You can point your telescope to any reflection or light (even fluorescent ones) on a room, and the induce vibration will be enough to create a signal to listen.

You can point your telescope to any reflection or light (even fluorescent ones) on a room, and the induce vibration will be enough to create a signal to listen.. I accidentally figured that out when I was 13 or so, and tried to build a led walkie-talkie.. I kept hearing other voices, and that is what it was..