What is the measure of a decibel(db)?

Answer 1

The decibel (dB) is a logarithmic unit of measurement used for expressing ratios. It uses a logarithm to allow very large or very small ratios to be represented with a conveniently small number, in a similar manner to scientific notation. It is a dimensionless unit. Decibels are useful for a wide variety of measurements in acoustics, physics, electronics and other disciplines.
The decibel is not an SI unit, although the International Committee for Weights and Measures (CIPM) has recommended its inclusion in the SI system. Following the SI convention, the d is lowercase, as it represents the SI prefix deci-, and the B is capitalized, as it is an abbreviation of a name-derived unit, the bel, named for Alexander Graham Bell. The full name decibel follows the usual English capitalization rules for a common noun.
When used to compare a variable quantity to a known reference quantity, the measurement is qualified with a suffix. For example, "dBm" indicates that the reference quantity is one milliwatt.

see here:http://en.wikipedia.org/wiki/Decibel#History

Answer 2

TO keep it simple it measures relative sound intensity. This simply tells you how loud something is compared to the lowest hearable sound (the Threshold of Hearing)

Answer 3

noise