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 how we perceive the world.

Kelly gets spinning attacks that send her falling to the floor. The sensation lasts for hours and with every attack she loses hearing. She’s been told it’s Ménière's disease - an inner ear disorder that affects balance.

Keen bird-watcher Bill recognises his hearing loss when he can no longer pick out the call of the smallest birds, but can hear elaborate musical tunes when there’s nothing playing.

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.

Produced by Sally Abrahams for the BBC World Service.

Photo: Kelly, who has been diagnosed with Ménière's disease Credit: BBC