OSHA Noise Dose & TWA Calculator

Compute 8-hour time-weighted average exposure and total noise dose.

Exposure Segments

Results Overview

Total Dose (D)
0.00%
8-Hour TWA
N/A
-
Level (dBA) Time (Hrs) Ref. Time T Dose %

About the OSHA Noise Dose & TWA Calculator

Industrial hygienists and safety managers can easily evaluate workplace acoustics using our OSHA noise dose & 8-hr TWA calculator. Input continuous or variable sound levels and exposure times to accurately compute dose percentages (D=100·Σ(C/T)) and Time-Weighted Averages. Instantly flag when exposures exceed the 85 dBA Action Level or 90 dBA Permissible Exposure Limit, simplifying your hearing conservation program compliance.

How it works

  1. Enter the measured noise level in decibels (dBA) for a specific task or environment.
  2. Input the duration of time the worker is exposed to that specific noise level.
  3. Add additional rows for workers moving between different noise environments throughout their shift.
  4. Calculate the results to see the cumulative noise dose percentage and the equivalent 8-hour Time-Weighted Average (TWA).

Frequently asked questions

What is the OSHA Permissible Exposure Limit (PEL) for noise?

The OSHA PEL for noise exposure is 90 dBA as an 8-hour Time-Weighted Average (TWA). Exposures at or above this level require feasible engineering or administrative controls, and mandatory use of hearing protection.

What is the OSHA Action Level for noise?

The Action Level is 85 dBA as an 8-hour TWA, which equates to a 50% noise dose. Reaching the Action Level triggers the requirement for employers to implement a formal Hearing Conservation Program, including audiometric testing and training.

How does OSHA calculate allowable noise duration?

OSHA uses a 5 dB exchange rate. This means that for every 5 decibel increase in noise level above 90 dBA, the allowable exposure time is cut in half. For example, 90 dBA is allowed for 8 hours, but 95 dBA is only allowed for 4 hours.

What does TWA stand for in noise monitoring?

TWA stands for Time-Weighted Average. It represents a worker's daily exposure to noise, normalized to an 8-hour shift, making it easier to compare variable noise exposures against regulatory limits.

References