A speaker is a transducer that produces sound in response to an electrical audio signal. The most common type of speaker uses a lightweight cone connected to a rigid frame. The combination of a permanent magnet and a speaker coil force the speaker cone to move back and forth in accordance with the electrical signal from an audio amplifier, thereby reproducing the sound. Many electronic devices incorporate a small, inexpensive speaker to alert users to conditions such as low battery charge level and other circumstances which require user intervention.
