PPE for hearing protection consists of earplugs and earmuffs, also known as ear defenders. Workers who are regularly exposed to high noise levels should be furnished hearing protection by the employers, as they are a low-cost intervention. Ear defenders protect the wearer from extreme noises. The head-band and outer covering is usually made from a hard thermoplastic or metal. The protection comes from acoustic foam, this absorbs sound waves by increasing air resistance, thus reducing the amplitude of the waves. The energy is transformed into heat. An earplug is a device that is meant to be inserted in the ear canal to protect the user's ears from loud noises.