wrt destruction being the only way to remove a pea from a whistle, I'm not sure that's true, although my evidence is ~40 years old. As a child I had a whistle that lost its pea. I don't remember how, but having 5 brothers probably had something to do with it (the superior force of nature that is 5 brothers can often overcome any design or engineered strength of structure). Without its pea, it was no whistle no more. I remember getting particularly steamed at brother Dan about this, and he hit me on the elbow with his metal kazoo, causing much bleeding and my second biggest scar at the time. Which endeared me to my 8 year old neighbor Molly (not her real name), who thought I was the bravest 8 year old ever, for about a week.

Why am I thinking this post is less about whistle testing than personal remembrances of a cute girl named molly?

But in any case - why an experiment about the function of frozen pea whistle when pea-less whistles are just as functional? I like the experiments that show the decibels generated don't actually carry very far in forested environments - that made me re-think what to tell my kids about blowing whistles until help came.