Duplication artifacts can be created through diffraction and refraction on interfaces, also if the acoustical impedances of tissue is too much different and the ultrasound is reflected multiple on tissue layers, where the detected echo does not come from the shortest sound path.

See also Mirror Artifact.

The duty factor is the product of the pulse duration and the pulse repetition frequency (the lapse of time the transducer is actively transmitting sound).
Most transducers are acting as the receiver 99 % of the time with a duty factor of 1.

See also Dwell Time.

The dwell time (also called ensemble length or packet size) is the transmitting duration of ultrasonic waves focused at one place or the Doppler samples for each line of sight. The reduction of the dwell time is of use if threshold pressures are exceeded.
The sensitivity to slow flow and accuracy of Doppler measurement increase with longer dwell times. With increased dwell times, the frame rates decrease and the capability of Color Doppler images to depict fast changes in hemodynamics is limited.

Dynamic focusing controls the axial position of the focus of an ultrasound beam. Dynamic focusing is often managed by controlling the phase of the signals detected by a transducer array.

See also Real-Time Transducer.

The dynamic range in signal processing is the range between the minimum low intensity and maximum high intensity signals that a system is capable of displaying.

See also QB-Mode.