We can illustrate the movement of sound waves quite simply by studying something we have all done at some time - dropping a stone into a pond.  A stone dropped into a smooth pond causes little ripples - or waves - to radiate out from the centre....

Whilst the television camera is picking up the picture, we must have some means of picking up the voices of the actors or commentators and all the other sounds connected with the scene being televised. The camera's job is to turn the sound into...