← Blog · March 8, 2026 · 7 min read

NIOSH and WHO Noise Exposure Guidelines Explained

If you've read anything about hearing protection, you've likely encountered references to NIOSH and WHO guidelines. These two standards — one American, one international — form the scientific backbone of most hearing protection advice, including the thresholds used by tools like SoundBrake. Here's a clear explanation of what they say, how they differ, and how to apply them to everyday listening.

What Is NIOSH?

The National Institute for Occupational Safety and Health (NIOSH) is a US federal agency, part of the Centers for Disease Control and Prevention (CDC). Its primary remit is worker safety — hence the "Occupational" in its name. NIOSH publishes recommended exposure limits (RELs) for workplace hazards, including noise.

Although NIOSH guidance was designed for industrial workplaces, its noise exposure recommendations are widely adopted beyond occupational settings because they are based on rigorous epidemiological research and represent one of the most conservative (and therefore protective) standards available.

The NIOSH Recommended Exposure Limit

NIOSH recommends a maximum noise exposure of 85 dB(A) averaged over an 8-hour working day. Above this level, risk of permanent hearing loss begins to accumulate with sustained exposure.

Crucially, NIOSH uses a 3 dB exchange rate (also called the trading ratio). This means:

• Every 3 dB increase in sound level halves the allowable exposure time.
• At 85 dB: maximum 8 hours.
• At 88 dB: maximum 4 hours.
• At 91 dB: maximum 2 hours.
• At 94 dB: maximum 1 hour.
• At 100 dB: maximum 15 minutes.
• At 106 dB: maximum about 4 minutes.
• At 112 dB: maximum about 1 minute.

The 3 dB exchange rate is rooted in acoustics: because the decibel scale is logarithmic, a 3 dB increase represents a doubling of acoustic energy. If you receive twice the energy in half the time, the total energy dose is the same — and NIOSH treats equal doses as equal risk.

What Is the WHO Standard?

The World Health Organization (WHO) has published guidelines on both occupational and recreational noise exposure. For recreational listening specifically, the WHO has been particularly active in addressing the global risk to young people from personal audio devices.

The WHO's Make Listening Safe initiative recommends that personal audio device users limit their weekly exposure to 80 dB for up to 40 hours per week. This is somewhat more conservative than NIOSH on weekly totals.

The WHO also uses a 5 dB exchange rate for recreational exposure (versus NIOSH's 3 dB), which produces slightly different safe duration tables:

• At 80 dB: maximum 40 hours per week.
• At 85 dB: maximum ~12.5 hours per week.
• At 90 dB: maximum ~4 hours per week.
• At 95 dB: maximum ~1.25 hours per week.
• At 100 dB: maximum ~25 minutes per week.

Why Do They Differ?

The difference in exchange rates (3 dB vs. 5 dB) reflects different models of how cumulative energy translates to hair cell damage. NIOSH's 3 dB rate is based on equal-energy hypothesis research and is considered the more physiologically accurate model. OSHA (the US Occupational Safety and Health Administration), by contrast, uses a 5 dB exchange rate — the same as the WHO's recreational guidance — which was set partly for regulatory practicality.

In practice, for everyday listening decisions, the difference is less important than simply understanding that both standards define 85 dB as the critical threshold above which meaningful risk begins.

How These Guidelines Translate to Headphone Use

The practical challenge is that consumer devices show you a percentage, not a decibel level. What 85 dB corresponds to on your volume slider depends entirely on your headphone model, your audio source, and the audio content.

Research studies have found that:

• Popular smartphone earbuds at 70–80% volume can produce 85–100 dB in real-world conditions.
• Many in-ear monitors max out above 115 dB at full volume.
• Open-back over-ear headphones typically produce lower levels at equivalent settings due to their acoustic design.

A conservative rule of thumb, adopted by many audiologists: if your audio is perceptible to someone standing about one arm's length from you while you wear headphones, you are above 85 dB.

How SoundBrake Uses These Guidelines

SoundBrake applies a pragmatic interpretation of both standards. Because device volume percentages don't map reliably to decibels, SoundBrake uses the percentage scale as a proxy:

• At 75–84% volume: warns after 60 minutes of continuous exposure.
• At 85–94%: warns after 20 minutes.
• At ≥95%: automatically reduces volume to 70% after 5 minutes.

These thresholds are intentionally conservative — they may fire sooner than the absolute limits suggest — because the dB output at any given percentage is unknown and almost certainly higher than users assume.

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Next reading: How SoundBrake Monitors Your Volume →