Use these interactive tools to practise common calculations used in occupational noise assessment, including logarithmic decibel calculations, task-based exposure assessment, daily exposure normalisation and hearing protection estimates.
Use this calculator to combine unrelated sound levels. Decibels are logarithmic, so values must be added by energy, not by simple arithmetic.
Ltotal = 10 log10(Σ 10^(Li/10))Use this calculator to find the logarithmic average of repeated sound level readings. This is useful when several measurements are taken at the same position or for similar conditions.
Lavg = 10 log10[(1/n) × Σ 10^(Li/10)]Use this calculator to estimate the remaining sound level when one known source is removed from a measured combined sound level. Decibel subtraction must be carried out by subtracting acoustic energy, not by simple arithmetic.
Lremaining = 10 log10(10^(Ltotal/10) − 10^(Lknown/10))Enter the sound level and duration for each task. The tool estimates the normalised daily exposure level, LAeq,8h.
| Task or activity | LAeq,T dBA | Duration | Unit | Remove |
|---|---|---|---|---|
LAeq,8h = 10 log10[(1/8) × Σ ti × 10^(LAi/10)], where time is expressed in hours.Use this calculator when you already have an equivalent continuous A-weighted level for a known exposure duration.
LEX,8h = LAeq,Te + 10 log10(Te / 8)Estimate the maximum exposure duration for a selected criterion level and exchange rate. Students may compare the 85 dBA / 3 dB approach with the 90 dBA / 5 dB approach used in some jurisdictions.
T = 8 × 2^((Criterion − L) / Exchange Rate), where T is in hours.Enter octave-band sound pressure levels and select A, C or Z weighting. The calculator applies the selected weighting correction to each band and then combines the bands logarithmically.
| Octave band centre frequency | Measured band level, dB | A correction, dB | C correction, dB |
|---|---|---|---|
| 16 Hz | -56.7 | -8.5 | |
| 31.5 Hz | -39.4 | -3.0 | |
| 63 Hz | -26.2 | -0.8 | |
| 125 Hz | -16.1 | -0.2 | |
| 250 Hz | -8.6 | 0.0 | |
| 500 Hz | -3.2 | 0.0 | |
| 1000 Hz | 0.0 | 0.0 | |
| 2000 Hz | +1.2 | -0.2 | |
| 4000 Hz | +1.0 | -0.8 | |
| 8000 Hz | -1.1 | -3.0 | |
| 16000 Hz | -6.6 | -8.5 |
Overall level = 10 log10(Σ 10^((Li + correctioni)/10)). For Z-weighting, the correction is 0 dB for each entered band.Estimate the sound level at the ear after applying a simplified hearing protector rating. This is a learning estimate only; actual protection depends strongly on fit, training, maintenance and wearing time.
Protected level = Measured noise level − (Rating × Derating factor). For formal assessment, use the rating method required by the relevant standard or regulation.Use these tools to practise common hearing protector calculations. They are designed to help students understand estimated protected level, wearing-time effects, dual protection and required attenuation. Actual protection depends on protector fit, training, maintenance and correct use throughout exposure.
Estimate the sound level at the ear after applying a hearing protector rating and an optional derating factor.
Protected level = Noise level − (Rating × Derating factor)Show how removing hearing protection for short periods can significantly reduce the effective protection achieved over a shift.
Leffective = 10 log10[(tworn × 10^(Lprotected/10) + tremoved × 10^(Lunprotected/10)) / (tworn + tremoved)]Estimate protection when earplugs and earmuffs are worn together. A common training approximation is to use the higher rating plus an additional 5 dB, before applying any chosen derating factor.
Dual rating estimate = max(Earplug rating, Earmuff rating) + 5 dBEstimate the minimum effective attenuation needed to reduce a measured noise level to a selected target level.
Required effective attenuation = Noise level − Target protected levelExplore the IEH Knowledge Hub for articles, resources and practical guidance on occupational hygiene, ergonomics, human factors and workplace health.
