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From a whisper to the roar of thunder, every sound creates vibrations in our ears which the brain decodes, to tell us what we’re hearing. But, as neurologist, Dr Guy Leschziner explains, when disruptions occur along the way, extraordinary things can happen, changing the way we perceive the world.

We meet Mark, whose hearing problems start in his forties. He can’t hear his friends in a noisy pub, but more disturbingly, the sound of every bodily function is amplified in his head. He even hears the squelch of his eyeballs moving. After years of misery, he’s diagnosed with superior canal dehiscence syndrome, caused by a tiny hole in his inner ear. Illustrating how even the smallest defect can cause big problems.

Kelly is in her twenties when she gets spinning attacks that send her falling to the floor. The sensation, like being on a child’s roundabout, lasts for hours. With every attack, she loses hearing. She’s told it’s Meniere’s disease, an inner ear disorder that affects balance - demonstrating its intimate link with our sense of hearing.

Keen bird-watcher Bill recognises his hearing loss when he can no longer pick out the call of the smallest birds. But Bill has another problem: he can hear elaborate musical tunes, when there’s nothing playing. These musical hallucinations are created by his brain, to compensate for what his ears can’t hear any more.

We rely on our brains and nervous systems to tell us the truth about the world around us – but they can deceive us. These astonishing cases show how tiny changes in our bodies can turn our understanding of the world upside down, leading us to question our own version of reality.

Presenter: Dr Guy Leschziner
Producer: Sally Abrahams