What do microphone vendors mean by 'sensitivity' ?

[Externet]

Can anyone explain what is meant by sensitivity in a microphone ?

And at what output impedance is the standard on plain vulgar electret capsules ? And that is not dBm, right ? Is it dBV ? Seen mostly expressed just as dB ! And for analog only; not digital output, right ?

 

[Lightium]

It means at 1KHz the softest sound it can hear is - 28dB at some distance away. I am not sure but I think it's one meter.

 

[rjenkinsgb]

It's the output voltage for a given pressure at its diaphragm.

The reference is 1V per pascal and the mic sensitivity is -28db (dBV as the unit is voltage) relative to that.
1V scaled by -28dBV is 0.040V

So it's sensitivity is 40mV per pascal.

For reference, the common Shure SM58 has a sensitivity of -56dBV, 2mV per pascal.

(The softest sound detectable is limited by noise level of the mic or preamp).


Impedance wise, electret capsules like that could be considered current sinks, I suppose?

It's operating current is given as 0.5mA; the load/power feed resistor needs to be appropriate to give a voltage across the capsule somewhere within it's stated working range. That resistor is a major part of the overall mic output impedance.

It could be anything from 470 Ohms at the low end of the voltage range to 10K or more at 10V. The overall circuit impedance will change significantly with the range of resistance.


The input impedance of the next stage should be at a minimum ten times higher than the load resistor value & preferably more, to keep distortion to a reasonable level.

 

[For The Popcorn]

I always wonder why people ask questions in forums that are quickly and easily answered with a simple Google search. The picture shows the first hit I got when I searched "microphone sensitivity".

An authoritative answer could be obtained in seconds rather than hours or even days.

Totally, asking questions to clarify points you don't understand is what the forum is best at.

 

[Lightium]

So there's no truth to my statement?

 

[For The Popcorn]

I was more commenting on the original question.

 

[rjenkinsgb]

So there's no truth to my statement?

No, sorry; the sensitivity is purely the ratio between sound pressure and output voltage.

 

[audioguru]

Some people whisper into a mic or scream. Some people "eat" it very close or at arms length away. HUGE differences in output level.