There is a school of thought that says even with a concrete screed floor the Earth's seismic activity will affect loudspeakers with spikes. Similarly footfall on wooden floors will have an impact. There is an app you can download on to a tablet to measure seismic activity by resting the tablet on top of your speakers. The effect manifests itself in the way musical notes decay, but at my age and with my hearing I'm not sure I could hear the difference.
