Answer the following question given this paragraph: 

Cell phone signals are carried through the air as microwaves. You can see how this works in the Figure below . A cell phone encodes the sounds of the caller’s voice in microwaves by changing the frequency of the waves. This is called frequency modulation. The encoded microwaves are then sent from the phone through the air to a cell tower. From the cell tower, the waves travel to a switching center. From there they go to another cell tower and from the tower to the receiver of the person being called. The receiver changes the encoded microwaves back to sounds.


Q: What is the name of the mechanism in which sounds are encoded in microwaves by changing their frequency?


A:
frequency modulation