Compare like with like
Keep the microphone, position, input gain and processing the same. Compare a quiet pause before and after one change, such as moving a fan. Changing devices or gain starts a different comparison. Open Current input settings to see what the browser reports.
Read the history
The chart retains the last 18 seconds of sampled peaks, with one observation approximately every 100 ms. Each observation is the peak of a 2,048-sample window, not the maximum of every sample between updates. Background tabs and busy devices may update less often. This is a short observation tool, not a continuous recorder.
Reset history clears the chart without stopping an active microphone or changing a pending request. Stop ends capture. dBFS measures a digital signal relative to full scale; it cannot directly tell you the room’s dB SPL. Learn about the readings.