The dimensions of which component determine the characteristics of the emitted sound beam?

• A. Case
• B. PZT or Active Element
• C. Matching layer
• D. Wire

Answer: (B)

The emitted sound beam is shaped mainly by the active piezoelectric element’s geometry. The aperture—the lateral dimensions of the PZT—acts like a diaphragm: a larger aperture makes the beam narrower and improves lateral resolution, while the thickness sets the resonant, and thus center, frequency of the emitted ultrasound. The matching layer influences how efficiently energy is transmitted and the bandwidth, but it doesn’t establish the beam’s basic pattern. The case provides mechanical support and damping, and the wire simply carries the electrical signal. So, the PZT or active element’s dimensions determine the beam characteristics.