In the first Demystifying Microphones blog entry, we focused on two of the most common types of transducer principles of microphones: dynamic and condenser. In this blog, we’ll be learning about the various “polar patterns,” of microphones.
First of all, no; polar patterns have nothing to do with cold temperatures or the North/South Poles, so feel free to toss that idea out of your head right now. Polar patterns are simply directional measures of microphones’ sensitivity to sound. Not simple enough? Okay, let’s break it down some more.
It should be noted that the diagrams below are relative to the “address type,” of the microphone. Fortunately, those aren’t difficult to understand, as there are only two: side address and top address, which just mean microphones pick up sound from either the top or the side. Easy, right?
Anyway, as of now, there are 7 main types of polar patterns:
An omnidirectional microphone, as you might infer, is one that picks up sound from all directions (hence the prefix “omni”). Technically, such a thing is physically impossible because the microphone’s body itself gets in the way of sound pickup. Try picking one up and recording something with the capsule facing away from the sound source and you’ll hear what I mean. Regardless, the idea is that it picks up sound from all possible directions, which can be fantastic for recording natural ambiances for use in post-production or video games.
If you were to do a Google search on “subcardioid microphone,” (as of the date of this blog) you’d find one Audio-Technica microphone in particular (the AT808G) and a few separate microphone capsules. The idea with this polar pattern is to combine the advantages of both omnidirectional and cardioid patterns; specifically, a fuller low-frequency response but less “proximity effect” (which is just an increase in bass that occurs when the microphone is placed close to the sound source), and clearer, more accentuated side and rear sound pickup than a cardioid. The usefulness of this polar pattern is debatable due to its relative scarcity.
Cardioid, plain and simple, is the most common unidirectional microphone, and is named such because of its heart shape. This pattern is most common due to its rejection of sound reflections (or “reverberation,” or “echoes”). It serves to reduce feedback (which can be terrible if it gets out of control, believe me), and can be particularly useful for picking up a specific sound amidst noisy environments. However, they are susceptible to “plosives,” (popping wind sounds that occur with “P” and “B” words) and the aforementioned proximity effect. Despite its shortcomings, the pros of this polar pattern certainly outweigh the cons.
You know, it seems like whoever came up with the names for these polar patterns probably should’ve given it a bit more thought. Rather than having 5 variations (that I know of) of “cardioid,” it seems like these other patterns could’ve had more descriptive, or at least more creative names. Anyway, I digress. The “supercardioid,” is a slight variation of the cardioid pattern, as you can see in the diagram. It does well to capture direct sounds and it has a little lobe in the back to pickup more natural reflections; great in situations where you want a little more environmental sound in the mix.
Hypercardioid is pretty much the same thing as supercardioid, but with a slightly larger lobe in the back to capture a little more environmental sound.
Bi-Directional or Figure 8:
Now, we have the bi-directional – or Figure 8 – pattern. Microphones with this pattern pickup sound equally as well from either direction. Most often, you’ll find this pattern in ribbon microphones. You’ll usually see bi-directional microphones used in headsets and broadcast microphones due to their natural, uniform sound quality.
At last, we have the shotgun polar pattern. Unlike their ammunition-filled counterparts, microphones with this pattern are highly directional. Due to their slim frames, shotgun microphones are often used in film and theater in order to pick up sound while remaining relatively out of sight. Shotgun microphones have a unique design that has the pickup capsule located behind an interference tube with tiny slits on the sides. This interference tube significantly diminishes sound from the sides because of phase cancellation. In short, the longer the tube, the tighter the pattern, thus greater sound rejection from the sides and greater focus in the front.
So, that’s that! For now, at least… I hope you all enjoyed and learned something valuable from this.