A snickometer or a snicko is a piece of useful technology that plays the video side-by-side with a graphical representation of sound as the ball passes the batsman.  Invented by an Englishman Allan Plaskett in the 1990s, it was later developed for use in cricket matches by BBG Sports. 

The Snickometer displays the audio from the stumps microphone in a visible wave format.  If there is a sound of leather on willow, which is usually a short sharp sound as the ball passes the bat, then the ball has touched the bat. Other sounds such as the ball hitting the batsman's pads, or the bat hitting the pitch, have a fatter shape on the graph.

The snickometer is controversial because it has showed many umpiring decisions as incorrect.  The umpire often has no access to this kind of technology and must use his own judgement.  In the Border Gavaskar Trophy during the 2007-08 series in Sydney, at the SCG. Andrew Symonds was given not out, even though snickometer showed an obvious snick. Umpire Steve Bucknor came under fire with a series of other blunders which led Australia to a historic 16th straight test victory under Ricky Ponting, the captain of the Australian Test side.

No noise

No contact made here ..... and no problem for the umpire with this 'not out' decision.

'Short' noise

The sharp peak on the graph gives the game away here, and it's curtains for the batsman as long as the 'nick' is safely caught by the waiting keeper and slips cordon.

Courtesy: Channel 4