By Kendal Rasnake
Oh No, I Can’t Use AI Voiceover!
While a lot of our narration may be produced by AI nowadays, there are times when you need to record audio, such as when you need someone in-house to do a voiceover, or you are recording an interview, job shadow video, demonstration video, etc. Now, the responsibility of recording high-quality audio falls on you.
Well, all you have to do is grab a mic and point, right? Wrong!
The last thing you need is to record the CEO and have him/her sound horrible or look ridiculous because they are holding a fuzzy mic on a long wire up to their mouth. Instead, just learn a little about mics and you can purchase and/or choose the right one.
All Mics Are Not Built Equally
I had someone who was having audio trouble tell me that they used a “Brand Name” mic before and it sounded good, so maybe they would go back to using a “Brand Name” mic. As you can imagine, choosing a mic for a certain purpose based on the brand name is equivalent to choosing a Chevy mini-hybrid car to tow an RV because your truck used to tow the RV well and it was a Chevy. Brands make different types of microphones and understanding how mics are built can help you to choose the right one, no matter the brand.
Mics basically follow three different types of construction:
1. Dynamic
- Do not typically “color,” or alter, the sound but will give more of an accurate representation of the original sound
- Works automatically with a mic cable and needs no external power
- Rugged and less susceptible to damage
2. Ribbon
- “Colors” the sound warmer, with an emphasis on lower frequencies (bass)
- Usually does not require external power
- Fragile and more susceptible to damage (Stop blowing or tapping on a mic to see if it’s on!)
3. Condenser
- “Colors” the sound as more airy and open, with an emphasis on higher frequencies (treble)
- Usually requires a power source (batteries or “phantom power” received through the mic cable of the recording device (indicated as +48V))
- More fragile and delicate than dynamic mics
Mics Have Polar Patterns
No, mics do not affect global weather, but their polar patterns affect which sounds they will receive well. Microphones are designed to accept or reject sounds coming from different directions. For example, a good mic to record an interview or on-set dialogue from an actor will accept sounds coming from the direction of the actor, but reject sounds from other directions, such as crew noise or traffic noise. Polar patterns deal with the “directional” capability of a mic.
There are several different polar patterns of which you should be aware:
Omnidirectional: Receives sound from all around
Bidirectional or Figure 8: This pattern receives sound from the front and back and rejects it from the sides.
Cardioid: “Cardio” means “heart” and the shape of this pattern is like an upside-down heart. This pattern receives well from about a 180-degree range in the front and rejects sound from the rear.
Hypercardioid: This is not a medical condition, but rather a pattern that receives sound from the front in an even narrower range than the cardioid and rejects more sound from everywhere else. Notice that the sides in the front are pulled in more than the cardioid, making it more directional.
Also, be aware that some mics have the capability to transform. They won’t turn into a cool robot, but they can change their polar patterns with the flick of a switch.
Frequency Response
As alluded to before, the frequency of the soundwave affects how we perceive the sound. Soundwaves that go by more rapidly and are more frequent are perceived as a higher pitch. (Mariah Carey has really rapid soundwaves!) Soundwaves that go by less frequently are perceived as a lower pitch. (Think Barry White talking romantically to his sweetheart!)
Not only do mics not respond to the directions of soundwaves equally but, you guessed it, they do not respond to frequencies equally either. One mic may record mid-range and high frequencies well, but not record low frequencies well. Another mic may record most frequencies equally in what is called a flat response.
Manufacturers will often list specifications of their microphones on their website, including an image of the polar pattern and a graph of the frequency response of their microphones. You can use their websites to find out about a mic you already own or to research a microphone more thoroughly before you purchase.
Frequency is measured in Hertz (Hz). So, 1,000 soundwaves going by equals 1 kilohertz, or 1 kHz. So, as you look at the frequency response graphs, you can see that lower numbers on the hertz range equal lower-pitched sounds, and higher numbers on the hertz range equal higher-pitched sounds. And just so you know, most human speech falls in the 2 kHz to 6 kHz range. So, if you need a mic that will mostly be for recording voiceovers, it needs to accept sound well in this range.
This microphone’s frequency response graph shows that it will emphasize the mid-range and some of the higher frequencies, making it a good microphone for vocal recording.
Make a Smart Choice
Now that you understand more about mics, you should already be able to put your knowledge into practice into choosing a mic for various scenarios.
- I need to record an SME (subject matter expert) describing his job in a noisy factory: dynamic or condenser mic with a cardioid or hypercardioid polar pattern
- I need a voiceover in a recording studio to sound warm and inviting: ribbon mic with cardioid polar pattern
- I need to record a table conversation between two people for a podcast: dynamic or ribbon with bi-directional polar pattern
What If I Can’t Choose the Best Mic
If you can’t choose the perfect mic, then learn about the characteristics of the mic(s) you do have and work with it/them. For example, if you have an omnidirectional mic and you have to record an interview with a SME in a noisy factory, then try putting the mic in an open box and pointing it at the subject, using the cardboard sides to block sound from other areas. The point is, you have learned about your microphone and its characteristics and you are working with it, rather than coming back from the factory and learning too late that your audio sounds bad.
In sum, check your mic before you wreck your project!
Image credits: Top image: Jacob Wackerhauser
All polar pattern images published under CC Attribution-Share Alike 3.0 by Galak76
