** In the past few weeks, our Kithchenaid dishwasher has made more noise than normal. Part of this is in the pipes when the dishwasher is filling ... Could air in the pipes be causing the problems? **
That may be a possibility as well as the tap for the dishwasher's water supply or the dishwasher's water fill valve partially plugged with lime and scale, etc. Those would likely just be a coincidence and only noticeable when the dishwasher was filling.
You can read about the water valves used on appliances at the following link:
** part of it is localized within the dishwasher itself when the machine is not filling. **
During both washing and draining or just one or the other?
** There are no clogged drains, no foreign materials within the dishwasher compartment that I can find. **
Something in the drain system would likely only create noise during the drain cycle. If something has gotten into the pump, at least some disassembly of the unit would likely be required to see it. That could create noise both during the wash and drain cycles.