You probably don't need this, but I made a block:
https://snap.berkeley.edu/snap/snap.html#present:Username=joecooldoo&ProjectName=Draw%20Microphone%20Spectrum%20Block
Nice looking display 
That's very nice.
I really wish the X axis were labelled by frequency. I got this picture:
So what's that yellow spike on the right? I'm guessing it's aliasing at half the sampling frequence, so 22 Hz or something, but I'd like to know for sure.
And maybe there should be an option to display the log of the Y value, since perceived loudness is the log of the power (or voltage or whatever that is). Then the Y axis could be labelled in dB.
"Users -- give them an inch and they take a mile." :~)
Negative values of the spectrum are only an "artistic impression" but that's very misleading, as this diagram is not showing the actual sample values.
Oh yeah good point!
Fixed