My best housemate (sorry Nate), who has been suffering from unusual headaches and insomnia for the past few months — leading to a diet that included several kinds of migraine medications and tension relievers — this evening discovered that his subwoofer, which sits in the corner of his bedroom, has been outputting a constant low-pitched waveform.
He only noticed it because he was underneath his room, in the basement, and heard what he thought may be an electrical fault related to the basement. The search for the source of the hum led back upstairs to the corner of his room. Unplugged, the subwoofer ceased its drone. And we are now expecting that he may find his headaches will now go away too.