|Radio and Electronics (DED Philippinen, 66 p.)|
As we said already: at the beginning of each modern communicationsystem the sound has to be converted into an electric signal and at the end again the electric signal has to be translated back into sound. This task is carried out by devices which are called in general TRANSDUCERS.
Whereby the transducers which translate sound into an electric signal are called MICROPHONES and those which translate an electric signal back to sound are called EARPHONES or LOUDSPEAKERS.
Until today there was not found a way of translating sound directly into an electric signal it must be always gone the roundabout via mechanical forces.
Hold a piece of paper sensitively in your hand, position it directly in front of your mouth and start talking loudly against the paper. You will experience, that the paper is moved (vibrated) to an for by the sound. Result: sound can move by light pieces of material which show a big area vertically to the direction of the movement of soundwaves. Sound waves are exerting forces on to these light and flat pieces which we will call from now on a DIAPHRAGM. On the other hand the leather on top of a drum is another type of diaphragm. This diaphragm is able to produce sound if it is moved to and for (if it is oscillating). These considerations make it very clear, why we will find at the beginning and at the end of our communication system always a diaphragm, as shown in fig. 8.