Which term describes the frequency at which the transducer naturally resonates, influenced by the propagation speed and thickness of the element and, in continuous wave, by the electrical frequency?

• A. Operating frequency
• B. Wavelength
• C. Bandwidth
• D. Pulse repetition frequency

Answer: (A)

The operating frequency describes the frequency at which the transducer naturally resonates. For a thickness-mode piezoelectric element, this resonance is determined by the element’s thickness and the speed of sound in the material. The fundamental resonance occurs when the thickness equals half the acoustic wavelength, so the resonant frequency is f = v/(2t). In continuous-wave operation, the transducer is driven by an electrical frequency that matches this resonant frequency, causing it to vibrate most efficiently and produce maximum output.

Wavelength is a property of how far a wave travels in one cycle and depends on the medium and frequency, not the transducer’s intrinsic resonance. Bandwidth refers to the range of frequencies the transducer can emit or receive. Pulse repetition frequency is how many pulses are emitted per second.