How is microphone SNR calculated?

Microphone SNR is referenced to 94 dB SPL, which equals 1 pascal at 1 kHz. The formula is SNR = 94 dB minus the equivalent self-noise in dBA. A mic with 14 dBA self-noise therefore has an 80 dB SNR.

What is equivalent self-noise?

It is the sound pressure level that would produce the same output as the microphone's own internal electronic noise. It is usually A-weighted to match the ear's sensitivity, so it appears as a dBA figure. Lower is quieter and better.

What counts as a low-noise microphone?

Self-noise below about 10 dBA (SNR above 84 dB) is considered very quiet and suitable for distant, ambient, or classical recording. Most general-purpose large-diaphragm condensers sit around 12 to 18 dBA.

What is the minimum detectable SPL?

It is the sound level at which the signal equals the noise floor, giving a 0 dB signal-to-noise ratio. Numerically it is the same as the equivalent self-noise figure: any quieter source is buried in the mic's own hiss.

Does sensitivity affect the SNR?

No. SNR is a ratio and is independent of sensitivity. Sensitivity only sets the absolute output voltage, which this tool also reports so you can compare the noise floor in microvolts against a preamp's input noise.

Microphone Self-Noise & SNR Calculator

This calculator turns the raw figures on a microphone spec sheet into the numbers that actually matter for quiet recording: signal-to-noise ratio, dynamic range, the minimum detectable sound level, and the absolute output voltage of the noise floor. Enter the values once and compare any two microphones objectively.

How it works

Microphone specifications reference everything to 94 dB SPL, which equals one pascal of pressure at 1 kHz. The signal-to-noise ratio is simply how far the self-noise sits below that reference:

SNR (dB)           = 94 − equivalent self-noise (dBA)
Dynamic range (dB) = max SPL − equivalent self-noise (dBA)

Sensitivity in dBV/Pa gives the output voltage for a 1 Pa signal (using V = 10^(dBV/20), where 0 dBV = 1 V RMS). The noise-floor voltage is that reference voltage divided by 10^(SNR/20), which is why low-noise mics can have a noise floor of only a few hundred nanovolts.

Example and tips

A microphone rated at 14 dBA self-noise, −37 dBV/Pa sensitivity, and 134 dB max SPL gives an 80 dB SNR, a 120 dB dynamic range, and a minimum detectable level of 14 dB SPL — roughly the threshold of a very quiet recording booth. When comparing microphones, the self-noise figure is the single most useful number for quiet work; the SNR is just the same information expressed against the 94 dB reference. A-weighted (dBA) and CCIR-weighted noise figures are not directly comparable, so make sure both mics quote the same weighting before judging.