Why am I hearing an evil laugh randomly

Yeah, he's only in the vampire pack, so if you don't have it it's not him.

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@Pick-a-boo_doo They’re all residential but I went to the park in oasis springs and it happens there. I put the traits for my home with the good lighting and one where the sims get the homey moodlet and the breezy trait too

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@Pick-a-boo_doo i had no mods in the first few weeks of playing and the laugh happened then too 

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@j1piter_fand @simsplayer818
Hi, Thanks for the reply.
So the phenomenon started without mods? Didn't it generate LastException, does it?
I wonder if the sound is still somewhere in the background, as like the one in Live Mode where the background music keeps playing. That's about all I can think of at this stage.
I'll try to find some video on YouTube.

Adding:

Unfortunately, I couldn't find any footage to reference; there was one on reddit, posted last month about Evil Laugh, but I think it was a little different because it said the whole house was covered in dust, along with laughter.
You don't mean that you hear laughter the whole time you are playing, but that you hear laughter at some point, right? Maybe there is some trigger.
There is a Malcolm Landgraab in Oasis Springs who has an Evil trait. Is it possible that he was nearby when you heard the laughter? (His laughter is a bit high toned.)
Also, are there any midi files mixed in with the Tray folder? If so, is it possible that it is a voice midi?
Here's what I can think of right now.
It doesn't feel good to hear that laughter while playing, does it...
Sorry I can't offer any clues. I hope you will be able to figure out this soon.
I'll post again if I think of anything else.

I was hearing a creepy laugh in my game recently too - high pitched rather than deep - and eventually discovered that my youngest Sim child is laughing in his sleep. I didn't know this was possible, and it's definitely a bit creepy... but is it possible one of your adult Sims is doing the same?