Permissible Noise Level Calculator

Calculate maximum allowable noise levels based on exposure time

Calculation Parameters

Based on ISO 1999, OSHA, and NIOSH standards

Calculation Results

Maximum Permissible Level: —

8-hour TWA Equivalent: —

Daily Noise Dose: —

With Protection: —

Noise Exposure Zones:

Safe: < 80 dBA - No action required

Caution: 80-85 dBA - Hearing protection available

Warning: 85-90 dBA - Hearing protection required

Danger: > 90 dBA - Engineering controls needed

How the Calculator Works

Permissible Exposure Limit

The maximum noise level for a given exposure time:

L_max = L_c + 10 × log₁₀(T_c / T)

where:

L_max — maximum permissible level (dBA)
L_c — criterion level (85 or 90 dBA)
T_c — criterion time (8 hours)
T — actual exposure time (hours)

Time-Weighted Average (TWA)

For varying noise levels throughout the day:

TWA = 10 × log₁₀[1/8 × Σ(t_i × 10^(L_i/10))]

Noise Dose Calculation

Daily noise exposure as percentage:

Dose = 100 × Σ(C_i / T_i)

where C_i is actual exposure time and T_i is allowable time at that level.

Standard Comparison

Standard	Limit	Exchange Rate	Max Level
OSHA	90 dBA	5 dB	140 dB peak
NIOSH	85 dBA	3 dB	140 dB peak
EU	87 dBA	3 dB	140 dB peak

Hearing Protection

Effective protection level calculation:

Effective Level = Noise Level - (NRR - 7) / 2

NRR = Noise Reduction Rating

Distance Attenuation

For point sources in free field:

Each doubling of distance = -6 dB
Indoor environments: -3 to -4 dB per doubling
Near reflecting surfaces: less attenuation

Health Effects by Level

< 70 dBA: No hearing damage risk
70-80 dBA: Possible annoyance
80-85 dBA: Possible hearing damage with long exposure
85-90 dBA: Hearing damage risk, protection required
> 90 dBA: Significant hearing damage risk
> 140 dB: Immediate hearing damage possible

📘 Noise Level Calculator (OSHA/NIOSH)

Determines permissible noise exposure for worker hearing protection. Calculates TWA (Time-Weighted Average) and dose per OSHA/NIOSH standards.

💼 Applications

Workplace Assessment: Pump room: 88 dBA, 8 hours. NIOSH criterion: 85 dBA. Dose: 200%. Mandatory hearing protection (NRR 23 earplugs) → effective 80 dBA ✓
Compressor Room: 94 dBA, operator 2 hours/day. OSHA permissible time: ~4 hours. Dose: 50%. Acceptable without PPE per OSHA, but NIOSH requires protection.
Combined Exposure: 3h at 90 dBA + 3h at 82 dBA + 2h at 95 dBA. TWA = 88.5 dBA. Dose: 67%. Wear protection at pneumatic tools.

Key Standards:

OSHA: 90 dBA for 8h, 5 dB exchange rate, max 140 dB peak NIOSH: 85 dBA for 8h, 3 dB exchange rate (more conservative) NRR Derating: Effective reduction = (NRR - 7) / 2

Permissible Noise Level Calculator | Vibromera.eu

Published by admin on October 20, 2025 December 9, 2025