Electret Condenser Microphones Explained

How Electret Condenser Microphones work –

Microphones convert sound energy (sound waves) to electrical energy (an audio signal).  An electret condenser microphone (ECM) consists of two plates, one fixed (back plate) and one moveable (diaphragm).  There is a small gap between each plate and when sound waves hit the diaphragm, the movement causes the capacitance between the diaphragm and the back plate to change.  This generates a flow of variable electric current and these electrical signals are sent to the designated output device.


A permanently charged electret material, either on the diaphragm or back plate, means that ECMs do not need a constant source of electrical charge making them very efficient and economical.



Typical electret condenser microphone circuit diagram –

ABM-702-RC circuit diagram




Electrical connections are made either by PCB pins, leads or solder joints.

Electret Condenser Microphone - ABM-714-RC               3mm Electret Microphone - ABM-716-RC         Omni Directional Microphone - ABM-705-RC


Directionality – this is a microphone’s sensitivity to sound from various directions:

  • Omni directional – These collect sound waves from all directions and are ideal for general applications.
  • Uni directional – These offer increased front sensitivity in comparison to Omni directional models. Sound waves from the front are picked up, while rear sensitivity is relatively weaker.
  • Noise cancelling – These have identical front and rear sensitivity.  Side sensitivity is significantly less.  Noise Cancelling microphones are useful when the objective is to hear sounds coming from short distances and cancel background noise, such as in mobile phones or headsets.




Applications –

ECMs are widely used to enable communication and recording as they are inexpensive and offer good performance.  Key applications include:

    • Telephones
    • Smartphones
    • Desk top computers
    • Tablets
    • Headsets
    • Hearing aids
    • PDAs
    • Access control systems
    • Lift controls
    • Parking meters
    • Surveillance equipment
    • Audio visual products


For more information on our extensive range of electret condenser microphones, visit our website at www.abcomponents.co.uk/product-category/electret-microphones/ or call 01258 456360.  We are able to customise our standard microphones by changing the lead length or type of connection and we will be happy to discuss this with you.*

*Minimum order quantities will apply.