INCREASING THE LENGTH OF TUBULAR OBJECTS THAT CAN BE MEASURED USING ACOUSTIC PULSE REFLECTOMETRY

Acoustic pulse reflectometry is a non-invasive technique for measuring the internal dimensions of tubular objects. A sound pulse is produced using a loudspeaker and injected into the object under investigation via a source tube. The resultant object reflections are recorded by a microphone embedded in the wall of the source tube. Analysis of the re flections yields information about the bore profile of the object. At present, there is a restriction on the length of object that can be me asured using the standard reflectometer. This restriction arises becau se after the object reflections pass the microphone they undergo furth er reflection at the loudspeaker. These source reflections return to t he microphone as unwanted signal. Hence, there is only a finite time o ver which the object reflections can be accurately recorded which, in turn, limits the length of object that can be measured. in this paper, a method for removing the length restriction is described. The method involves the cancellation of the incoming object reflections at the l oudspeaker, thus preventing the formation of source reflections. The r esults achieved indicate the potential of the method for accurate meas urement of longer objects.