Third-Octave Band

A third-octave band divides each octave into three sub-bands, providing higher frequency resolution than octave band analysis. The standard centre frequencies range from 20 Hz to 20 kHz, with each band having a bandwidth ratio of 2^(1/3) or approximately 1.26. Defined in IEC 61260-1:2014, third-octave analysis is used for detailed sound insulation measurements (ISO 10140, ISO 717-1), environmental noise assessments, and vibration analysis. Sound insulation parameters like Rw and STC are calculated from third-octave band transmission loss data between 100 Hz and 3150 Hz. Third-octave measurements require more time and more precise instrumentation than octave band measurements but reveal frequency-specific weaknesses, such as coincidence dips, that octave band analysis can mask.