How Do Microphones Work?

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  • The mic was invented by multiple inventors working independently.1
  • Thomas Edison found in 1878 that carbon connected to a circuit would change resistance when vibrated by sound waves.1
  • Most notably, Alexander Graham Bell use a magnet and a diaphragm that was sensitive to sound waves and would vibrate.1
    • The magnet created a current in a coil via induction.1
  •  All these innovations were intended for telephone, not amplification.1
  • The inventions of what is called a condenser microphone and the vacuum tube made effective radio broadcasting and the amplification of public performances possible.2
  • In 1929 and 1930 NBC used parabolic dishes with their microphones to create directional recording techniques.2
    • “Paved the way for shotgun mics”2

How it Works

  • Dynamic
    • Dynamic mics use a magnet with a wire coiled around it. When a diaphragm is vibrated with sound waves, it moves the coil along the magnet creating a current in the coil wires as an audio signal.3
    • Described as cold sounding, but very durable and not as sensitive as other mics.
  • Condenser
    • Condenser microphones use two plates. The plate that faces the sound waves acts as a diaphragm.4
    • The system is loaded with 48V of what is called phantom power.4
    • When the diaphragm vibrates the modulation between the plates sends the audio signal in the form of the signal modulation down the wires connecting the plates.4
  • Ribbon
    • Ribbon microphones are highly sensitive mics that use a similar tech as dynamic mics.5
    • In the case of a ribbon mic there is a thin ribbon that both acts as a diaphragm and is also a part of the circuit, such as the coiled wire in a standard dynamic mic. The magnet is in the shape of a U and the ribbon modulates between the U shape to create the audio signal.5
    • They are extremely sensitive (storing on the side, wind, or any kind of voltage spike can break them.5


  • Most mobile phones and small electronics have traditionally used an electret microphone which is a “condensed” condenser microphone.6 
  • The new kid on the block is the MEMS microphone.
    • MEMS mics use the same principle as the electret condenser mic but on a much smaller scale.7 
    • Used for smaller electronic applications.
  • Company called ReSpeak makes a Raspberry Pi unit with four speakers so that people can mess with voice applications such as the Amazon Echo.7
  • Noise Canceling applications.


  • Internet of Things.
  • Wireless and smaller mics/earbuds.
  • As wearable tech becomes more useful, better mics will become important, as well as the software that can filter the signals and improve voice recognition and clarity.







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