OEMS Occupational Exposure Management Systems LLC

Exposure assessment tools for Health & Safety Professionals

Noise Reduction Calculator

Enter noise exposure and protector details to get the protected level, pass or fail, minimum NRR needed, and hearing conservation program status under 29 CFR 1910.95.

8-hour TWA

Measured time-weighted average noise level.

dBA

Target reduction level

Level to stay under while wearing protection. Switches to 85 dBA if the worker has an STS.

85 dBA 90 dBA

Set to 85 dBA because the worker has a standard threshold shift (STS).

Protector type

NIOSH derating applies by type: earmuff 25%, foam 50%, other 70%.

Earmuff Foam plug Premolded plug Other plug

Protector NRR

Labeled NRR on the package.

dB

Double protection

Adds 5 dB to the higher NRR.

No Yes

Second protector type

Needed when double protection is Yes.

Earmuff Foam plug Premolded plug Other plug

Second NRR

Second protector's labeled NRR.

dB

Standard threshold shift

Yes if the worker has a recorded STS.

No Yes

Fit-test PAR (optional)

Replaces NIOSH derating.

dB

OSHA compliance

29 CFR 1910.95 Appendix B formula

dBA

Protected level

Minimum NRR needed

Real world

NIOSH derating by protector type, or fit-test PAR

dBA

Protected level

Minimum NRR needed

Program status (1910.95)

Note

For informational purposes only. This is a free reference tool that supports a qualified professional's judgment. It is not legal, medical, engineering or compliance advice, and using it does not make OEMS anyone's consultant.

Results depend on your inputs. The tool assumes an accurate 8-hour TWA from calibrated, correctly set-up instruments, an accurate protector NRR, and, if used, a valid fit-test PAR. It does not account for impulse or peak noise, measurement uncertainty, chemicals that can damage hearing (ototoxicants), noise exposure outside work, or how much a protector actually blocks for a given worker. Real-world protection depends on fit, condition and wearing the protector the entire time in noise. The NIOSH derating is a general estimate, not a measurement for any one person. The tool does not determine whether a worker has a standard threshold shift. That determination comes from audiometric testing reviewed by a qualified professional.
Not a compliance determination. A PASS result does not mean a workplace complies with OSHA. A hearing conservation program also requires monitoring, audiometric testing, training and recordkeeping. Regulations change and may be stricter in OSHA State Plan states, in other industries, or under contracts. OEMS is not affiliated with or endorsed by OSHA or NIOSH. Check the current standards that apply to you.
No warranty; limitation of liability. The tool is provided "as is," without warranties of any kind, including accuracy, completeness or fitness for a particular purpose. To the fullest extent permitted by law, OEMS is not liable for any loss, injury, hearing loss, penalty or damage arising from use of the tool or reliance on its results. You are responsible for how you use the results.
Your data. All calculations run in your browser. OEMS does not receive or store anything you enter, and the page does not use cookies. Like most websites, the page is delivered by a hosting provider and loads its font from Google, which receive standard request information such as your IP address.
Sources. OSHA 29 CFR 1910.95 and Appendix B; NIOSH Criteria for a Recommended Standard: Occupational Noise Exposure (1998), NRR derating by protector type; double protection +5 dB per OSHA Technical Manual, Section III, Chapter 5, Appendix F; fit-test PAR with double protection +5 dB per OSHA Safety and Health Management System Manual, Chapter 16.

© 2026 Occupational Exposure Management Systems LLC. All rights reserved.