Refraction of sound waves often takes place when:
A. there are temperature differences in air
B. there are walls around a room to bounce back sound
C. sound wave frequencies are increased
D. complete sound waves slow down
Refraction is where the direction of travel of sound waves is altered by passing through a material of much higher or lower density. Walls that allow sound through are one example, but answer B is more about walls bouncing sound back - that's an example of reflection. The most likely change of density is answer A, air with big temperature differences.
