Sound travel at night vs. day
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Dear Tom,
I've noticed that sounds carry better at night than during the day. Could you provide
an explanation?
Louise, Park Forest
Dear Louise,
Sounds do carry better and farther at night. Because it tends to be quieter then,
individual sounds are easier to distinguish. By far the most important factor, however,
is a difference in the temperature structure of the lower few hundred feet of the
atmosphere between day and night.
Sound travels through cold, dense air more slowly than through warmer, less dense
air. When air temperatures change on the path along which sound waves are
traveling, the waves always bend toward the colder air.
By day, it's warmer near the ground and colder above; sound bends up and away from
the ground (and you). At night, it's colder near the ground and warmer above; sound
waves bend down.