The percentage of the intensity that bounces back when a sound beam strikes the boundary between 2 media is the _______.

• A. Transmission coefficient
• B. Absorption coefficient
• C. Energy ratio
• D. Intensity Reflection Coefficient (IRC)

Answer: (D)

When a sound beam hits an interface between two media, some energy is reflected back. The portion that bounces back is described by the Intensity Reflection Coefficient. It represents the fraction of the incident acoustic intensity that is reflected at the boundary and depends on the impedances of the two media. Mathematically, IRC = [(Z2 − Z1) / (Z2 + Z1)]^2. If the impedances are the same, there’s no reflection (IRC = 0); a larger impedance mismatch yields more reflection. The transmission coefficient would describe the energy that passes into the second medium, and the absorption coefficient relates to energy lost to absorption rather than reflection.