A loudspeaker (or “speaker”) is a transducer that converts electrical energy into acoustical energy. When an electric signal is applied to the input pin of speaker, it generates sound waves. The other pin is connected to ground. A speaker is commonly used to produce sound in response to a sensor output. For example, in an intruder alarm, the speaker goes on whenever an intrusion takes place.
The speaker diaphragm moves in accordance with the variations of applied electrical signal and causes sound waves to propagate through a medium such as air. In a speaker, the driver produces sound waves by vibrating a flexible cone or diaphragm made out of paper, plastic or metal which is attached to wide end of suspension. The suspension is attached to a metal frame called Basket and is made up of some flexible material allowing the cone to move. The narrow end of the cone is connected to voice coil, which is then connected to Spider (a ring of flexible material) allowing coil to move back and forth and producing sound waves. Click to read more about internal structure of speaker with its images.