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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.

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  • Thanks for the helpful answer. I also later found this article which was pretty helpful. Check out the table further down the page...
    – bpert
    Sep 5, 2010 at 14:03
  • @bpert Don't forget to pick the best answer to your question ;) Sep 5, 2010 at 15:24

1 Answer 1

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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.

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  • @endolith I think your html code got jumbled - I don't understand your answer :(
    – Utopia
    Sep 2, 2010 at 20:53
  • @Ryan I've added to it. Which part don't you understand?
    – endolith
    Sep 2, 2010 at 21:09
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    @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, 2010 at 21:24
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    Thanks for the great explanation with math to show what you mean too! I wanted to assume that it would be about twice the output since it is twice the voltage, but I was unsure if their were other aspects that I hadn't considered. For some reason I thought that different SPL's might react differently for each microphone, sort of how different frequencies react differently with each microphone. But when you said it "would produce a voltage oscillation with an amplitude of 13 mV at the XLR pins" it makes more sense to me.
    – bpert
    Sep 3, 2010 at 1:25
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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, 2010 at 14:00

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