The portion of time a transducer is transmitting a pulse is referred to as:

The portion of time a transducer is transmitting a pulse is referred to as the duty factor. Duty factor is the ratio of the time the system is actively transmitting ultrasound waves (the "on" time) to the total time of the pulse repetition period (the sum of "on" time and "off" time). It is usually expressed as a percentage.

A higher duty factor indicates that the transducer is on for a larger portion of the time, which can enhance the signal received from the tissue being imaged. This is particularly important in applications where higher temporal resolution is needed, such as in Doppler ultrasound.

Understanding the duty factor is crucial for optimizing imaging techniques and can significantly impact the quality of the ultrasound images obtained. In contrast, while the period refers to the duration of a single cycle of a wave, it does not specifically account for the time the transducer is actively emitting pulses. The pulse repetition period (PRP) relates to the total time between one pulse and the next, but again, it encompasses both transmitting and receiving times, rather than focusing solely on the transmitting aspect. Longitudinal wave describes the type of wave being transmitted but does not relate directly to the duration of transmission.