Carpeting and other floor coverings help block the passage of sound to rooms below. Noise in a room may be reduced by carpeting, draperies, and upholstered furniture, all of which absorb sound. For additional sound absorption, acoustical tiles may be installed on the ceilings and walls. These tiles have tiny holes that trap sound and prevent it from bouncing back into the room. In industry, insulation against sound reduces noise in factories and in machines used at construction sites.
Some factories have sound barriers between the workers and the machines.
In others, sound-absorption materials are moulded to the machines to lower their noise level. Insulation is also used to reduce noise in such construction machines as air compressors and pneumatic drills.