The warranty is 2 years, most nano stream noise issues stem from one of the following problems:
Broken or pulled out metal shaft, the metal shaft is fixed in the pump and not replaceable, it should never come out. The earliest pumps from 2006-mid 2007 used a lower grade of stainless steel that could break, after mid 2007 we switched to a German made 316TI alloy. In those later pumps, the shaft could pull out if calcium cemented the drive unit to the shaft.
Broken or worn out drive unit and disk, over time, especially with on and off cycling the prop will fit loose on the magnet and begin to slip and rattle. Replacing these parts will solve it.
Bent shaft, check that the shaft is not bent such that the drive unit rubs against the side of the pump, this can usually be carefully bent back to give a more even gap.
Even out of warranty I would work with you to get it replaced at a reasonable price. I head to Germany tomorrow however and from the 28th- 9th no repairs will be done, I can however arrange to have spare parts shipped. I will be back online on the 1st.