The Audio Recording Signal Chain : Microphones

Neumann U87 Microphone A microphone, sometimes referred to as a mike or mic captures the sound of your voice and converts that sound into an electrical signal.

All modern microphones are designed to accomplish the same thing. A microphone takes varying pressure waves in the air and convert them into varying electrical signals.

There are five different technologies commonly used to accomplish this conversion:

Carbon Microphones

The oldest and simplest microphone uses carbon dust. This is the technology used in the first telephones and is still used in some telephones today. The carbon dust has a thin metal or plastic diaphragm on one side. As sound waves hit the diaphragm, they compress the carbon dust, which changes its resistance. By running a current through the carbon, the changing resistance changes the amount of current that flows.

Dynamic Microphones

A dynamic microphone takes advantage of electromagnet effects. When a magnet moves past a wire (or coil of wire), the magnet induces current to flow in the wire. In a dynamic microphone, the diaphragm moves either a magnet or a coil when sound waves hit the diaphragm, and the movement creates a small current.

Condenser Microphones

A condenser microphone is essentially a capacitor, with one plate of the capacitor moving in response to sound waves. The movement changes the capacitance of the capacitor, and these changes are amplified to create a measurable signal. Condenser microphones usually need a small battery to provide a voltage across the capacitor, Phantom Power or USB power from a computer. At Voices.com, we've chosen the Samson USB Condenser CO1U microphone for recording the Vox Talk podcast and the new Voice Casting podcast.

Ribbon Microphones

In a ribbon microphone, a thin ribbon is suspended in a magnetic field. Sound waves move the ribbon which changes the current flowing through it. You can read a review of the Samson VR88 ribbon microphone at eMusician.

Crystal Microphones

Certain crystals change their electrical properties as they change shape (see How Quartz Watches Work for one example of this phenomenon). By attaching a diaphragm to a crystal, the crystal will create a signal when sound waves hit the diaphragm.