Ever wondered how whistles work? Depending on the type of whistle, there are a few different phenomena in play, but the most fundamental one is the oscillation of a fast-moving air stream. Any small deviation in the air stream can set up a situation where the flow shifts side-to-side, and most whistles use this oscillation to drive the sound they produce.
Many whistles direct the air flow onto a wedge-shape to strengthen the oscillation; then they have a cavity that amplifies the sound using resonance. Water whistles — which warble in a bird-like way — do the same thing, but the water inside them creates a shape-changing cavity, thereby changing the pitch to create an unsteady, warbling sound. You can see all these whistles and more deconstructed in Steve’s video. (Video and image credit: S. Mould)
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