That's the sound all Japanese cars make while in reverse, but you only hear it on the inside so what's the point?
Anyway, I'm backing up because I think maybe, just maybe Wyatt has confused the sign for "more" with the sign for "hey mom, bring on the cheerios". Hmmmm.......am thinking back and realizing that I almost always used the O's as examples of the more concept and can see how this might have happened. Now I have to correct this issue or take the easy way out and make up a new sign for "more". Good times.