Microphone and its testing

Picture a is the internal structure of the microphone. Pictures b and c are the output contact forms of the microphone. There are two types of contacts: two-contact type and three-contact type. Picture d is the test method. Set the multimeter to R×1kΩ, connect the black meter to any contact point, and the red test lead to the other contact, write down the measured resistance value; exchange the contact points with the test leads, write down the measured resistance value, and compare the two As a result of this test, for the smaller resistance value, the black test lead is in contact with the source and the red test lead is in contact with the drain. Picture e is the sensitivity of the test microphone. When the sound pressure acts on the microphone, there will be an output on the millivolt meter. When someone blows air into the microphone, the pointer of the multimeter will swing accordingly. The greater the swing, the higher the sensitivity.