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Noise Exposure Calculator

Computes the permitted exposure time at a given A-weighted sound level, the daily noise dose and the 8-hour time-weighted average under both the NIOSH recommended exposure limit (85 dBA, 3 dB exchange rate) and the OSHA permissible exposure limit (90 dBA, 5 dB exchange rate).

When to use

You want to know how long a person may be exposed to a measured noise level, whether a shift, concert or tool use exceeds the NIOSH or OSHA limit, or the dose of a single-level exposure.

Do not use when: The level varies over the day (sum the partial doses C/T of each level instead) or you need decibel arithmetic such as adding sources or distance attenuation (use decibel); the result is informational only and no substitute for a workplace noise survey or medical advice.

Formula

NIOSH: T = 8 / 2^((noise_level_dba − 85) / 3) h; OSHA: T = 8 / 2^((noise_level_dba − 90) / 5) h; dose D = 100 × duration_hours / T; TWA = 10 × log10(D / 100) + 85 (NIOSH) or 16.61 × log10(D / 100) + 90 (OSHA)

NIOSH (1998) recommends an 85 dBA 8-hour TWA with a 3 dB exchange rate (equal energy); OSHA 29 CFR 1910.95 enforces a 90 dBA PEL with a 5 dB exchange rate and an 85 dBA action level (dose 50 %). Neither integrates levels below 80 dBA, and no exposure above 115 dBA continuous or 140 dB peak is permitted. Informational only.

Inputs

Parameter	Type	Unit	Required	Description
`noise_level_dba`	number	dBA	yes	A-weighted sound level of the exposure (slow response). Range: ≥ 40, ≤ 140
`duration_hours`	number	h	yes	Length of the exposure at that level. Range: > 0, ≤ 24
`standard`	enum: niosh \| osha		default niosh	Criterion used for exceeds_limit, time_weighted_average_dba and hearing_protection_recommended; both standards are always computed.

Outputs

Output	Type	Unit	Description
`allowed_duration_hours_niosh`	number	h	8 / 2^((L − 85) / 3): time at this level that reaches 100 % of the NIOSH REL.
`allowed_duration_hours_osha`	number	h	8 / 2^((L − 90) / 5): time at this level that reaches 100 % of the OSHA PEL (Table G-16).
`dose_percent_niosh`	number	%	100 × duration_hours / allowed_duration_hours_niosh.
`dose_percent_osha`	number	%	100 × duration_hours / allowed_duration_hours_osha.
`exceeds_limit`	boolean		true when the dose under the selected standard is above 100 %.
`time_weighted_average_dba`	number	dBA	Equivalent 8-hour time-weighted average for the selected standard: 10·log10(D/100) + 85 (NIOSH) or 16.61·log10(D/100) + 90 (OSHA).
`hearing_protection_recommended`	boolean		true when the TWA reaches 85 dBA: dose ≥ 50 % under OSHA (action level, hearing conservation program) or ≥ 100 % under NIOSH (REL).
`comparison_table`	object		NIOSH allowed exposure in minutes keyed by sound level in dBA (85, 88, 91, 94, 97, 100).

Example

95 dBA for 2 hours (NIOSH): {"noise_level_dba":95,"duration_hours":2,"standard":"niosh"} → {"allowed_duration_hours_niosh":0.79,"allowed_duration_hours_osha":4,"dose_percent_niosh":252,"dose_percent_osha":50,"exceeds_limit":true,"time_weighted_average_dba":89,"hearing_protection_recommended":true,"comparison_table":{"85":480,"88":240,"91":120,"94":60,"97":30,"100":15}}

100 dBA for 30 minutes (OSHA): {"noise_level_dba":100,"duration_hours":0.5,"standard":"osha"} → {"allowed_duration_hours_niosh":0.25,"allowed_duration_hours_osha":2,"dose_percent_niosh":200,"dose_percent_osha":25,"exceeds_limit":false,"time_weighted_average_dba":80,"hearing_protection_recommended":false}

GET https://tttkmbb.com/api/v1/calculate/noise-exposure?noise_level_dba=95&duration_hours=2&standard=niosh

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/noise-exposure (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/noise-exposure · Markdown: https://tttkmbb.com/health/noise-exposure.md · JSON definition: https://tttkmbb.com/health/noise-exposure.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="noise-exposure"
OpenAPI operationId: calculate_noise_exposure
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

Why do NIOSH and OSHA differ so much?

NIOSH halves the allowed time for every 3 dB increase (equal energy rule) starting from 85 dBA, OSHA for every 5 dB starting from 90 dBA. At 95 dBA that is 47.6 minutes versus 4 hours; NIOSH's limit is the health-based recommendation, OSHA's the enforceable minimum in the US.

How do I handle several noise levels in one day?

Compute the dose of each period separately (100 × C/T) and add them; the total must stay at or below 100 %. Run this calculator once per level and sum the dose outputs.

What about the EU?

EU Directive 2003/10/EC uses a 3 dB exchange rate like NIOSH with an exposure limit of 87 dBA and action values of 80 and 85 dBA (8-hour Lex), so the NIOSH allowed duration is the closer comparison.

Related calculators

Decibel Calculator — Add sound sources or convert between sound level and intensity.