New England. I've never paid enough attention when traveling to notice (those words aren't exactly the most common to hear), but when I say "woom" my lips end closed, and when I say "womb" my lips end opened after closing. The b isn't "voiced", per se, but it does change the way the word sounds to me.

And to be fair, I am aware New England English is its own distinct thing so I might have grown up in a bubble:

https://en.wikipedia.org/wiki/New_England_English