Hearing loss can vary in type ranging from conductive, mixed to sensorineural, as well as in degree from mild, moderate, severe to profound. There could also be multiple permutations and combinations like moderate mixed hearing loss or severe conductive hearing loss. In addition, the hearing loss could be unilateral or bilateral. While cochlear implants were devised for bilateral profound sensorineural hearing loss, various other devices have been invented for other types of hearing losses. Research continues to design a suitable implant which would amplify sound for patients who cannot be candidates for cochlear implants.