GarageYears
As one who spends his life creating sound simulations for all classes of aircraft (at the highest fidelity Level D for commercial aircraft and equivalently for military sims), I find it almost impossible to believe that anyone could believe such ice shedding would be audible - the location of the pitot tubes themselves and, above all else, the small quantity of ice involved (due to the physical size of the tube) makes this claim extremely unlikely.
As it stands, for the many simulators I have been involved in, ice shedding from propellers, with the ice being flung from the blades and hitting the cabin sides, is about the only sound cue related to icing that I believe might be audible to any cockpit crew.
Totally accept the thrust of your point, but think that there is another source of ice-related sounds.
I dimly remember claims made in the original AF447 thread of hearing ice on the windscreen. Cannot find those posts, but this later one captures the idea.
http://www.pprune.org/6538743-post1871.html
EMIT
I have seen the TAT anomaly (TAT probe icing due to high ice crystal content) when flying through "light green" radar returns in the neighbourhood of CB's, in other words, while avoiding CB's. Turbulence then was only light, occasionally moderate, nothing out of the ordinary. Saint Elmo's and a sound like rain on the windscreen were also present.
To summarise:
a) The claim about hearing ice shedding from the pitots sounds like b/s. [Or a journalistic misunderstanding.]
b) Hearing ice shedding from elsewhere is highly unlikely. [You are the expert.]
c) In de-briefings several pilots have reported hearing something (later identified as ice-crystals) hitting the windscreen prior to a high-altitude "anomaly". So it may well have happened on AF447. [IIRC it is often reported as quite a distinctive sound.]