There was a startup up here that was pushing real hard into ion fans. They started out by building duct inserts for moving air silently and then discovered that if they modulated the high voltage with a harmonic they could turn the affair into speakers. It was pretty cool. You'd feel air blowing on your face, but you'd hear Bach. It was a little thin and tinny but it was totally Bach. On the downside it took two humungous variacs to drive the things. A stereo speaker system used like 1000W and it was humpin' it at like 50kV. I'm impressed they were able to loft a battery capable of giving the thing 50m of augmented flight but I'll be still more impressed if they push it much further than that. You're basically building yourself an ultra-light-weight Taser with really weird contacts. And you can't shock those things for too long before the battery's flat.