I have a dishwasher that when new was very quiet - now when the DW is running is makes noises that appear to be related to when it is pumping water out… I am not sure. the noises cycle on and off. This was one of the Stainless Steel DW’s that was in the $600 price range… so we (probably falsely) believed it was a better unit. It is so loud that we have to turn up the TV in the living room to hear over it.
We also live in a area with extremely hard water… as a side note.
A model number may help others help you.
Has the unit done this from day one?
It could be a problem with the drain pump.
If you feel it is related to the hard water start a hot/heated cycle.
Let it get to the second wash as this is usually the longer cycle.
Then open the door and add a quart of vinegar.
Let it run for a couple minutes then stop it and let it sit for 15 minutes.
Then let it run for a couple minutes and stop and wait again.
Do this several times and then let it go to the drain cycle.
Let it start to drain and then again open the door and let it sit for half an hour.
Then let it complete the cycle.
With luck this will dissolve/loosen any deposits in the main pump and drain pump.