Wolf note?

klaatu

A new problem has surfaced on one of my guitars. When I play a C at either the 13th fret of the B string or the 8th fret of the high E (same note), this weird resonance occurs, C an octave lower. It lasts for a few seconds and then quickly decays. If I press on the strings behind the bridge OR press the top firmly, it stops. You can feel the top resonating.

Is this what they call a wolf note or wolf tone? Any idea why it would start happening now? I recently changed strings from 10s to 11s. Would the increased tension account for the change (as in possibly bringing out a problem that was not evident before)?

klaatu

As mysteriously as the weird note appeared, it has now just as mysteriously disappeared. In the meantime, Bob Holo offered by PM a very learned dissertation on possible causes, and the actual builder suggested that in this case it had to do with the Bilardi tailpiece, which is bent severely on the sides and nearly touches the top in places.