Which material is used to damp the crystal and shorten ringing time?

• A. Matching layer
• B. Backing material
• C. Lens
• D. Element

Answer: (B)

The key idea is damping the crystal to shorten the emitted pulse. A backing material sits behind the piezoelectric crystal and absorbs vibrational energy, reducing the ring time and the duration of the pulse. This damping lowers the transducer’s Q factor, so the ultrasound signal decays quickly after emission, improving axial resolution. The matching layer, placed in front of the crystal toward the tissue, is for impedance matching to transfer energy efficiently rather than dampening ringing. A lens focuses the beam, and the element refers to the crystal itself. So, the material used to damp the crystal and shorten ringing time is the backing material.