Wrap the other end around your fingers. Stick you fingers in you ears and let the coat hangers dangle freely and bump into each other. The vibrations carried up the string make an impressive sound since vibration travel though solids better than through the air. Blow up balloons and pinch both side of the neck and stretch it tightly as the air escapes. This sounds terrible, but the vibration can be easily sensed.
Loudspeakers cause sound waves when an electromagnet makes the speaker vibrate.