Which two components increase the efficiency of sound transfer between the transducers PZT and the skin?

• A. Matching Layer And Gel
• B. Backing Material And PZT
• C. Gel And Skin
• D. PZT And Skin

Answer: (A)

Impedance matching and acoustic coupling determine how much ultrasound energy actually enters tissue. The transducer face made of PZT has a high acoustic impedance, so without an intermediate layer much energy would reflect back. The two components that best boost transfer into the skin are the matching layer and the coupling gel. The matching layer sits directly on the transducer and is designed to have an impedance between PZT and tissue, reducing reflections at the boundary and widening the bandwidth. The gel fills any tiny gaps and provides a medium with impedance closer to tissue, so there’s minimal air-related reflection at the gel–skin interface. Together, they bridge the impedance gap and eliminate air gaps, allowing more sound to pass into the skin.