vibration
is what causes sound
(shaking-trembling-quivering)
sometimes a phone vibrates
electric chairs vibrate
rubber bands vibrate
a jack hammer vibrates
earthquakes cause vibrations
http://www.youtube.com/watch?v=LfRqoV-bf_c
http://www.learninggamesforkids.com/science_songs/vibration-science-song.html
http://www.sciencekids.co.nz/sciencefacts/sound.html
http://www.kids-science-experiments.com/sound-vibration-facts.html
Interactive
http://resources.woodlands-junior.kent.sch.uk/revision/science/sounds.html
http://www.exploratorium.edu/listen/activities/dean/audio_pong/activity_pong.php
http://www.exploratorium.edu/listen/online_activities.php