... I'm sure - I've read something Amdur sensei wrote about a shout that froze his son in his tracks - one of those "where did that come from" things, but it did keep the boy from running in front of traffic, if I recall correctly. When you "do" a "true" kiai, you won't have planned it, your inhibitions won't block it, and you'll wonder what happened - likely so will those around you.
Hasn't happened to me yet.
I'm sure you can appreciate that Mr. Amdur trained in this very long and very hard so it didn't 'just happen'.