Decibel Meter (Sound Level Meter)

About the Decibel Meter (Sound Level Meter)

Measure how loud it is around you with your phone’s or computer’s microphone. The meter shows the sound level in dB(A) — weighted like human hearing — or dB(C) and unweighted dB(Z), with the standard Fast (125 ms) or Slow (1 s) response, the average level (Leq) since you started, the maximum, minimum and peak, the levels exceeded 10 % and 90 % of the time, and a graph of the level over time.

Browsers normally process the microphone for calls — automatic gain, noise suppression, echo cancellation — which would make every sound read about the same. The page asks for all three to be switched off and tells you if the browser keeps one on. Because phone and laptop microphones are not calibrated, the reading is an estimate: you can calibrate it against a real sound level meter, and the setting is remembered for that microphone. It measures on your device; nothing is recorded or uploaded.

Common uses

• Getting an idea of how loud a room, a road, a machine or a party is.
• Comparing the noise before and after soundproofing, or of two appliances.
• Checking that music in a nursery, a gym or a café stays at a sensible level.
• Keeping a log of noise from neighbours or traffic over a few minutes, as a rough record.
• Learning how A and C weighting and Fast and Slow responses change a reading.

What the readings mean

• Sound level is the level now, with the chosen frequency weighting and response. A weighting turns down low and very high frequencies the way our hearing does (−19.1 dB at 100 Hz, −2.5 dB at 10 kHz); C weighting stays within 3 dB of flat from 31.5 Hz to 8 kHz; Z is no weighting. The curves are those of IEC 61672-1.
• Fast and Slow are the standard time weightings: an exponential average with a time constant of 0.125 s or 1 s, so a sudden sound shows almost at once on Fast and builds up over a second on Slow.
• Average (LAeq): the energy average since the start or the last reset — the single number most noise limits are written in.
• Maximum and minimum (LAFmax, LAFmin): the highest and lowest time-weighted level, counted once the average has settled.
• Peak (LApeak, LCpeak or LZpeak, after the weighting you chose): the highest instantaneous level, on the same scale.
• L10 and L90: the level exceeded 10 % of the time (louder events) and 90 % of the time (the background); L5, L50 and L95 likewise.

How accurate is it?

The weighting filters follow the IEC 61672-1 curves within 0.15 dB up to 5 kHz and within 1.6 dB at 10 kHz, and the time weightings and averages are exact. The uncertainty is the microphone: its sensitivity, its frequency response (phone microphones roll off the deep bass and often boost speech frequencies), the gain your system applies and the case around it.

Without calibration the page assumes that a full-scale signal is 120 dB SPL, the full scale of a digital microphone whose sensitivity is −26 dBFS at 94 dB SPL. Real devices can be 10 dB or more off, so treat uncalibrated readings as a rough guide and calibrated ones as an estimate. Very quiet rooms read too high (the microphone’s own noise), and very loud sounds can overload the microphone — the page warns you when its samples hit full scale.

Noise levels for comparison

The US NIOSH notes that sounds of about 85 dB(A) often make you raise your voice to be heard by someone 1 metre (3 feet) away, and that at 95 dB(A) or more you are likely to have to shout. It recommends limiting workplace exposure to 85 dB(A) averaged over 8 hours, halving the time for every 3 dB more; the US OSHA limit is 90 dB(A) over 8 hours, with a hearing conservation programme from 85 dB(A).

Those limits are checked with calibrated sound level meters or dosimeters worn by the worker. This page cannot show compliance with them, or with any noise rule; use it to get an idea of how loud something is, and ask a professional with a certified meter when it matters.

Limitations

• Not a sound level meter to IEC 61672 and not for workplace, legal or planning noise assessments: the microphone is uncalibrated and its frequency response is unknown.
• Some browsers or devices keep their gain control or noise suppression on even when asked not to; the page tells you when the browser reports it.
• Phones and laptops cannot measure very quiet places, where the microphone’s own noise is louder than the room, or very loud sound that overloads the microphone.
• The measurement runs while this page is open; a phone may pause it when the screen locks.
• The free preview shows the live level, the average, maximum, minimum and peak, the first half of the statistics and a watermarked graph; the summary and the log export come with a pass.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.