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Sound Accelerator

Target Audience

Lower Key Stage 2

Link to the National Curriculum

Sc4 Physical Processes (Sound)
Pupils should be taught to:

  • “identify how sounds are made, associating with some of them with something vibrating”.
  • “recognise that vibrations from sounds travel through a medium to the ear”.


  • To enable the children to understand that sounds are transmitted by vibrations in any medium and that the more closely compacted the medium the more readily that sounds are transmitted. In this particular instance the emphasis is on transference of sound through the air.

Download worksheet

What you need

  • A hollow plastic or stiff card tube,
  • balloons
  • candle.

What you do

  • See the video clip “The Sound accelerator” from the website practicalprimaryscience.co.uk
  • Having cut the necks off two balloons, stretch each one over the ends of the tube
  • Make a hole in one of the stretched balloons. The easiest way is to pinch a very small area in the centre of the balloon and cut it with a sharp scissors. Trim the hole if necessary, but do not make the hole too large. It would be useful to have around half a dozen of these tubes available, so that the whole class can take part in the activity at the same time.

How it works

  • The trapped air in the tube is in a comparative state of rest. Tapping one end with the hole end facing the lighted candle, the air inside will be vibrated causing collisions of air molecules with the outcome that a stream of compressed air will be forced through the hole causing the flame of the candle to be extinguished.
  • This apparatus helps to mirror what occurs when vibrations of air are transmitted from a sound source to the receptor (person receiving the vibrations translated into sound via the ear).

Group / Class Organisation

  • Depending on the number of adult helpers and apparatus available the class could be split into groups of threes or fours to perform this relatively safe activity making sure the candles are stored in a safe environment.
  • Much will depend on the maturity of the children involved and their past experience of practical activity.

Preliminary Activity

  • Preliminary activity work on sound transference should start well before Key Stage 2 in the Foundation Stage with the identification of sounds and a realisation that sounds get fainter with distance and that sound can be muffled with insulation.

Follow up Work

  • This could take the form of investigations of how sound can be muffled which is very much sought after in this age of ever increasing noise pollution.
  • An ideal problem solving situation is to ask the children which noises are most annoying. They could then be challenged to produce a pair of ear muffs to cancel out annoying noises.
  • Another problem situation could surround an alarm clock with the ringing bell mechanism. The children could be challenged with suppressing this sound, starting with placing it in a box and then surround it with different sound insulating materials in turn. The success could be further evaluated with sound monitoring equipment linked to a computer.

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