More About Bat Radar were an 80s student band fronted by my brother's friend. Here's a TV programme that tells you more about bat radar and you can actually see bat ultrasound (so it's really sonar not radar).
http://www.bbc.co.uk/iplayer/episode/b08h9ctd/sound-waves-the-symphony-of-physics-series-1-2-using-sound I watch a lot of Science TV but this is one of the best I've seen because it tackles things that I've never really bothered with and yet turn out to be really interesting. And the moment when a deaf woman gets to hear again is fabulous...