The inside of pipe multiplex antireflection manner null in the sonic type pipe conduit investigation

摘要

PROBLEM TO BE SOLVED: To obtain a preventive method that can prevent the multiple reflection of sound waves and that makes only reflected sound waves from an existing reflection source possible to be received, by arranging a sound gathering means in a position before a place, in which reflected sound waves reach a sound generating means, and changing over one end of a conduit to a nonreflection state immediately after sound waves are sent out. ;SOLUTION: A loudspeaker 1 is arranged at one end of a conduit S, and a microphone 2 is arranged at its front part so as to be connected electrically to a control part 3. Then, when pulse-shaped sound waves are sent out from the loudspeaker 1, the reflected waves (1) of reflected sound waves at an end part other than one end part of the conduit S is gathered by the microphone 2. When the control part 3 discriminates the reception timing of the reflected waves (1), the control part 3 applies a voltage to the loudspeaker 1 so as to send out sound waves whose amplitude is identical to it and whose phase is opposite to it, and it is changed over to a nonreflection state. Thereby, reception data on sound waves in a reflection part (2) and a reflection part (3), which are to be reflected by the loudspeaker 1, i.e., multiple- reflected sound waves, is not obtained. Consequently, only the reception timing of the reflected wave (1) can be made clear.;COPYRIGHT: (C)1998,JPO