I am wondering what methods are normally employed to quietly reduce water flow through lines?

My application is a water souce heatpump (open loop) which I have installed. Now I need to get the bugs out.

The specifics of the problem are: The system is an open loop system, pumping water from one well, into a return well. To minimize mineral deposits, the water going through the heat exchanger is kept under pressure, and flow reduction is done prior to returning water to the return well.

sourcewell -> filter -> heat exchanger -> flow activation motor (wax motor valve) -> flow limiting device -> returnwell

Initially, for debug, I used a 3/4" sweat ball valve. That was noisy. B&G has a flow control valve, which is essentially a calibrated ball valve, with about a 1/4" diameter. It's in a 3/4" brass fitting, which I sweated in place. It gives better flow, but and is less noisy than the 3/4" ball valve.

Other specifics: the water pressure from the source well is 50psi (constant pressure, inverter driven 3 phase well pump), and the desired flow rates are 5 to 9 GPM.

I'm thinking of putting a three piece union line, and machining it to insert a disc, with small holes in it. The real problem is how to do this with minimal noise.

Any ideas?