Pulse duration PD equals n × T, with T = 1/f. If a transducer emits 4 cycles at a center frequency of 3 MHz, what is the pulse duration?

• A. 0.333 µs
• B. 1.0 µs
• C. 2.0 µs
• D. 1.333 µs

Answer: (D)

Pulse duration represents the total time the pulse is on, equal to the number of cycles times the period of one cycle. The period is the reciprocal of the frequency: T = 1/f. With a center frequency of 3 MHz, T = 1 / 3,000,000 s ≈ 0.333 µs. If the transducer emits 4 cycles, the pulse duration is PD = n × T = 4 × 0.333 µs ≈ 1.333 µs. So the pulse duration is about 1.333 µs. The other values would correspond to fewer or more cycles at the same frequency.