Decibels (dB) are a measurement of noise levels; the higher the number of decibels, the louder the noise. By comparison, a mosquito's buzz is about 40 decibels, while a jet take-off is about 150 decibels.
This is a scale of various sounds from very quiet (0dB) to loud (140dB). Now, of course, 140dB, isn't the loudest a sound can get, in fact, the Tunguska Meteor reached decibel levels of a staggering 300 - 315dB! The effects of prolonged exposure to loud sounds, such as a rocket launch or jet take-off can include eardrum rupture or temporary deafness,