Having sex at night

Whenever my hubby and I have sex, (and yes we close the door because I'm loud) my 9 year old daughter becomes scared in her room and cries...her room is across the hall from ours, and she believes he's hitting me. We believe she is asleep, but learned she isn't...I had to explain to her that my hubby isn't hitting me, but we are just "talking". Any suggestions on what we could do???