First thing would be to check to make sure the fan is clear of dust -- it takes very little to cause an imbalance and vibration.   If the noise continues or worsens thereafter, it's probably a fan bearing going bad -- in which case you will need to replace the fan (or heatsink-fan if the system has nVidia video).  
Hi There I had to reset my Inspiron 14 7472.  Since then I get strange noises which I believe originate from the fan.  I have applied the recommended patches from Dell related to power (Dell Power Manager Service) and Intel (Intel Dynamic  Platform and Thermal Framework + Management Interface Driver).  The sound originates on the right side near the power button and causes vibrations for a up to 5 minutes and then stops for a while and will come back again for a few minutes.  Not sure if this is a defective fan or something else.  I have been monitoring the temperature and nothing seems out of the ordinary.   Anyone experienced something like this before & if so how did you fix it? Thank You  Roger  
Strange Noises on Inspiron 14 7472