A Weighted Level⚠ unverified
Physics / Acoustics · Apply an approximate A-weighting correction to a sound level
Parameters
| Input | Symbol | Unit | Default | Description |
|---|---|---|---|---|
| L | L | dB | 1.0 | Unweighted sound level |
| f | f | Hz | 1.0 | Frequency at which the level is evaluated |
| Output | Symbol | Unit | Description |
|---|---|---|---|
| result | LA | — | A-weighted sound level, in decibels (dBA) |
The science & history
Understanding the Parameters
- $L$ — usually $L_p$ in a narrow band or pure tone.
- $f$ — A-weight is strongly frequency-dependent (attenuates lows and extreme highs).
- True A-weight (for reference, not what the registry equation shows): the IEC 61672 curve $A(f)$ in dB is added to SPL: $L_A = L_p + A(f)$, with $A(f)$ from a rational function of $f$.
Derivation (Approaching a Proof)
What should be implemented. Equal-loudness contours (Fletcher–Munson / ISO 226) motivate a filter that matches hearing sensitivity at moderate levels. The standardised A-weighting is defined by poles/zeros in the standards; tabulated $A(f)$ values are applied band-by-band for broadband noise.
What the calculator currently exposes. The latex string 100 <= f < 1000 is a boolean domain
condition, not an A-weight formula. Do not treat the numeric output as a validated dBA without
checking the ToolBox implementation path.
History
A-weighting became the occupational and environmental noise default mid-20th century; C- and Z-weight serve other purposes.
Related Concepts: Sound Pressure Level, Sound Intensity Level, Octave Band Center
Notes: Registry calculator a-weighted-level (unverified). Registry defect: equation is not
A-weighting — Track B must replace latex + implementation with IEC $A(f)$.