When someone says something you didn't hear or you weren't sure you heard correctly, and you say "sorry?" or "excuse me?" to get them to repeat or clarify, would you say you are in fact apologizing at that point, or are those words filling some other social or technical purpose?
Also, is there another similarly polite way to tell someone you couldn't hear them that is not an apology?
I suppose "could you repeat that?" comes to mind, but I'd welcome other ideas.