BTW - Wouldn’t it be a hoot if muons showed up on a particular detector as 1/f^2 noise ??

Nigel, Since you noticed the fit initially, were you looking for it based on phenomena from another field ? I see from Alan’s posting that the context is no mystery – except to someone who was not paying attention to every detail of an excellent presentation <g> However, I think Nigel is looking for deeper significance. Universal theories of pink noise are incomplete. According to Wiki, the Tweedie hypothesis has been proposed to explain the genesis of pink noise on the basis of a mathematical convergence theorem related to statistical analysis in many systems, yet … this signal is not pink noise per se. In general the spectrum of pink noise is 1/f for what are said to be one-dimensional signals. Perhaps two-dimensional signals have a weaker power spectrum which is the reciprocal of f^2 ? At any rate, pink noise would be an obvious place to start a search for statistical significance.