LIQUID MICROPHONES

Liquid microphones, invented by Alexander Graham Bell and Thomas Watson, were among the first working microphones to be developed. They were a precursor to what would later become the condenser microphone. Early liquid microphones used a metal cup filled with water and sulfuric acid. A diaphragm was placed over the cup with a needle on the receiving side of the diaphragm. Sound waves would cause the needle to move in the water. A small electrical current ran to the needle, modulated by sound vibrations. The liquid microphone was never a particularly functional device, but it made a great science experiment [source: Pemberton].

CARBON DUST 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. The changing resistance changes the amount of current that flows by running a current through the carbon.

FIBRE-OPTIC MICROPHONES

Fibre-optic systems, which use super-thin strands of glass to transmit information instead of traditional metal wires, have been revolutionizing the field of telecommunications in recent years, including microphone technology. So what's the big deal? Unlike conventional mics, which are often big and send an electrical signal, fibre-optic microphones can be extremely small, and they can be used in electrically sensitive environments. They can also be produced with no metal, which makes them very useful in magnetic resonance imaging (MRI) applications and other situations where radio frequency interference is an issue [source: Fibersound Audio].

DYNAMIC MICROPHONES

A dynamic microphone takes advantage of electromagnetic 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.

ELECTRET MICROPHONES

Electret microphones are among the most widely used microphones on Earth. Because they're cheap and relatively simple, electret mics are used in cell phones, computers and hands-free headsets. An electret microphone is a type of condenser microphone in which the external charge is replaced with an electret material, which by definition is in a permanent state of electric polarization [source: BeStar Acoustic Components].

RIBBON MICROPHONES

In a ribbon microphone, a thin ribbon -- usually aluminum, duraluminum or nanofilm -- is suspended in a magnetic field. Sound waves move the ribbon, which changes the current flowing through it. Ribbon microphones are bidirectional, meaning they pick up sounds from both sides of the mic. The RCA PB-31 was one of the first ribbon microphones. It was produced in 1931 and changed the audio and broadcasting industries because it set a new standard when it came to clarity. Several other microphone makers made comparable models, including the BBC-Marconi Type A and ST&C Coles 4038.

LASER MICROPHONES

A laser microphone works by capturing vibrations off of a plane, like a windowpane, for example, and transmitting the signal back to a photodetector, which converts the reflected laser beam into an audio signal. When sound hits the windowpane, it bends and causes the laser beam to bend, which can be translated to sound using a photocell. In recent years, scientists have been developing a new type of laser microphone that works by streaming smoke across a laser beam aimed at a photocell, which is then converted to an audio signal [source: Van Buskirk].

A condenser microphone is essentially a capacitor, with one capacitor plate 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.

CARDIOID MICROPHONES

If you're looking to record sound located in front of and on the sides of the mic -- but not behind it -- the cardioid microphone is for you. A polar plot of the gain for cardioid is heart-shaped (hence the name), with the highest sensitivity located directly in front of the mic and slightly less on the sides. Because of this, cardioid mics are ideal for recording live performances without capturing too much crowd noise. Many handheld microphones used to amplify vocals are cardioid mics [source: VoiceCouncil Magazine].

CRYSTAL MICROPHONES

Certain crystals change their electrical properties as they change shape. By attaching a diaphragm to a crystal, the crystal will create a signal when sound waves hit the diaphragm. It gathers the sound waves and creates movement in whatever technology is used to create the signal.

PARABOLIC MICROPHONES

A parabolic microphone is a microphone that uses a parabolic reflector to collect and focus sound waves onto a receiver in much the same way that a parabolic antenna (e.g., satellite dish) does with radio waves. Typical uses of this microphone, which has unusually focused front sensitivity and can pick up sounds from many metres away, include nature recording, field audio for sports broadcasting, eavesdropping (for example, espionage), and law enforcement.

BINAURAL

Binaural recordings are great for several reasons, but using them for VR applications in which a user can turn their head and still needs to be able to locate sounds, even (or especially) without seeing it, a binaural recording is not the best solution. They provide an excellent virtual surround picture when listened to through headphones, but only from one perspective/direction. When binaural recordings are rotated afterwards, the idea of binaural recordings and the resulting image gets destroyed. Binaural for VR is only the delivery format. The result is calculated from one or several audio sources to create a believable and engaging acoustical 3D environment on only two channels, the headphone left and right speakers. In short, as most have come to realize, binaural recordings are not the best recording format for VR, 360° videos or any other interactive 3D media.

AMBISONIC

Pretty much the same misunderstanding is widespread when it comes to Ambisonic. Ambisonic is a system developed in the 60s / 70s. Today it is mostly a delivery format to decode a specific sound location into a wide range of speaker setups, one being binaural for headphones. That means there is no need to have native Ambisonic recordings to deliver audio in Ambisonic format for VR or 360° videos to create a 3D environment. Not at all! The remaining question then is: Do you choose any Ambisonic microphone because of how it sounds, because it does sound better than other surround recording techniques?