Volume Shield · Listening guides

WHO–ITU 80 dB / 40 hours

WHO–ITU 80 dB / 40 hours describes an adult weekly sound-dose reference for personal audio systems. The standard’s more conservative reference is 75 dBA for 40 hours. Volume Shield uses these reference choices with estimated Mac headphone exposure.

Sources: WHO–ITU standard overview

By the Volume Shield team · Product information checked October 8, 2026

What do the adult and conservative references mean?

ITU-T H.870 defines the adult reference as 1.6 Pa²h, equivalent to 80 dBA over 40 hours per week, and a conservative reference of 0.51 Pa²h, equivalent to 75 dBA over 40 hours. WHO’s overview calls these the adult and children’s modes.

Sources: ITU-T H.870 reference modes · WHO overview of the two modes

How does Volume Shield use the reference?

The app combines its estimated level and captured listening duration into a rolling seven-day allowance. A 3 dB increase approximately doubles the contribution for the same duration. Earlier listening leaves the window as it becomes more than 168 hours old. The reference is separate from the user’s current-level limit.

Is this the same as NIOSH’s 85 dBA limit?

No. NIOSH’s 85 dBA, eight-hour time-weighted average is an occupational recommendation with its own assumptions. NIOSH explicitly says it is not a recommendation for general environmental noise outside the workplace. Do not interchange that daily reference with the WHO–ITU weekly personal-audio reference.

Sources: NIOSH: occupational versus environmental exposure

Does using the reference make the app certified?

No. Using a reference formula does not establish compliance testing or certification. Recognition of a headphone model is separate from accepted acoustic evidence. A category estimate remains an estimate, and Mac history does not include all sound in your day.

Volume Shield provides estimates for personal awareness. It does not measure sound pressure at your ear, certify a headphone, or guarantee a safe listening level.