Sound Level Meter

What it's for

See roughly how loud it is where you are, using your microphone. It shows the level of the sound in dBFS (decibels relative to the loudest signal the microphone input can carry), an estimate in dB(A) (decibels weighted to match how the ear hears quiet and high or low sounds) and the highest level so far.

For example, when you want to compare a quiet room with a noisy one, or see whether a fan got louder, start measuring in each place and compare the dB(A) figures and the highest level.

How to use it

Press Start measuring and allow the microphone. The big number is the A-weighted estimate in dB(A), the smaller one is the unweighted level in dBFS, and the bar follows the dBFS level. Readings use the last sixth of a second. Highest dB(A) and Highest dBFS keep the loudest readings since you started; Reset highest clears them.

The Calibration offset is added to the A-weighted level in dBFS to give dB(A). Every microphone and device has a different offset, so to get closer, hold a reference sound level meter beside the microphone, play a steady sound, and change the offset until the two read the same. The offset is remembered in the browser.

Example

Press Start measuring, leave the offset at 90, and say “aaah” at a steady volume about 30 cm from your device. The dBFS figure settles at some value below 0 (for example −30) and the dB(A) estimate shows that figure plus 90 and the A-weighting (for example 60). Move closer and both rise together.

Good to know

This is an estimate, not a calibrated meter: phones and laptops differ by 10 dB or more, and without a reference meter the dB(A) figure is a guess. Browsers and microphones may limit very loud sound or reduce low frequencies, and cheap microphones can’t show levels near the top of the range. The page turns off the browser’s echo cancelling, noise reduction and automatic gain, but some devices apply their own. The weighting is the A curve only, with no C or Z curves, and the reading isn’t suitable for checking noise limits at work or hearing safety. Nothing is recorded, stored or sent anywhere; closing the page or choosing Stop releases the microphone.