Refraction of Sound
Here is something interesting about refraction. Our school level physics book associates refraction phenomena only with light but not with sound. But the reality is that sound waves also bend. When waves hit a denser medium the speed slows down and shortens the wavelength. The best manifestation of refraction of sound is felt by early morning fishermen. This link explains well. Water early morning is cool near the lake and sunlight heat up the air above. Because the speed of sunlight is faster in warmer air bends sound backward. Never felt it. Maybe someone who visits river or lake before dawn may observe. So sound that wouldn’t have reached someone on the lake rest of the day reaches his/her ear before dawn.