Aloudspeaker converts electrical energy into the kinetic energy of the speaker. this kinetic energy is transferred to air, and the motion of the air is the sound that people hear.

It all starts from a radio with a loudspeaker . It produces and converts electrical energy and make this a formed of kinetic energy coming out of the speaker. Then, when this kinetic energy is moving and transferred to surroundings or air, it will let people feel the motion being created by the air. Finally, it reaches the people and hears this as sound. 

This is an example on how we trace the transformation of on signal from radio and how it reaches to people as sound or as a music.

Amplify and switch electrical power and electronic signals