Advanced Bionics, a former Alfred Mann company that makes advanced hearing systems, is launching a voluntary recall of its latest cochlear implant, the HiRes 90K, and is retrieving all unimplanted devices.

The Valencia company said late Tuesday it has informed the Food & Drug Administration of two confirmed instances where malfunctioning required removal of the device. These patients experienced severe pain, overly loud sounds or shocking sensations roughly 8 to 10 days after the device was implanted and activated.

Advanced Bionics, which Mann sold to Swiss hearing aid maker Sonova Holding AG last year, said it is evaluating the root cause of the problem and is working closely with the FDA to address questions and concerns.

“The risk of any significant adverse medical events appears to be remote at present,” the company said in a statement.

A cochlear implant is an electronic device that allows many people with hearing loss to hear better. Unlike hearing aids, which amplify sound, cochlear implants bypass the damaged inner ear and send sound directly to the brain.