Listen to an extended podcast of fire crackers at Chinese New Year. Fire crackers symbolize the driving away of evil spirits and can be heard for the first two weeks of the Chinese New Year.
In fact, in places like Beijing, Shanghai, Hong Kong and other large Chinese cities it is best not to count on a lot of sleep due to the firecrackers and fireworks being set off in all parts of the city. Beijing sounds like a city under attack!
Of course, gunpowder was invented in China sometime between 600-850 AD as geomancers and alchemists searching for the elixir of life experimented with various substances commonly used in the iron smelting process. Eventually, after much trial and error, gunpowder was discovered - a mixture of charcoal, sulfur and saltpeter (potassium nitrate)
Over successive centuries bombs, grenades, cannonballs and rockets were developed in China and eventually gunpowder found its way to the Arab world and Europe between the 11-13th centuries. It seems fireworks and firecrackers may have been used initially as a method of scaring enemies in battle but gradually pyrotechnics became used in festivals to frighten evil spirits and provide an enjoyable spectacle. Early fireworks were bamboo shoots filled with gunpowder.
China is now the largest manufacturer and exporter of fireworks in the world.