Violent shaking!

For no particular reason I remembered MR's version of [first name omitted] Downing's adventure is ripping one.

Picture this: the old stand alone high school chairs with the right arm slab on which to write. It's bare metal frame holds nearly any reasonable weight, but not dimensions. Downing was not the slimmest person, so fitting in was difficult anyway. Apparently he had to let one go, but rather than letting it squeak by naturally or quietly, he gripped the slab with both hands and shook it like a paint shaker. I'm not sure how this helped the escape of the gas, but it was funny to see. The sight alone was memorable, but the punctuating sound (s) were memorable too. Most people scooted away, of course. I believe MR tells us the sound was, "FWANHK!"

That would be a dusk with a balloon in its mouth, for imagry or understanding.