tube noise

Aimed at the jet noise which is induced by the expand structure and tail tube in the resistant muffler, a finite element model at low Mach number was developed.

针对抗性消声器中扩张结构和尾管引起的射流噪声问题，建立了低马赫数射流噪声有限元分析模型。

Basing on theory of noise it is obtained detection equation of neutron streak image tube, from which minimal detectable neutron yield threshold of neutron pulse is induced. Also the influence of sensitivity of recording system on the detection threshold is discussed.

本文从噪音理论出发导出了中子扫描变象管的探测方程，从而求得了中子扫描变象管可探测的最小脉冲中子产额，而且讨论了记录系统灵敏度对探测阈的影响。

Detection technology of boiler tube leakage is based on the principle: the sensor picks up the noise with a certain intensity and frequency range, produced during boiler tube leakage, and distinguishes leakage noise source from background noise source.

锅炉炉管泄漏检测技术是通过传感器捕捉炉管泄漏时产生一定强度和频率范围的噪音，并区分泄漏声源和背景声源。

To the problems in the tube eddy testing, some improved ways are given by using a three-point probe matching the eddy instrument model ET-204 with low field voltage, and selecting a phase having the optimum singnal-to-noise ratio with impedance plane technique.

针对管材涡流探伤中存在的一些问题，研制出可匹配低激励电压ET－204型涡流仪的三点式探头，并采用阻抗平面显示技术选择最佳信噪比相位。

China is now capable of building the world's first underwater vacuum tube train, a futuristic form of transportation that can achieve supersonic speed and reduce airborne noise, according to Chinese academics and scholars.

据中国的学者和学术研究人员表示，中国现在有能力建设世界上第一条水下真空管列车--这种未来的交通方式，其速度可以超过音速、且能大幅度降低噪音。