Firstly regarding aircraft microphones - the vast majority of aircraft comms systems are designed to provide power to the mic, down the signal+ line, with the signal- line acting as the return. So if you measure across the +signal and -signal pins you will see a voltage of between +8 to +30VDC.
This voltage is typically required to provide power to an "electret" mic, although some aviation headsets do use a small pre-amp. Neither are particularly "special".
The matching impedance (the load presented to the headset mic) is typically required to be in the range 50-600 Ohms, though a higher load will work just fine (the system I am most familiar with presents a load of around 1k Ohm and works great).
The earphone part of a headset in most modern headsets typically measures 150-300 Ohms, though it is worth pointing out that some older headsets may measure MUCH lower (the David Clark H10-76 used by many military aircrew measures 19 Ohms...). The majority of comms systems
should handle this just fine.
Electret mics are actually fairly cheap and are very common (used in cell phones, etc) and therefore are not the cost driver.
Personally I am hard pushed to explain why some of the more revered headsets are as expensive as they are - it is certainly NOT a function of the components, since there are many better performing headsets used in the broadcast industry for example that cost less.
One reason for the cost may be FAA TSO certification, though not all headsets used in aviation are certified. Certainly certification adds cost.
Obviously headsets that use active noise reduction have an excuse to cost more, since there is a tangible R&D cost to be covered, in addition to the additional circuitry required.
Regards, GY
