I also now know that the sound is called a “palatal click”, and that the lip smacking has little to no involvement. A palatal click is similar to the clucking sound (probably called a palatal cluck.) you make by putting your tongue against the roof of your mouth and quickly drawing it down to the bottom, where it makes the clucking sound. This isn’t annoying, to me. The palatal click is where you put your tongue on the roof of your mouth and then quickly draw it backwards, instead of straight down.