Halloween might be a whopping five months away, but ghosts don't adhere to a calendar when it comes to making themselves known to the living. Some might appear in mirrors or dreams, while others will create an air of dread around the location of their demise. Perhaps most commonly, however, spirits will make noises when they wish to reach out to the other side.
Among the many, many stories, complaints, and questions that are posted to the Paranormal and Ghosts subreddits, there are a few frequently cited sounds that users mention when describing their possible haunting. They hear voices, disembodied footsteps, or, perhaps most chillingly, the sound of a woman sighing. Of course, any noise that's out of the ordinary can be unsettling, but there's something about these sounds in particular that leads people to believe that they are, truly, otherworldly.
It bears mentioning that the sounds you're hearing could be perfectly of this world. Make triple sure that you aren't actually dealing with a vermin infestation, carbon monoxide leak, faulty plumbing, or some other normal explanation before going too far down the paranormal rabbit hole.
That said, if you're convinced you've got a spirit on your hands, your next step should be to record it. Leave a camcorder running overnight or take a voice memo on your phone around the time you normally hear the spooky sound in question. You can play it back to your roommates or neighbors to see if they heard it, too, or even send the recording to any investigators you decide to consult. If you're really lucky — or, depending what kind of spirit you're dealing with, unlucky — you'll pick up even more sounds on tape.