Sounds - groups of particles moving to and fro

The physical nature of sounds

Wrong Track: Sounds travel to your television through the cable from the TV company.

Right Lines: Electrical signals pass down the cable to your television. Here they are decoded and the loudspeaker in the television produces the desired sounds.

Codes are not sounds

Wrong Track: You buy CD sounds at a record shop.

Right Lines: The sound does not just sit on the CD. The code on the CD is read by the CD player, which drives the speakers in the headphones and they produce the sounds (music to your ears!).

The nature of sound in teaching and learning

Thinking about the learning

This learning challenge involves being clear about the physical nature of sounds… what they really are.

The challenge here is for pupils to come to recognise and to understand the scientific view of what sound is: the disturbance created by the source, which travels out through the surrounding medium. The disturbance itself consists of successive regions of high

and low-density air created by the forwards and backwards motion of millions of air particles. No to and fro motion – no sound.

Thinking about the teaching

It is worth emphasising the message:

Teacher: If it does not involve the to-and-fro movement of a medium, is is not a sound.

So sound is not stored on a CD; it is not transmitted to a radio set; it is not delivered down a cable to a television.

Sounds can be produced by decoding what is stored on these artefacts. You need to take care to refer to sound only when you want to speak of the to and fro movements of the medium. Sound only exists in each of these cases after the loudspeaker.