Abstract: Ultrasonic apparatus for visualizing the internal organs of the human body using an ultrasonic array probe is characterized by means for digitising the ultrasonic echo signals and means for processing the digitised signals. Data may be sampled from each array element excited separately, or on a group of elements sequentially with a very small time increment between samples. Processing of data can include switching the transmit carrier frequency between scans, compensation for ringing effects in the transducers, synthetic aperture focussing techniques, software envelope or transform demodulation, attenuation or time gain correction and data compression.