You might need a supplemental hearing amplifier if you have any degree of hearing loss. Your degree of hearing loss – mild, moderate or severe -, as determined by the tests administered by your audiologist, is used to establish whether or not you need a hearing aid. The term degree of hearing loss can be translated to mean how loud sounds need to be before you hear them clearly. You have mild hearing loss if you can only hear sounds at 30dB, moderate if you only hear at 50dB and moderately severe if you only hear sound at 60dB. (Source)