共查询到19条相似文献,搜索用时 453 毫秒
1.
2.
驻波法测量声速实验的讨论 总被引:1,自引:4,他引:1
根据声波在2个换能器之间多次反射和声波在空气中的衰减,研究了驻波法测量声速实验中接收器输出信号随接收器到发送器间距离的变化.理论推导结果表明:声波在一般情况下不是严格的驻波,但是当反射比接近-1时则是双曲函数形式的驻波,这与实验测量结果一致.只有接收器到发送器的距离比较远,反射比接近-1时,才能得到几乎理想的驻波. 相似文献
3.
利用智能手机自制简易实验装置,搭建了一套驻波法声速测量系统,实现了声波在空气和不同液体介质中的传播速度的准确测量。实验使用手机FreqCounter APP产生单频声波信号,采用DaTuner APP软件检测实时频率和声音强度,通过测得相邻波腹或波节间的距离,根据其与频率和声速间的关系即可求出所测声速值。所取得实验结果与理论值具有良好的一致性。 相似文献
4.
5.
6.
讨论了驻波法测空气中声速的实验,分别用相位比较法和李萨如图法来确定超声波波长.在不同温度条件下测量了声速并与理论值进行比较,实验结果显示测量温度接近室温时实验值与理论值基本一致,测量温度与室温相差较大时实验值与理论值偏差较大. 相似文献
7.
8.
9.
10.
11.
实验室中水声材料声学参数的测量主要在水声声管中进行。管内平面波声速是正确测量这些参数的基础。该文提出一种基于四水听器结合不同边界的测量充水弹性管中声速的新方法。该方法利用4个固定位置处的水听器,采用最小二乘的方法,使得两组水听器分别得到的声管末端入射波声压差值的平方最小的声速即为管内平面波声速。该方法利用单频信号,在每一频率点均可测得声速,可以在任一种声管末端边界下进行测量,同时无需知道各水听器到边界的精确距离,在文中的3种边界下声速测量结果具有很好的一致性,实验操作简单、误差很小。该方法的仿真结果与管内声速的理论值吻合得很好,同时实验测量结果与仿真值之间的误差很小,证明了方法的准确性以及鲁棒性,为声管声速测量提供一个很好的思路。 相似文献
12.
Local variation in surface skimming longitudinal wave (SSLW) velocity has been measured using a scanning acoustic microscope. A very narrow width electrical impulse has been used to excite the transducer of the acoustic lens. This permits the separation of the SSLW signal from the direct reflected signal in the time domain. A simple method of measuring the time delay between the directly reflected signal and the SSLW signal at two defocuses has been utilized for the local measurement of SSLW velocity. The variation in the SSLW velocity measured over an area of the sample is scaled and presented as an image. The method has been implemented to image the variation of the SSLW velocity around a crack tip in a sample of Ti-6Al-4V. Since the SSLW velocity is known to change linearly with the stress, the SSLW velocity image is considered as a representation of the image of stress around the crack tip. Local stress variation in the same region of the crack tip is directly measured using x-ray diffraction. The SSLW velocity image is compared with the x-ray diffraction stress image. The contrast in the two images, spatial resolution, and the penetration depth into the sample of acoustic waves and x rays are discussed. 相似文献
13.
14.
Acousto-electric well logging by eccentric source and extraction of shear wave 总被引:1,自引:0,他引:1 下载免费PDF全文
The nonaxisymmetric acousto-electric field excited by
an eccentric acoustic source in the borehole based on Pride seismoelectric
theory is considered. It is shown that the acoustic field inside the borehole,
converted electric and magnetic fields and coupled fields outside the borehole
are composed of an infinitude of multipole fields with different orders.
The numerical results show that
both the electromagnetic waves and the seismoelectric field in the borehole,
and the three components of both electric field and magnetic field
can be detected. Measurements on the borehole axis will be of
advantage to determining shear velocity information. The components
of the symmetric and nonsymmetric acoustic and electromagnetic fields
can be strengthened or weakened by adding or subtracting the two full
waveforms logged in some azimuths. It may be a new method of directly
measuring the shear wave velocity by using the borehole
seismoelectric effect. 相似文献
15.
16.
通过由一个声压换能器和一个质点速度换能器所构成的传感器(p-u声强探头)同时测量材料表面附近的声压和质点振动速度,可直接得到其声学阻抗,进而得到材料的反射因子、吸声系数。本文利用一个p-u探头声强测量系统,在半消声室内测量了三聚氰胺泡沫的吸声系数,分析了声源高度和入射角度、材料样本尺寸和厚度对吸声系数测量的影响,并和阻抗管中测量得到的法向吸声系数进行了对比。最后分析了声阻抗率的幅值和相位误差对吸声系数的影响,推导了它们的误差传递公式。 相似文献
17.
We report on direct imaging, by means of stroboscopic x-ray topography, of phonon-induced dislocation vibrations. X-ray images taken from LiNbO3 crystals excited by 0.58 GHz surface acoustic waves, showed individual acoustic wave fronts as well as their distortions when crossing the dislocation line. The observed contrast is well explained by considering the dynamic deformation field of vibrating dislocation. Comparing simulated deformation maps and x-ray images permitted determination of the local velocities of vibrating dislocations and their viscosity coefficients. We found unexpectedly high velocity values (not far from the speed of sound) and extremely low viscosity coefficients, 2-3 orders of magnitude lower than previously measured in ductile materials. 相似文献
18.
A new method of measuring velocity and attenuation of leaky surface waves is presented. A single focused transmitting transducer and linear receiving array in a pitch-catch arrangement are used in the proposed system. The spatial distribution of the acoustic field in the leaky wave is recorded by the array, and the parameters of the leaky wave can be obtained by processing the output waveforms. In comparison with existing material characterization systems, the mechanical scanning of the transducers is not used any more, and the measurement time is only limited by the time of the wave propagation and speed of the electronic data acquisition system. 相似文献