An accurate pipe length measurement using an acoustic sensor

The authors previously developed an online length measurement system for pipes with closed ends by making use of the stationary waves in the pipes. The system adopted sound pressures and their derivatives of several modes of the stationary waves as the state variables of a linear dynamic system and reduced the length measurement to a parameter estimation problem, and thereby realized a highly accurate real-time pipe length measurement. This paper presents a new length measurement system for pipes with open ends.