Octave Band A-Weighting Adjustment Calculator
This calculator turns unweighted octave band sound pressure levels into an overall A-weighted level. Enter the levels you measured in the nine octave bands from 31.5 Hz to 8000 Hz, and the page applies the A-weighting correction for each band centre, then combines the weighted bands into a single figure in dBA.
Each weighted band level is the measured level plus the A-weighting correction for that band: Li,A = Li + Ai. The weighted bands are then added on an energy basis, so the loudest weighted bands dominate the total while low-frequency bands with large negative corrections contribute little.
The method reproduces the worked example of the source: unweighted bands of 85, 86, 90, 94, 98, 101, 102, 104 and 105 dB give weighted bands of 45.6, 59.8, 73.9, 85.4, 94.8, 101.0, 103.2, 105.0 and 103.9 dB, and an overall level of 109.7 dBA.
Enter unweighted octave band levels
Enter at least one band level.
Overall A-weighted level LA
—dBA
| Band centre (Hz) | Typed level (dB) | A-weighting correction (dB) | Weighted level (dB) |
|---|---|---|---|
| — | — | — | — |
How to use the calculator
- Enter the unweighted level in dB for each octave band you measured, from 31.5 Hz to 8000 Hz. Leave a band empty if you have no reading for it: an empty band is left out of the sum. A level of 0 dB is a valid level and counts, and negative levels are valid too.
- The A-weighting correction is added to each filled band: -39.4 dB at 31.5 Hz, -26.2 dB at 63 Hz, -16.1 dB at 125 Hz, -8.6 dB at 250 Hz, -3.2 dB at 500 Hz, 0.0 dB at 1000 Hz, +1.2 dB at 2000 Hz, +1.0 dB at 4000 Hz and -1.1 dB at 8000 Hz. This gives the weighted band level Li,A = Li + Ai.
- The weighted bands are combined as an energy sum: LA = 10 × log10( Σ 10^(Li,A / 10) ), summed over the filled bands only.
- Read the overall level in dBA and check the table, which lists each filled band with the level you typed, its correction and its weighted level. Results update as you type; the Calculate button runs the same calculation.
- If a field shows a message, correct it: a level below -50 dB or above 250 dB, or an entry that is not a number, stops the calculation until it is fixed.
Frequently asked questions
What happens to a band I leave empty?
An empty band counts as no signal and is left out of the energy sum. A band set to 0 dB is different: 0 dB is a valid level, so it is weighted and included in the total.
How are the weighted bands combined into one level?
Each weighted band level is the unweighted level plus its A-weighting correction. The overall level is the energy sum of the weighted bands: LA = 10 × log10 of the sum of 10^(Li,A / 10) over all filled bands.
Where do the A-weighting corrections come from?
They are the A-weighting values at nominal octave band centres (IEC 61672-1), as given in Grinshpun, Kim and Murphy, Noise Exposure and Control, chapter 30 of Occupational Ergonomics: Theory and Applications, Table 30.2, pp. 803-804 (CDC).
Can I use third-octave bands or C or Z weighting?
No. The calculator covers the nine octave bands from 31.5 Hz to 8000 Hz with A-weighting only. Third-octave bands and C or Z weighting are not supported.
Disclaimer
The result is an estimate only and is not a substitute for a qualified engineer. The corrections are the A-weighting values at nominal octave band centres (source: Grinshpun, Kim and Murphy, Noise Exposure and Control, chapter 30 of Occupational Ergonomics: Theory and Applications, Table 30.2 and Sample calculation 7, pp. 803-804, CDC). The overall level is the energy sum of the weighted bands. Empty bands count as no signal. Third-octave bands are not covered, and C or Z weighting is not provided.