The frequency of an ultrasound transducer is determined by which of the following?

• A. All Of The Above
• B. Propagation Speed
• C. Thickness Of The Piezoelectric Material
• D. Center Frequency Of The Drive Signal

Answer: (A)

The frequency you get from an ultrasound transducer comes from how its piezoelectric element is built and what material it’s made of. The resonant, or center, frequency is set mainly by the speed of sound in the piezoelectric material and the thickness of that layer. For a thickness-mode element, the fundamental resonance occurs when the thickness is about half of the wavelength, so f is roughly v/(2t), where v is the material’s sound speed and t is the thickness. A faster material or a thinner element pushes the frequency higher.

The drive electronics also influence the emitted frequency because the center frequency of the electrical drive is chosen to match that resonance. Driving near the transducer’s natural resonance makes vibration most efficient and shapes the actual frequency content that’s radiated.

So the transducer’s frequency is determined by propagation speed, the thickness of the piezoelectric material, and the center frequency of the drive signal, all contributing to the final output.