How can we recieve audio sound at a very long distance through wireless media? For example, a man talking to another man at a distance of 500 meters, I want to record that at the same distance through wireless media!
You can use wireless repeaters to increase quality over such distances. You need to have 2 pairs of Receiver and transmitter. Connect the Output of one Receiver with the Input of the Second transmitter. Also gain the Signal a bit on the second transmitter. Use different frequencies for each pair.
You're right, it can't be done purely acoustically.
It may be able to be done instead with a laser, I can't imagine the quality is great though, its just a surveillance technology.
I don't know for sure, but I betcha you could pull this off with a good professional quality transmitter and receiver along with a pair of shark fin antennas.
Some good quality receivers can receive up to 1000-1200 feet away from the transmitter, so with the shark fin antennas, I bet you could make up the other 400-600 feet
In order to receive a wireless signal from a distance such as that you will need to do two things:
a) use a high powered transmitter such as a Lectrosonics SMQV b) use either shark-fin Log Periodic receiver antennas, or c) obtain a pair of high gain directional yagi antenna and point them down range. Pretty much any TV antenna should do the trick as most TV antennas are working on the same frequency band as most professional wireless gear.
or... (and this is the one I like best)
d) use something like a Lectrosonics PDR which is a personal digital recorder. Use Lavalier microphones (you will have to do this anyway) and instead of putting a transmitter in the pocket, put the recorder in the pocket instead. That way you can get your recording and you can be wherever you want to be and get perfect audio.