Gaunty ... you know me too well, mate.
Absolutely fascinating stuff ...
Is this phenomenon, by any chance, related in any way to that which I observed (as a young hoon .. weren't we all ?) in my then vehicular pride and joy, a Morris 1000. Coasting downhill, I observed that, by turning the ignition to "off", singing a brief refrain of "God Save the Queen", and then selecting the ignition to "on", a loud report was heard to occur at the rear of the vehicle (music to a young hoon's ear .. other young hoons who could afford decent cars would, no doubt, find alternative measures of automotive delight).
Quite sadly, after a pleasing number of repetitions, I found that I couldn't hear the desirable loud report above the ambient exhaust note as effectively as before ... after 99.99% of the exhaust system disengaged itself from the vehicle during one such repetition ....