Which of the following describes the spectrum of frequencies emitted by a pulsed-wave transducer?

• A. Reynolds number
• B. Center frequency
• C. Bandwidth
• D. Resonance frequency

Answer: (C)

When a pulsed-wave transducer emits, it produces a short burst of ultrasound that contains multiple frequencies. The range of these frequencies is described by the bandwidth—the width of the spectrum. A shorter pulse carries a wider range of frequencies, increasing bandwidth, while a longer pulse narrows the range. The center frequency is simply the midpoint of that spectrum, not the entire range of frequencies. Reynolds number is not related to the transducer's emitted spectrum, and resonance frequency refers to a natural tendency of the element rather than the overall spectrum width. So the spectrum of frequencies emitted by a pulsed-wave transducer is described by bandwidth.