A New Measuring Method of Cylinder Diameter using Sound Phase Delay

研究了一种利用声信号，特别是利用声波相位变化测量圆柱体直径的新方法。该方法是基于被障碍物散射的声波相位根据障碍物的特性而发生延迟的现象。利用扩音器、传声器和fft分析仪对平面声波所撞击的圆柱体的声压相位延迟与圆柱体直径的关系进行了实验研究。对圆柱对平面波的扰动问题进行了理论分析，得到了相位延迟与直径的关系。在较宽的直径范围内，根据相位延迟与直径成线性比例的关系，确定了直径的精度为（]SY.+- . [）0.04 mm。为了提高精度，一对刚性墙，感兴趣的圆柱体被放置在中间，平行于入射声波。结果表明，在与声音频率有关的一定直径范围内，相位延迟随直径的增加速率变大，精度提高到(]SY.+-。[) 0.01 mm。

A new measuring method of the diameter of a cylinder by means of sound signals, particularly by means of changes in phase of sound waves, is studied. This new method is based on the phenomenon that the phases of sound waves scattered by an obstacle are delayd according to the character of the obstacle. Phase delay of sound pressure behind a cylinder, which plane sound waves impinged on, was related to the cylinder diameter up to the 100 mm.Experiments have been made using a loudspeaker, microphone and a FFT-analyzer. The problem of the disturbance of plane waves by a cylinder has been analyzed theoretically and the relationship between the phase delay and the diameter was obtained. The diameter was determined with precision of(]SY.+-。[)0.04 mm from the relationship that the phase delay was linearly proportional to the diameter over a wide diameter range. For the purpose of improving the precision, a pair of rigid walls, which the cylinder of interest was placed midway between, were located parallel to the incident sound waves.It was found that the increase rate of the phase delay with diameter became larger within a certain diameter range which was dependent on the frequency of sound and that the precision was improved up to (]SY.+-。[) 0.01 mm.