| 摘要 |
PROBLEM TO BE SOLVED: To simply measure the shape inside a conduit without a need of skill by a method wherein sound waves are transmitted from the end of the conduit into the conduit and the impulse response waveform of the sound waves is found by a transmitted waveform and by a reflected waveform which is reflected at the end of the conduit. SOLUTION: Sound waves which enter from a loudspeaker 1 pass through a point P0 in which a microphone 2 is situated. The sound waves are reflected by a recessed part 101 as a reflecting object inside a conduit 21 by a deposit 102, positions P1 , P2 , a position P3 at a connection part 103 and a conduit end position P4 . The sound waves are measured again by the microphone 2. Distances between the position P0 and the reflecting object inside the conduit as well as between the position P1 and the position P4 as ends of the conduit are found by a prescribed expression on the basis of the arrival time difference between a sound velocity and the sound waves, and the sound velocity is computed from temperature inside the conduit, which is measured by a temperature sensor 3. A reflected waveform from the inside of the conduit 21 is decided unequivocally so as to correspond to change in the cross section inside the conduit and to the waveform of the incident sound waves. Consequently, by finding a relationship between insident sound-wave data and reflected sound-wave data inversely, the change in the cross section inside the conduit, i.e., the shape inside the conduit, can be estimated. |
