Q+A: How Do Carbon Microphones Work?

• The carbon microphone is seen as a simple device to turn sound into electronic signal. Some examples of their use where in telephones, radio broadcast systems and the popularity was at a peak around the 80's. These where eventually replaced by more powerful and less noisy microphones. Some are still used today due to their durability and working in low power environments.

  The tapping of microphones came from this microphone as the carbon atoms would get stuck together sometimes and so needed to be hit to separate them to ensure the microphone worked properly, this is still carried on today even though there is no advantage compared to just talking into it.

• With reference to the diagram below. Carbon is a resistor, which isn't very efficient at conducting electricity as it tends to resist, hence being a resistor. A current runs from the diaphragm which is the first plate, through the carbon to the other plate. The carbon molecules normally resist it somewhat, lowering the power flow. When a sound wave pushes down on the top plate, however, it squeezes the carbon molecules more tightly between the two plates. This increases their conductivity, creating more electric current. As the plate moves up and down with the sound wave, the current increases and decreases, creating an electric wave in the shape of the sound wave.
  
  
  

  

  Grey Circles = Carbon Granules - Diaphragm (flexible electrode) moves, changing signal output strength

  If you feel i have missed anything or want to comment feel free.

• • Thanks,

    - Matt Price