Noise Exposure Calculator

Calculate TWA noise dose and determine hearing protection requirements per OSHA standards.

Inputs

Noise Level (dBA)

Exposure Duration (hours)

Hearing Protection NRR (dB)

Tab to move between fields

Results

TWA (dBA)

Noise Dose (%)

200

Allowable Exposure (hours)4

Protected Noise Level (dBA)86

Protected Dose (%)57.43

Action Level Exceeded (85 dBA)1

PEL Exceeded (90 dBA)1

How to Use This Calculator

Enter noise levels (dBA) and duration (hours) for each noise source or area.
Read the 8-hour time-weighted average (TWA) noise dose (%).
A dose exceeding 100% or TWA above 90 dBA triggers OSHA Hearing Conservation Program requirements.
Engineering controls must be implemented first; hearing protection is supplementary.
Compare results against the OSHA action level (85 dBA TWA) and PEL (90 dBA TWA).

How the result changes with Noise Level (dBA)

Noise Level (dBA)	TWA (dBA)	Noise Dose (%)
59	55.2	0.8
82	82	32.99
109	109	1,392.88
131	131	29,406.68

What each input means

Noise Level (dBA): Measured sound level in A-weighted decibels.
Exposure Duration (hours): Hours exposed to this noise level per shift.
Hearing Protection NRR (dB): Noise Reduction Rating of hearing protector.

How this is calculated

Worked example, using the default values

Identify Input Parameters
Noise Level (dBA) = 95, Exposure Duration (hours) = 8, Hearing Protection NRR (dB) = 25 = 3 input(s) provided
Calculate TWA
95 = 95
Calculate Noise Dose
Noise Dose = max(0
200 = 200
Calculate Allowable Exposure
Allowable Exposure
4 = 4
Calculate Protected Noise Level
Protected Noise Level
86 = 86

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