Burning Hydrogen

Hydrogen is a colorless, odorless, tastelessn, non-toxic, higly combustible diatomic gas. What is interesting about the combustion of hydrogen, that it depends on what is the purity of this gas. If there is a very low concentration of oxygen in hydrogen gas it burns with quiet sound, but if there's more oxygen it makes really sharp sound.

In this video you can see how quite pure hydrogen burns. I've made this hydrogen by electrolysis of aqueous sodium carbonate solution.