Let's say I had a mic on a gooseneck on a podium, and the PA was blaring and very loud.

The gooseneck is pretty much bolted to the floor.

There is usually a huge feedback ring around 250-300.

Could this theoretically be caused by a sympathetic vibration from the floor of the stage as well as the neck of the gooseneck?

How would one go about isolating a gooseneck such as a podium mic from the floor or any other surface which might be rumbling?

Thanks in advance for your help.