I hear this on average maybe a few times a month. For like 8 years. I'm 46. I think it's because laughter is rather loud and as such travels far. I just hear once HA HA HA HA and that's it. I don't hear any other voices or anything like that. EXp: Last night my roommate was watching TV and laughed. I thought I was hearing things lol. It can be a bit unnerving though. Usually happens when I'm deep in thought and always at night when I'm thinking about Hegel or Zen Buddhism. I read a lot about psychedelic experiences and stuff like that and it's possible that some minds are not fully insulated in this world unlike most "normal" minds. It comes of as if a trickster or perhaps a less benign "entity". Again, maybe it's just a real sound. There are homes around and people watch TV late at night. I am Type O negative and a leftie. Furthermore psychiatry to say the least by far is no gospel it's 19th century modernist way of thinking that hasn't changed much. I wouldn't rely on it. Michelle Foucault was highly critical of it. "Crazy people" were Oracles in ancient Greece and throughout history "they" we're considered to have a sort of uncanny wisdom. In Greece generals went to war based on what some "crazy person" (oracle) told them. Highly intuitive people. It is the establishment and their psychiatric institutions that won't give any room for further investigation into this. The reason is that the status quo suits them. They are making a lot of money maintaining this order and making sure it stays that way. Big pharma is responsible for more deaths and they are responsible for compromising peoples minds with psych drugs while in fact there are natural alternatives that actually work like Psilocybin and Ibogaine. I found that microdosing psilocybin mushrooms incredibly effective. All that being said, ignore it. Find your center and move on.