Subject: What is the 'best' method for transporting a sound signal?

I'm designing a sonic pest deterrant, with a signal generator generating a 
signal of around 30kHz, which is then transported to speakers (and 
amplifier if necessary.) The whole system will be outside, hence subject 
to all weather conditions, and the speakers will be up to a few hundred 
metres away from the signal generator. What is the 'best' method of getting 
the signal from the generator to the speaker? I've tried looking into 
ordinary wires, microwaves, IR, laser, etc, but the data has not proved 
conclusive. 

Re: What is the 'best' method for transporting a sound signal?