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Free Decibel Meter

40 Decibels — How Loud Is It?

Moderate

40 dB is about as loud as quiet home, no appliances running. 40 dB is the level of a quiet home with no appliances running, or birdsong heard from indoors. It's also WHO's recommended ceiling for outdoor night-time noise, chosen specifically because levels at or below it are not expected to meaningfully disturb sleep across a population.

What does 40 dB sound like?

  • 40 dB — Quiet home, no appliances running
  • 42 dB — Birdsong nearby
  • 45 dB — Refrigerator hum

Safe exposure time at 40 dB

Under NIOSH's Recommended Exposure Limit (85 dB, 3 dB exchange rate), safe unprotected exposure at 40 dB is effectively unlimited. Under OSHA's legal Permissible Exposure Limit (90 dB, 5 dB exchange rate), it is effectively unlimited.

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    Frequently asked questions

    Is 40 dB loud for sleeping?
    No — 40 dB is WHO's recommended outdoor night-time guideline value for undisturbed sleep. It sounds roughly like a quiet refrigerator hum: present, but not loud, and a reasonable target for a bedroom's background noise level.
    What is a good decibel level for a bedroom?
    WHO recommends outdoor night-time noise stay at or below 40 dB Lnight to protect sleep; indoors, aiming lower still gives extra margin, especially for light sleepers.
    Does 40 dB disturb sleep?
    Generally not for most sleepers — WHO sets 40 dB as the level below which no substantial biological sleep effects are expected across a population, though individual sensitivity varies.

    Sources