Science Fun

Train Horn Sound Science Experiment

This is one of the easiest and most impressive sound science experiments for kids. All you need are a few easy to obtain items to create this sound experiment that kids are sure to love. Not only does this experiment sound surprisingly similar to a train horn, but it provides an extra learning opportunity as the vibrations which create the sound are visible and easy to investigate. 



  • 1 cardboard toilet roll
  • 1 balloon
  • 1 large milkshake straw. A regular straw will also work. 
  • Optional – Masking or painters tape. This may be required to reinforce your cardboard toilet roll. 



  1. Cut the rounded end off of the balloon. Do not cut off the end of the balloon with the mouth that you use to inflate.
  2. Stretch the cut off end of the balloon over one end of the cardboard toilet roll. Do your best to position the neck of the balloon near the edge of the toilet roll and avoid centering the neck over the middle of the toilet roll if possible. 
  3. Insert about an inch of the straw into the mouth of the balloon. You do not want the straw to come out on the other side of the balloon.
  4. Pinch the balloon around the straw to keep any air from escaping.
  5. Hold the cardboard toilet roll with your other hand so it is close enough to your face that you will be able to blow into the straw. 
  6. Pull the straw and balloon so it becomes slightly taunt and straight out from the stretched surface of the balloon.
  7. Blow firmly and steadily into the straw.
  8. It may take several attempts to make a sound. Once you begin hearing sounds, adjust the tautness of the straw and balloon. You will be able to see the surface of the balloon vibrate as you adjust the sound.
  9. Once you get the hang of it, with a little extra force you can create an impressively loud sound that closely resembles a train horn. 
  10. Optional – Your balloon may cause the cardboard toilet roll to lose shape and potentially collapse. Simply add a few layers of tape to reinforce the toilet roll to add some extra strength. 





How it Works:

The taunt balloon creates a membrane that vibrates easily. As air is forced through the straw, it travels quickly over the surface of the balloon in a way that creates thousands of tiny vibrations. The vibrations create sound waves that come together to make the loud and impressive train horn sound. The sound is further amplified by the tube making it even louder. 


Make This A Science Project:

Try a bigger tube. Try a conical shaped or different shaped tube. Try other materials like wax paper to try and create a surface that will vibrate and create sound. Try different sized and shaped balloons. Try different sized straws and lengths of straws.