A kettle whistles every time it has got the tea prepared. Ever wondered why? An Indian aero acoustics has found the reason, according to a recent report.

Dr. Anurag Agarwal and colleagues claimed that they have unraveled the poser. For over a century, the mystery has baffled researchers. Now, Dr. Agarwal and student Ross Henrywood said to have discovered the sound source.

Two different mechanisms have been identified by them that are being said to create that resonance. The team said that this was also the reason why the kettle was unlike other items, including hair dryer, in the household. These things produced a rushing sound in a flow.

The first ever precise model has also been designed by the group for the whistling mechanism in a classic stove kettle. The connoisseurs said that they had found a way to stop such noises, which sometimes turn out to be irritating.

A series of simplified kettle whistles were made, which were examined in a rig that was impelled through these at different paces. The sounds produced by them were recorded. Plotting the sound amplitude and frequency, the data was analyzed non-dimensionally. The spout was then determined using a two-microphone technique.

The team noted that swirling flow's small vortices-regions produced a sound beyond a specific flow speed.

"The effect we have identified can actually happen in all sorts of situations - anything where the structure containing a flow of air is similar to that of a kettle whistle", said the department of engineering's Ross Henrywood.