It is unimportant whether the vibration is occurring at a resonant frequency or not- its vibration either way- just more of it if its at a resonant frequency
Again, I tend to agree with Ralph on this one and find it hard to believe that airborne vibration, even not at the resonance frequency, has no effect on the turntable system playback.
I would propose yet another simple test, similar to the one I proposed before:
Lower the cartridge on a stationary platter / LP, ideally the turntable system should be on an anti-vibration platform to filter out the structural borne vibrations,
Play music through the CD system,
Connect the cartridge to the phono / preamp as usual,
Listen to the phono system with a headphone, preferably in another room.
I am pretty sure you could hear the music through the headphone (although it would sound funny as it has gone through the RIAA stage).