Hesitation sound and surprise sound are separate in french.
When you hesitate, you make the sound “euh…” (like the first sound in “earth”),
And when you are surprised, or if you misheard something, you say “hein ?” (half-voyel not present in english, same sound as the number one “un” in french, with an upward inflexion).
The repetitive use of both of those sounds is considered a sign of poor education, since the upper class children are told from a very young age to replace them with “pardon” (sorry) and “comment” (how).
