PICTURES: Yamaha records its rivals.

These exclusive pictures (top and middle), taken by Toby Moody, show a Yamaha engineer recording acoustic data from rival machines on the Qatar pit wall, during this morning's final free practice session.

The technique is commonly used in Formula One and works by analysing the sound waves produced by a passing machine to calculate such information as revs per minute, gear changes and cylinder firing pattern (particular significant for big bang engines).

Further information on the strengths and weaknesses of each rival machine can then be found be matching up the speed trap data for each bike - as recorded at the entry into turn one at Qatar and provided by Dorna throughout the pit lane - to the acoustic data recorded.

An example of what can be found is shown in the lower picture, which is of audio waves from a 2005 Virgin Yamaha BSB spec R1, fitted with a 'big bang' engine. The recording was made in pit lane.

The three peaks indicate that the engine was firing one cylinder on its own, then two cylinders together (hence the bigger middle peak), then the fourth cylinder on its own. All three pulses were grouped closely together before the cycle was completed by a long 'gap', during which the tyre can recover.

Since each four-stroke engine cycle takes 720-degrees of crank rotation, it can be seen that the second (biggest) firing pulse was 180-degrees after the first and the third pulse a further 180-degrees after the second. The 'rest' duration was then for 360-degrees before the cycle began again.