I plug the power supply in, and there is no noise. I then move the motors and when they come to a stop, there is a low hissing sound coming from them. There is also a high pitch sound. I have checked the pots and they are all inbetween .7v and .8v. I turn them down to .2v and that is where the noise stops, but the motors are too weak at this point to move anything. I have the DRV8825 drivers with 3 jumpers under each of them. I am using the stepper motors linked in the parts page, https://www.amazon.com/Stepper-Motor-Bipolar-4-lead-Printer/dp/B00QEYADRQ/ref=as_li_ss_tl?ie=UTF8&qid=1436660578&sr=8-11&keywords=nema+17&linkCode=sl1&tag=vicicn-20&linkId=088cc788be292ba77982af769398a4a6.
Noise is fine, they are energized, some steppers and drivers are noisier than others. The import stuff seems to be getting worse though so I stopped carrying them for that reason.
Check out my other recent postings. tl;dr: don’t care about it.