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Daily Noise Exposure Calculator

Calculate daily noise exposure (LEX,8h) and noise dose for multiple tasks.

Disclaimer: This calculator provides a planning estimate. Actual workplace noise measurements must be conducted by a competent person using calibrated sound level meters per AS/NZS 1269.1 or equivalent standard.
Noise tasks (up to 10)
Task 1

Noise-Induced Hearing Loss and the Workplace

Noise-induced hearing loss (NIHL) is one of the most prevalent occupational diseases globally. In Australia, it remains among the top-five compensated occupational conditions, affecting workers in construction, mining, manufacturing, agriculture, and entertainment industries. Unlike many injuries, NIHL is entirely preventable — but it is also irreversible. Once hair cells in the cochlea are damaged by excessive sound energy, they do not regenerate.

The critical measure for regulatory compliance is daily noise exposure, expressed as LEX,8h (or TWA under OSHA). This represents the total sound energy a worker receives over their working day, normalised to an 8-hour reference period. It accounts for the well-established equal energy principle: 3 dB more noise = twice the acoustic energy = half the allowed exposure time.

The LEX,8h Formula (ISO/AU/EU)

LEX,8h = 10 · log₁₀ [ Σ (Tᵢ / 8) · 10^(Lᵢ / 10) ]

Where:
  Tᵢ = duration of task i in hours
  Lᵢ = A-weighted sound level during task i in dB(A)

Example:
  Task 1: 90 dB(A) for 2 hours
  Task 2: 80 dB(A) for 6 hours
  LEX,8h = 10 · log₁₀ [(2/8)·10^(90/10) + (6/8)·10^(80/10)]
         = 10 · log₁₀ [0.25 × 10⁹ + 0.75 × 10⁸]
         = 88.2 dB(A)

Australian Noise Exposure Standards

  • Lower Action Level (LAL): 80 dB(A) LEX,8h — provide hearing protection on request, initiate hearing conservation program
  • Upper Action Level (UAL): 85 dB(A) LEX,8h — hearing protection is mandatory, engineering/admin controls must be evaluated
  • Exposure Limit Value (ELV): 87 dB(A) LEX,8h — must not be exceeded
  • Peak Noise Limit: 140 dB(C) — instantaneous peak (explosion, gunshot, air tool bursts)

OSHA Noise Standards (USA)

OSHA uses a 5 dB exchange rate (also called the doubling rate), meaning that for every 5 dB increase in sound level, allowable exposure time halves. The Permissible Exposure Limit (PEL) is 90 dB(A) TWA over 8 hours. The Action Level is 85 dB(A) TWA, above which a hearing conservation program is required. This approach is considered less conservative than the ISO 3 dB exchange rate.

Selecting Hearing Protection

When LEX,8h exceeds the upper action level, hearing protection must be selected to reduce the effective in-ear level below 85 dB(A). The calculator estimates the required SNR (Single Number Rating) as: Required SNR ≈ LEX,8h − 85 + 4 (4 dB safety margin for real-world fit factors). For example, a LEX,8h of 98 dB(A) requires SNR ≈ 98 − 85 + 4 = 17 dB. However, over-protection (SNR too high) should also be avoided as it can impair communication and warning signal detection.

How to Use This Calculator

  • Select the standard: ISO/AU/EU (3 dB exchange) or OSHA (5 dB exchange)
  • Add a row for each task or activity during the workday
  • Enter the measured sound level in dB(A) and duration for each task
  • Click Calculate to see LEX,8h, dose percentage, compliance status, and required SNR
  • The bar chart shows which tasks contribute most to the noise dose

คำถามที่พบบ่อย

What is LEX,8h?
LEX,8h (also written LAeq,8h) is the A-weighted equivalent continuous sound level normalised to an 8-hour working day. It is the primary metric used to evaluate daily noise exposure under ISO 9612, AS/NZS 1269, and EU Noise at Work Directive. A worker exposed to 94 dB(A) for 1 hour and 80 dB(A) for 7 hours has a LEX,8h significantly below 94 dB(A) — the 1-hour high-noise period contributes significantly due to the logarithmic scale.
What is the difference between the 3 dB and 5 dB exchange rate?
The exchange rate defines how much extra time equates to a given increase in noise. The 3 dB exchange rate (used by ISO, AU, EU) is based on equal energy principle: doubling exposure time equals +3 dB. The 5 dB OSHA exchange rate is more lenient, allowing more time at higher levels before the permissible exposure limit is reached. The 3 dB rate is scientifically better supported for predicting hearing damage.
What are noise action levels in Australia?
In Australia (AS/NZS 1269.1), there are two action levels and an exposure limit: Lower Action Level = 80 dB(A) LEX,8h — employer must provide hearing protection on request and implement a hearing conservation program; Upper Action Level = 85 dB(A) LEX,8h — hearing protection is mandatory, and engineering/administrative controls must be implemented; Exposure Limit Value = 87 dB(A) LEX,8h — must not be exceeded.
When must workers wear hearing protection?
In Australia under the model WHS Regulations, hearing protection must be provided when LEX,8h exceeds 80 dB(A) (if the worker requests it) and is mandatory when LEX,8h exceeds 85 dB(A). Under OSHA, hearing protection is mandatory when TWA exceeds 90 dB(A) and must be provided on request at 85 dB(A). Hearing protection should always be selected to bring the effective in-ear level below 85 dB(A).
How do I reduce noise exposure at work?
Follow the hierarchy of controls: (1) Elimination — remove the noise source entirely; (2) Substitution — replace loud equipment with quieter alternatives; (3) Engineering controls — enclosures, vibration isolation, acoustic barriers, maintenance programs; (4) Administrative controls — job rotation, schedule noisy work when fewer workers are present; (5) Hearing protection — ear muffs and plugs as last resort. Controls 1–4 are always preferred over PPE.
What does SNR or NRR mean?
SNR (Single Number Rating) is the European measure of hearing protector attenuation in dB. NRR (Noise Reduction Rating) is the US equivalent. Both indicate how much a protector reduces sound. Real-world attenuation is significantly less than rated values — standards recommend a 4 dB derating factor for SNR. A protector with SNR 30 provides approximately 26 dB of real-world attenuation.

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