Grayson Clamp made headlines for being the first U.S. child to receive an auditory brain stem implant. Image Credit: WBTV/ABC News

After being born severely hearing-impaired, Sarah Churman heard her first clear sound at age 29 and promptly burst into tears.

"I hear Melinda say, "How does it sound?" Churman wrote in her memoir, "Powered On," about the experience. "I start to answer her, and I realize I can hear the noises in my mouth. Then I realize how I sound. Then I get choked up. Then I laugh. Then that sends me into a fit of tears and choking up."

Churman received a new hearing implant called The Esteem at age 29. A video of her implants being turned on for the first time went viral in 2011.

Read More of Churman's Biography Here

With the spread of implanted hearing aids, including cochlear implants, videos of deaf people hearing for the first time have become a staple on such video sites as YouTube and Vimeo, garnering millions of views.

But what's really happening when people gain a new sense?

In the video shot by her husband, Churman lights up when she hears the noise for the first time and then quickly starts crying and laughing as she says, "This is weird."

In another memorable video, an infant responds to hearing his mother's voice for the first time by dropping his pacifier and looking at her in awe.

The most well-known hearing implants are cochlear implants, which help people hear by electronically simulating the auditory nerve. According to the American Speech-Language-Hearing Society, more than 30,000 people have used the cochlear implants.

Churman's Esteem implants, unlike cochlear implants, are completely implantable devices, which turn sounds into amplified vibrations sent to the inner ear.

Hearing implants are not a replacement for an ear, but they can help many people who were effectively declared deaf. By stimulating the auditory nerve, signals are transmitted to the brain, which turns into "hearing."

Dr. Daniel Lee, director of the Pediatric Ear, Hearing and Balance center at the Massachusetts Eye and Ear Infirmary, said many adults sometimes describe the sound from cochlear implants as metallic or robotic at first.

"[Usually you] are communicating through thousands of channels of information that are being sent to your brain," said Lee. "These implants have no more than 22 electrodes."

Lee said that the implants are key for many children or infants born with severe hearing loss who receive the devices so that they can grow up with auditory skills and have stronger language skills.

Doctors, however, have to be careful when exposing small children to sound for the first time. Since the children often do not have the means to communicate, doctors have to be very careful that the children have a positive experience and aren't frightened by their new sense.

Lee said the key is to keep the electronic data to a minimum in the beginning of using the implant.

"[You] don't want to overwhelm them," said Lee. "Over a period of days to weeks to months [the implant] is slowly ramped up to provide more information to the ear or the brain."

In videos usually a family member speaks to the child for the first time. In one memorable video an infant responds to hearing his mother's voice by dropping his pacifier and looking at her in awe.

While cochlear implants have significantly helped people who were previously profoundly deaf, they do not work for people who either lacked an auditory nerve or had a damaged nerve.

But new technology is now being used that sends messages directly to the brain itself. A Food and Drug Administration clinical trial currently underway is looking at the effectiveness of electrical implants placed directly on the brain stem.

Placed directly on the brain stem, it bypasses all auditory nerves.

Grayson Clamp made headlines earlier this week for becoming the first child in the U.S. to receive the procedure.

Lee, who is involved in the trials but not in Grayson's case, said that the auditory brain stem implants could be used to help deaf children communicate and develop lip reading skills. He said once children like Grayson are older, they can see how effective the devices are by evaluating their language skills.

Read More About Grayson's Surgery Here

But even before the implants can be measured and quantified, Grayson's immediate response delighted his father, Lee Clamp.

"It was phenomenal to see him take that sound in and try to figure out what in the world is this? I've never had this sensation before,'" said Clamp.