Alexander Graham Bell invented the first microphone in 1876 as part of the telephone. Microphone is an electromechanical device that uses vibration to create an electrical signal proportional to the vibration, which is usually an air pressure wave. There are many different types of microphone, ranging from the old condensers to the modern. Microphones are commonly used in television, radio, concerts, telephones, and public address systems, but also in other unusual applications.
A microphone is an example of a transducer, a device that changes information from one form to another. Sound information exists as patterns of air pressure; the microphone changes this information into patterns of electric current. A variety of mechanical techniques can be used in building microphones. Microphones are also categorized according to how well they pick up sound from certain directions. Omni-directionals detect sound equally well from all angles, bi-directionals pickup from the front and back but not the sides, and uni-directionals only pick up sound from the front.
