To get a feel on decibels, a chart of various sounds and their loudness. And realize that for every 10 decibel increase you're increasing the volume of the sound by 10 times. 20 decibels, 100 times. It's a logarithmic unit.

rustling leaves: 20 dB
whispers: 30 dB
quiet home: 40 dB
quiet street: 50 dB
conversation: 60-70 dB
telephone dial tone: 80 dB
car in traffic: 85 dB
possible hearing damage over a long time: 90-95 dB
average Walkman settings: 94 dB
diesel truck: 100 dB
power saw: 110 dB
normal amplified music: 120 dB
point of pain and hearing damage: 125 dB
jet engine at 100 ft.: 135 dB
loudest rock music: 150 dB
loudest possible noise: 194 dB