Microphone sensitivity is usually measured in mV/Pa. If one mic is say 25 mV/Pa and another is 13 mV/Pa how much more sensitive is it in application? How can I figure out how much more gain the mic is actually outputting in dB? I feel like I should know this but I don't.

  • Very nice question. – Utopia Sep 2 '10 at 19:20

Sensitivity measures the voltage at the output pins of the mic for a given sound pressure level. 13 mV/Pa means that an air pressure oscillation with an amplitude of 1 pascal (94 dB SPL) at the mic capsule would produce a voltage oscillation with an amplitude of 13 mV at the XLR pins.

Gain is basically the ratio of output level to input level.

In this case we're not talking about an input and output, but you can still talk about the relative gain difference, which would be (25 mV)/(13 mV). The sound pressure level (1 pascal) is the same for both, so it cancels out. The relative gain difference is then 25/13 = 1.9, or about 2x as much voltage for the same pressure.

In decibels, the difference would be 20·log10(V1/V2), so +5.6 dB for your example. A doubling in voltage is about 6 dB, so you could guess this just by recognizing that 25 is almost twice 13.

  • @endolith I think your html code got jumbled - I don't understand your answer :( – Utopia Sep 2 '10 at 20:53
  • @Ryan I've added to it. Which part don't you understand? – endolith Sep 2 '10 at 21:09
  • @endolith Excellent explanation. I do know this stuff but usually it takes some effort to get my head around the concepts of loudness, sound pressure level and dB scales and how they translate into each other. To me, your answer is very clear, thus required no such effort, thanks :) (@Ryan I don't see any html in there?) – EMV Sep 2 '10 at 21:24
  • 20*log10(V1/V2) Log? – Utopia Sep 2 '10 at 21:39
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    @endolith loudness is proportional to frequency varying from person to person. generally 10dB SPL is twice as loud, but for mid-range frequencies only. 6dB difference in SPL or Voltage is equivalent to moving twice as far away from a sound source or halving the distance between source and mic. (in free-field conditions, exact figure variable indoors) – jb1t Sep 4 '10 at 14:00

Thanks for the helpful answer. I also later found this article which was pretty helpful. Check out the table further down the page...

  • @bpert Don't forget to pick the best answer to your question ;) – Justin Huss Sep 5 '10 at 15:24

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