Safeguarding coffee grinders from hidden stones with acoustics

Most coffee connoisseurs are familiar with the gentle hum of their favorite café’s grinder while they wait in eager anticipation of that aromatic first sip. But behind this everyday scene lies a surprisingly tricky problem. Coffee beans often come mixed with small stones—accidental stowaways from harvesting and processing. Nearly identical to beans in size, shape, and color, stones routinely evade even the most meticulous of inspections.