YOUR VOICE AND THE TELEPHONE

now adjust the sound bottom that's all when this Bell system seal fades out shut off the projector everything will be properly set for your show to begin [Music] [Applause] [Music] we all know so well what telephones look like how simple they appear to be and how easy they are to use that we seldom give them a second thought it's hard to believe that the telephone once looked like this down through the years since it was invented the telephone has been redesigned again and again one purpose being to make voices sound clearer and more natural over telephone when you use the telephone many interesting things happen to your voice we might start with the fact that voices are made up of sound waves caused by vibrations as a matter of fact all sounds come from vibrations if you pluck a guitar string you can see the vibrations of course you can't see you the sound waves but we do know what they are like sound waves are waves of pressure traveling through the air they occur this way air is made up of very small particles or molecules that can move about as the spring vibrates the molecules of air next to the string are moved back and forth they push the ones next to them the motion going on and on from molecule to molecule in waves of pressure that travel outward from the vibrating string if you make the string move far the sound is loud and of course if you make the string move only a little the sound is soft if the vibrations are slower the sound is lower in pitch if the vibrations are faster the sound is higher in pitch in much the same way the vocal cords in your throat make the sounds of your voice variations in pitch and in breathing produce variations in the sound waves these waves are modified as they bounce around in the air passages and are then formed into words when the sound waves come out of your mouth they have a distinct complex pattern that is your very own as individually yours as your fingerprint now let's see what happens when the sound waves of your voice enter the telephone mouthpiece the transmitter hear the waves strike against a thin metal plate called a diaphragm the movement of the diaphragm though unbelievably slight corresponds truly to the sound of your voice behind the center of the diaphragm is a tiny package of carbon grains when a sound wave strikes the diaphragm it sends a wave of pressure through these grains electricity flowing along a wire goes through the carbon grains they resist the flow of electricity when the diaphragm presses heavily the grains allow more electricity to flow on the other hand when the pressure is lighter less electricity flows through thus when your voice strikes the diaphragm it changes the flow of electricity the resulting electrical pattern corresponds to the pattern of your voice this is the way your voice is transformed from sound to electricity the electric current carries the pattern of your voice along the wire it goes through central offices where it is directed to any one of millions of telephone lines the pattern of your voice may travel by cable or for long distances perhaps by microwave radio strengthened at intervals by amplifiers along the way the electricity carries your voice almost instantaneously to the telephone receiver at the our end of the line inside the receiver is another diaphragm it is moved back and forth by the action of two magnets one of these is a permanent magnet it exerts a constant pull on the diaphragm the other one is an electromagnet it's pull depends on the amount of electricity flowing through its windings the electric current that is carrying the pattern of your voice flows through the electromagnet and the variations caused the diaphragm to vibrate the movements of the diaphragm creates sound waves in the air new sound waves that have the same pattern as those you sent into your telephone your voice has been changed from saw to electricity and back to sound again all quick as a wink to do this job well the telephone has to be quite complex in the transmitter and receiver unit alone there are 84 tiny parts and in the base of the telephone there are four hundred and eight parts [Music] all these parts are made and assembled with great precision so that the naturalness of your voice will come through the modern telephone conveys your very mood if your voice is Pleasant and courteous it will sound just as pleasant and courteous to the person who is listening that's good to remember for the fact that the telephone carries your personality Preston your voice has a lot to do with the pleasure and fun of using the telephone [Music]