I'd like to recommend that, if the horn must be used to acknowledge plug-in charging, an option be presented to suppress the charging confirmation horn honk- perhaps on the same screen where we have to change the default amps from 8 to 12.
For some people the honking probably does not pose a problem. My garage happens to be under my neighbor's bedroom window so when I come home late in the evening I absolutely cringe as I plug in my car because I know the horn will sound. It's so rude that sometimes I'll just drive on gasoline the next day to avoid disturbing my neighbors.
And what makes it worse, is that I use time of day and departure time scheduling. The later at night a charge schedule Volt driver comes home, the closer it is to the scheduled AM departure time, and the more likely they are to get the dreaded quadruple "not-e-nuff-time" warning honk. As if one honk at 10PM isn't bad enough, four honks at 1AM will surely wake the neighbors.
Please add a way to turn that thing off in future models. Even if it has to be set each time it would be better than having to not charge at all to avoid the rude honking at night.