dec ‧ i ‧ bel /ˈdesəbel, ˈdesɪbel, -b ə l/ BrE AmE noun [countable] ( written abbreviation dB )
[ Date: 1900-2000 ; Origin: deci- + bel unit of sound power (20-21 centuries) , from Alexander Graham Bell (1847-1922), US inventor ]
a unit for measuring the loudness of sound:
noise levels exceeding 85 decibels