Snicko uncertainty (or why Ross Taylor got away with it)

As I write this, Joe Root is firmly entrenched at Seddon Park and is moving steadily on towards another double-hundred. I was there on Saturday, and can report that the pitch is as flat as an optical bench, and even I fancy my chances of getting three figures against any bowling attack on this surface.

One clear frustration for the England bowlers on Saturday, as BJ Watling looked good for another massive score, was their lack of remaining reviews. Root’s record in the NZ innings was 2 reviews, 2 failures. On the other hand, NZ were successful with both the reviews they had in their innings, thus keeping a full complement in stock. NZ appeared to be lucky though – Ross Taylor’s review after being given out lbw to Stuart Broad proved a bit controversial. He was adjudged to have got the very finest of edges on the ball before it thudded into his pad, thus saving him from certain dismissal. This was despite the Decision Review System seemingly showing the ‘sound’ of the bat on ball, as shown on ‘Snicko‘, not time-aligned with the video imagery.

But here we have to be careful. It’s never going to be straightforward to align the sound as picked up by the stump microphone (as shown graphically on, basically, an oscilloscope trace) with the video. That’s down to the finite speed of sound. At 330 m/s or so, it’s only about 8 or 9 times quicker than the ball, and so certainly cannot be considered infinite. To put this in context, the popping crease is 1.22 m (4 feet) in front of the stumps and so sound takes about 3.7 milliseconds to cover this distance. If the frame rate of the video is 330 frames per second* (or about 3 milliseconds per frame) then there’s an entire frame of video difference between the sound of the ball hitting the bat at 4 feet from the stumps and the video imagery of the same event.

Now, presumably, this approximately one-frame delay is taken into account. But there’s an obvious issue – the bat isn’t always the same distance from the stumps when the ball hits it. One might imaging about a metre worth of ambiguity, depending on whether the batsman has played forward or back. And a metre in terms of sound delay corresponds to a frame or so. One might imagine that more sophisticated corrections could be done based on how far forward or backward the batsman has moved, but it could be tricky.  So I am not surprised that the microphone trace (‘snicko’) doesn’t quite align with the video imagery. Clearly the third umpires know this too. DRS, in my opinion, is a great step forward, and allows awful decisions to be overturned, but it’s never going to be without its problems.

And there’s Root’s double hundred. Another 136 and he’ll annoy David Warner, and not for the first time this year…


*Actually I am struggling to find a definitive value for this – anyone know it?



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