More than half the sounds in a wildlife documentary are artificially generated. Be prepared for a few surprises as Simon Fanshawe lifts the lid on some of the bizarre techniques used to mimic the noises of the natural world. Find out why created audio is often superior to the real thing and why a pillowcase full of cornflour and a pair of rubber gloves are essential props in the BBC Natural History Unit's dubbing theatre. Producer Alison Ayres