The girls labored twelve hours straight at Boott’s looms, and the noise was so great that if an accident happened—if a girl lost an arm in the carding machine, for example—no one could hear her scream. To cope with this and other problems, the workers evolved a sign language to communicate over the din of looms. When at last the machinery was switched off at the end of the workday, a guide says, the relative silence was so unnerving that some of the new girls started to scream, from shock instead of pain this time, and could not stop.

George Michelsen Foy, Zero Decibels, loc. 157