h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The idea of trying to detect radio frequencies is perhaps not the right on. Why only this part of the specrum? I think because this is what we, humans, have been using for about 100 years. But that doesn't mean other civilisations out there have evolved the same way. Perhaps these far-out aliens do not bother with radio-waves but use, say, telepathy or some other form of brain waves. We would'nt be avare of their presence if they had developed a means of communication like the dolphins, for exemple. Any ideas?