If you have not already, you may want to view video-displays of the modal resonance of the structure. This will also give you an idea of what is happening when you run the physical experiment remotely at Hudson Hall. The videos can be found on the introduction to this tutorial. At the moment, viewing the videos requires Windows Media Player and Internet Explorer. Browser-independent video formats will be posted soon. Notice that at the first natural frequency all floors move in phase with each other. By looking at the video, can you determine the phase relationship between the floors at the higher natural frequencies?