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

当压缩空气吹到两端开口的小管的开口面上时，会产生声音。声波频率和声压级随着靠近管道另一个开口端面放置的固体的位移而变化。空气的温度可以从随空气温度而变化的声速来检测。本文研究了一种新型的复合材料管，它能通过测量管内声的频率变化来实现非接触测温和小位移检测，并将其应用于实际。本文利用管内声阻抗和管端面声阻抗，从理论上分析了压缩空气吹到管上时的声产生。在不同的测深条件下进行了抽样计算，并与实验结果进行了比较。为了建立一种上级的测量方法，本文提出了一种利用管道中产生的声频信号的非接触式测量方法。该方法具有精度高、经济、适用性广、结构简单等优点。位移与声频率变化之间有很好的对应关系，可以实现小于1 μ m的高精度位移测量。

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.