Ron,

Another factor that contributes to sound seeming louder at night is
your brain (the 'device' that processes sound and light). When your
eyes are receiving less light, a portion of the brain that normally
processes light signals is diverted to other senses, such as hearing.
This will also make sounds appear to be louder at night than during
the day.

In a former life, I was a submarine sonar technician. We had
mandatory hearing tests bi-annually, and we all learned early on that
you can increase your score by closing your eyes during the test -
same phenomenom as I described earlier.

rob jones


On Tue, 14 Sep 2004 20:09:25 GMT, Ron Hardin
wrote:

Depending on time of day, you get ducting (when the ground is cooler
than the air). In that case sound travels huge distances because
sound sent upwards comes back down, bounces off the ground, and
relaunches itself for another bounce. Rather than just disappearing
into the blue sky. So it weakens like 1/distance rather than
1/distance^2 which means it really hangs in there.

If you have a duct, you have something in the sky that reflects
sound back down; and in particular sound that clears the sound wall
comes back down some distance away.

If the sound wall weren't there, you wouldn't comment on it, because
the close houses would also hear noise. But in this case they don't.

I have a highway a half mile away that I hear at night but not in
the day; in the day, the ground is warmer than the air, and that
anti-ducts the sound, sending horizontal sound upwards over my head.