Mic Response Curves
Pink noise is basically static that we engineers and mixers use to calibrate our gear, our PA systems, our listening environments etc.. But we can also use it to see a microphone's response curve. On a frequency analyzer Pink noise looks something like this.
It has a very linear slope in that the frequency gain drops off on roughly a straight line from 20khz to 20hz. But put it through a mic or an EQ, and the slope changes to reflect how the pure sound source is being affected. This is called your EQ curve or response curve.
In the above photo you can see all the EQ that had to be applied to approximate the response curve of a Shure Beta 58A. That is how that mic is affecting your voice.
Given that the source is an earbud, the massive bass cut is not indicative of the true curve, but in this case (apples to apples), you can see the various mic curves.
Below I've mapped out the frequency responses of the various good quality mics previously tested on this blog. The Audix OM5 and OM2, Shure Beta 58A, and the Sennheiser e835
You're probably saying to yourself... ok that's cool, but that means absolutely nothing to me. How am I suppose to use this information?
Well, let's say you're having feedback issues using one of these mics, and are thinking of getting a different one. You can record your performance - feedback and all, get the SPAN plugin, and analyze which frequency is feeding back. then look to see; is there a mic that has a built in EQ curve to curtail that frequency?
I hope this helps a little.