Sound refracts because temperature changes its speed in air.

Evidence

This is analogous to the refraction of light at the boundary of different materials. In the optical case refraction arises because the speed of light is different in different materials; for example it is slower in water than it is in air. In the acoustic case refraction arises for the same reasons, because the velocity of sound in air is dependent on the temperature, as shown in Equation 1.5. — David Howard, Jamie Angus, coustics and Psychoacoustics, 323

Categorization

• XREF: Connects to optics knowledge — same refraction mechanism in light and sound. — connects to: Climate change alters how far animal acoustic signals travel. — Bernie Krause and Almo Farina, Using Ecoacoustic Methods to Survey the…, 32
• DEFINE: Analogous definition of acoustic refraction via the optical case.