Most movie fans are familiar with boom microphones...those big microphones on long poles that are held above the actors when scenes are being filmed. But what is not often seen - because you're not supposed to see it - are the small microphones, called Lavalier microphones (or "Lavs" for short), that are hidden beneath the actors' costumes. With all the different kinds of costumes that actors wear, it can get really tricky for a sound technician to hide a microphone.

In this "4 Minute Film School" video from Aputure, a sound technician shares his tricks on how Hollywood hides lavalier microphones on actors.

So, the next time you watch a movie, you'll know that each actor you see on screen is secretly wired for sound.