Abstract: An ultrasonic measuring apparatus that includes an ultrasonic transducer for emitting ultrasonic pulses at a predetermined repetition frequency towards an object having a plurality of walls such as a blood vessel, receiving echoes reflected from such walls, and producing an echo signal having a plurality of elementary echo components (E.sub.ant, E.sub.post). A digitizer digitizes the echo signal into a series of digital values that are stored in a buffer memory under control of a circuit. A computer transfers the series of digital values stored in the buffer memory into a memory. The computer is programmed to process the digital values stored in the memory in the period between consecutive pulses and to remove a group of the digital values digitized between consecutive elementary components (E.sub.ant, E.sub.post) from those digital values to be treated between such consecutive pulses.

Abstract: A process for measuring the position of at least one mobile wall using ultrasound and an apparatus for carrying out this process are described.The measuring process of the invention has an initialization phase during which the elemental echoes of an echo signal produced by the reflection of an ultrasonic impulse from mobile interfaces (P.sub.o,1 ; P.sub.o,2 ; P.sub.o,3 ; P.sub.o,4 ;) are processed, to determine the position of these interfaces in this echo signal and in which the temporal positions of the reference points (Z.sub.o,1 ; Z.sub.o,2) of the elemental echoes of a group of echo signals assimilated afterwards, are simultaneously tracked so as to ascertain the position of the interfaces in the most recent of the echo signals of this group, an assimilation phase in which the position of said interfaces is tracked and an organizational or processing stage for the memorized data.