---
title: "Noise Exposure Calculator (NIOSH & OSHA) | City Hum Daily"
description: "Allowed noise exposure time per level under NIOSH (85 dBA, 3 dB) and OSHA (90 dBA, 5 dB), plus daily noise dose and 8-hour TWA from several exposures."
url: https://cityhumdaily.buzz/noise-exposure-calculator/
---

NIOSH · OSHA · WHO

# Noise exposure calculator

How long a day can you spend at a given noise level, and how much of the daily limit did your shift use? Type levels in A-weighted decibels (dBA).

## How the limits work

Both US limits allow 8 hours at a reference level and shorten the time as the level rises. **NIOSH**, the research agency, recommends 85 dBA for 8 hours and halves the time for every **3 dB** more, because 3 dB is a doubling of sound energy: 4 hours at 88 dBA, 1 hour at 94, 15 minutes at 100. **OSHA**, the regulator, allows 90 dBA for 8 hours and halves the time every **5 dB**, so it permits 4 hours at 95 dBA where NIOSH recommends 30 minutes at 97.

The **dose** adds up each exposure as a share of its allowed time: 2 hours where 4 are allowed is 50 %. A dose of 100 % is the limit, and the **TWA** is the steady 8-hour level that would give the same dose. OSHA also has an **action level**: at a TWA of 85 dBA (a 50 % dose, counting levels from 80 dBA) employers must run a hearing conservation program with hearing tests and protectors. For the PEL itself OSHA counts only levels of 90 dBA and above, and NIOSH counts from 80 dBA.

The **WHO** tile is for listening rather than work: WHO and ITU set 80 dB for 40 hours a week for adults and 75 dB for children, halving every 3 dB.

Levels should be A-weighted averages over each period, ideally from a dosimeter or a calibrated meter. Readings from a phone are rough estimates. These limits protect most people, not everyone, and this page is not medical or legal advice.

## Questions

**Why do NIOSH and OSHA give different times?**

OSHA's limit dates from 1971 and uses 90 dBA with a 5 dB exchange rate, which assumes the ears recover during quieter breaks. NIOSH reviewed the evidence in 1998 and recommends 85 dBA with a 3 dB exchange rate, which follows the equal-energy rule and protects more workers. The OSHA limit is the legal one for most US employers; the NIOSH one is the safer target.

**Do earplugs change the dose?**

The dose here is the noise around you, which is how both standards measure exposure. Hearing protection lowers what reaches your ears; the sound level chart page estimates by how much from a protector's NRR, using the OSHA and NIOSH derating rules.

**What if my shift is longer than 8 hours?**

Enter every period, however long the day. The dose counts all of it, so 10 hours at 85 dBA comes to 125 % under NIOSH even though each hour is at the reference level. The TWA is still expressed as an 8-hour equivalent.

## Sources

1. NIOSH, *Criteria for a Recommended Standard: Occupational Noise Exposure, Revised Criteria 1998*, DHHS (NIOSH) Publication No. 98-126: 85 dBA REL, 3 dB exchange rate, 80 to 140 dBA integrated, 140 dBA ceiling, TWA = 10.0 × log(D/100) + 85.
2. OSHA, [29 CFR 1910.95 Occupational noise exposure](https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.95), Table G-16 and the action level in paragraph (c), and [Appendix A, Noise exposure computation](https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.95AppA): T = 8 / 2^((L − 90)/5), D = 100 C/T, TWA = 16.61 log10(D/100) + 90.
3. OSHA Technical Manual, [Section III, Chapter 5: Noise](https://www.osha.gov/otm/section-3-health-hazards/chapter-5) (90 dBA threshold for the PEL, 80 dBA for the action level).
4. WHO and ITU, [Safe listening devices and systems: a WHO-ITU standard](https://www.who.int/publications/i/item/9789241515276) (2019), and WHO, [Safe listening questions and answers](https://www.who.int/news-room/questions-and-answers/item/deafness-and-hearing-loss-safe-listening).

Educational estimates only. Not medical advice and not a substitute for workplace noise monitoring by a qualified person.