A loudspeaker is a device that converts electrical signals into sound you can hear. When you listen to music through a stereo, watch a movie in a theater, or hear announcements at school, you're hearing sound from loudspeakers.

Inside a loudspeaker, electricity makes a cone-shaped piece of material vibrate rapidly back and forth. These vibrations push air molecules, creating sound waves that travel to your ears. The bigger the loudspeaker, generally the louder and deeper the sounds it can produce. That's why concert speakers are enormous: they need to fill huge spaces with sound.

The word loudspeaker tells you exactly what it does: it makes sounds loud enough for many people to hear. Before loudspeakers were invented in the early 1900s, if you wanted a room full of people to hear music, you needed live musicians playing acoustic instruments. Now a single loudspeaker can project a singer's voice or a symphony orchestra recording to thousands of listeners.

People often shorten the word to just speaker, as in “turn up the speakers” or “these speakers sound great.” Whether it's the small speaker in a phone or the powerful speakers at a stadium, they all work the same basic way: turning electricity into sound waves you can hear.