20180606 Rough data is good enough to decide if there is suspicion.

Wednesday, 6 June, 2018 – 05:40

Late yesterday, I posted to LinkedIn a message about the way sound travels around the concrete canyons in Kuala Lumpur. I had tried to work out the location that a sound originated from but had fallen into helpless giggles when I realised that I could only calculate the position of the source if I had the location of the source. That, of course, was a circular argument and of no value to anyone.

Why, one might ask, would anyone bother?

In my case, it’s partly that I really hate not knowing stuff once I’m interested in it. The second is this: when we are dealing with suspicion, we are dealing with imprecise data. We have facts but the conclusion we reach is an opinion based upon our own subjective (i.e. personal) interpretation of those facts.

Here, with the answer to the puzzle which woke me after two hours sleep and refused to let me go back to bed until I’d documented it, is how and why this is important in financial crime risk management.

Here’s what I posted on LinkedIn:

“Sitting at my desk, a bus (or similar) horn was blown on one side of my flat and came from my right. About a second later (don’t ask how I know that, I just do) its echo reached me, via buildings, from my left. So, given that sound travels about 330 metres at sea level in dry air conditions (it’s humid here so sound travels slightly faster but then again, it has to climb 36 floors to get to my windows so we’ll assume the two cancel each other out), the vehicle must have been about .. well, that’s the thing. The distance from me, sitting in my chair, cannot be calculated.

There are so many tall buildings around, all facing slightly different directions that there

a) isn’t a “clean” echo and

b) it’s impossible to tell which building the dominant echo came from. All I can say is the distance from bus-building-me is, roughly 330 metres and it still made enough noise, twice, to distract me. Oh, well, it was interesting to try to work it out.

Why did I have so much trouble with the equation in the first place?