Q: DUO wireless talkback units can work with headsets that have either a dynamic or an electret (condenser) microphone. What is the difference between dynamic and electret microphones?

Electret microphones are very small. They are typically a capsule of less than 1cm diameter.


They have a very thin conductive diaphragm isolated with a tiny air gap from the main body. A small polarizing bias voltage (from the DUO) sets up a capacitive charge between the diaphragm and the main body. As sound waves hit the diaphragm it moves slightly in and out in sympathy with the incident sound waves. This movement changes the capacitance value and results in a changing voltage on the main body which is an electrical representation of the sound hitting the microphone. This electrical signal is amplified and ultimately transmitted by the DUO when the Push To Talk button is pressed.


Dynamic microphone elements are larger than electrets. They work like a loudspeaker in reverse.


The diaphragm is mounted on a coil of wire that is suspended in the air gap inside a magnet. It is free to move inside the magnetic field. When sound waves hit the dynamic microphone’s diaphragm the coil moves in and out of the magnet field producing a current in the wire. This current is an electrical representation of the incident sound waves and can therefore be amplified and ultimately transmitted as DUO audio.


So, which to choose?

Dynamic microphones are tougher than electrets and are often used where headsets may experience rough handling. They are more likely to be used in military applications for example.

Electret microphones provide very good sound quality but they do need some extra amplification compared to dynamic mics which have a higher signal output level. Dynamic microphones aren’t as good at responding to sharp transients in sound due to the coil having to physically accelerate through the magnetic field. The electret diaphragm being so small and light and doing nothing but carrying a small electric charge can respond instantly to any sound you throw at it.

The standard headsets that Wood & Douglas supply for our DUO talkback units have electrets microphones and they produce crisp clear audio quality. Some of our customers prefer the ruggedness of dynamic microphones and we can supply headsets with dynamic microphone elements upon request.

Inside the DUO there is a pin header (PL9) that enables and disables the small bias voltage for electrets mic elements. This needs to be set according to the type of headset being used.   


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