Make some noise
Exterior microphones, especially parabolic and laser mikes, can be defeated by ambient noise. For the parabolic mike, all you really need to do is crank some music, turn on a blender, or hire a guy with a keytar to jam as you speak. Laser mikes are a little better at resolving the human voice from background noise. To be absolutely certain, you’ll want to buy some custom-made laser-mike jammers for about $100 (per window). These little machines stick to your windows and put out white noise in the same frequency as the human voice, making it impossible for a laser mike to isolate your voice from the background. Alternatively, you can attach other noisemakers to your windows—things like sonic toothbrushes, small fans, or, if you’re feeling saucy, vibrators work great. These common household objects may not work as well as a purpose-built jammer, but they will save you some money.
Shotgun mikes are a little harder to jam. They can target individual sources of sound from hundreds of feet away, so ambient noise is useless. A wall, however, is a pretty efficient means of blocking their audio pickup. If you’re going to have a sensitive conversation, do it in an interior room, away from windows, and almost any form of remote audio pickup will be useless.