Octaves and thirds

As in music, octaves are used to divide the listening range into frequency intervals. An octave (from Latin octava: “the eighth”) is an interval where the frequency of the lower tone is in a ratio of 1:2 (doubling the previous frequency) to that of the higher tone. Acoustic parameters like the sound absorption coefficient or the sound pressure level are usually given in increments of octaves and thirds.

Third-octaves, i.e. 1/3-octaves, are commonly used as smaller frequency intervals (frequency ratio 1:1.28). Measuring instruments used for frequency analysis usually contain octave and one-third octave filters that allow the sound process to be recorded in its individual octave or one-third octave ranges and displayed as a sound spectrum. The entire human hearing range covers 10 to 11 octaves.