A microphone is a device for converting acoustic power into electric power that has essentially similar wave characteristics. Microphones convert sound waves into electrical voltages that are eventually converted back into sound waves through speakers. They were first used with early telephones and then radio transmitters.
In 1827, Sir Charles Wheatstone was the first person to coin the phrase "microphone."
The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone (then called transmitter). This was independently developed by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent (after a long legal dispute) in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention.
Hughes' device used loosely packed carbon granules – the varying pressure exerted on the granules by the diaphragm from the acoustic waves caused the resistance of the carbon to vary proportionally, allowing a relatively accurate electrical reproduction of the sound signal. Hughes also coined the word microphone. He demonstrated his apparatus to the Royal Society by magnifying the sound of insects scratching through a sound box. Contrary to Edison, Hughes decided not to take out a patent; instead he gave his invention as a gift to the world.
The carbon microphone is the direct prototype of today's microphones and was critical in the development of telephony, broadcasting and the recording industries.
Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886.This microphone was employed at the first ever radio broadcast, a performance at the New York Metropolitan Opera House in 1910.