Abstract: The invention provides a process and apparatus for the detection of obstacles by means of ultrasound waves having an enhanced ability to distinguish between echoes caused by obstacles and those caused by interference signals. Ultrasound pulses are emitted by an ultrasound transmitter unit, and are received by an associated ultrasound receiver unit. (A plurality of such transmitters and receives may also be used.) Ultrasound echoes detected by the receiver units are used to form echograms in which detected echoes are projected. The echogram thus measured is used to generate an analysis echogram, based on information contained in the measured echograms. In particular, the most recent analysis echogram is modified depending on the size and location of echoes contained in the measured echogram. Signals contained in the analysis echogram are then compared with predetermined threshold values to distinguish between echoes reflected from obstacles and echoes due to interference.