Bar type waveguides are frequently employed as a buffer rod between ultrasonic senor and hard-to-access object in many measurement applications. Difficulty in pulse echo measurements using a buffer rod is caused by spurious echoes due to reflection, mode conversion and interference within the buffer rod of finite size. These spurious echoes degrade the signal to noise ratio (SNR) because of their possible interference with desired target signals. A tapered buffer rod or rods with non-symmetrical cross sections were used before to reduce these unwanted spurious echoes. In this paper, we propose signal processing techniques to remove the spurious echo signals. Experiments were performed in order to examine the refocusing and recovering the initial input waveform in the long range propagation of ultrasonic waves in cylindrical waveguides. Two different time reversal processes (regular TR and reciprocal TR or inverse filtering) are tested and the experimental results were compared

Abstract
 1. Introduction
 2. Signal processing
 3. Experiment
 4. Summary
 Acknowledgement
 References

• 정현조(원광대학교 공과대학 기계자동차공학부, 원광대학교 부설 공업기술개발연구소 연구위원) | Hyunjo Jeong Corresponding Author