The Environmental Protection Agency requires headset manufacturers to test their products and determine by how much they reduce noise. Active noise reduction headsets may give two figures one for the noise reduction when the electronics are turned on and one for when they are not. After protecting your hearing, the greatest value of a headset is in allowing you to communicate more clearly and easily both inside the cockpit, through the use of an intercom, and outside the cockpit when talking to air traffic control, flight service, or other aircraft. To make sure that a headset is helping, not hurting, the quality of your communications, you need to know a little about its microphone and speakers. There are three primary types of microphones electret, carbon, and dynamic.
Electret microphones are the most popular for aviation use.
They are smaller and lighter than other microphone elements and work by placing a charged, flexible diaphragm a given distance from a fixed plate. Sound waves created by speaking into the microphone cause the diaphragm to vibrate, changing the distance between the diaphragm and the plate. Those changes are translated into electrical signals and transmitted. Carbon microphones are the simplest and least expensive. In carbon mics, the movement of a diaphragm is transmitted to carbon granules inside a small container connected to the diaphragm.