About 15 years ago, I was the lead programmer for a virtual reality ride prototype for Disney. We had added pterodactyls flying overhead.<p>The night before the demo presentation, I created a good pterodactyl scream by taking a recording of dolphins, reversing it, and dropping the frequency. Sounds strange, but I didn't have much time, and the effect was surprisingly good. A woman from marketing was trying the ride and raved that we got the pterodactyl scream just right.