Transcript for Baby girl hears sister for first time after not being able to hear since birth
America strong. The mother, the baby, and this moment. 11-month-old scarlet, on her mother's lap. Scarlet lost her hearing as a baby, medication damaging her inner ear. She's about to try hearing AIDS for the first time. Her big sister, right there in the room with her, about to say hello. Baby sister! Baby sister! Baby sister! Oh, my gosh. Reporter: That laughter, pure joy. Her mom, with her hand to hear heart, and it's her turn to say hello. Hi, baby. Hi! Reporter: A kiss from mom. Scarlet can hear her, too. You can hear me! I know! I know! Reporter: Mom overcome. And the family sending us this tonight. Hi, David. Hi, David! The benjamins here from Madison, Georgia. Carol, Haley and scarlet, smiling. People just take for granted the things that they think they're supposed to automatically have, and when you don't have it, it's -- it's just amazing that we can do things like this. Reporter: She's grateful to raise awareness about hearing loss and grateful her baby can hear again. The power of a baby's laugh. We are grateful, too. I'm David Muir. I hope to see you right back here tomorrow. Good night.
This transcript has been automatically generated and may not be 100% accurate.