My box fan white noise plan woke up the whole block

I was dealing with late night garbage trucks, so I dug out my loudest fan and pointed it at the window. The hum was perfect, but the fan shook so hard it made my blinds rattle like maracas. Next thing I know, the guy downstairs is texting me asking if I'm running a generator at 2 AM. I fixed it by putting the fan on a towel, but now I just use a free sound app on my tablet.