Exposure dose and TWA · Sound propagation · Octave band analysis
How to use
Select your jurisdiction, then add each noise source with its level (dBA) and duration. Press Calculate to see TWA, dose, and compliance against all relevant standards.
Optionally enter a peak noise level (dBC) and enable the hearing protector section to assess HPD adequacy.
Jurisdiction
Noise sources
Description
Level (dBA)
Hours
Minutes
Peak exposure
Hearing protector
Enter H, M, L values from HPD datasheet. Select spectrum type matching the dominant noise character.
Over-attenuation: protected level is below 70 dBA. Consider a lower-rated protector to avoid communication loss and signal isolation.
Ototoxic Co-exposure
Certain chemicals can potentiate noise-induced hearing loss. Indicate any ototoxic substances present in the work environment. When co-exposure is indicated, a precautionary note will appear alongside your results.
No ototoxic co-exposure
Solvents
Asphyxiants
Metals
Other
OTOTOXIC CO-EXPOSURE DETECTED
Results
Source contribution to total noise energy
Understanding your results
Time-Weighted Average (TWA) is the equivalent continuous noise level over an 8-hour shift that produces the same dose as the actual mixture of levels and durations.
Noise dose (%) is the fraction of the permissible daily exposure consumed. 100% dose = the criterion level held for 8 hours. Doses above 50% trigger hearing conservation program requirements; doses at or above 100% require engineering controls or HPD use.
Standard differences: OSHA uses a 90 dBA criterion and 5 dB exchange rate. NIOSH and ACGIH both use 85 dBA and a 3 dB exchange rate. Where standards disagree, the most protective standard is the recommended engineering target.
Hearing protector adequacy: Adequate = protected TWA below action level. Marginal = below limit but above action level. Inadequate = HPD is insufficient for the measured exposure.
Add a noise source above to begin.
How to use
Enter the known sound level at a reference distance from the source, then set the target distance and receiver environment. The tool applies inverse square law (point source) or inverse distance law (line source), plus optional corrections for directivity, atmospheric absorption, and ground effect. Press Calculate to see results.
Source characteristics
Source type
Point source: level drops 6 dB per distance doubling (spherical spreading). Typical for isolated machines, stacks, or vehicles at distance.
Receiver and environment
Optional corrections
0 = omnidirectional; +3 = half-space; +6 = corner
Typical 1-3 dB/km at 1 kHz, 20 deg C. 0 = neglect.
Noise barrier, enclosure, or other control.
OEL / limit comparison
Results
Correction breakdown
Level vs distance
Understanding your results
How to use
Select octave or third-octave band resolution, then enter the measured sound pressure level (dB, unweighted) for each frequency band. Leave bands blank to exclude them. Press Analyse to compute overall A-weighted and C-weighted levels, identify dominant frequency regions, and compare against an occupational exposure limit.
Band resolution
OEL comparison
Band SPL values (dB, unweighted)
Results
Spectral profile — A-weighted contribution per band