(Valladolid - España)


Amazing dance

Amazing dance

▪ 10 pearls of polystyrene or 10 cereal flakes
▪ 10 threads
▪ a clothes hanger
▪ elastic band

▪ Tie a thread around each polystyrene pearls or cereal flakes
▪ Tie the other end of the bar thread of clothes hangers
▪ Hang it the back of a chair, or ask a colleague to keep it
▪ Hold one end of elastic band between teeth clenched, extending toward the other end of elastic grains of polystyrene, without touch
▪ Move your finger stretched elastic band


As you see, the pearls of polystyrene begin to move back and forth, reaching their neighbors on each side. They are dancing.


How does it work ?
Elastic vibrations shake the air molecules around and inside the polystyrene pearls. They dance from side to side until the vibration stops.

Sound vibrations

Hear and feel sound vibrations

Material: a balloon and a colleague

What you have to do:
1) Blow up the balloon.
2) Hold it against your ear.
3) Ask your colleague to press their lips against the balloon and speak.
4) After that you should speak and your friend should listen.



Did you discover what we did?
You can hear the vibrations through the balloon and you can feel them.
You can feel your own voice through your lips as the balloon’s skin vibrates against them.


Conclusions: Sound is created when an object moves and the air around it
vibrates creating sound waves.

Pan’s pipe

How to make a Pan’s pipe ?

You need:

8 plastic straws of 5mm in diameter and 21cm long

A pair of scissors

A ruler Scotch tape

What you have to do:
If you want your pan’s pipe to render the musical range, cut the straws in the following way:
Straw 1 L= 8,5cm ; Straw 2 L= 7,7 cm; Straw 3 L= 6,8 cm
Straw 4 L= 6,2 cm; Straw 5 L= 5,6 cm; Straw 6 L= 5,2 cm;
Straw 7 L= 4,9cm; Straw 8 L=3,3 cm

Cut the upper part of each straw at an angle below 45. Then put them on a horizontal surface in decreasing/increasing order of the lengths at 1 cm distance between them.
Put two 2 cm long straws between two straws . Put all these together by using scotch tape.
You made a pan’s pipe that renders the musical notes.


The lengths of the air columns of the straws that form the panpipe are different and vibrate differently when we blow them making different sounds (the sounds of D major)

Screaming Balloons

Screaming Balloons


  • Latex balloons
  • Zinc hexagonal nuts



  • Pick one balloon
  • Get one or few hex nuts and put them into the balloon. Make sure that the hex nut goes all the way into the balloon so that there is no danger of it being sucked out while blowing up the balloon.
  • Blow up the balloon and tie it off.
  • Hold the baloon at the top and move it in a circular motio



  • The hex nut may bounce around at first, but it will soon begin to roll around the inside of the balloon. What is that sound? Could the balloon be screaming? It is like a vuvuzela sound.
  • What happens when you change the size of the balloon or the size of the hex nut?
  • Experiment with other objects whose edges may vibrate against the balloon
    How does it work ?
    The hex nut make a circle inside the balloon due to centripetal force and the laws of inertia. The multiple sides of a hex nut cause it to bounce and vibrate while on its path around inside the balloon. The vuvuzela sound comes from the sides of the hex nut vibrating along the sides of the balloon. And it is so fun when we have the classroom full of screaming balloon

Sound means Vibration

Sound means Vibration


  • A loudspeaker
  • A tone generator
  • Polystyrene balls of 1-3mm in diameter
  • Meal
  • Tinfoil
  • A cardboard tube of 50-100mm in diameter, 30-50 mm high with an elastic membrane cut off a balloon stuck on one edge


Produce low frequency tones of 30-100Hz in the loudspeaker
1. -Listen to the sound produced by the loudspeaker and look at its membrane. You will not observe its vibration. ( If you gently touch the membrane with your finger you will feel it vibrate)

  • But if you sprinkle polystyrene balls on the membrane you will observe how they move up and down/jump on the membrane and thus visualize the vibration of the membrane through a suggestive dance.



Conclusion: The sound is produced by the vibration of the source, in our case the source is the membrane of the loudspeaker.



2. But how does the sound get to our ear?

  • Repeat the previous experiment and put some polystyrene balls on the carcass of the loudspeaker. You will observe that it won’t vibrate.
  • Lay the tinfoil on the carcass of the loudspeaker in front of the membrane and sprinkle polystyrene balls on it. You will observe that the dance of the balls starts again although the tinfoil doesn’t touch the membrane. Raise the tinfoil a few millimeters off the carcass and you will observe that the dance of the balls continues.



  • This time use the cardboard tube with elastic membrane instead of the tinfoil . Sprinkle meal on it and hold it in front of the speaker. You will observe how the meal grains move up and down on the membrane and form surprising pictures on it.



Conclusion: The vibrations of the membrane are transmitted through the air and produce the vibrations of the tinfoil or elastic membrane.

Sound reflection

Sound Reflection

▪ a jar
▪ a ticker
▪ a piece of glass
▪ a colleague for help

▪ Place the jar on the end of a meal at least 1 m long, and you sit on a chair at the other end of the table. If more hear the clock tick-cue, move away than table until you hear the sound.
▪ Ask a colleague to use piece of glass so you do hear the clock again, but without moving from place jar. Is it difficult?

▪ If the glass (or piece of metal) is held over the jar, tilted at an angle of 45 0, watch the sound will be heard again.


Clock sound will be heard again because of the reflection phenomenon that occurs on the glass.

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