Proximity effect has nothing to do with property taxes or social distancing. It’s the natural increase of low frequency reproduction that occurs when a sound source gets very close to a directional microphone. Think of your favorite broadcaster’s deep, rich “radio voice”. In this article we’ll go over what causes proximity effect, the types of microphones and polar patterns that are affected, and whether proximity effect is good or bad.

Why Proximity Effect Happens

            Microphones use capsules with very thin diaphragms that react to different sound pressure levels, then converts that acoustic energy into an electrical signal. When a microphone’s diaphragm picks up sound from both the front and the back, it’s directional. Proximity effect is the cause of varying pressure differences between the front and rear of a microphone’s diaphragm. However, not every microphone works like this. Omnidirectional microphones only pick up sound using the front of the diaphragm, while the rear is fixed and doesn’t move. This does not produce a proximity effect since the front and rear of the diaphragm don’t interact in the same way.

How Proximity Effect Works

Distance of the sound source from the microphone is the driving force behind proximity effect. The increased amplitude (“signal strength”) of low frequencies at close distances gets over-exaggerated because microphone capsules are designed to dampen higher frequencies to offer a flatter response.

Different Polar Patterns 

Bi-directional or Figure-8 microphones (typically ribbons) pick up equally from the front and back of the capsule. Since proximity effect is directly related to the variation in pressure between the front and rear or the diaphragm, and bi-directional mics use both sides equally, it is most clearly represented in this pickup pattern.

The hypercardioid polar pattern mostly picks up from the front, but also picks up a good deal from the rear of the microphone. This variation of the cardioid pattern has the next most proximity effect compared to a bi-directional microphone, since the front and rear of the capsule interact together so much.

The supercardioid polar pattern picks up sound from the front and only a small amount from the rear, so it will still produce a proximity effect, but less than hypercardioid.

A regular cardioid polar pattern picks up from the front of the capsule but rejects sound from the rear. This pattern is still quite susceptible to the proximity effect, but less than all the previously mentioned pick up patterns.

How to Utilize Proximity Effect

You can strategically add more low end or “oomph” to a vocal by getting closer to the microphone. The same method could help beef up instruments with a lot of low frequency information, like a kick drum, bass cabinet or piano. Recordings with sparse arrangements could benefit from these methods to help fill out the mix.

On the other hand, if you’re dealing with recording many instruments and voices all in similar ranges, it’s best to avoid using the proximity effect to keep the low end more focused on actual sources of low frequencies, like the ones mentioned above. Reduce muddiness and get a more accurate and articulated capture by moving the microphone away from the sound source in small increments until you find the right balance of frequencies you’re after.

Written by: Dan Cohn