Pretty good
To be a pedant for a second, throughout the recording there's this kind of medium-pitched buzzing sound which gets a little distracting, I don't know whether it's just because of the recording itself or whether it was deliberate, but whatever it was, it got a little grating.
The story was fairly imaginative, but perhaps a little too much so. The stories in The Dark Knight, while far-fetched, both simply involved someone taking a knife and cutting the smile in themselves. To think an ill-placed knife in the middle of a carnival show would create the same effect takes one leap of the imagination too many, in my mind. But who knows, maybe they were sharp knives. Or maybe the Joker's just making things up as he goes along, as per the usual.
As far as the actual voice goes, you do a pretty good imitation. The intonation of the voice you got down pretty well, and you definitely had the psychotic demeanour down, but perhaps not the pitchy variation that Ledger's Joker does; going from the kind of maniacal highs to the more ominous low rumbles. And I was half-expecting at least one maniacal laugh in this track, but perhaps that would have been too obvious a thing to put in. I can't quite tell how well the "Why so serious?" line was delivered because the victim's interjections kind of overpowered them a little, but as far as I could tell it was done pretty well, if a little more aggressively than Ledger's; I think you both did the same thing, but that he did it at a much lower level so instead of a more aggressive shout, it was more of an incredibly threatening growl. But in general, I think the impression's pretty good, and with a few more tweaks it'll be pretty damn convincing.
As has been mentioned, the ending is a little abrupt, you could probably think about how to dress the death of the victim up a little more if you do any more tapes. And in the same way, the victim's breathing were the only real indication that things were getting progressively worse for him, ie the Joker getting his knife out/advancing on him, so a few more sound effects wouldn't go amiss there. In general though, it's a nice impression; good work.
-Review Request Club