As the name implies, one-third octave band analyzers display sound pressure levels for one-third octave bands, to provide better resolution of frequencies. The third octave bands can also be added up to obtain the overall sound pressure level.
All octave and third octave bands have been internationally standardized, and although the ranges are precisely defined, they are most commonly designated by their center frequency. For instance, the 500-hertz center frequency octave band includes frequencies from 355 to 708 hertz. The third octave band for the same center frequency ranges from 447 to 562 hertz.