What are the two characteristics of the active element that determine the frequency of sound from a pulsed wave transducer?

• A. Speed of sound in the PZT and Thickness of the PZT
• B. Electrical impedance and Temperature
• C. Density and Elasticity
• D. Crystal orientation and Doping

Answer: (A)

Frequency for a pulsed-wave transducer comes from the thickness-mode resonance of the piezoelectric element. The sound speed in the PZT material and the element’s thickness together set the resonant frequency, roughly described by f ≈ v/2t, where v is the speed of sound in the PZT and t is its thickness. So the two characteristics that determine the frequency are how fast sound travels in the PZT and how thick the PZT layer is.

Other factors like impedance, temperature, or crystal orientation influence performance or operating conditions but do not establish the nominal resonant frequency in the same direct way.