Live Decibel Meter / Methodology
Methodology
The digital level is 20 × log10(RMS), relative to full scale (dBFS). We add +120 dB as an arbitrary starting offset, plus your calibration adjustment. That offset is not a physical SPL reference and cannot determine real-world dB SPL without reference calibration.
· Indragni Solutions
Weighting
Approximate reading. A weighting filters frequencies; Z is flat. Neither makes an uncalibrated microphone a certified meter.
Calibration offset
Place your device beside a trusted sound level meter in steady broadband sound. Use matching weighting and response, then adjust the offset to match. Do not use an arbitrary phone tone as a calibrated reference.
NIOSH reference time
Educational reference only: the NIOSH model uses 85 dBA for 8 hours and halves the time with every 3 dB increase. An uncalibrated browser reading cannot establish a safe exposure time. Reduce noise and use suitable hearing protection.
RMS → dBFS → dB
20 log₁₀(RMS) + 120 + offset
The digital level is 20 × log10(RMS), relative to full scale (dBFS). We add +120 dB as an arbitrary starting offset, plus your calibration adjustment. That offset is not a physical SPL reference and cannot determine real-world dB SPL without reference calibration.
A / Z · 125 ms / 1 s
Approximate reading. A weighting filters frequencies; Z is flat. Neither makes an uncalibrated microphone a certified meter.
Rimell, Mansfield & Paddan — Design of digital filters for frequency weightings (2015)
Educational reference only: the NIOSH model uses 85 dBA for 8 hours and halves the time with every 3 dB increase. An uncalibrated browser reading cannot establish a safe exposure time. Reduce noise and use suitable hearing protection. NIOSH
Have an iPhone? Try dB Pulse.
Get dB Pulse for iPhone ↗