Cochlea a protein motor called prestin on their outer membranes; it generates additional movement that couples back to the fluid–membrane wave. This "active amplifier" is essential in the ear's ability to amplify weak sounds. The active amplifier also leads to the phenomenon of soundwave vibrations being emitted from the cochlea back into the ear canal through the middle ear (otoacoustic emissions). Otoacoustic emissions are due to a wave exiting the cochlea via the oval window, and propagating back through the middle ear to the eardrum, and out the ear canal, where it can be picked up by a microphone. Otoacoustic emissions
Jock Stirrup plans could be afforded over the coming years. The planning for the invasion of Iraq required new equipment and Stirrup became increasingly involved in planning for urgent operational requirements. A particular difficulty faced by Stirrup was the need to place equipment orders with industry before the Government was prepared to publicly commit to the action. Stirrup briefed ministers on this point but was prevented from placing the orders according to his desired timescale. In the end some critical items such as body armour, boots and desert clothing were not available to all the personnel who needed them when they deployed.