Yes, you can hear their leathery little wings flapping. Unfortunately, the combination of being overly awed, and attempting to capture the whole thing with a crappy video gadget, means that the footage doesn't come anywhere near to doing this event justice. You can't, for example, feel the wind caused by this nightly exodus; neither do you experience the thrill-mixed-with-fear of having a flying mammal dive bomb your face. Just before you realize that this cave serves as nature's clown car (it took almost an hour for all of the inhabitants to come out, and this at non-peak season), you can feel something about to happen, a different sort of silence that no cinema producer could ever really capture.
One interesting fact? The poor little guys make their way out and up in spiraling motions in order to gain altitude; they're unable just to set out and zoom straight off into the beyond.
This wasn't my first encounter with this sort of reality; I come from a place that has an enormous urban bat population. It was, however, my inaugural peek at what goes on in a protected wildlife area, where everything is quiet, and where each stage of the process is apparent, not only visibly, but aurally and, I'll venture, tactilely (due to backdrafts and the near-misses of wayward pilots) as well. An absolutely brilliant and beautiful adventure that I'm fortunate to have witnessed. If you have the chance, don't think twice.