Comment:
Cello's top plate vibrates(/fluctuates) with beats 2->1->2->1->1 after a pizzicato, on the other hand the endpin keeps 2-beat persistently.
However both two components of cello sustained their vibration over 3 seconds in this measurement. The D note(148Hz) might be well matched to the top plate and also to the endpin on the floor or to their combination.
