Facebook social media iconTwitter social media iconYouTube social media iconSubmit to Reddit

The technology of the omnidirectional microphone

Some microphones are sensitive in all directions. How is this achieved? Is there such a thing as a truly omnidirectional mic?

Come on the FREE COURSE TOUR

Looking at directional characteristics from an academic standpoint, the omnidirectional microphone is sensitive to the pressure of the sound wave.

The diaphragm is completely enclosed, apart from a tiny slow-acting air-pressure equalizing vent, and the mic effectively compares the changing pressure of the outside air under the influence of the sound signal with the constant pressure within.

Pressure acts equally in all directions, therefore the mic is equally sensitive in all directions, in theory as we said.

In practice, at higher frequencies where the size of the mic starts to become significant in comparison with the wavelength, the diaphragm will be shielded from sound approaching from the rear and rearward HF response will drop.

So in fact, although a microphone may be described as omnidirectional, it will only be truly omnidirectional up to around 5 kHz, above which its directivity will become more focused.

Some microphones have a special attachment that can help randomize the directivity of incoming sound.

By David Mellor Wednesday April 30, 2003
Come on the FREE COURSE TOUR
Online courses from Audio Masterclass

Free Ebook - Equipping Your Home Recording Studio

Set up your home recording studio in the very best way possible. Learn how to select equipment and solftware all the way through from microphones to monitors. Learn more...

Welcome to Professional Audio

Come on the Audio Masterclass FREE COURSE TOUR. A short series of tutorials to welcome you to the challenging world of professional audio. Learn more...

How to Avoid These 4 Huge Mistakes In Audio

Are you making these 4 simple mistakes again and again in your home recording studio? They are easy to identify and avoid, so you don't have to. Learn more...