Melody woke her husband up after midnight, on the morning of the 26th., saying she had heard a terrifying scream. That is his testimony and he has never waffled on this. She did not say, "I heard a terrible scream two nights ago, please listen and tell me what you hear tonight".

It is obvious that something woke her up, and that she thought that something was a scream. Being asleep at the moment might make the event seem surrealistic afterwards, especially if one wants to disassociate themselves from the investigation
but her husband's recounting of events has never changed. That plus the fact that the air duct acts as a megaphone amplifying sounds in the direction of the Stanton house, and the probability of the murder taking place in the basement boiler room tell me that there probably was a scream that she heard.

I don't believe in "negative energy" and it is possible that she heard a scream from some other source than the Ramsey's house.

Aside from the scream question, Mr. Stanton did hear a metal striking concrete sound coming from the Ramsey house, and he wasn't asleep when he heard it. I think that is very significant.