What is the purpose of damping in a transducer?

• A. Increase sensitivity
• B. Shorten pulse and broaden bandwidth, improving axial resolution
• C. Increase focal depth
• D. Increase Q factor

Answer: (B)

Damping suppresses the ringing of the transducer by dissipating energy quickly after excitation. This makes the emitted pulse shorter and broadens its frequency spectrum, so more of the higher frequencies are included. A shorter pulse directly improves axial resolution because closely spaced reflectors along the beam path are distinguished by the time difference of their echoes, which is more precise when the pulse length is shorter. The broader bandwidth that comes with damping also enhances image fidelity by supporting a wider range of frequencies. Keep in mind that damping tends to reduce peak amplitude (and thus sensitivity) because energy is being lost more quickly, which is the trade-off. The other ideas don’t fit: increasing sensitivity would require less damping, damping does not increase focal depth, and damping lowers the Q factor rather than increases it.