Here’s a great way to eavesdrop on an unknowing sap’s conversation. Objects in Flux’s Scott Mitchell has turned a vintage lamp into a parabolic microphone for recording. It’s got volume control and a headphone socket mounted in the lamps base. This way, no one other than the headphone wearer gets to hear the goods. And by goods I mean the sound of your roommate banging away the night.
The whole project is powered by a 9V battery, which is fitted inside the lamp shade, out of site out of mind. While it does amplify the sound, it suffers in performance due to the small size of the parabolic dish. Mitchell provides circuit diagrams and instructions for the project, perhaps you’d like to make your own, more effective, lamp microphone?