A flashing blue light appears out of nowhere and with it a worn, wooden British police box, accompanied by a whirring, grinding sound not unlike a car ignition refusing to turn over. Except in reverse.
(In fact, the signature sound was created in the BBC Radiophonic Workshop by dragging a set of keys along the strings of a broken piano and cranking up the reverb. Stick that in your sonic screwdriver.)
http://www.toronto.com/article/682443?bn=1