So, a few months ago I began noticing that my office desk was vibrating. It would sort of come and go, usually lasting for a few minutes at a time. I tried, but failed, to ignore it. I assumed it was related to the eternal construction next door. I told my landlord, but I'm not sure she believed me.
I wondered if I could get a desktop-sized seismograph to record it and convince people that I'm not imagining it. Then I thought, there must be an app for that.
The three images above are from the (free) iSeismometer app with an iPhone sitting flat on my desk. On the left is the normal (non-vibrating) state. The middle shows the display during the vibrations. Notice the wavy Z-axis line. The right picture shows the spectral analysis feature of the app. It calculates the vibrational frequency (sharp peak in the blue line) as about 14.4 Hz.
I'm still not sure what the cause is. I'm pretty sure its not cars or trucks rumbling down the street. It sort of feels like an unbalanced washing machine, except more bursty. Here's a video of it happening:
