An ultrasonic transducer having a conduit (15) and means for causing vibrations (5) within the conduit Ultrasonic transducers are devices that generate and/or detect ultrasonic signals. A commonly used transducer/receiver is based on piezoelectric technology. Piezoelectric materials undergo a dimensional change when subjected to an electrical stimulus. In order to use the piezoelectric material as an ultrasound transmitter, a pulsed electrical stimulus of appropriate frequency is applied to the piezocrystal. This causes it to change dimensions with the frequency of the applied signal, which in turn can induce ultrasonic waves in an abutting medium. Often transducers/receivers will be tailored to specific applications using additional mechanical components such as backing and matching to extend the bandwidth. The relative mechanical stiffness of these devices makes them suitable for use with liquid and solid mediums. Transducers/receivers may be grouped together into a phased array. In this configuration, the phases of the signal from each of the transducers in the array are matched such that the signal is reinforced in selected directions and suppressed in other directions. The overall shape of the array may also be used to control the spread of emitted radiation. However, there are some limitations in applying phased receivers to transducer/receiver systems. These include the generation of crosstalk, where the operation of one array element affects the performance of other array elements.