Convince them

Just to get people to worry about you, to get you locked up, or just for a laugh, a little speaker stored in a button, or similar item, like a handbag. The volume would be just loud enough for you and person a few feet away to hear, faintly.

You go see doctor/mum/friend/loonies next door, and you tell them you've been hearing stuff. Your mum/doctor/friend/loonies next door will probably say that it's nothing, have another choccie biscuit. While their backs are turned, you press the button, and little voices come out, with words like 'midnight' 'end of the world' and so on, or you could pre-order some voices, or something like that. They turn around, the sound goes off (lips mouthing words optional, I'd prefer keeping lips sealed to maximise effect). They turn back to what they're doing, and the sounds go back on.

Continue to convice person that you are hearing stuff, and can't they hear it to?

Maximum scare...