A microphone is a transducer that converts sound waves into electrical signals. This electromechanical device converts air pressure fluctuations into a corresponding pattern of electrical signal pulses. Different microphones use different approaches to achieve this conversion. The most common designs are dynamic and condenser microphones.

Dynamic microphones convert pressure fluctuations created by sound waves into an electric current. This approach is based on Faraday’s law. According to this law, an electric current is induced when a conductor passes through a magnetic field. In a dynamic microphone, a permanent magnet is used to produce a magnetic field. The most common design of dynamic microphones uses a coil of wire as a conductor attached to a membrane. An electric current is generated in the copper wire every time the pressure fluctuation causes the coil to pass through the magnetic field.

Condenser microphones use a capacitor-like model that features a back plate and a diaphragm. While the back plate remains stationary, the diaphragm is designed to move when there are fluctuations in the air pressure. This movement of the diaphragm causes changes in capacitance and electric potential. The electric charge (Q), capacitance (C), and electrical potential (V) are related by the following equation: Q=CV. A battery is used to provide the electric potential and the small current that flows when the diaphragm moves is amplified.

Factors to consider when selecting a microphone include overload characteristics, linearity, sensitivity, noise, and frequency response.