Cindy, 14, broke the rules at a friend's house. The punishment changed her life forever.

When Cindy Redmond answered a phone call at a friend’s house, her life changed forever.

Sitting at the kitchen table at a friend’s family dinner, Cindy was punished by her friend’s stepfather for talking on the phone during dinner.

When Cindy didn’t hang up the phone, her friend’s stepfather blasted Cindy in the face with an air horn.

The cruel punishment changed her life forever.

Immediately after being punished with the air horn, Cindy felt a horrific pop in her head.

And ever since, the pain hasn’t left.

The day after the family dinner, Cindy went home from school early. She felt ill and her peers and teacher’s voices seemed incredibly loud.

Now, the pain is so intense that the 14-year-old, who lives in Delaware, can no longer attend school at all.

"It felt like a giant pop in my head and ears, and from then on my ears hurt like someone was stabbing me or I'm getting burned," Cindy told the Daily Mail.

After the air horn incident, the young girl was diagnosed with hyperacusis – a rare hearing disorder.

The condition has left Cindy with a permanent feeling of pain and pressure in her ears that "feels like someone is stabbing me in my ears", meaning the 14-year-old is forced to be home-schooled and even miss family functions and parties as the noise is too much to handle.

While simple sounds like ice clinking in a glass or the sound of voices on the TV create a pain level of six, it can take Cindy up to two or three days to recover from the pain caused by being exposed to prolonged noise or high-pitched sounds.

"Having hyperacusis is like walking into a bear's cave," Cindy told People. "You don't know what noise is coming your way next. It's a living nightmare."

To cope with the pain, Cindy often wears earplugs and earmuffs.

But with Cindy's condition invisible to the eye, she has often been bullied by others who do not believe in her condition.

On one day while visiting a group of friends, Cindy was left in severe pain when one of the girls squealed.

"Cindy started sobbing from the pain," Cindy's mum Laurie told People.

"Her friends insisted she was faking her injury, or her face would have turned more red," she added.

"I hear these stories over and over. She cries herself to sleep. My heart breaks for her."

At this point, the man who blew the air horn in Cindy's face has not apologised for his life-altering actions.

Cindy and her mother Laurie have tried to find forgiveness towards the man and have chosen not to take out legal action.

Hyperacusis is a relatively rare condition.

The condition, which is commonly caused by damage to the nerves in the ear, leads sufferers to become extremely sensitive to everyday sounds.