What is dBFS?
dBFS is a digital level relative to full scale. We calculate sample peak as 20 × log10(p), where p is the largest absolute magnitude in a 2,048-sample window and magnitude 1 is 0 dBFS. A peak of 0.1 is −20 dBFS. All-zero samples show a dash, meaning no digital signal in that window.
The numeric reading is not clamped to the chart range. The chart alone clips values to −100 through 0 dBFS. This is a sample-peak display, not RMS, true peak, LUFS or perceived loudness.
Why this is not a room decibel meter
Microphone sensitivity, input gain and processing affect digital readings. There is no fixed conversion from these values to calibrated environmental dB SPL. Do not use this tool for noise exposure, medical decisions or compliance measurements.
Echo cancellation, noise suppression and automatic gain are requested off. The browser reports available settings, but hardware processing may still affect your input.
What each check establishes
The microphone waveform shows input reaching this page. A recording lets you listen through your current output. Left and right playback lets you compare channel directions by ear. None certifies hardware quality or guarantees another app’s setup.
History retains up to 18 seconds of observations taken about every 100 ms. Timing follows the browser clock and can slow in background tabs. The text summary reports the retained observations.
References
MDN: digital waveform samples · Adobe: monitoring digital levels