[Armaegis]

Sitting at home with a wicked headcold, bored, and with a microphone...
 
 

(click to enlarge)
 
Singing the same note twice, but the top one is humming. It's interesting that the basic shape is the same but a bunch of higher order harmonics are missing.

 

[NA Blur]

Is the basic sound you make during both tests roughly the same?  If that is the case then the results are pretty reasonable considering how resonators work.

 

[Armaegis]

More or less. Sing a note, then shut my mouth and hum that note instead. Actually, I also tried it while plugging my nose and the result is similar.
 

 
As an aside, I can simulate ground loops pretty well when I'm sick

 

[NA Blur]

Hope you feel better.  If you have not done so already try some hot tea with honey.  Zinc is also great, but do not over do it with the Zinc.  Makes my head colds go away in 2 days.