Lets make a string phone!

Sound waves are longitudinal waves with frequency between 20 Hz and 20,000 Hz, that travel through air, solids or liquids.


  • 2 paper cupboards
  • 3m string


With a pencil make a small hole in the bottom of each cup and pass the end of the twine inside each cup. Tie 3 knots at the ends of the twine in the cups. Stretch the string and one student speaks in the cup and the other listens to it through the other cup at the other end of the string!!


Speaking into the cup creates sound waves which are converted into vibrations at the bottom of the cup. The vibrations travel along the string and are converted back into sound waves at the other end so your friend can hear you. Sound travels through the air and through solids such as your cup and string.