Self Noise in Dynamic Microphones

[jamesadrian]

The diaphragm in a dynamic microphone moves a wire coil in the presence of a magnet to induce a current related to the movement. Other types of microphones, like electret and condenser microphones have self noise - noise not attributable to the amplifier. I wonder if all of the "self noise" that supposedly comes from a dynamic microphone is really just the electromagnetic background of the environment. The electrical noise do to the current in the wire is ridiculously little and so is the mechanical noise from the diaphragm.

So here is my question: Is there any noise attributable to the permanent magnet? I can't imagine that there is, but any news would be greatly appreciated.

Thank you for your help.

James Adrian

 

[marcusl]

It's probably Johnson noise arising from the resistance of the coil.

 

[Bobbywhy]

My guess is that the self-noise is NOT due to the permanent magnet. After all, just sitting there the magnetic field is completely static.

I found this: http://bartus.org/akustyk/noise_testing.php

It may contain answers for you.