Sound: The decibel scale
The Decibel Scale is used to measure how loud a sound is.
140 dB is loud enough to cause you pain - 0 dB is the threshold of hearing - quieter sounds than this cannot be heard.
A typical classroom of students 'actively engaged' in a lesson - discussing with each other is about 70 dB and a typical library is about 30 dB.
A rock concert is usually at the threshold of pain and can cause damage to your ears. Rock musicians wear ear protectors when they play!
Click here for details on how decibels relate to the intensity of sound.