Hearing safety · headphones
Headphone safe listening time.
Enter the headphone sensitivity from the spec sheet and the power or voltage from your amp. Get the level at your ears and how long per day that level is considered safe.
Inputs
Result
Enter the sensitivity and the drive level.
From headphone specs to listening time
Headphone sensitivity is quoted in dB SPL per milliwatt (dB/mW) or per volt (dB/V). The level at your ears is SPL = sensitivity + 10 x log10 (power in mW) for dB/mW, or sensitivity + 20 x log10 (volts RMS) for dB/V. The two units convert as dB/V = dB/mW - 10 x log10 (impedance / 1000), which is the relation in Wikipedia's Headphones article, with power = voltage squared / impedance. The listening time then comes from the NIOSH formula (85 dBA, halve every 3 dB) and the OSHA formula (90 dBA, halve every 5 dB), the same ones as on the allowed time calculator.
Worked example. Headphones rated 100 dB/mW at 32 ohms. At 0.1 mW the level is 90 dB, and treating that as dBA, NIOSH allows 2.5 hours per day. At 1 mW the level is 100 dB and the NIOSH time falls to 15 minutes. The voltage at 1 mW into 32 ohms is 0.18 V RMS, and 100 dB/mW corresponds to 114.9 dB/V.
Wikipedia reports that the European standard EN 50332-1:2013 recommends a warning above 85 dB(A) with an absolute maximum of 100 dB. Phone volume sliders are not calibrated, so for a real figure use a measurement (a coupler or a sound level meter app is only a rough guide). If the music sounds loud enough that you cannot hear someone speaking nearby, or your ears ring afterwards, it is too loud whatever the arithmetic says.
Frequently asked questions
How loud is too loud for headphones?
NIOSH recommends keeping an 8-hour average under 85 dBA, with the allowed time halving for every 3 dB louder. At 94 dBA that is about an hour.
How do I find out my headphone volume in dB?
Phone sliders are not calibrated in dB. The arithmetic here needs the drive power or voltage from your amp. A measurement with an ear coupler is the accurate way.
What is the difference between dB/mW and dB/V?
dB/mW is the level for 1 milliwatt of power; dB/V is the level for 1 volt. They convert using the headphone impedance: dB/V = dB/mW - 10 log10 (impedance / 1000).
Does noise-cancelling mean I can listen louder?
It lets you hear music at a lower volume in noise, which is safer, but it does not make a given level at the ear any less harmful.
Sources
Checked
- Wikipedia: Headphones (sensitivity section)
- NIOSH 98-126: Criteria for a Recommended Standard, Occupational Noise Exposure, Revised Criteria 1998
- CDC NIOSH: Noise-Induced Hearing Loss
- OSHA 29 CFR 1910.95: Occupational noise exposure
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Hearing safety guidance, not medical or occupational-health advice. These are published limits and rules of thumb applied as arithmetic, not a noise survey. Measure real levels with a sound level meter or dosimeter, follow the rules that apply to your workplace, and see an audiologist if you have ringing, muffled hearing or hearing loss.