Why is it when velocity pressure is less than condenser static pressure you

[bwd111]

Get heat,noise and viberation?

[Grizzly]

It's related to the gas flow through the machine or at least the lack of it!
Also I am assuming you are describing a part loaded machine.
Running speed is also related.
Some manufacturers give the facility to block certain run speeds.
Mechanical gyro forces (Balanced!) have a part to play as well.

Your question is non specific and open ended.
Which means it's difficult to guess to what depth what you need the question answering ?
Grizzly

[RANGER1]

http://www.enggcyclopedia.com/2012/01/centrifugal-compressor-surge/

http://www.pipelineandgasjournal.com/protecting-centrifugal-compressor-surge

Assuming we are talking about surge in centrifugal compressors