DIAGNOSIS A coffee ground or mineral scale fragment is jammed in the precision brewer's spray head or pump. The noise is the pump struggling against the blockage.
FIX Immediately cancel the brew cycle and unplug the machine. Let it cool. Remove the brew basket and the stainless steel shower head (twist counter-clockwise to unlock). Inspect the small holes in the shower head and the opening in the machine. Use a toothpick or pin to clear any debris. Rinse all parts. Run a water-only brew cycle (no basket) to flush the system. The noise should stop.
IF THAT DIDN'T WORK Hard water scale has built up inside the internal tubing. You need to descale. Mix equal parts white vinegar and water in the reservoir. Run a full brew cycle into the carafe, then discard. Follow with 2-3 cycles of clean water to rinse.
HEADS UP Always use the coarse grind setting for this machine. Fine espresso grinds will clog the system every time. Never run it without the shower head installed.