A method and an apparatus for generating short ultrasonic echo pulses by means of an ultrasonic transducer (2) utilizes a shift register (6) for storing a signal for excitation of said ultrasonic transducer. The stored signal is a weighted least squares filter signal to the transducer proper and is supplied to said transducer via a digital-to-analogue converter (7). Repeated adjustment of the stored signal can be effected by supplying, via an analogue-to-digital converter (11), the echo pulse signals from the ultrasonic transducer to a logic unit (12) for analysis.