Which medium provides the fastest ultrasound propagation speed?

Which medium provides the fastest ultrasound propagation speed?

• A. Bone
• B. Air
• C. Water
• D. Gel

Answer: (A)

Propagation speed of ultrasound is mainly determined by how stiff the medium is and, to a lesser extent, its density. More stiffness means the medium resists deformation less as the wave passes, so the wave energy moves faster. Bone is extremely stiff compared to water, gel, and especially air, so ultrasound travels through bone much more rapidly. Typical speeds are about 4000–4500 m/s in cortical bone, around 1500 m/s in water and gel, and roughly 343 m/s in air. That makes bone the fastest medium among the options.

Propagation speed of ultrasound is mainly determined by how stiff the medium is and, to a lesser extent, its density. More stiffness means the medium resists deformation less as the wave passes, so the wave energy moves faster. Bone is extremely stiff compared to water, gel, and especially air, so ultrasound travels through bone much more rapidly. Typical speeds are about 4000–4500 m/s in cortical bone, around 1500 m/s in water and gel, and roughly 343 m/s in air. That makes bone the fastest medium among the options.