I am very particular about people's chewing. Silly, but. ... Lip smacking is my absolute worst "ear-grinding" sound, in any context really, but of course this is most common in eating. (Some people do it in their sleep and it's just as awful for me.) But, yes, that smacking noise... OMG. If I'm sitting next to someone doing it, I have to change seats or get up. I could flip a table during dinner, haha!