Distant sirens

[cauberallies]

There are numerous volunteer fire departments around here, and I thought I could hear only 3(2 SD-10s and an STH-10) from my house, but the other night, I heard all 3 of the normal sirens, plus another SD-10 about 8 miles from me, and (faintly) a STL-10 about 10 miles from me. The terrain between my house and the two distant VFDs is uneven, with numerous hills. In the 17 years I've lived here, that was the first time I've ever heard these two sirens. Would there be any reason I heard them the other night, and not at any other time?

Oh, and hearing 3 SD-10s, an STH-10, and an STL-10 all at the same time was pretty awesome.

[Justin]

Depending on the 'acoustical properties' of your surrounds (weather included), you may be able to pick up sounds that you wouldn't normally be able to hear.

Someone else better post something more technical. I don't think a simple answer will suffice here.

[JasonC]

Cool, calm, quiet nights will let sound propagate far. I've hear my hometown's model 3 many miles away before under certain conditions. Must have been a big fire somewhere for all of those sirens to be going off!

[SirenMadness]

The air is more passive and less absorbent at night, causing the sound to travel allot further. Even though I didn't hear sirens at night since I was around six years old, I can hear the movement of our passenger-trains far better at night than at day time!

[PhRed]

LIFA used to have a clip of a particular municipality's system doing three rounds (fire?) at six miles from the recording source.