Sutli bomb or Hydro-bomb is an Indian
firecracker
A firecracker (cracker, noise maker, banger) is a small explosive device primarily designed to produce a large amount of noise, especially in the form of a loud bang, usually for celebration or entertainment; any visual effect is incidental to ...
popular during the festival of
Diwali and other celebrations. It is the noisiest firecracker, exceeding the permissible sound barrier of 145 decibels (dB).
About
Sutli bomb is made with
jute twine
Twine is a strong thread, light string or cord composed of two or more thinner strands twisted, and then twisted together ( plied). The strands are plied in the opposite direction to that of their twist, which adds torsional strength to the co ...
(sutli) that is green in color and has a red band that has manufacturer's name. The twine is wrapped around the explosive component and results in producing a powerful sound.
What produces this sound is the tight packaging of gunpowder inside. When the gunpowder is heated, lot of gases (carbon dioxide, carbon monoxide, oxides of sulphur) and the noise comes due to these gas pressure tearing through the tight packaging.
Banned
It is banned by many governments under Arms Act, because of the noise level it produces that is almost double the permissible level of 75 decibels.
References
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Types of fireworks
Diwali