ISO 266 Octave Bands (1/1 and 1/3 RTA) for Room Acoustics

Understanding 1/1 and 1/3 fractional octave band real-time analysis (RTA), ISO center frequencies, and standard acoustic measurement applications.

f_n = 1000 · 2^(n/3) Hz (1/3 Octave Center)

Logarithmic Pitch & Constant Proportional Bandwidth

Human hearing perceives musical intervals logarithmically: each musical octave represents a doubling in frequency (e.g., 250 Hz → 500 Hz → 1,000 Hz). Constant Percentage Bandwidth (CPB) filters group frequencies into proportional fractions of an octave according to IEC 61260-1:2014 ↗.

ISO 266 Standard 1/1 Octave Frequencies

The 10 standard 1/1 full octave nominal center frequencies established in ISO 266:1997 ↗ are:

31.5 Hz, 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz, 16 kHz

1/3 Octave Bands (31 Bands)

Provides three frequency bands per octave (bandwidth factor ≈ 23%). Standard for architectural room tuning, acoustic treatment placement, and noise criteria (NC) rating curves.

Audition in Visualizer Studio

Test these acoustic concepts with live microphone or test tone signals. Visualizer Studio (Octave RTA).

Open Octave RTA