Whether it's someone biting their nails, rustling a crisp bag, or scraping a knife on a dinner plate, some everyday sounds have the power to make us angry or upset.
The only sounds were the soft whisper of the breeze as it blew through the long grasses, still green in the early spring, and the distant thunder of the water cascading over Victoria Falls into the frothy pools below.
But when they looked like trees, it was like strangely human trees, and when they looked like people, it was like strangely branchy and leafy people, and all the time that queer lilting, rustling, cool, merry noise.
There was a sudden rummaging for quills and parchment. Over the noise, Snape said, " And a point will be taken from Gryffindor House for your cheek, Potter."
The breaking of a twig echoed loudly and the tiniest rustle of movement, even though it might have been made by an innocent sparrow, caused Harry to peer through the gloom for a culprit.
10 times more powerful than this at 20 decibels is the rustling of leaves in the wind, and then 10 times more powerful than that at 30 decibels is a whisper.