| 摘要 |
PURPOSE:To measure the vacant cross-sectional area in a pipe having the bend quantitatively by inputting the specified sound wave signal from one end of the pipe, receiving the sound wave signal at the other end, and obtaining the auto-correlation function at the time, which is different from the sample value from the received sound wave signal. CONSTITUTION:A speaker 2, which is attached to one-end part of a pipe 1, is driven with a sound generator 4. The sound wave signal, which is received with a receiver that is attached to the other end part of the pipe 1, is sent into a data processing device 7 through a signal line 6. Then, the data processing device 7 extracts the sample value from the waveform of the sound wave signal. The auto-correlation coefficient at the time, which is different in the waveform, is computed. A partial correlation coefficient is computed by utilizing a linear prediction coefficient based on the auto- correlation coefficient. The computed partial correlation coefficient is made to be the reflection coefficient. The distribution of the vacant cross-sectional areas in the pipe at each position of the pipe 1 in the axial direction is computed based on a recurrence formula, which is formed between the reflection coefficient and the value of the cross-sectional area of the opening, which is measured beforehand at either end of the pipe 1. |
