WOLF,
The ‘dikduk’ative term for this is a PATACH GENUVA.
It applies to the letters ayin, ches, & hay b’sof hamila,
with a patach.
Common examples are Mizbeach, Noach, Sheyismamay-AH in Ani Maamin, and, (of course, the most commonly mispronounced one) Meelifney Elo-AH Yaakov in Hallel.