It doesn't seem like a KR sound at all, not that "hard" of a noise. I'll connect my little Bluetooth OBDII adapter and monitor it a little tonight. No lights on the dash either.
Although, it did happen after I put a full tank of gas in it (ethanol blend 87 octane). Bad gas maybe? But it doesn't sound that harsh like it is knocking, and the power seems to still be there. Hmmm...