Way 1 · best default
Sorry, what was that?
Friendly and natural. Works with almost anyone when you simply didn't hear.
Examples
Sorry, what was that? The music's really loud.
Sorry, what was that? I was miles away.
In a conversation
A: Do you want to grab food after this?
B: Sorry, what was that? The train was going past.
Common mistake
Not: What?
Say: Sorry, what was that?
A bare "What?" can sound rude or annoyed. Adding "Sorry" fixes it.
