Airline pilots and flight attendants, working in the cockpit and cabin, are exposed to noise from aircraft engines, high-speed airflow, and other sources. Exposure to elevated noise levels can cause permanent changes in hearing, diminished ability to communicate, and fatigue. GAO ( US Goverment Accountability Office) was asked to provide information on noise levels experienced by crewmembers working in commercial service aircraft and their access to hearing protection. This report examines: (1) what is known about aircraft cabin and cockpit noise levels compared with occupational noise exposure standards and (2) selected airlines’ policies on hearing protection for crewmembers. GAO reviewed OSHA’s occupational noise exposure standard, NIOSH’s recommended occupational noise exposure limit, and regulations and guidance from FAA, as well as other sources.