the exchanger casing. Another important application is in a reverberation chamber; in many cases a suitable direct excitation experiment is very difficult, or even impossible to perform, while the corresponding reciprocal experiment is relatively easy.     

The diffuse sound field in energetic analysis

Measuring the degree of diffuseness of a sound field is crucial in many modern parametric spatial audio techniques. In these applications, intensity-based diffuseness estimators are particularly convenient, as the sound intensity can also be used to obtain, e.g., the direction of arrival of the sound. This contribution reviews different diffuseness estimators comparing them under the conditions found in practice, i.e., with arrays of noisy microphones and with the expectation operators substituted by finite temporal averages. The estimators show a similar performance, however, each with specific advantages and disadvantages depending on the scenario. Furthermore, the paper derives an estimator and highlights the possibility of using spatial averaging to improve the temporal resolution of the estimates.