Microphony occurs with older video cameras. The mechanics of
the video pickup tubes of the camera vibrate in response to loud noises (such as
gunshots), which translates into regular fluctuations in the resultant video
signal coming out of the camera. The end result is a banding pattern across the
resultant image.
Dr. Who-The Caves Of Androzani (Episode 4, 4:08)
Note the regular horizontal bands across the image.
