Microphone directionality and polar patterns

Hi I am Chris Farrell from Western Australia. The following lesson is for week 1 of Introduction To Music Production at Coursera.

Today I will be teaching you about microphone directionality and polar patterns and how they affect what sound is recorded from different directions. A polar pattern is essentially a diagram showing a microphone's sensitivity in picking up sound from different directions, and some of the more common polar patterns include:

• cardioid (and variations including super or hyper cardioid): with this pattern, the microphone is most sensitive to sound coming from in front of the microphone
• bidirectional (also called figure 8): with this pattern the microphone is sensitive to sound coming from in front of and behind the microphone, but it will reject sound coming from the sides
• omnidirectional: with this pattern the microphone will pick up sound from all directions equally.

I have created three recordings using a budget condenser microphone, where during each recording I changed the polar pattern setting on the microphone. You will be able to hear how omnidirectional, figure 8 and super cardioid settings on my microphone affect how the sound is recorded from different directions.

Take a look at the diagram below to see how I set up the microphone in relation to a number of sound sources:

• I stood directly in front of the microphone to record my voice
• Directly behind the microphone I placed a metronome
• On the other side of the room away from the microphone I placed a radio playing some music

Omnidirectional pattern

For the first recording I set the microphone to use the omnidirectional pattern. Omnidirectional means from all directions, so recording with this pattern should pick up a lot of ambient sound from around the room.

Take a listen and make a mental note of what you hear. 

Hint: Turn up your volume level so that you can just hear the radio music playing in the background of this recording. This will help you as you analyse all the recordings.

In the recording, you can clearly hear music playing on the radio, the metronome, and my voice doesn't sound as focussed as it should. The recording also sounds noisy as it is picking up other noises such as my computer's fan. This is all because using an omnidirectional pattern the microphone is picking up sounds from all directions. For a voice recording it would be better if the microphone was more focussed on the direction of my voice.

Figure of 8 (bidirectional) pattern

For the next recording I set the microphone to use a Figure 8, or bidirectional, pattern. Recording with this pattern, the microphone should pick up the sound directly in front and behind the microphone.

Listen to the figure 8 recording and hear how it is different from the first recording.

In the recording with the Figure 8 pattern, the level of the ambient sound and noise is considerably lower, and the metronome and my voice can be heard more clearly. This is because with a Figure 8 pattern the microphone is more sensitive to picking up sounds directly in front of and behind the microphone, and rejecting sound from the sides. This voice recording sounds much better, however it could still be improved!

Supercardioid pattern

For the final recording I set the microphone to use a super cardioid pattern. Cardioid and super cardioid patterns are unidirectional, meaning they will be focussed on picking up sound from directly in front of the microphone. Super cardioid has a narrower pickup to the front of the microphone compared to a cardioid pattern, but will also pick up a little from behind.

Listen to the final recording and hear the difference from the previous recording.

In this final recording, the ambient sound is a little quieter, the level of the metronome has dropped, and the sound of my voice is more focussed. This is because the microphone is rejecting more sound from the sides and behind the microphone, and picking up sound from directly in front of the microphone better.

With this budget microphone set to a super cardioid pattern, I have managed to isolate the sound of my voice to a reasonable extent without using an isolation booth. You can hear that by using a cardioid or super cardioid pattern it is much easier to isolate sound sources based on their direction – and this applies to recording any sound source in the studio such as individual drum sounds, instruments and vocals. Recording with an omnidirectional pattern is useful to capture ambient sounds such as a busy street, or to capture various sound sources from multiple directions at the same time. A Figure 8 pattern is useful for recording two different sound sources at once, such as two vocalists or instruments - by picking up sound in front of and behind the microphone and rejecting sound to the sides.

Thanks for listening!

I'd love to hear your feedback of my recordings and descriptions, and please let me know if I could have explained anything better or if any of this information is incorrect. I've never recorded a band before, so also feel free to share your tips about using different polar patterns while recording drums, instruments and vocalists.

I haven't run any effects over the audio recordings as I wanted you to be able to hear how the omnidirectional recording has much more ambient noise than the others. In a studio recording situation you would normally try to isolate a vocalist better, and you could also look at applying noise reduction in an audio editor to clear up low level noise. As it is a budget microphone recorded through a budget preamp it would be noisier than more expensive microphones, and I made no attempt to dampen other background noises such as my computer. Oh, and I should have used a pop filter!