Mrs. Bell was deaf.
She's not even gonna hear you knock.
The Big Bang Theory Season 1, Episode 14
MRS. WOLOWITZ (SHOUTING):
Howard, get the door!
The Big Bang Theory Season 2, Episode 8
That's very unlikely, Mrs. Koothrappali.
The Big Bang Theory Season 2, Episode 23
Coming, Mrs. Wolowitz!
The Big Bang Theory Season 7, Episode 23
MRS. WOLOWITZ:
The hell you will!
The Big Bang Theory Season 2, Episode 19