The principle mechanism of attenuation in air is ______.

• A. Reflection
• B. Refraction
• C. Absorption
• D. Scattering

Answer: (C)

Attenuation in air mainly comes from absorption, where part of the sound energy is converted into heat by the air itself through viscous and thermal interactions. As the wave propagates, air molecules absorb energy from the sound and dissipate it as a tiny amount of heat, with higher frequencies experiencing greater loss. Reflection happens at boundaries and changes the direction or amount of energy that continues forward, not the energy loss along the path itself. Refraction describes a bend in the wave due to speed changes, and scattering redirects energy in other directions due to inhomogeneities. But along a straight path in air, absorption is the dominant mechanism reducing the wave’s amplitude.