You may noticed that a number of USB microphones have a feature that enables you to change the ‘recording pattern’ (or ‘polar response’).
Often it is not understood how this feature can be used to achieve much higher quality sound recordings.
For instance, if you are a podcaster recording audio at your desk, you will probably find that a microphone with cardioid recording pattern will help ensure your record the sound pointing at it rather than the sound elsewhere in the room (like fan noise from your computer).
A polar pattern is simply the directionality of the microphone, ie what directions the microphone is most sensitive to sound.
Here is a short outline of the main types:
A microphone with this polar pattern will pick up sound from the front only. Which is why it is often referred to as uni-directional.
You can imagine the microphones sensitivity to sound like a torch beam from the front of the microphone.
This pattern is particularly useful when using your microphone an your desk for vocal podcast recording. If done correctly this pattern can help reduce the noise from sources other that the voice pointing at it.
As you might think from its name, an omni directional microphone picks up sound from all directions.
Not so good for recording podcasts, but this is a good pattern to use if you’re trying to capture a number of different instruments or sound sources in a room.
Super Cardioid and Hyper Cardioid
This type of polar pattern (heart shaped) is a highly directional. It has less response to sound at its sides than a straight cardioid.
A hyper-cardioid microphone is has even less response at its sides.
Again this is going to be a good choice if you are recording your voice and don’t want to pick up other noises, although there is a slight pickup from directly behind the mic.
The bi-directional or figure of eight pattern picks up from the front and back of the microphone, but will rejects sound from the sides.
Not so useful for the podcaster, but are a really good option when recording groups of musicians.
The bi-directional effect can be used to concentrate recording on particular groups of musicians while ignoring others that may be recorded with a separate mic.
Here is a video that gives some great audio and visual examples and explanations of microphone polar patterns.