Acoustic signals can be heard over large distances if conditions are right.
I live at about 5km north-east from the place where the famous "Rock Werchter" festival takes place, one of the largest rock festivals in Europe (http://www.rockwerchter.be/en/home/).
Their sound system is many 10kW. If the the wind comes from south-west I can understand every word said throught the microphones. With other wind directions I only hear the low tones.
Most of the time I find ths very annoying, except for that one time I could hear a full Bruce Springsteen concert as if I were on the concert.
My grandmother told me that in 1940 they could hear the bombing of Antwerp harbour near their home, about 70km from Antwerp, but only at the banks of the channel that goes in a almost staight line to Antwerp. I guess the channel
acted as some kind of wave guide.
But all this has nothing to do with electromagnetic communication at very low frequencies.
This is experimenting and fun. Finding out how far one gets with just few mW or less ERP. Testing different types of antennas.
73, Rik ON7YD
As observed by others, I have heard car audio music several hundred metres away. Out in an open field I think it would be possible to hear a 1Kw audio system by ear a couple of miles away, and maybe further downwind. Dreamers
would need to be aiming for several miles distance minimum and preferably hundreds of miles using radio.
mal/g3kev
