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Analog Microphones: Estimate SPL from Microphone Output

Estimate SPL for Analog Microphones

Estimate the Sound Pressure Level (SPL) directly from an analog microphone output. Enter the mic sensitivity in dBV re. 1 V/Pa, choose the Pa reference used on the datasheet (0.1 Pa or 1 Pa), and type your measured signal in volts. The calculator returns the received signal in dB SPL.

Example: sensitivity −26 dBV re. 1 V/Pa, Pa reference 1, measured signal 0.1 V → about 100.0 dB SPL.

We apply the conversion from voltage to acoustic pressure using the mic sensitivity, then reference to 20 µPa:

SPL = 20·log10( [ ( V · Pa_ref ) / 10^(Sens_dBV/20) ] / (2·10^-5) )
  • Sens_dBV is mic sensitivity in dBV per Pascal (dBV re. 1 V/Pa).
  • Pa_ref is the datasheet reference pressure (0.1 Pa or 1 Pa).
  • V is your measured (preferably RMS) voltage.
SPL — Analog Microphones
Enter the microphone sensitivity (dBV re. 1V/Pa), the pressure reference (0.1 or 1 Pa), and your measured signal in volts. The tool outputs the received level in dB SPL.
Pa
V
Received signal
in dB SPL
—

Tips for
Accurate Results

 

  • Use RMS voltage: SPL is an RMS quantity; peak values will overestimate the level by ~9 dB for sine waves.
  • Mind the signal chain: If your preamp/ADC adds gain, divide the measured voltage by the known gain before entering it.
  • Units: Sensitivity in dBV re. 1V/Pa; voltage in V; reference in Pa.
  • Bandwidth & filtering: If you apply A-weighting or band-pass filters, the reported SPL will reflect that scope.
  • Calibration helps: A 94 dB SPL calibrator (1 Pa) is handy to verify the full chain.

Assumptions
&
Limitations

 

  • Assumes the microphone behaves linearly around the operating point and that sensitivity is valid at the measured frequency band (datasheet often states 1 kHz).
  • Ignores directionality and room reflections; it converts the measured voltage to SPL at the capsule, not the room response.
  • Noise floor, clipping, and DC offsets are not corrected here; make sure the signal is within the linear range.

FAQs

What’s the difference between dBV and dBu?

dBV is referenced to 1 V, dBu to 0.775 V. Microphone sensitivities for capsules are usually given in dBV re. 1 V/Pa.

Some datasheets specify sensitivity at 0.1 Pa (≈ 94 dB SPL is 1 Pa). Use the same reference listed on the datasheet.

Use RMS. For a sine: Vrms = Vpk/√2 = Vpp/2√2.

No. Enter the RMS of your weighted or unweighted signal; the calculator performs a level conversion only.

Need help characterizing your microphone chain (preamp, ADC, filtering) or validating SPL measurements?

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