If you use an iPhone with headphones, it is keeping a running total of your sound exposure and will tell you when you pass a limit. The limit is 80 decibels for 40 hours in seven days, and it is not Apple's number.
Apple says so, once: "Exposure limits derived from World Health Organization recommendations." The standard that implements those recommendations is ITU-T H.870, and it contains two explicit warnings against things Apple's implementation does.
What the standard says
The sixty-page standard, published in March 2022, comments on the reliability of the dose figure itself:
"Since some of these uncertainties are typically several dB, and an error of 3 dB constitutes a 100% dose error, uncertainties of dose estimation can be expected to be hundreds of percent. It is therefore suggested to refrain from signalling 'safe' and 'green' to the user based on dose readings below a certain limit."
And on the behaviour of automatically turning the volume down when the budget runs out:
"If, upon reaching 100% of the user's weekly allowance, the level is automatically reduced to 80 dBA (75 dBA for sensitive listeners), the user's sound exposure will continue to increase beyond 100%. Such an action is therefore not fully protective against further risk to hearing."
There is a third caveat that matters more than either for anyone with a noisy job:
"It should be also noted that the sound allowance determined as described by this Recommendation ignores sound exposure from sources other than personal audio devices."
Apple's ladder reproduces the standard's arithmetic
Apple publishes the exposure ladder in plain language. Run the standard's own formula against it — 40 hours at 80 dB, halving the time for every 3 dB — and it reproduces:
T(L) = 40 / 2^((L − 80) / 3) hours per week
85 dB → 12.60 h Apple says "around 12 hours and 30 minutes"
90 dB → 3.97 h Apple says "4 hours"
95 dB → 1.25 h Apple says "around 1 hour and 15 minutes"
100 dB → 23.6 min Apple says "around 20 minutes"This is not an approximation; it is the standard's own arithmetic.
The attribution goes missing exactly where you read the number
We checked which of Apple's pages name the source. The results are a properly controlled absence:
| Apple support page | "World Health Organization" | Controls present in the same page |
|---|---|---|
| Headphone Notifications | 0 | "headphone" 22, "decibel" 2, "40 hours" 1 |
| The Noise app | 0 | "decibel" 10, "noise" 25, "40 hours" 1 |
| Hearing Protection | 1 | "40 hours" 1 |
⚠️ The two pages a person actually reads about their own exposure state the WHO's number and never name the WHO. The attribution lives on a third page — which, as we found separately, is the page several markets do not receive at all.
What this does not mean
None of this makes Apple the villain, and the credit due here is substantial. Almost no consumer-audio maker ships exposure tracking at all. Apple ships it on by default, names an actual numeric limit rather than a vague warning, publishes the whole ladder in plain language, and enforces reduction where regulators require it.
Apple also did not pick a lax standard to flatter itself. It picked the strict one. At 100 dBA the WHO-derived budget is about 20 minutes per week; the American occupational limit at the same level is two hours per day. Apple is roughly six times stricter than the standard it could have chosen, and Apple's user interface does not, in fact, print the word "safe".
H.870, for its part, is not accusing anyone. Its notes are addressed to the engineers implementing the standard, in a design context. "Refrain from signalling safe" is advice about interface design, not a claim that dose tracking is worthless.
⚠️ The number is not wrong. It carries an uncertainty the screen does not show, and excludes sound the screen does not mention.
Where the criticism does land
A percentage on a phone screen reads like a final verdict, but the standard it is based on warns that dose estimation can be uncertain by hundreds of percent, that the automatic volume reduction is not fully protective, and that the figure ignores all sound that did not come through the headphones.
Someone who spends a shift in a loud kitchen and then listens to podcasts on the bus home is being told about a fraction of their real exposure, presented as a total. Apple's own footnote adds one more exclusion in the same direction: phone calls do not count toward the headphone total either.
What to do with it
The headphone-levels figure measures one source, and it does that usefully — how loud you listen, over time. It is silent about everything else, and it is not a verdict on your hearing.
If your exposure is mostly not headphones, the number is close to meaningless for you, and the fix is not a phone setting. If you have crossed 100% and the volume dropped automatically, read that as the standard reads it: a partial measure, after which exposure keeps accumulating.
And one precision point worth carrying away, because it is widely misstated: the standard's lower 75 dB setting is not "the children's limit". H.870 defines it as the level "for users that prefer or may benefit from lower sound levels (e.g., for children)". Children are an example in that sentence, not the definition.
Where this comes from, and what will date it
The three warnings are quoted from ITU-T H.870 (03/2022), a 3,376,915-byte PDF of sixty pages, read directly. Its own controls confirm the document: "safe listening" appears 71 times, "sound allowance" 16, "exchange rate" 4. The reference dose reproduces from the standard's own formula — 80 dB(A) at 40 hours is 1.60 Pa²h, and the 75 dB setting is 0.51 Pa²h. Apple's ladder, the attribution sentence and the phone-call exclusion are quoted from Apple's own support articles, and the attribution counts above were taken from those same fetched pages.
⚠️ One thing we did not check, and it matters if you want to argue about the interface. We read Apple's support documentation, not a live device screen. What the Health app's headphone-levels view actually says — how it labels a reading as acceptable or loud — we have not verified, and nothing above rests on it. We also did not test whether the volume-limiting behaviour required in the EU is implemented identically elsewhere.
This dates if H.870 is revised to soften those notes, if Apple begins attributing the standard on the notification pages, or if Apple folds non-headphone sound into the same budget. The current edition is March 2022 and the arithmetic above will hold for as long as it stands.
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