Contact Microphone

A contact microphone, also known as a pickup, is a type of microphone that transmits audio vibrations through solid objects. Used widely as a substitution for normal air microphones, contact microphones pick up vibrations usually from musical instruments and convert them into a voltage that can be made audible. Here are three uses of a contact microphone:

A violin can usually compete with another acoustic instrument in a concert hall or orchestra; however, in an electric environment, such as a rock band, a normal microphone doesn't work. A normal microphone picks up too much sound for the surrounding instrument. The contact microphone serves as a perfect solution, since it is mounted on the violin and picks up vibrations from the violin and violin only. 

The following video includes examples of many uses of a contact microphone. Some examples include the following: At 2:36, a contact microphone is used to pick up the vibration of a wine glass as water is poured into it. At 3:58, the vibration of a crumbling magazine is picked up by the contact microphone. At 4:05, a contact microphone is attached to a container full of liquid.