Your keyboard's clatter can reveal your e-mail's content! - Newindpress.com:
Next time when you are typing something secret on your computer keyboard, make sure no one is snooping around, as even if the person is not in sight, the very sound of your typing can reveal all the secrets of your confidential text, with researchers in America now claiming that eavesdroppers can decipher your messages just by listening to the sound of your keyboard.

Using a 10 dollar microphone, which needn't be placed in the same room as the typist, they are able to recreate up to 96 percent of what was typed. Our algorithms require no information about the typist, keyboard, room, or text typed," New Scientist quoted Tygar, as saying. The method relies on the 'tap' produced when your finger strikes the keyboard, as keys at the edges sound different to those in the centre. Every key makes an ever so slightly different noise. It's a very clever attack.

Thanks Ayan for the link.