How is it that sound
travels longer distances at night?
Sound,
like light, can undergo reflection and refraction.
Refraction
of sound waves is most noticeable when they travel from cold air into warm air.
During
the night, the earth starts cooling, and the mass of air in contact with it
becomes cooler than the air a few metres above. When sound waves originating at
ground level travel obliquely through these masses of air, which are at
different temperatures, refraction takes place at the interface between the two
masses, and the sound waves, which in the daytime would have continued to
travel upwards, are directed back to earth. This is the reason why sounds
travel longer distances at night.
