An information processing device 10 according to an embodiment includes an acquiring unit 111 that acquires information concerning sound propagating in a space separated from an outside world by a support member that separates the space including an eardrum of a user and the outside world, a measuring unit 1121 that measures a sealing degree of the space by the support member based on the information concerning the sound acquired by the acquiring unit 111, and a determining unit 1122 that determines, based on sealing degrees measured by the measuring unit 1121 for a respective different plurality of support members, an optimum support member for the user out of a plurality of support members.