Soundproofing glossary definition of band pressure level

band pressure level :

Sound pressure level for sound contained within a restricted frequency band. Unit, decibel (dB); symbol, L{sub pb}. A band may be identified by its nominal lower and upper band edge frequencies, or by its nominal midband frequency and nominal bandwidth. The nominal width of the band may be indicated by a prefatory modifier, e.g., octave-band sound pressure level, one-third-octave-band sound pressure level, or 50- Hz band level at 400 Hz.