Products delivered under this specification are intended for use in high and moderate ambient noise level environments. These environments are areas where the ambient noise levels are between 105 dB SPL and 125 dB SPL (i.e., groundcrew and aircrew). All hearing-protective requirements in this document and its slash sheets (intelligibility, noise-attenuation, sensitivity) were developed by the Air Force agency having sole responsibility for the approval of such products intended for use by Air Force personnel (Air Force Materiel Command, Human Systems Center, Armstrong Laboratory, Biological Acoustics and Biocommunications division (AUCFB), Wright-Patterson Air Force Base, Ohio 45433, in cooperation with guidelines established by the United States Air Force Office of the Surgeon General). These field-reparable parts are repaired in accordance with Air Force Technical Order 12R2-2AIC-222CL-1, which is available from the Air Force Custodian upon request. Products are expected to be effectively used for a period not less than 4 years, including authorized maintenance and repair.