I know the hangul ㅁ is equivalent to "m", but I've also heard it sounds more like "b"
This is based on anecdotal observation where the former is usually the case in song lyrics and the latter in drama, reality shows, etc.
Which is correct? Or maybe a better question would be which is the norm?
Is this something influenced by accents?
EDIT for examples:
ㅁ as "b":
ㅁ as "m":