Which property is primarily increased by the use of multiple matching layers on a transducer?

• A. Damping
• B. Field of view
• C. Focal depth
• D. Bandwidth

Answer: (D)

Multiple matching layers are used to smooth the transition of acoustic impedance from the piezoelectric element to the tissue. By stacking layers with progressively different impedances, reflections at each boundary are reduced across a wider range of frequencies. This creates a broader, more broadband acoustic response, so the transducer can emit and receive a wider range of frequencies. In other words, the energy is transmitted more efficiently over a wider frequency spectrum, which increases bandwidth.

Damping is mainly controlled by the backing material and energy loss inside the element, not by the matching layers. Field of view depends on the aperture and focusing, and focal depth is set by the lens or electronic focusing—not by the matching layers.