What Are Microphones?
Microphones are transducers of sound waves, which means they convert sound into electrical signals that can be used in analog or digital formats. There are different ways sound gets converted into electric signals. We’ll discuss the three most commonly used in video production, dynamic, condenser, and ribbon.
Dynamic microphones are built with a diaphragm that reacts to sound. The diaphragm has a strong magnet with a wire coil around it. The magnet creates a magnetic field and when the wire moves when sound waves enter, it creates an electric signal (See figure 10.2.1).
These microphones are very sturdy and travel well (See figures 10.2.2 and 10.2.3). They are better at picking up louder sounds than softer ones, which is why news reporters use them when they report from an outside location. The microphone will be able to pick up the reporter’s voice more so than the noise around them. The same can be said for why dynamic microphones are used at music concerts. It will pick up the sound of the singer better than any of the other sounds around them.
Condenser microphones are built with two metal plates that are charged with electricity. One plate is a fixed plate, called the backplate, and the other plate, the diaphragm, moves when sound hits it. When the distance between the two plates changes, it creates an audio signal (See figure 10.2.4).
A battery needs to be placed inside the microphone or it needs power from what it is connected to, most commonly a camera or audio recorder. Many video cameras and audio recorders (but not DSLR or mirrorless cameras) have a setting called Phantom Power. This setting tells the camera or recorder to send an electric signal to power the two plates inside the microphone. This will drain the battery of the camera or recorder a little faster than normal.
Condenser microphones are able to pick up soft sounds much better than dynamic microphones. They are used in many productions, like studio interviews, sitcoms, and dramas (See figures 10.2.5 and 10.2.6).
Ribbon microphones are with a very thin piece of folded metal, usually aluminum, suspended in a magnetic field (usually two strong magnets). When sound waves move the metal ribbon back and forth in the magnetic field it creates an electric signal (See figure 10.2.7).
Most Ribbon microphones have a figure 8 or bi-direction pickup pattern because of how the ribbon is suspended. Older ribbon mics were very sensitive and easily broken, but the ribbon microphones of today are more sturdy. Care needs to be taken to prevent gust of wind or bursts of air (like when people pop their "p"s) from hitting the ribbon and stretching it out. It is best to use this mic with a pop filter like shown Figure 10.2.5 (the disk in front of the mic) or angle the mic to prevent a direct burst of air.
Ribbon microphones are used a lot in music recording. Since ribbon microphones pick up sound much like our ears do, musical instruments sound very natural (See figures 10.2.8 and 10.2.9).
You may have noticed in the figures above that some of the microphones look similar, like the handheld dynamic in figure 10.2.2 and the handheld ribbon mic in figure 10.2.8. Similar-looking microphones can have different internal transducers. Make sure that the microphone you have has the type of transducer you need for your production.