dBs measure sound. Every day the sounds we hear usually fall between 0dB (the faintest detectable noise) and 120dB (a thunderclap). Although 0 to 120 may not seem like a big difference, it actually represents an increase of sound energy 1 trillion fold! This is because dBs are special units used to represent significant differences in energy with smaller, more manageable numbers.
All you need to remember is one simple rule: an increase of 10dB means 10 times more energy. So an increase of 20dB means 10*10=100 times more energy. Going from 10dB breathing to a 40dB library means 10*10*10=1000 times more sound energy!