What is the principle of singing in a kettle when the water is boiling?

There is a disk inside the lid, and there are several reeds on the disk. There are several slits around the handle of the lid, and air can rush out of the slits after passing through the reeds. When water is boiled, it will produce a lot of steam. These high-pressure steam will pass through the reed in the pot cover and then rush out of the gap around the pot cover. Reed vibrates and makes sound when it passes by, so when the water boils, it sings.

Because the reed is fixed, no matter how much water is in the kettle, the tone of the kettle is the same after the water is boiled. In order to let the steam flow away as much as possible, there is also a cover at the spout to cover the spout when boiling water.

Extended data:

There are two basic principles of kettle singing: the first is similar to the principle of whistling, which uses high-speed air flow through a small gap to cause chaotic flow, so that the air in the cavity vibrates and sounds. The second, similar to the principle of harmonica sound, is that when blowing, turbulence is generated because the airflow hits the reed, thus producing marginal sound.

After the water is boiled, a large amount of steam gushes out, and there is a resonant cavity on the lid that can produce resonance. When water vapor passes through, it will resonate, similar to the sounding principle of harmonica or whistle, and it will make a sound. When the water is not boiled, because the amount of water vapor gushed out is too small, it will not resonate, and only when the water is boiled will the kettle sing.

The whistle is between 1000 and 2000 Hz, and almost everyone can hear it. Therefore, it is a safety measure for the kettle to chirp when it is boiling. When the kettle began to chirp, it proved that the water had boiled. When the water is not turned on, the water flow is in an evaporation state, and the speed of the water flow is very slow, so the vibration frequency is very low. Although there will be sound waves, it is far below the range that the human ear can distinguish.

If the water is boiled, because it is sealed all around, the water can only come out from the spout or the top cover, so the kettle will sing.

The essence of sound is a wave. When air vibrates at a certain amplitude and frequency, waves will be generated. When this wave meets the frequency range of human ears, people will hear it. Sound waves are all pressure waves, and the frequency range that people can hear is between 20 Hz and 2000 Hz, but the sensitivity of different ears is different.