Link: Understanding the Decibel
The decibel is a very commonly used yet often misunderstood unit of measurement. The “bel” in “decibel” comes from the name of Alexander Graham Bell. He was interested in the way in which the human ear responds to sound intensity. He used a logarithmic scale to express this sound intensity, in which range from the softest sound to the loudest (threshold of pain) sound is one to a billion (1012) or zero to 12 bels. The decibel is one-tenth of a bel and is abbreviated as dB.
See the full article here: Understanding the decibel :: RadioComms.