hmm; well ...; humph; huh; pshaw; pish
roughly; harshly; violently
ふん、そんなこと知らない。
Hmph, I don't know about that.
ふん、どうでもいいよ。
Hmm, I don't care.
ふん、勝手にすれば。
Humph, do what you want.