A heartwarming video has emerged from the US of a one-year-old hearing her mother's voice clearly after getting a cochlear implant.

The footage, captured on April 24, shows Annabelle Lawless - who was born with profound hearing loss - crying as her cochlear implant is turned on for the first time.

Annabelle could hear her mother’s voice for the first time last summer thanks to a hearing aids. But the device was limited: she couldn’t hear speech clearly and it wouldn’t be permanent.

Finally, on April 24, they implanted a hearing device into her cochlear.

''I am completely amazed at how well she is doing. She leaves it on her head and seems to understand that leaving it alone will make her be able to hear,'' Annabelle's mother later wrote online.

''She's normally a baby that pulls everything off.. shoes, socks, hats. She doesn't leave anything alone. But since we've had the external part of the cochlear implant on her she hasn't been trying to take it off. I guess she loves to hear.''

''She's been really happy, social, and excited. She sleeps longer during naptime and at night because this new ability of hearing well has her brain worn out I believe,'' she added.