interjection indicating approval, appreciation or agreement
嗯
=
口
+
恩
:
Albert Einstein (Ø) and René Descartes (恩) had an argument on the roof of the encampment ((e)n5). René wants to be friends again with Albert and hands him a mandarin (口) as a present, and Albert just answers "嗯" as he accepts the gift.
哼
=
亨
+
口
:
In front of the engine ((e)ng1), Joseph Henry (亨) finally has the idea how to build his coil and exclaims "hurrah!", accidentally throwing away Hamlet's (h) mandarin (口) so Hamlet just says "humph!" (哼).