The speed used to calibrate range-measuring circuits on diagnostic sonography instruments is approximately

• A. 1.54 m/s
• B. 1560 m/s
• C. 1.46 m/s
• D. 1,540 m/s

Answer: (D)

In diagnostic ultrasound, range measurements are based on converting the echo travel time into depth using the speed of sound in tissue. The standard value used for soft tissue is about 1540 meters per second, because it best represents the average speed of sound through most body tissues at body temperature. Depth is calculated with depth ≈ (speed × time) / 2, so using 1540 m/s gives accurate distance estimates for the returning echoes.

Among the options, the one matching this canonical value is 1,540 meters per second. The other choices are either far too slow for sound in tissue (1.54 m/s and 1.46 m/s) or a slightly different near-value (1560 m/s) that isn’t the conventional calibration speed.