Although sophisticated spying technology is available for purchase that uses contact microphones and amplifiers to listen through walls, it's also possible to create a listening mechanism using a small drill and plastic wrap. Because of the way the plastic wrap vibrates as sound passes through it, the sound wave travels faster as it goes through the hole, allowing for focused and efficient transmission of the sound.Continue Reading
Drill an extremely small hole in the wall. A hole that is smaller than the wavelength of the sound waves involved permits more sound to pass through.
Stretch plastic wrap across the drilled hole on the listening end.
Listen through the plastic wrap to the sound on the other side of the wall. Recording devices can also be set up to record the sounds.