How is amplitude measured?

• A. From middle to maximum
• B. From peak to trough
• C. From baseline to peak
• D. From zero to peak

Answer: (A)

Amplitude is the maximum deviation of the wave from its resting value. In ultrasound, the signal oscillates around the center or baseline pressure, so amplitude is the height from that center line up to the crest. That makes measuring from the middle to the maximum the correct way to quantify how large the wave’s excursion is. Measuring from peak to trough would give the full swing (peak-to-peak), which is a different quantity, and measuring from baseline or zero to the peak can be ambiguous if there's any offset. So the standard way to express amplitude is the distance from the center line to the maximum value.