Tone of micro phonic "ring"

[mortron]

I have several RCA tubes and when I tap on the top plate, I get distinctly different tones of ring from each tube. Is it a sign of a poor match, or of no concern? The reason I ask, is that other sets of tubes have sounded more or less the same tone, or somewhat "in tune" when you tap the plate. Thanks and happy holidays.

[Paul Birkeland]

This can change depending on how the tube is actually stuck into the socket. 

There are no criteria for matching tubes based on how they ring microphonically.