Section 10.306 - Hearing requirements(a) If the medical practitioner conducting the general medical exam has concerns that an applicant's ability to hear may impact maritime safety, the examining medical practitioner must refer the applicant to an audiologist or other hearing specialist to conduct an audiometer test and a speech discrimination test, as appropriate.(b) The audiometer test must include testing at the following thresholds: 500 Hz; 1,000 Hz; 2,000 Hz; and 3,000 Hz. The frequency responses for each ear must be averaged to determine the measure of an applicant's hearing ability. Applicants must demonstrate an unaided threshold of 30 decibels or less in at least one ear.(c) The functional speech discrimination test must be carried out at a level of 65 decibels. For issuance of an original MMC or endorsement the applicant must demonstrate functional speech discrimination of at least 90 percent. For renewal or raise of grade, the applicant must demonstrate functional speech discrimination of at least 80 percent.(d)Hearing waivers. An applicant who is unable to meet the hearing standards of the audiometer test, but who can pass the functional speech discrimination test; or who requires hearing aids to meet the hearing standards, may be eligible for a medical waiver in accordance with § 10.303 of this subpart.(e)Hearing operational limitation. If hearing aids are required in order to meet the hearing standards above, a mariner may not serve under the authority of the endorsement unless hearing aids are worn in the operational mode, and spare batteries are carried onboard a vessel. This operational limitation will be placed on his or her medical certificate.