original template by Ray Lam, Fall 97

revised template by Rachel Shorey and Steve Bergen 2/9/98

A microphone is an instrument that amplifies sound, such as the sound of a person's voice. When a person speaks into a microphone, the sound of his or her voice becomes amplified, making it sound much more powerful and deeper than it really is. When a person speaks into a microphone, it changes sound waves into electrical current. This electrical current is then fed into an amplifier which causes the sound to become more pronounced. Microphones come in various sizes and shapes and colors, although most are usually black. Some are cone-shaped and meant to be held in your hand like an ice cream cone, the type singers typically hold. There are microphones that are as small as a button and can be pinned to your blouse or on your jacket lapel. Some microphones are so small that they can be hidden from view. Of the many different types of microphones three of them are used most often today. They are the (1) carbon microphone; (2) the dynamic or "moving coil" microphone; and (3) the crystal microphone which is also known as the "piezoelectric effect" microphone. The most common microphone of these is the carbon microphone. It is made of metal and has a thin metal disk, or "diaphragm", that is coupled to a large number of carbon granules inside the microphone. When the diaphragm vibrates, a change occurs in the electrical resistance of the granules, producing a varying current. This allows the person speaking into the microphone to be heard from very far distances. The dynamic, or moving-coil, microphone has a metal wire attached to the diaphragm. The vibration of the diaphragm moves the coil in a magnetic field, thereby generating a voltage. The microphone's shape is usually an ice-cream cone shaped bottom with about a 2 in. by 2 in. sphere on top of it. The crystal microphone makes use of certain crystals which create something called the "piezoelectric effect". When these crystals are bent by the vibrations of the diaphragm in the microphone, an electric force is created which sends the sound waves to the amplifier where the voice sounds larger than it really is. The microphone was invented by Thomas Alva Edison in 1877. It was first constructed in Edison's hometown of Milan, Ohio. Thomas Edison was not a very good student. In fact, his teacher complained that he was curious by nature, but often appeared distant and not really interested in his class work. He dropped out of school at a very early age and was schooled at home by his mother until he was 12. This marked the end of his formal education but he went on to invent many items, of which the microphone was one. The microphone was the basis for many everyday items such as telephones, radios, hearing aids, and public-broadcasting systems. Without this invention we would not hear what people were saying at the theater or on loudspeakers. Telephone conversation became much clearer and easier to understand once Edison's microphone was placed into the mouth piece of telephones. Prior to Thomas Alva Edison's microphone, Grandma wouldn't hear a word you were ever saying on the early telephones, and you might want to develop a sense for predicting storms. The microphone changed all that. It is definitely a very practical invention.