DEVELOPMENT OF A COMPOUND SENSOR FOR ACCURATE DISPLACEMENT AND TEMPERATURE BY MEANS OF SOUND SIGNAL

当压缩空气吹到一个两端打开的小管道的开放式表面时，就会产生声音。声频和声压级随放置在管道另一个开口面附近的固体的位移而变化。空气的温度可以由随空气温度变化的声速来测定。本研究工作的目的是开发一种新型复合传感器，通过获取管道内声音的频率变化，实现无接触温度和小位移的检测。利用管道和管道端面的声阻抗，从理论上分析了压缩空气吹向管道时的声产生。在各种测深条件下进行了样例计算，并与实验结果进行了比较。为了建立一种优越的测量方法，设计了一种利用管道内产生的声音频率进行测量的新型非接触方法，该方法精度高、经济、适用范围广、结构简单。得到了位移与声频变化的良好对应关系，可以以低于1ma的精度测量位移。

SOUND GENERATES WHEN THE COMPRESSED AIR IS BLOWN ONTO AN OPEN-ENDED FACE OF A SMALL PIPE WHOSE BOTH ENDS ARE OPENED. THE SOUND FREQUENCY AND THE SOUND PRESSURE LEVEL VARY WITH THE DISPLACEMENT OF A SOLID PLACED CLOSE TO THE OTHER OPEN-ENDED FACE OF THE PIPE. THE TEMPERATURE OF THE AIR CAN BE DETECTED FROM THE SOUND VELOCITY WHICH VARIES WITH THE TEMPERATURE OF THE AIR. THE PURPOSE OF THIS RESEARCH WORK IS TO DEVELOP AND PUT TO PRACTICAL USE A NEW COMPOUND SENSOR WHICH CAN DTECT THE TEMPERATURE AND SMALL DISPLACEMENT WITHOUT CONTACT BY OBTAINING THE FREQUENCY VARIATION OF THE SOUND GENERATED IN THE PIPE.SOUND GENERATION WHEN THE COMPRESSED AIR IS BLOWN ONTO THE PIPE IS THEORETICALLY ANALYZED BY USING THE SOUND IMPEDANCES IN THE PIPE AND END FACES OF THE PIPE. SAMPLE CALCULATIONS ARE CONDUCTED UNDER VARIOUS SOUNDING CONDITIONS AND COMPARED WITH THE EXPERIMENTAL RESULTS. INORDER TO ESTABLISH A SUPERIOR MEASURING METHOD, A NEW NON-CONTACTING METHOD USING THE SOUND FREQUENCY GENERATED IN THE PIPE IS DEVISED WHICH IS HIGHLY ACCURATE, ECONOMICAL, WIDELY APPLICABLE, AND STRUCTURELLY SIMPLE. GOOD CORRESPONDENCE BETWEEN THE DISPLACEMENT AND THE SOUND FREQUENCY VARIATION IS OBTAINED, AND IT IS POSSIBLE TO MEASURE THE DISPLACEMENT WITH HIGH ACCURACY LOWER THAN 1mum.