Me and my brother didn't manage to initiate a baby giggle until - out of sheer frustration - we started playing
Didju Rike It?: Insane Edition into the mic.
I'm guessing that there's something about the high/low pitch of the recording that triggers something in the game, as we were able to complete the Teaser multiple times using this method, even on separate PS4's.
This is the video he recorded earlier. I've trimmed down the length of the haunting for him to save time, and added Didju Rike It in postproduction so you can hear when to start playing it.
Perhaps it'll work for you too?
Silent Hills P.T. Completion: Did you rike it?
Disclaimer: I know this sounds like a troll, so If there's any doubt, I also have a messier version of the first live playthrough on my PC where you can hear Didju Rike it? being played through my phone.