Octave Band

An octave band is a frequency range where the upper frequency is exactly twice the lower frequency. In building acoustics, the six standard octave bands centered at 125, 250, 500, 1000, 2000, and 4000 Hz are used for nearly all calculations and specifications, as defined in IEC 61260-1:2014. Each band captures a different aspect of room behavior: 125 Hz relates to bass and room modes, 500–1000 Hz to speech fundamentals, and 2000–4000 Hz to speech consonants and clarity. Absorption coefficients, transmission loss values, and noise criteria curves are all specified per octave band. Extended measurements may include 63 Hz and 8000 Hz bands for specialized applications such as vibration or high-frequency intelligibility analysis.