How to align a browser reading with a reference meter

Set up a comparison you can repeat

Check the reference meter’s instructions and calibration status. Note its frequency weighting and time response. Decibel Reader does not apply A weighting, so a match with an A-weighted meter can depend on the source’s frequency content.

Choose a reasonably steady sound at an ordinary, comfortable level. There is no reason to create a loud exposure for this check. A source that surges, clicks, or overloads either microphone makes a poor reference.

Place the microphone openings close enough to receive a similar sound field without touching or covering them. Leave both devices still. Note the source position and microphone orientation; you will need them to repeat the comparison.

Collect the 10-second sample

1. Start measuring and allow microphone access.
2. Open Settings & calibration, then the reference-alignment controls.
3. Collect the 10-second sample while watching the reference meter.
4. Enter the reference level for that same interval and apply the alignment.

Use the reference’s average for the interval where available. If its reading varied widely, repeat the sample with a steadier source. Choosing a convenient maximum or minimum would align the devices to different observations.

The browser energy-averages its valid raw samples and calculates offset = reference level − sampled dBFS. A reference of 65 dB and a raw average of −35 dBFS would give a 100 dB offset. This is a worked example, not a measurement or a suggested setting.

Applying alignment sets the manual adjustment to zero and resets the statistics. If measurement is running, a new record starts on the adjusted scale. Save any report you need before applying the change.

What the offset changes

The microphone supplies a digital signal. Decibel Reader calculates its RMS level using 20 × log10(RMS), in dBFS. The default display adds +94 dB, with an Uncalibrated label. That default is not a known acoustic sensitivity for your device.

Reference alignment replaces the default with an offset calculated from your sample. Every subsequent estimated reading shifts by that amount. The adjustment does not correct the microphone’s frequency response or noise floor, and it cannot remove gain control hidden in the device.

A professional acoustic calibrator supplies a defined sound pressure through a suitable microphone coupling. Comparing two devices beside a sound source is a different procedure. The display says Reference aligned to describe what you actually did.

Check a fresh reading before relying on the match

Leave the setup in place and take a new reading. Agreement at the original condition checks that the offset took effect. Then, if practical, compare another ordinary level or a different source.

Does the difference stay about the same? If it changes, a single offset does not describe both conditions. Repeatedly adjusting each reading until it matches would hide the disagreement. Keep a note of where the match holds and where it does not.

NIOSH publishes tested performance for its own iOS app and specified microphone arrangements. Those results do not validate Decibel Reader, a different browser, or your microphone setup. This tool has no equivalent acoustic validation claim.

Without a reference, use a relative baseline

A room that seems quiet has no known decibel value. It may contain low-frequency sound, and the microphone’s own noise or processing may affect the signal. Entering a guessed reference would carry that guess into every later reading.

The quiet-room check instead samples a relative dBFS baseline and leaves the offset unchanged. It can help you watch for changes with the same setup. For a before-and-after task, follow the repeatable room-comparison method rather than assigning the room an invented SPL value.

Recheck after changing the setup

A saved offset belongs to the microphone and settings you checked. Revisit it after switching microphones or browsers, changing input gain, or altering device audio settings. An alignment for a built-in microphone should not automatically carry over to a headset.

Manual adjustment also resets the statistics, so readings from two scales do not enter one average. Reset offset removes reference alignment, restores the uncalibrated +94 dB default, and returns manual adjustment to zero.

When sharing a report, include the reference meter’s weighting, the source, and the placement with its recorded offset and accuracy status. The report preserves the adjustment; it does not verify the reference. Decisions requiring traceable sound pressure or workplace exposure assessment need an appropriate instrument and procedure.