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。这种方法是基于声波在障碍物上散射时，由于障碍物的特性，其相位会发生延迟的现象。在圆柱体后面的声压的相位延迟，其中平面声波的冲击，与圆柱体直径到100 mm。实验已经使用扬声器，麦克风和FFT分析仪。从理论上分析了圆柱体对平面波的扰动问题，得到了相位延迟与圆柱体直径的关系。直径的测定精度为（±）SY. ±。[）0.04 mm，从该关系可知，相位延迟在宽直径范围内与直径成线性比例。为了提高测量精度，在平行于入射声波的方向上设置一对刚性壁，在该刚性壁中间放置感兴趣的圆柱体，发现相位延迟随直径的增加率在一定的直径范围内变大，该直径范围取决于声音的频率，并且精度提高到（]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.