Tea-kittle-whistle-sound

mechanism which gives you a tone when you blow over an empty bottle.”

When air is blown over the open neck of a bottle, the Helmholtz resonator mechanism causes sound to radiate from the neck. The air just inside the neck is bouncing up and down – the air in the main body of the bottle being compressed and released each time like a spring.

For the kettle, the spring is the air inside the whistle, while the air within the whistle opening reverberates like the air in the neck of a bottle. “In a kettle, of course, the air is blown through, rather than over, the neck – the effect is similar to whistling by mouth,” Henrywood added. “In some kettles, both these mechanisms are happening. Because our study enables us to assess the mechanisms in action, we can potentially make modifications to stop the noise – if we want to.”

Henrywood and Agarwal are now working on a project to make quieter high-speed hand-dryers, by looking at how the jet of air released by these devices creates noise. Their paper on kettles - The Aeroacoustics Of A Steam Kettle – can be found in the October issue of The Physics Of Fluids.