Daily Noise Exposure Calculator

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