It is one-tenth of a belio (relative unit for sounds). As they are logarithmic factors, a difference of 1 dB (one decibel) is much more manageable than 1 B (one belio).
decibelio:e a logarithmic expression, or a unit of measurement that is relative. It expresses a ratio between quantities, and not a single number. its symbol is db and can be decibel, or decibel.