STILL / FIELD NOTES 09

Octave and third-octave bands: grouped sound frequencies

Octave views combine frequencies into bands whose boundaries scale by a ratio rather than a fixed number of hertz. Third-octave views divide each octave more finely. A band's level is a grouped quantity, not the height of a single FFT bin.

September 8, 2026 · Arve Tech, maker of Still

Choose the view for the task

Still offers octave and third-octave analysis alongside FFT. Broader bands can make broad frequency changes easier to compare. A finer view can show more structure, but it does not automatically provide greater microphone accuracy.

Keep the comparison compatible

Use the same band view, frequency weighting, input and position. Do not directly compare an individual FFT-bin height with a band's combined energy. Record the view name in screenshots and notes so a later reader knows what was displayed.

Try a repeatable approach

1. Select octave or third-octave before collecting comparison sessions.
2. Keep frequency scale and measurement setup fixed.
3. Describe changes by their band labels and conditions.

Source and scope

Brüel & Kjær: environmental noise measurement handbook

Measurement guidance is educational. Still is not a certified sound level meter and does not establish medical, legal or workplace-compliance conclusions. App-specific statements describe version 1.0.0, currently awaiting App Store review.