Wanted to add the #1 thing that you can offer them to step over the awkwardness they may feel in honest ignorance... Is to, when they make that face say "excuse me" like you had politely held in a burp or something. Then if they don't say "it's ok" or " take your time" or they don't look obviously un-bothered you can say "I have a speech impediment" or "I stutter" I understand how this may sound as those phrases don't look easy but it will make your life easier to practice any way you can. It really made me feel less helpless out in the world. I'm not at the mercy of these clowns who take confusion and turn someone with a disability into their own amusement.