Illustration: Michael Haddad
Phone calls, video chats, voice activation, musical recordings – microphones make it all happen by measuring sound waves.
Microphones have become one piece of audio technology that we simply can’t do without, and are absolutely essential when it comes to recording live instruments, vocals, or any other sound from the environment. But what exactly is happening when you speak into one, and what are the most common types out there? Join us as we explore a few of the most common microphone designs to see just what sets them apart.
It all begins with a transducer
All microphones work under the common principle of taking in sound waves, which exist as mechanical vibrations that pass through fluids like air or water, and converting them into a measurable electrical signal. A transducer is an electronic mechanism that makes this all possible by taking in one type of energy and putting out a different type. Being at the core of a microphone’s identity means that we can usually tell a microphone apart by looking at its transducer. Different transducers convert sound differently, which is important to keep in mind when you want to record something specific (more on that later). Fun fact: a loudspeaker is basically a microphone in reverse, since it’s receiving electrical signals and throwing that sound back into the air as vibrations we can hear!
Once a microphone converts sound waves into an electrical signal, the amplitude level (or gain) of that signal needs to be boosted through an amplifier or preamp. This brings the signal up to what’s called line level so it’s powerful enough for audio equipment like a mixing console or DAW to work with. Most audio interfaces have their own preamps for this exact purpose, and will also bring the analog signal into the digital domain by means of analog-to-digital conversion so your computer can read, store, and edit that recording.
So what are the most common types of microphones, and what makes them special? Here’s our rundown.
Perhaps the most recognizable and widely-used type of microphone is the trusty dynamic. These microphones employ a moving-coil transducer, which essentially acts like a loudspeaker in reverse. Incoming sound pressure causes a thin membrane called a diaphragm to vibrate. The diaphragm is attached to a coil of wire which also moves in relation to a magnet. The wire’s movement within the magnetic field generates a voltage we can use to measure the original sound!
Dynamics are known for being relatively cheap to manufacture, very hard to break, and able to withstand high sound pressure levels without distortion. This makes them perfect for touring and live performances with a variety of sound sources. However, that rugged, jack-of-all-trades nature comes at a cost – low sensitivity and frequency response make it harder for a dynamic microphone to pick up finer sonic details when compared to other models.
Condensers are another common type of microphone, and are especially popular when it comes to recording music. The transducer inside of a condenser has an especially thin diaphragm that moves in relation to a metallic back plate. Because this backplate is electrically charged, incoming sound waves will cause the distance between it and the diaphragm to change and generate a signal we can measure.
The high sensitivity and more detailed frequency response of condenser microphones make them great for recording pretty much any sound at high quality. The transducer can be really small as well, which is why many headset or lavalier microphones are condensers. However, they do require a dedicated power source, sometimes in the form of phantom power straight from the device they’re recording into. Their more delicate construction also means condenser microphones are going to be more expensive, easier to damage, and harder to deal with in noisier environments.
Ribbon designs are among the earliest forms of microphone technology, having graced many classic radio broadcasts back in the day. The transducer consists of an incredibly thin ribbon of aluminum or other conductive material placed between the pole ends of a magnet, and any movement in that ribbon due to incoming sound waves will create a voltage.
As you might have already guessed, ribbon microphones need to be handled with even more care than condensers due to their fragile transducer component, which could break if dropped or subjected to high sound pressure levels. The advantage is that these microphones produce an unmistakable vintage sound that’s difficult to reproduce; the frequency response of some ribbons has been equated to our own human hearing. You can’t get much more natural than that.
Here’s a fun bonus: contact microphones! These transducers are unique in that they don’t actually pick up sound from the air, but rather focus on the vibrations coming from physical objects. They function through piezoelectricity, in which mechanical vibrations applied to certain solid materials will actually build up an electric charge. This means you can attach a contact microphone directly to a musical instrument or other material and record its physical vibrations rather than the sound waves it creates in the surrounding air. One example of this technology in music is the piezoelectric pickups you’ll sometimes find on hybrid acoustic-electric guitars.
What’s your favorite kind of microphone? Which do you think sounds best? Let us know in the comments!
August 10, 2020