Abstract: Apparatus for the pulse-echo ultrasonic examination of an object comprised of transducer means for transmitting pulses of ultrasonic energy and receiving reflected echoes of said pulses immersed in a coupling medium contained within a housing, the pulses being transmitted and echoes received through an aperture in the housing which may be covered with a flexible coupling membrane and the housing including a storage header tank open to the atmosphere to maintain the pressure to the coupling medium on the membrane constant during flexing of the membrane.