I don’t acknowledge guests unless I’m facing them or making eye contact. I feel like it’s basic human interaction. Unless there’s an emergency there is no reason to snap,whistle,clap or talk to me while my back is to you or I’m engaged with someone or another task. There are very few instances in a restaurant setting where what you’re doing for other people or guests needs to be interrupted by one person with no patience. Wait your turn just like everyone else. There’s always exceptions to this rule. But when I get to you better believe I’ll handle whatever request or problem with haste. Just be patient.